E) Health risks to seafarers

E.5 Radiation

Details

Published: 09 January 2022

OLE JACOB MØLLERLØKKEN

Introduction

Radiation, or electromagnetic fields, can be categorized into two parts, ionising and non-ionising, based on the energy the radiation possesses and the ability the fields have in ionizing molecules or not.  

Figure 1 shows the Electromagnetic Spectrum and displays the relation between the non-ionizing fields, less energy, with the ionizing fields, high energy.

Typical for non-ionizing fields are longer wavelengths and different segments for different use, for example,

• the extremely low frequency fields that are common in powerlines,
• the mid- and high frequency fields which are used in communication, and
• the intermediate phase with infrared-, normal and UV-light

before the ionizing part of the spectrum typically used for medical purposes and nuclear power.

Figure 1 The electromagnetic spectrum

Electromagnetic fields surround us everywhere, and on maritime vessels they are used for many different purposes, for example, communication, navigation and powering the ship. Due to environmental considerations, an electric engine instead of a combustion engine now powers more and more vessels. This will further increase the presence of electromagnetic fields in the maritime environment, and makes it important to have knowledge about these fields.

Non-ionizing electromagnetic fields

Units used and their significance

As the phrase indicates, electromagnetic fields are made up of, electric- and magnetic fields and non-ionizing fields simply indicates that each wave of energy does not have the ability to ionize a molecule (that is to move electrons away from their original position).

Electric fields consists of, electrons moving in a particular direction and are measured in terms of Volt/meter.

The magnetic field consists of magnetic forces developing from the electrons movement. This field is measured by the magnetic flux density that is measured in units of Tesla and the magnetic field in Ampere/meter.

The electric field and the magnetic field are dependent of each other and if you are in the ‘far-field’ region, defined as being within a few wavelengths from the source, these fields have a fixed relation, whereas in the ‘near-field’ region they must be measured independently.

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) is an international, non-governmental organization that collects and reviews current scientific knowledge on electromagnetic fields and produces recommendations for exposure to such fields on a regular basis.

The recommendations are made to ensure that the exposure allowed is not known to cause documented negative health effects (1) (2) (3). The recommendations vary with frequency because the different fields can exhibit different effects due to frequency. For example, the frequency of the field will determine how well it can penetrate the skin, or if the effects are only to the surface. The frequency also determines how it might be absorbed in different tissues. The recommendations also vary with type of field and type of radiated object, for example, the whole body, a limb, head and so on. The recommendations form the basis for the guidelines in the European Union that can be found at the Directive 2013/35/EU^[1]. In other parts of the world, the recommendations are used in different ways so details of about specific limit values are not given here.

In all exposure situations to electromagnetic fields it is recommended that the employer carries out a risk assessment and considers efforts to reduce any risk. All workers should be given information and training regarding exposure to electromagnetic fields. If there are documented risks for exposure and negative health effects, appropriate health surveillance shall be carried out.

Health effects

Electrical injury

The incidence of injury caused by exposure to electricity is difficult to ascertain. BMJ best practice states that there were 134 fatal occupational injuries in the US in 2015^[2] However there is no data on the specific incidence in the maritime sector.

Normally the injuries are divided according to whether they were caused by high-voltage electricity,1000 V or more, or low voltage, less than 1000 V. The injuries can cause different health effects according to the amount of voltage, the duration of the injury and how it happened. Burns are common and injury may cause respiratory arrest, cardiac arrhythmia and different neurologic symptoms. BMJ best practice describes these clearly.

Prevention of these injuries are essential! If an accident happens and a worker has been exposed to any of the following, they should be given first aid immediately:

• electricity which passes through the heart region/upper body
• high-voltage electricity
• lightening
• electricity and feels unconscious, dizzy or uncomfortable
• electricity and has burns
• electricity and develops neurological symptoms

What medical aid is available will depend on where the vessel is, but general first aid and, if possible, an ECG is key to investigating a patient after an electrical injury. Other diagnostic tests and treatment will depend on the symptoms and severity of the electrical injury.

Other health effects

• Induced currents: Strong low frequency electric fields, > 10 kVolt/m, and powerful magnetic fields, >1000-10000 microTesla, can induce currents in the human body, which are powerful enough to cause nerve and muscle activation.
• Thermal effect: Electromagnetic fields contain energy that is deposited in the tissues. Heating due to this deposition is strongly connected to the frequency and power of the field and the volume and electromagnetic properties of the tissue that is being radiated. If heating occurs this can lead to cellular and tissue burns, damage to the retina and genotoxic damage to the cells.
• Vulnerable groups: People with metal joint and other prostheses are more vulnerable for exposure to non-ionizing radiation due to induced currents and magnetic effects. In addition, cardiac pacemakers maybe vulnerable to incorrect triggering in an area with exposures above the given limits for these devices.

Controversial health effects

There is no existing consistent scientific evidence of other adverse health effects caused by non-thermal exposure to electromagnetic fields. However, several studies have investigated this and several are still being conducted. They have conflicting findings, and the quality of exposure assessment is varying. These conflicting results and limitations of methodology are one of the reasons why the question of health effects from non-thermal electromagnetic fields still is open for discussion.

Two main health effects have been discussed:

1. Environmental hypersensitivity attributed to electromagnetic fields.

This topic has been investigated several times in many different research environments. The studies generally have very good protocols and designs. These studies have not led to the presenting symptoms being classified as caused by electromagnetic fields.

2. Brain cancer caused by cellular phones.

Some years ago, the World Health Organization (WHO) classified radiofrequency electromagnetic fields as a possible cancer inducer in humans. This classification is mainly due to two large multi-centre studies, the Hardell study and the Interphone study. The studies investigated persons who used cellular phones in the 1980’s and 1990’s and most users had cellular phones with the GSM or NMT technologies. These were very different from the technology used today in more recent GSM-, 3 G, 4 G and 5 G mobile phones. Today’s technology emits considerably less radiation than the older phones. For example, a new cellular phone using 3 G technology emits in the order of 0.01 – 1 Watt, while the old NMT technology could emit as much as 15 Watts. 

Several major reviews have been published looking at the current status of scientific knowledge about health risks from electromagnetic fields. Their conclusions are similar: there is no consistent evidence for any adverse health effect from exposure to electromagnetic fields below the thermal exposure limit. 

The maritime environment

On board vessels and maritime installations, most exposure to these fields comes from the communication and navigation devices on board, from surrounding vessels and from nearby large scale generating equipment. In addition, it is important to remember the risk of electric shock from installations on board and to follow the guidelines and safety rules concerning these. When monitoring fields on board vessels and in the maritime environment it is important to assess the actual exposure. Such measurements are relatively easy to conduct, specialist firms and public institutions usually have the equipment and skills. When there is concern that potential overexposure incidents might have occurred, mapping of the actual exposure is essential. A proper exposure assessment and dose-estimate for the exposure will be important when answering workers’ questions on potential risks from the exposure. The frequency of exposure, amount of energy deposited and length of exposure will all determine the likelihood of health risks from exposure.

Treatment

Treatment of those who may have been overexposed or may have concerns about this is individual and symptomatic, but some guidelines can be followed.  If possible, try to get an assessment of the actual exposure before assessing individuals:

• What happened? In terms of the type of exposure, duration in time, position of the exposed person.
• Were there any acute symptoms such as heat sensation, tingling sensation, nausea etc. Has there been any development of the acute symptoms, or any new symptoms, since the exposure?

A thorough medical history and clinical examination must be performed. In the acute phase it is very important to look for skin burns or red markings in the skin. In addition, examination of the visual function and of the retina can be useful. Extensive eye-examination by a specialist may be necessary.

There have been many incidents with overexposure to these fields. These have given us much information about the possible symptoms and health consequences arising from such exposures. Damage has only been seen when the exposure has been sufficient to cause thermal effects, that is, the person exposed would normally would feel a temperature increase in the skin and significant pain if the exposure is severe. There are a number of articles discussing this topic and providing helpful advice for such situations (6, 7).

Levels of exposure

Only a few studies have investigated the field levels on board certain vessels. These show that exposure to these fields is not large on board vessels and maritime installations. However, often the exposure assessments are lacking in studies.

In addition to continuous exposure, acute exposure incidences can also happen due to malfunctions in equipment or disregard of precautions. One example is an episode in the Barents Sea in the autumn of 2012 (8). A Coast Guard vessel came to close to the radar beam of a frigate during a military exercise. In the weeks following the incident, personnel on board the Coast Guard vessel became ill with diverse symptoms, ranging from visual difficulties, changes in sensation and in cognitive skills. A research project mapped the different symptoms of the personnel and followed the group over time^[3].

Type of exposure in the maritime environment

• Natural solar ultraviolet radiation: Outdoor work is normally recommended not to exceed 30 Joule/m² during an eight hour work day if the worker is not protected.
• Low frequency electromagnetic fields and static magnetic fields: These exist surrounding electric installations.
• Radio frequency electromagnetic fields: These are produced by communication devices and radar facilities. Exposure is normally reduced by restrictions on the distance between emitting aerial and crew access areas, as well as safety guidelines on the operation of the installation.
• Magnetic fluxes: These are produced in the vicinity to large scale generating equipment.

Laws and regulations

 National governments regulate the use of and protection from these fields through national protective agencies, and often base their regulations on the international recommendations given by WHO and the International Commission on Non-Ionizing Radiation Protection.

Reference List­­

1.         ICNIRP. For limiting exposure to electromagnetic fields (100 kHz - 300 GHz). Health Phys 118 (00): 000 - 000; 2020.

2.         ICNIRP. For limiting exposure to time-varying electric and magnetic fields (1 Hz - 100 kHz). Health Phys 99 (6): 818 - 836; 2010

3.         ICNIRP. On limits of exposure to static magnetic fields. Health Phys 96(4); 504-514; 2009.

Ionizing electromagnetic fields

Units and their significance

In this part of the spectrum the fields contain so much energy that they have the ability to ionize molecules. This in turn is potentially very harmful to the function of the molecules. In medicine, this effect is used deliberately to cure cancer and other diseases, or to investigate tissues, through X-rays. But with increasing dosage this becomes a health hazard rather than a health benefit.

These types of fields are measured with different units describing the level of energy in the field. Gray is a unit of energy being absorbed by the tissue, 1 Gray equals that 1 kg of tissue/substance have absorbed 1 Joule of energy. Sievert is another way of describing absorbed energy, but this unit also adds a factor for what tissue is absorbing the dosage. If you heat food in the microwave, the food becomes warm, whereas the plate remains cold. This is due to the  different absorbing ability of the two substances. Sievert is Gray multiplied with a tissue factor describing how much energy is absorbed by the specific tissue.

A method of measuring these fields is to use a Geiger counter. This instrument measures the radiation and presents the results as Gray.

The International Commission on Radiation Protection (ICRP) is an international, non-governmental organization that collects and reviews current scientific knowledge on electromagnetic fields and produces recommendations for exposure to such fields on a regular basis (1) (2) (3). These recommendations are used by the World Health Organization (WHO) and by most governmental authorities.

To assess the level of exposure to radiation in the different occupations the workers can wear personal dosimetry, and in many situations concerning ionizing radiation this is mandatory. All areas with exposures between 1 – 6 mSievert per year are normally defined as a supervised and controlled area. All persons working in such areas shall wear personal dosimetry. 

Table 1:

                                                                                    Radiation report 2005:15  (1)

Figure 2: www.NRPA.no modified by Ole Jacob Møllerløkken      

Health effects

Ionizing radiation can be inflicted externally or internally through swallowing, breathing or the contamination of wounds. The health effects associated with exposure to ionizing radiation vary depending on the total amount of energy absorbed, the time period, the dose rate and the particular organ exposed. Ionizing radiation affects individuals by depositing energy in the body that can damage cells or change the cell’s chemical balance. Tissues that have a high rate of regeneration are most vulnerable to the radiation.

Small doses (whole body exposure < 0.1 Gray)

• Local acute radiation injury in the intestine will give diarrhoea, constipation, haemorrhages, urgency and pain
• Cataract
• Permanent or temporary sterility
• Cancer induced by ionizing radiation. This is no specific type, but exposure to radiation at some point has been identified in the formation of different cancer types. As with many other cancers, these also have a relatively long latency time of 10 – 20 years and more.
  • Leukaemia: findings from Hiroshima and Nagasaki
  • Breast: findings from women treated for tuberculosis and monitored with very many x-rays to follow the development
  • Liver: findings after the use of radioactive medications
  • Bone: findings in Asian workers who ingested radioactive paint in their work).
  • Thyroid: findings from the Chernobyl accident

Large doses (whole body exposure exceeding 1 – 2 Gray)

With an increasing exposure dose the extent of failure of the immune system increases. Survival has been documented with doses up to 4-5 Gray, but doses exceeding this are fatal. Experience from such exposures is gathered mainly during war and accidents.

The radiation syndrome

If the radiation is external and depending on the radiation dose, there may be outer signs of radiation exposure. The exposed area can show erythema, oedema, dry or wet desquamation, blisters and sometimes necrosis that can be painful. Large doses of ionizing radiation lead to a massive impact on the rapidly regenerating cells of the human body, typically immune cells, blood cells, epithelial cells and likewise. The impact on and destruction of these cells leads to haemorrhages, diarrhoea and vomiting.. In addition to an increased susceptibility for infections, this can be lethal when the immune system is not functional. The syndrome is characterized by the following:

• The prodromal phase of nausea, vomiting, tiredness, fever and diarrhoea.
• The latency period of varying length.
• The sickness phase with infections, haemorrhages and gastrointestinal symptoms due to the lack of blood cells and other rapidly regenerating cells.

Exposure in the maritime environment

Ionizing radiation exists on board nuclear powered vessels and vessels transporting nuclear materials. It can also be present in some gauges and fire detection systems. Lastly, a vessel can accidentally be contaminated due to accidents nearby or deliberate actions.

Specific guidelines on the risk management and prevention of injury and guides on how to assess and treat personnel who experience overexposure or contamination are complicated and depend on numerous factors. The Department of the Navy, Bureau of Medicine and Surgery in Washington, U.S. have made an extensive guideline to radiation health protection, which can be useful for additional information and for health and safety work (1). This manual includes extensive information on how workers should be followed up prior to, during and after service that includes potential exposure to ionizing radiation. It also includes information on standardised medical testing before, during and after service, but also testing that should be performed in the event of any excess exposure, such as after accidents. It also has sections on administrative follow up and the importance of the documentation requirements in such a situation.

The same department has produced guidance on the evaluation and treatment of irradiated or contaminated personnel(2). In this guideline, they provide advice for the initial exposure assessment and the management and treatment of individuals who are irradiated externally or internally radioactively contaminated. Generally, the following quick rules may apply to the treatment of personnel exposed to ionizing radiation:

• Radiation does not rapidly produce life-threatening symptoms
• Normally a radiated person does not pose any risk for the helping personnel. If there is suspicion of exposure to a large dose, protective garments with shielding such as lead can be used
• Do not touch unidentified objects that the patient/ personnel have. Leave such objects pending identification by a radiation specialist
• Move the patient and cleaning personnel to a room free of unidentified objects
• In case of suspected contamination, isolation procedures must be initiated

Laws and regulations

National governments regulate the use of and protection from this type of radiation through very strict guidelines. The regulations are often based on the international recommendations given by WHO and the International Commission on Radiological Protection.

References

1.         Radiation Health Protection Manual [Internet]. NAVMED. 2011. Available from: http://www.med.navy.mil/directives/Pub/5055%20%28Feb%202011%29.pdf.

2.         Initial management of irradiated or radioactively contaminated personnel [Internet]. Department of Defence USA. 2003. Available from: http://www.med.navy.mil/directives/externaldirectives/6470.10b.pdf.

^[1] https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A32013L0035

^[2] British Medical Journal 2017; 357:j1418 doi: 10.1136/bmj.j1418

^[3] Int Mar Health 2013; 64, 4: 177-182

E.9 Ship building and repair

Details

Published: 09 January 2022

DAVID LUCAS

Work in a ship yard 

Introduction

Humans have long used ships as a means of transport for goods or people, for discovery or invasion purposes. Consequently, ship construction and repair have been industrial activities for many years. Within this sector, there are many different occupations, such as engineers, boilermakers, welders, pipefitters and ship painters, and each type of worker is exposed to multiple risks, mainly physical and chemical.

Historically, the major centres for construction and repair were linked with military activity, and developed in Europe, later in North America, and later still in Southeast Asia and India. In 1998, the proportion of worldwide naval construction and repair taking place in South Korea, Japan and China rose above 80% and many of the largest shipbuilding companies are from these countries. In Western Europe, the sector has one or two large companies per country, and a multitude of small and medium-sized companies. In 1999, 182 firms in the EU had fewer than 1,000 employees, 17 had between 1,000 and 2,000 employees, and the 28 largest shipyards had a total of 64,000 workers^[1]. In 2020, there are about 150 large shipyards in Europe. Around 40 of them are active in the global market for large seagoing commercial vessels. Some 120,000 people are employed by shipyards (civil and naval, new building, and repair yards) in the EU.

With a market share of around 6% in terms of tonnage and 35% for marine equipment, Europe is a major player in the global shipbuilding industry²

Shipbuilding and ship repair both have high rates of occupational accidents, more so than building and public works, but generally, accidents are less serious in shipbuilding. Naval construction, and particularly naval repair, has high rates of occupational accidents. Historical data from the UK show 8,939 recorded accidents and an incidence of 7,010 accidents per 100,000 in 1974, with 19 fatal accidents in 1973 and 1975^[2].

In a later study looking at 48 accidents involving ship repair workers, the most frequent part of the body affected by the accidents were hands, lower limbs and eyes, with the more serious accidents involving mainly hands and upper limbs. Most accidents, 62.5%, occurred on board, and the rest in the workshop³. This is likely due to the ergonomic and organisational constraints, short deadlines, on board ships that are being repaired.

Physical risks 

Noise exposure

Noise exposure is one of the major occupational risks to which workers are exposed, particularly those involved in repair. The source of noise may be

• machines used as tools for cutting wood,120 dB peak noise^[3],
• machine tools,
• impact, for example, hammering, cutting and falling sheet metal
• grinding and associated activities, for example, engine room machinery, welding, and grinding in resonant spaces

In studies of workers in a shipyard, peak noise exposure was recorded as

• 135 dB from falling sheet metal,
• 111 dB for grinding,
• 117 dB for planing and hammering

Exposure averaged over 8 hours was 93 dBA for a boilermaker and 94 dBA for a pipefitter.

For this particular group of workers there is one additional, aggravating factor. Many such workers are exposed to aromatic solvents such as toluene, xylene and styrene. These have been shown in the industry to be ototoxic and can, via cell toxicity, increase noise-linked hearing loss^[4]. A study by Triebig involving 248 shipyard workers exposed to styrene showed that chronic intense exposure above regulatory limits (> 50 ppm) led to an increased risk of hearing loss^[5]. Further information about noise can be found in Ch xxx

Musculoskeletal problems

Musculoskeletal problems, either acute or chronic, are frequent causes of time off work and declared occupational diseases in this population group.

Upper limb injuries

Use of vibrating tools such as grinders, scurfers and turners expose workers to the risk of harm to the hands and upper limbs. In a study of 114 construction workers using tools vibrating at 6.32 and 13.39 m/s2 respectively, a mean use of 4.64 hours per day was investigated, and the period to onset of Raynaud’s disease was half as long as that given in the ISO 5349 PARK standard^[6]. This severe impact on the hands was confirmed by findings of reduced nerve conduction velocity in the wrist, hands and fingers in a population of workers in an American shipyard^[7] and by the positive correlation between rates of vascular symptoms in the hand and the intensity of exposure to vibration via tools in 214 subjects^[8]. Tendinopathies in the shoulders, 18% of welders in one shipyard^[9], and elbows are also linked to such exposure.  Further information on the effects of vibration can be found in Ch xxx.

Handling and staying in cramped positions for long periods are common in some types of welding and sheet metal jobs. A full welding kit can weigh over 30 kilos, and the nozzle can weigh 2.5 kilos. Electromyography tests on welders show heavy strain on the trapezium, deltoid and finger flexor muscles^[10].

Lower back injuries

Effects on the lumbar muscles have also been observed. Axelopoulo studied 853 workers in a shipyard^[11] and confirmed the increased incidence of lower back pain in welders working in shipyards. Over one year, 14% of workers took time off work because of lower back pain, and welders had the highest rate of absence at 18.3%. The recurrence rate reached 41% over the year, and was greater for those who had spinal disc herniation but reduced when working conditions were changed in favour of workshop work or limiting handling. This confirmed the considerable ergonomic constraints to which workers are subjected, particularly welders, pipefitters and sheet metal workers.

For engineers, the most risky aspect of work is handling, with equipment weighing tens or over a hundred kilos (stern post) that must be manipulated within confined spaces and with little leverage assistance, apart from hoists.

Eye injuries

The risk of ophthalmological disease is also high as reported by Brigham in 1985^[12]. There are 2 main categories, foreign bodies in the eye and diseases related to ultraviolet (UV) and ionising radiation (IR) exposure. Grinding work is primarily responsible for exposure to the risk of foreign bodies in the eye. Acute corneal lesions, keratitis and secondary effects in the form of traumatic cataracts and ocular siderosis can all arise due to foreign body exposure^[13]. Such accidents represented 27% of all occupational accidents in ship repair in 2007, and 18.8% in 2008^[14]. Welding is the main activity that causes UV exposure, with the subsequent risk of ocular melanoma^[15] and keratoconjunctivitis photoelectrica, known as “arc eye” ^[16].

Chemical risks

Asbestos

Asbestos was used in various forms in ships, in particular chrysotile, white asbestos, which is present in insulation and in Klinger jointing sheets (cross reference to chemicals chapter). Fibres from this known carcinogen are also present in flooring in engine rooms and living quarters^[17]. It causes specific respiratory diseases that can be benign conditions of the parietal pleura, such as pleural plaques, benign pleurisy or fibrosis, or a form of pulmonary fibrosis called asbestosis. However, it can also cause malignant conditions such as primary malignant mesothelioma, cancers of the bronchi and lungs and, less specifically, cancers of the digestive, urinary or genital regions, including the kidney and ovary^[18][19]. Workers employed in shipyards before 1980 suffered heavy exposure to asbestos with cutting and removal of insulation being the activities that involved the most exposure. In a study of 18,211 North American metalworkers, shipyard work represented a 1.85-fold increased risk of asbestos-related disease^[20]. A long term study, between 1966 and 1975, followed 253 workers in a British shipyard. The study observed 17 deaths from asbestos-linked malignant disease and pleural plaques were present on the chest X-ray in 21% of these workers^[21]. The extent of exposure was significant. Between 1999 and 2005 there were 1,879 declared cases of asbestos-linked occupational disease in one French shipbuilding yard^[22]. 22% of CT scans carried out routinely on workers over the age of 50 years showed disease with plaque or pleural thickening. The occupations with the most exposure are boilermakers (27%), pipefitters and welders. In a 2012 study, Bianchi included 2776 people who worked in Monfalcone shipyards in 1942. In this population, 18% have a diagnosis of mesothelioma and in the population of 14 years old workers in 1942 (557 workers), 6 have declared mesothelioma^[23]. Those who worked in shipyards before 1980 must be monitored carefully, but this should not obscure the fact that there is still a risk, mainly in ship repair.

Refractory ceramic fibres used as a replacement for asbestos have similar biopersistance characteristics and are classed as 2B carcinogens by the International Agency for Research on Cancer IARC. Care is needed to monitor the effect in coming years.

Hydrocarbons

Aromatic hydrocarbons are found in solvents that contain toluene and xylene and these are widely used by engineers and painters, as is styrene, which is used in boatbuilding^[24]. These are central nervous system depressants, and carry a long-term risk of diseases such as attention deficit hyperactivity disorder (ADHD). They are irritant to the skin and respiratory system, and in large quantities carry a risk of pulmonary oedema, anorexia and abdominal problems. Toluene is classed as a teratogen and carcinogen class 2 in European Union (reglement Classification Labelling Packaging  and kidney conditions such as glomerulopathy have been described^{[25] [26]}. Exposure to carcinogens such as benzene, a leukemogen, and trichloroethylene (which causes kidney cancer) also occurred before these substances were banned^[27]. Occupational exposure can be direct by use of a product, or indirect, via the products being transported as petroleum derivatives^[28].

Styrene is used in the polymerisation of polyester resins, and represents 40% of the weight of these resins²⁴ It is classed as a 2B carcinogen by the IARC, because of the possible risk of effects on the blood.

Paints

In painting, there is exposure to aromatic solvents such as xylene and toluene, which are present in paints and solvents used to clean equipment. There are also ketones, aldehydes, esters and glycols. Low molecular weight hydrocarbons are asphyxiants and central nervous system depressants whilst ethylene glycol acetates carry a risk of haematological disorders such as bone marrow depression. Exposure is increased when work is done in confined spaces such as in ballast tanks and fuel tanks, as demonstrated by Kim, with mean levels which were 4 times higher than for painters working on deck^[29].

Hand washing in solvents still occurs. Painters may therefore have been exposed to high concentrations of trichloroethylene until the 1990s. This is a definite carcinogen according to the IARC, In addition to high proportions of xylene, anti-corrosion and anti-fouling paints contain epoxies that cause skin sensitivity, pigments and antifouling molecules. Since tributyltin (TBT) was banned in 2003, pigments mainly consist of copper oxides, and zinc, titanium, nickel and iron oxides. These pigments irritate the respiratory tract, and copper may cause an increased risk of cancer of the urinary tract. There is little human toxicology data on these substances. Respiratory exposure experienced by ship painters was evaluated, and exposure to copper was 3 mg/m3 for spray-painting and 0.8 mg/m3 for sandblasting, 0.14 for Dichlofluanide^[30] and 52.6 and 33.2 ppm for xylene and ethylbenzene respectively. Grandjean found blood and plasma nickel levels of 5.2 µg/dL in a population of ship painters, levels that were statistically greater than for a group of welders^[31]. As Chang proved^[32], wearing respiratory masks reduces the concentrations of xylene and ethylbenzene to which painters are exposed by 96% and 94% respectively.

Additional references:

1-E C. Alexopoulos, T Tsouvaltzidou. Hearing loss in shipyard employees. Indian J Occup Environ Med. 2015 Jan-Apr; 19(1): 14–18. doi:  10.4103/0019-5278.157000

2- Sliwinska-Kowalska M. Exposure to organic solvent mixture and hearing loss: literature overview.  Int J Occup Med Environ Health. 2007;20(4):309-14. Review

3- Cherniack M, Brammer AJ, Lundstrom R, Meyer J et al. Segmental nerve conduction velocity in vibration-exposed shipyard workers. Int arch Occup Environ Health. 2004 Apr;77(3):159-76

4- Alexoploulos EC, Konstantinou EC, Bakoyannis G, Tanagra D, Burdof A. Risk factors for sickness absence due to low back pain and prognostic factors for return to work in a cohort of shipyard workers. Eur Spine J.2008;17:1185-1192.

5-Park BC, Cheong HK, Kim EA, Kim SG. Risk Factors of Work-related Upper Extremity Musculoskeletal Disorders in Male Shipyard Workers: Structural Equation Model Analysis. Saf Health Work. 2010 Dec;1(2):124-33. doi: 10.5491/SHAW.2010.1.2.124.

6-Tomioka K, Natori Y, Kumagai S, Kurumatani N. An updated historical cohort mortality study of workers exposed to asbestos in a refitting shipyard, 1947-2007.Int Arch Occup Environ Health. 2011 Dec;84(8):959-67. doi: 10.1007/s00420-011-0655-2.

7-Lee KH , Ichiba M, Zhang J, Tomokuni K et al. Multiple biomarkers study in painters in a shipyard in Korea. Mutat Res. 2003 Sep 9;540(1):89-98.

8- Kim V, Lee NR, Kim KS, Yag Js et al. Evaluation of exposure to ethylene glycol monoethyl ether acetates and their possible haematological effects on shipyard painters. Occup Environ Med 1999;56:378-382.

9-Lucas D,  Jegaden D, Loddé B. Toxicologie des peintures navales (peintures de coques et antifouling) In Textbook de Médecine Maritime Ed Lavoisier. Paris Chap 29 ; 2015 : 251-59.

10- Wastensson G1, Sallsten G, Bast-Pettersen R, Barregard L. Neuromotor function in ship welders after cessation of manganese exposure. Int Arch Occup Environ Health. 2012 Aug;85(6):703-13. doi: 10.1007/s00420-011-0716-6.

11-  Jegaden D. santé, sécurité. Modèles applicables en médecine maritime. In Textbook de Médecine Maritime Ed Lavoisier. Paris Chap 34 ; 2015 : 291-300.

Shipbreaking and wreck removal

This sector of the industry has developed massively in recent years as a response to

• the increase in the number of ships, especially big ships such as supertankers and container ships,
• the price of steel and
• new environmental regulations.

The Nairobi International Convention on the Removal of Wrecks, published by the International Maritime Organisation (IMO)^[33] will provide the legal basis for states to remove, or have removed, shipwrecks that may have the potential to adversely affect the safety of lives, goods and property at sea, as well as the marine environment. The convention was adopted in 2007 and entry into force the 14 april 2015. Clearly stated is the obligation for the registered owners of a ship to remove a wreck at their own expense. Some wrecks are removed after accidents and others broken up and recycled are bat the end of the vessel’s life. From a health perspective, major problems are not far from workers in this industry. There is a high rate of occupational accidents resulting in trauma, especially when removing is done at sea or on a beach/rocks, with an explosion and subsequent fire. Other physical risks include exposure to:

• noise and vibrations
• chemicals including asbestos in older vessels and lead in old paints
• gases in confined spaces like tanks
• welding fumes
• hypoxia when cutting a ship’s hull

Many sites for shipbreaking are in countries with a low level of occupational health legislation, including, for example, no ban on the use of or exposure to asbestos or lead.

Whilst studies have been published on the environmental impact of the removal of wrecks, no studies have been yet published on the impact on workers in this industry. Much research in this area is needed.

Crew health and safety considerations 

In shipbuilding, but more, in the ship repairing yard, occupational safety and health impact for crew is from coactivity. During maintenance, most of the seafarers stay onboard and have specific tasks to do. Relevant safety coordination between ships crew and shipyard workers is the gold standard. A very open communication between the ship owner, health and safety staff and shipyard production service is the first step. (linked to chapter XX) Docking is one of the most accident prone work steps with deaths amongst crew, port and ship facilities workers. Another problem is multinational and multicultural crew. Further information is available in Ch xxx and there are no big differences in the ship building and repairing sector.

^[1] The Shipbuilding and Ship repair sectors in the candidate countries : Poland, Estonia, the Czech Republic, Hungary and Slovenia. Final Report PSE/99/502333.

²https://ec.europa.eu/growth/sectors/maritime-industries/shipbuilding-sector_en

³Lucas D, Loddé B, Pougnet R, Dewitte JD, Bronstein JA, Jegaden D. Study of the pathologies at the origin of sick leaves of more than 30 days in a population of workers of the naval repair in 2009 and 2010. ISMH 12 4-7 june 2013 Brest.

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^[11] Alexoploulos EC, Konstantinou EC, Bakoyannis G, Tanagra D, Burdof A. Risk factors for sickness absence due to low back pain and prognostic factors for return to work in a cohort of shipyard workers. Eur Spine J.2008;17:1185-1192.

^[12] Brigham C.R, Landrigan P.J. Safety and health in boatbuilding and repair. Am J of Ind Med 1985 169-182.

^[13] Schechner R, Miler B, Gonzales M, Pelmar I. A long term follow-up of ocular siderosis: quantitative assessment of the electroretinogram. Doc Ophtalmol 1990-1991;76:231-240.

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^[19] O’Reilly KM, McLaughlin AM, Beckette WS, Sime PJ. Asbestos-related lung disease. Am Fam Physician 2007 Mar 1;75(5):683-8.

^[20] Welch SL, Haile E, Dement J, Michaels D. Change in prevalence of Asbestos-related disease among sheet metal workers 1986 to 2004. Chest 2007;131:863-869.

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^[22] 23- Roos F, Guimon M. Prévention des pathologies liées à l’amiante. Pathologies professionnelles et de l’environnement in Encyclopédie Médico-chirurgical 16-002-A-12. French

^[23] Bianchi C, Bianchi T Shipbuilding and Mesothelioma in Monfalcone, Italy Indian J occup Environ med 2012 jan; 16(1):14-7.

^[24] Brigham C.R, Landrigan P.J. Safety and health in boatbuilding and repair. Am J of Ind Med 1985 169-182.

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^[26] Moen BE, Riise T, Todnem K, Fossan GO: Seamen exposed to organic solvents. A cross-sectional study with special reference to the nervous system. Acta Neurol Scand, 1988, 78 (2), 123-135

^[27] Pascual D, Borque A. Epidemiology in kidney cancer. Adv Urol 2008;782381.

^[28] Moen BE, Riise T, Helseth A: Mortality among seamen with special reference to work on tankers. Int J Epidemiol, 1994, 23, 4, 737-741

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^[30] Links I, Van Der Jagdt K, Christopher Y et al: Occupational exposure during application and removal of antifouling paints. Annals of Occup Hyg 2007;51(2):207-218

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^[33] http://www.imo.org/en/About/Conventions/ListOfConventions/Pages/Nairobi-International-Convention-on-the-Removal-of-Wrecks.aspx. Adoption: 18 May, 2007; Entry into force: 14 April 2015

E.6 Noise

Details

Published: 09 January 2022

FROM 2^ND EDITION BY DOMINIQUE JÉGADEN. REVIEWED AND UPDATED BY KAIA IRGENS.

Introduction

Noise is a significant stressor on board ships. Increases in engine power, the emergence of significant vibration and the fact that living facilities are located above the propulsion mechanism all mean that noise reduction has become a matter of onboard comfort as well as  of crew health..

Main noise sources on board ships

Engines

The vast majority of ships are propelled by diesel internal combustion engines. Based on the revolutions per minute of the engine, a distinction can be made between “slow” engines with a relatively low noise level and ‘high-speed’ or ‘medium-speed’ engines. The latter are more powerful than other types of engine but which create more noise.    

At equal power levels, the airborne noise produced by these engines is proportional to the speed of rotation and the maximum combustion pressure. Noise is produced by the scavenger and exhaust housing, as well as by the gear case. As well as noise from the combustion process, there is a high-frequency noise created by turbo blowers. In addition to noise created by the engine itself, we should take into account the noise transmitted via combustion gas exhaust pipes or funnels.

Apart from noise generated by the main engine there is also noise from secondary engines, such as electricity generators, reducers and ancillary machinery such as winches and hydraulic motors. Mounting an engine or auxiliary motor on silencers does not affect the amount of noise it produces, but can reduce the level of vibration transmitted to the ship’s structure and by extension, the noise from the acoustic radiation produced in this way.

Some of the largest ships, with a gross tonnage greater than 60,000, particularly oil and gas tankers, are equipped with steam turbines. In general, steam turbines are much less noisy than internal combustion engines, for equal levels of power production. However, steam valves can cause loud noise, particularly at high frequency, when they are open and/or unsophisticated in shape.

Electric propulsion systems

In the future, there will be more and more electric motors, which cause considerably less noise than any other type of propulsion system. The idea for the generalised electrification of ships began in the United States in the early 1980s and was called Integrated Electric Drive. The term electric ship is ambiguous, and does not imply that diesel engines and gas turbines will disappear completely, at least not for another 20 years. The term denotes an integrated system of electrical energy production and distribution to all users on board. One remarkable consequence of this is that it becomes possible to remove the drive shaft, which are large parts that entail constraints both in design and installation and use, for example the alignment, watertightness, noise and vibration. Moreover, a naval architect is more able to optimise equipment positioning, for example by placing the gas turbine away from the bottom of the ship and by choosing the positions of the diesel engines wisely. Electrification also enables the removal of various fluid systems that are associated with conventional types of architecture. The principle of electrification has already been widely adopted in civil shipbuilding, particularly of passenger ships, because of the increased comfort it provides with low noise levels and no vibration. A relevant example is the Star Princess, a cruise ship carrying 1700 passengers built by Chantiers de l’Atlantique in France and equipped with a diesel-electric propulsion system. Independent propulsion pods have also been developed, which enable energy savings of around 10%. These external pods, which contain electric motors and drive shafts, are positionable, which means that ships equipped with such pods in a suspended omnidirectional propulsion system, no longer need rudder blades. The Queen Mary II¸ also built by Chantiers de l’Atlantique, has six of these pods.

Propellers

Noise emitted by a propeller is linked to turbulence created by the phenomenon known as “cavitation”, due to the bubbles that form on the propeller blades, and by the characteristics of the blades themselves, such as number, type and surface. Propellers are one of the main sources of noise emitted by the ship. The noise is particularly obvious and can enable the ship to be identified.

On board high-speed ships, water jets created by turbines replace propellers, which saves a considerable amount of weight and levels of noise pollution fall.

Ventilation

Noise produced by a ventilation system mainly comes from the ventilators and their drive motors and shafts. Noise is caused by their shape and circulation speed, and their air intake and discharge vents.

Transmission of noise on board

Noise generated by engines and ancillary devices tends to spread throughout the ship.

The level of noise in engine rooms mainly comes from the various engines housed there. The overall noise level in one location is the sum of the acoustic intensities there, caused by each engine in the location, and to which is added any influence of sound reverberation on the walls. In a generally reverberant engine room, as a first approximation it is reasonable to consider that the noise level is the same throughout the room, unless one is less than 2 metres from a particularly noisy engine.

In common areas, most noise is transmitted via partitions, floors and ceilings. Ventilation systems and doors, furniture and partitions that are subject to deformation can have an influence over the level of noise in a particular place by generating parasitic noise. Noise transmitted by partitions, floors and ceilings mainly originates from vibration energy produced by the propulsion system and propeller, but also comes from impact and movement of the ship caused by sea conditions. Appliances on tables or fixed to walls are also sources of disruptive noise.

Noise transmitted by the structure in question reduces in proportion to the distance from the source of excitation and in inverse proportion to the size and transmission coefficient of the surface.

Apart from noise transmitted by the structure, there can also be airborne noise caused by exhaust systems of motors, ventilators and appliances such as hydraulic generators, steam valves etc.

The noise level inside a gangway is often higher than the level measured inside the accommodation. This is generally due to airborne noise from internal combustion engine exhausts, ventilation systems, some ancillary systems such as hydraulic cargo systems, lift machinery and the wind. Some equipment that is located inside gangways, for example, VHF and BLU, is also a source of noise. In terms of noise from gas exhausts, the position of the upper part of the funnel with respect to the gangway determines the level of noise in the gangway. The sound spectrum of exhaust noise is mostly low frequency, so glass partitions in the wheelhouse should not be relied upon to provide sound isolation that is sufficient to reduce noise levels noticeably. If ventilation system casings are nearby, this is another very troublesome source of external noise. Ventilator noise is loud and can sometimes reach 120 dB(A). This noise is transmitted directly to the outside via slats, and these slats can cause troublesome noise if air travels through them at high speeds. In addition, on some ships, some ancillary systems such as air conditioning units are found near the gangway. Finally, if the wind is high and reaches speeds of approximately 60 km/h (force 8) with respect to the ship, there can be whistling in the handrails and hoist halyards. In addition, because of the high drag coefficient of the wheelhouse, the wind’s effects on the wheelhouse lead to significant levels of background noise.

Noise levels on board ships

Merchant vessels

As mentioned above, the main source of noise is the propulsion mechanism, and therefore the highest levels of noise are found in its vicinity. In most ships, the noise in machinery spaces is greater than 100 dB(A), and can sometimes be as high as 110 dB(A). Table 1 provides mean noise levels in various types of engine room on merchant ships.

Table 1

In other locations, however, noise levels are generally between 60 and 75 dB(A). Technological progress has ensured that on passenger ships, particularly cruise ships, cabin noise levels are around 40 dB(A).

Fishing vessels

Fishing vessels are generally smaller than merchant ships, and fishers spend much longer on board over the course of a year than merchant seafarers do. These vessels pose noise problems that are more difficult to remedy. The above noise sources on merchant ships are obviously also present on fishing vessels but in addition, there is the noise of the winches used for launch and for lifting fishing equipment. The table below reproduces the noise levels found on board various fishing vessels of the same tonnage:

Table 2

Noise in the engine room exceeds 105 dB and is perceptually equivalent to levels found on board merchant ships of any size. The difference between merchant ships and fishing vessels is that there is not always a soundproofed engine control room on smaller fishing vessels. Noise levels in sleeping quarters on fishing vessels less than 30 m in length are very high because the crew quarters and engine room are so close together. There is also a high level of noise on the fishing deck. Modern fishing trawlers have covered fishing decks, which provide greater safety and comfort than outside work, but which increase noise levels as they act as resonance chambers.  

Some authors^[1] have measured median noise levels for ships - it is best not to use the term “mean”, as decibels are logarithmic values that cannot be added arithmetically. For a common type of 24-metre trawler, median noise levels were 76 dB on the gangway, 80 dB in the wardroom, 86 dB in the steerage compartment, 84 dB on the fishing deck, 82 dB in the crew quarters and 106 dB in the engine room.

The most relevant exposure measurement in relation to the risk to hearing is the equivalent continuous level (Leq) to which the seafarers are subjected during one day and during one trip. Data recorded in situ show that in 55-60 m trawlers, there are equivalent average noise levels of around 85 dB over a 14-day trip.

As fishers are on board for 24 hours a day over several days, levels that would be considered to be disease-causing in workers on land cannot easily be applied to them. Much also depends on the job an individual carries out on board. Table 3 shows average equivalent dosimeter levels for a whole trip for crews of four semi-industrial 34-metre fishing trawlers. 

From Andro & Dorval                                 Table 3

The only fisher on board who is not exposed to a level of noise that causes trauma to the auditory system is the skipper. All others are. The recognised threshold above which there is a risk of hearing loss is 80 dB(A), 8 hours per day. This is derived from onshore studies, where the working day is normally around 8 hours. However, if the formula for calculating equivalent continuous levels is used and applied to exposures over the the full 24 hour day , we notice that a Leq_24h of 82 dB(A) corresponds to a Leq_8h of 95 dB(A), according to energy equivalence laws. This means that a seafarer who is exposed to a noise level of 82 dB(A) over 24 hours is exposed to a stressor and a risk to hearing that is equivalent to that of a worker who is exposed to 95 dB(A) for 8 hours a day. In this type of fishing, engineers are subject to highly traumatic levels of noise.  If we study the noisiest times of the workday, we see that length of stay on deck, handling fishing equipment, mending nets, processing the catch etc., means that fishers are exposed to 85 dB for an average of 13 hours per day. Then there is time spent in the crew quarters, during sleeping periods, around 5-6 hours per day, exposed to 83 dB, and meals in the wardroom, 81 dB for three hours, and gangway watch, 73 dB, for 2 hours. For a conventional trawler of between 15 and 25 metres in length, the equivalent continuous noise level over 24 hours has been calculated as Leq_24h = 83.6 dB(A).

Therefore, we have to consider that fishers, apart from skippers of large industrial trawlers, are at high risk of hearing damage due to noise, whatever job they do on board.

Effects on seafarers’ hearing

Several international studies have been published regarding the effects of ship noise on seafarers’ hearing^{[2] [3] [4] [5] [6]}.

Merchant vessels

We should remember that if a person is exposed to noise greater than 80 dB(A) for 8 hours per day or more, this can harm the inner ear, bilaterally and more or less symmetrically. This damage will worsen as the period of exposure lengthens and will affect higher frequencies, primarily above 4000 Hz. This is permanent endocochlear perception hearing loss in the context of chronic auditory fatigue.

As is shown, it is the engineers on board merchant ships who are exposed to the most noise, with equivalent average levels generally being above 85 dB(A). An audiometry study carried out in 1983^[7] concluded that there was a small region of hearing loss at 4000 Hz in merchant ship engineers, which was most noticeable in those over 40 years of age. Seafarers involved in other occupations were not affected.

Median values, combined results from both ears.

At similar ages, onboard engineers had noticeably less hearing loss than did subjects who worked in noise levels of 95 dB or 100 dB 8 hours per day.

A 1998 study^[8] found hearing loss in 26.8% of engineers, compared with 16% of seafarers in the deck department and 9.9% of supervisors. These differences were statistically significant.

The moderate levels of hearing loss observed in engineers may be explained by the fact that their exposure to engine noise is tempered by soundproofing of the engine control roomsin merchant ship engine spaces, which means that exposure to significant noise is confined to routine patrols and maintenance tasks, and the fact that they wear ear protection when carrying out such tasks. If the noise is constant or only slightly fluctuating, this can also moderate its effects. If work is distributed throughout the year in the form of 2-3 months of work followed by a holiday of the same length, this is a significant factor responsible for the moderate nature of hearing loss.

Fishing vessels

The situation on board fishing boats, however, is very different. As already noted, Andro and Dorval have shown that seafarers on board high-sea fishing vessels are subjected to constant noise levels 24 hours a day. Taking a ‘average’ vessel, seafarers are exposed to 84-86 dB when working on deck, 76 dB when on gangway watch and 82 dB when resting in the crew quarters. In parallel with this audiometric study, a similar study was carried out on 113 fishers on board the same type of vessel^[9]. The results showed that there was noise-related hearing loss with a window of hearing loss at 4000 Hz, which worsened with age and length of service. The hearing deficits were compared with the French standard NF S 31-013. This contains estimations from international epidemiological data of hearing in workers over 40 years old who had been exposed to quasi-stable levels of industrial noise, at 90, 95 and 100 dB, for 20 years. The hearing deficit for fishers with an average age of 40 and with an average of 23 years of exposure, lay between the levels of deficit for standardised subjects exposed to 90 dB and those exposed to 95 dB in terms of high frequencies, and were still greater for low frequencies.

A continuous noise level of 85 dB 24 hours a day, as experienced by fishers, is calculated as equivalent to a continuous noise level of 90 dB over 8 hours. In other words, a seafarer who experiences 85 dB 24 hours a day has hearing loss equivalent to that of a worker exposed to 90-95 dB of factory noise 8 hours a day. These results clearly show that high-sea fishing is an occupation that carries a risk of hearing loss due to noise.

This risk was specifically recognised in a report by the European Parliament on safety and accidents in sea fishing, dated 12 March 2001^[10] that states ‘Incessant noise creates an aggressive climate on board and means that fishermen sleep little and badly, making it difficult for them to obtain the rest they need...’ The results of a 2006 study^[11] involving 18,000 audiography tests on French seafarers confirmed the findings of the previous studies. This study confirmed that fishers are at greater risk than commercial seafarers. In maritime transport, seafarers on board oil tankers and cargo ships are observed to be at the greatest risk.

The problem with noise on fishing vessels is one of individual protection; as we have seen, in current standard practice, vessels do not have specific soundproofing. Individual protection could be effective^[12], but the fishers would have to wear it 24 hours a day, which is not practicable, although it could potentially be possible to constantly wear custom-made earplugs. For all vessels, the only valid improvement would be soundproofing of quarters when the vessel is built.

Non-hearing effects of noise on seafarers

Introduction

All signals picked up by the auditory system are transported via the nervous system either :

• directly, via specific pathways, which link the inner ear with the auditory cortex that takes in the signal and recognises its significance;
• or via an indirect route, a non-specific pathway. These are collaterals of the direct pathways that lead to the reticular activating system that regulates arousal, and is in turn connected to the limbic system and other parts of the brain, to the autonomic nervous system and the neuroendocrine system that play crucial roles in regulation of physiological functions in attention and behaviour.

These non-specific pathways explain why an irritant noise, even if it is of low intensity, generally in excess of 60 dB, introduce a subjective dimension and can cause psychological harm and other problems, such as a stress reaction, not directly or solely linked to the physical properties of the noise. The level of harm to an individual does not fully correlate with the level of noise, however, there is a correlation between harm to an entire population and noise levels.         Noise therefore belongs in the category of environmental stressors. This kind of stress is often more severe than expected because the subject has little or no control over the source of the stressor.

Sleep and alertness

On board non-soundproofed ships, the greatest risk not related to hearing is that sleep is disturbed by noise. A seafarer lives 24 hours a day in the confined environment of the ship, and should experience the good-quality sleep that is essential if the body is to recover from fatigue and maintain proper biological functions.

• Slow-wave sleep is involved in repair of tissues that are involved in physical effort.
• Rapid eye movement (REM) sleep restores the higher functions of the nervous system (alertness, learning, memory, adaptiveness and intent).

However, noise above 60 dB causes sleep problems in the form of

• reduced total amount of sleep,
• reduced duration of REM sleep,
• increased occurrence of night-time waking.

This sleep disturbance leads to increased fatigue and irritability. The problems are cumulative, and a vicious circle can develop whereby serious sleep dysfunction can arise, leading to physical exhaustion and overwork. Such noise is frequently found on all types of ships. It is therefore reasonable to think that seafarers in general suffer from sleep problems that worsen general fatigue.

Tamura et al.^[13] studied the sleep patterns in three subjects exposed to 65 dB noise from a ship’s diesel engine for five nights. Their sleep in such conditions was compared to their sleep in a quiet environment. They found that the number of episodes of REM sleep, and the duration of these episodes, were reduced, and that the time between these episodes of REM sleep was increased. They also reported a reduction in subjective sleep quality and difficulties in falling asleep. At noise levels of around 60 dB, the same authors^[14] in 2002, observed that, although seafarers got used to such noise levels in terms of subjective sleep parameters, there were still disturbances in the physiological parameters.

Rabat et al.^[15] carried out a sleep study on rats exposed to a recording of warship noise for 9 days, and compared the results to those of rats sleeping in a quiet environment. They confirmed that normal sleep structure was distorted, leading to a ten-hour debt of slow-wave sleep. The number of episodes of deep sleep was increased, but the duration was shorter than normal. Also, like Tamura et al., they found a six-hour debt of REM sleep - the number of episodes of REM sleep was reduced, as was their duration. The consequences of such sleep disturbance were significant, and appeared after the noise stopped. Such consequences involved the ability to commit information to long-term memory and the extent of the memory problems positively correlated to the extent of the debt of slow-wave sleep. They also demonstrated two types of sleep-related behaviour. One group of rats was resistant, and rats in this group rapidly recovered their ability to memorise, and one group of rats was vulnerable, and had significant problems. These results strengthen the theory that there are differences between individuals in terms of noise sensitivity.

Tirilly^[16] studied sleep patterns in coastal sea fishers and demonstrated the importance of sleep at night, which can be of short duration but which must occur at the same time each day for a given individual. This is known as ‘anchor sleep’ and maintains biological rhythms. In this study, the mean level of alertness in seafarers fell very soon after leaving port and the sleep deficit was between 60-90 minutes/24 hours, caused by fragmentation of sleep. On average six episodes of sleep were observed, with a total daily sleep period of between 5.5 and 6.5 hours. 

Alertness may be defined as maintaining attention during activities requiring prolonged periods on watch, particularly gangway watch. Alertness is reduced in proportion to the intensity of the noise, and this can result in attention problems. Noise also increases the risk of human error^[17] and, particularly in fishing, this can be a non-negligible cause of accidents.

Intellectual performance, in terms of psychomotor ability, reasoning and capacity to commit to memory, seems to be reduced if noise is above 85 dB and, as discussed, this is linked to sleep problems. There may also be effects in intellectual capacity at sound levels above 80 dB, but this depends on the frequency of the noise, whether it is intermittent or not, how long it lasts and its significance. Poulton^[18] observed that people working in constant noise initially performed better than those in quiet environments, but that there was gradual deterioration in performance if the noise persisted. Poulton thought that the physical intensity of the noise masked the signals produced by the machines used by the operator as a guide to performance when the environment was quiet. When the signals were masked, performance levels worsened.  When the noise began, the stressor seemed to cause a sudden burst of physiological and behavioural stimulation that overcame the harmful masking effects of the noise. This effect, however, gradually loses its impact, and subsequently there is an inescapable loss of performance. Another explanation might be that processing of noise using cortical filtering might impose an additional workload on this central brain structure. The capacity devoted to this task would be unavailable for other tasks, which would cause a reduction in the ability to reason and process information.

These problems could cause errors of judgement on board ship, which in some cases could have dramatic consequences including failure to properly understand orders when undertaking difficult manoeuvres, a risk of damage to machinery through negligence caused by reduced judgement or abnormal levels of fatigue.    

Noise-induced cardiovascular problems

It is generally agreed that noise causes generalised vasoconstriction. This vasoconstriction persists as long as the noise exposure continues^[19].

This phenomenon has been discussed frequently^{[20] [21]}, and the problem of the link between noise and blood pressure problems has been the subject of many studies. Despite the fact that the methodology of many of these studies has been criticised, 80% of the studies suggest the existence of such a link.

Blood pressure increases in those exposed to noisy conditions and the duration of the increase correlates to the length of exposure to the stressor. The increase depends not only on the level of sound but also on many other factors in the work environment such as the type of work and the category of staff^{[22] [23] [24]}. In addition, it has been demonstrated that employees with work-related hearing loss have significantly higher diastolic blood pressure than a control population with no hearing problems^{[25] [26]}

Link between noise and hypertension

The link between noise and hypertension was first suspected after it was noted that use of anti-hypertensive drugs was greater in areas near airports than it was in quieter areas^[27]. Many subsequent studies have confirmed this link^{[28] [29] [30] [31] [32] [33] [34]} and there have been several studies in shipping, with similar results^[35][36]. It is shown that levels of hypertension are significantly higher among engineers aged over 40 on board merchant ships (18.90%, N=164) than they are among non-engineer personnel of the same age (N=291) of whom 11.68% were hypertensive. This difference is not found in younger subjects. Levels of hypertension in the engineer group were independent of other risk factors such as a family history of hypertension, obesity and alcoholism. The relative risk of hypertension due to noise has been calculated at 1.62 and this is similar to the results of other studies^[37]. Roodenko et al.^[38] also found increased levels of hypertension in engineers when compared to deck crew and catering personnel. Noise can also be responsible for myocardial infarction^[39].

The difference between engineers and non-engineers aged between 40 and 55 is significant (p=0.05) (D Jégaden, C Le Pluart, Y Marie, B Piquemal 1986)

Effects on vision

Subjects who are regularly exposed to noise experience a reduction in nocturnal visual acuity and difficulties with depth perception, associated with a narrowing of the visual field. This narrowing can be as much as 10° at the red end of the spectrum. These abnormalities can be very troublesome when on gangway watch at night, when night vision is needed, and when the ambient lighting is red, but usually only occur if noise levels are above 100 dB. Noise-induced stress seems to reduce dopamine synthesis and dopamine is a neurotransmitter that is used by the retina.

Effects on endocrine system

Stress caused by noise of 60 dB or above causes the same type of endocrine change that is seen in all types of stress, that is, the release of catecholamines and cortisol. One study^[40] showed that three days of noise exposure appears to cause significant increases in corticosteroid and adrenaline levels. An effect on immune functions has also been observed, with an increase in oxidative stress.

Indirect noise-related effects

Noise limits people’s ability to communicate, and contributes to isolation, which is already a significant phenomenon on board merchant ships. Intelligibility of a conversation reduces in proportion with the increase in background noise and the distance between the participants. At a distance of one metre, communication is only possible if the noise level is lower than 75 dB.

A high level of noise may mask a warning or alarm indicating danger, or may lead to incorrect interpretation of instructions. Noise may be a direct cause of accidents. In 1955, Sir Lionel Heald confirmed that ‘men who worked on the flight decks and were exposed to tremendous noise from aircraft and ventilating machinery became extremely careless, got into the way of the planes, fell over things and got themselves injured.’^[41] According to Poulton (1979^[42], 1981^[43]), noise has a masking effect on non-intentional auditory signals and on the ‘internal monologue’ that each individual uses to overcome deficiencies in short-term memory. More generally, it is possible that noise, by masking a whole range of auditory signals that are characteristic of an environment, creates an impression of isolation, which leads to lack of attention and negligence. It is therefore essential, when choosing alarm equipment, to check that the acoustic power and frequency of the signal (low-frequency sounds mask high-frequency sounds) are adequate for the planned area of use. In addition, it has been demonstrated^[44][45] that ambient noise increases the risk of accidents, particularly in subjects with hearing loss.

The problem of multiple stressors

Noise is just one of many stressors that affect seafarers on board ships. Among others, there is also vibration, and heat in some cases. The question arises as to whether these stressors interact with each other. This area is very complex, and little is known about it. In the maritime field, which is greatly affected by this problem, the scientific literature is particularly sparse.

Noise and vibration

Some studies^[46][47][48] suggest that whole-body vibrations play a role in the aetiology of noise-induced hearing problems. Effects on low frequencies seem to be increased if there is combined exposure to noise and vibration (Pinter 1973)and some studies consider that while vibrations play a role in noise-induced hearing problems, this would only be of the order of 5 dB at temporary threshold shift (TTS)² that is, auditory fatigue measured 2 minutes after exposure. ^[49][50] Pekkarinen (1995^[51]) indicates that whole-body vibrations of between 2 and 10 Hz at 10 ms^-2 seem to increase auditory fatigue (TTS) when noise levels are above 90 dB_A.

Noise and heat

Several authors have attempted to show that there is an antagonist interaction between noise and heat.  However, it seems as though the effects of associated noise and heat may be synergistic, antagonistic or negligible, depending on the intensity of the stressors, type of work and length of exposure. According to Pekkarinen^[52], high temperatures increase auditory fatigue

Noise and chemical agents

It has also been established that there is a synergistic effect between exposure to noise and exposure to various solvents, toluene, styrene, xylene and trichloroethylene in particular, as well as carbon monoxide, which increases ototoxicity and therefore also hearing loss^[53][54][55].  (Sass-Kortsak et al. 1995)

Smoking can also increase the ototoxicity of noise^[56] (Molvaer and Lehmann 1985^[57]). However, Bur^[58]finds that smoking is an independent risk factor for incidence of hearing loss.

Bibliography

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• Sokas RK, Moussa MA, Gomes J, Anderson JA, Achuthan KK, Thain AB, Abu Risheh Z: Noise-induced hearing loss, nationality, and blood pressure.
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^[1] Andro M, Dorval P. Nuisances sonores et pêches maritimes – exposé des résultats obtenus lors d’une campagne de mesures effectuée à la pêche industrielle. Xth World Congress on the prevention of occupational accidents and diseases. Canadian Center for occupational Health and Safety Editor, Hamilton, Ontario, Canada, 1984: 77-81

^[2] Kaerlev L, Jensen A, Nielsen PS, Olsen J, Hannerz H, Tuchsen F. Hospital contacts for noise-related hearing loss among Danish seafarers and fishermen: A population-based cohort study. Noise Health 2008;10:41-5

^[3] Irgens-Hansen, K., Sunde, E., Bråtveit, M. et al. Hearing loss in the royal Norwegian navy: a cross-sectional study. Int Arch Occup Environ Health 88, 641–649 (2015). https://doi.org/10.1007/s00420-014-0988-8

^[4] Erlend Sunde, Kaja Irgens-Hansen, Bente E. Moen, Truls Gjestland, Vilhelm F. Koefoed, Gunnhild Oftedal, Magne Bråtveit, Noise and Exposure of Personnel Aboard Vessels in the Royal Norwegian Navy, The Annals of Occupational Hygiene, Volume 59, Issue 2, 1 March 2015, Pages 182–199, https://doi.org/10.1093/annhyg/meu075

^[5] Mohamed A. Zytoon, Occupational noise exposure of fishermen aboard small and medium-scale fishing vessels, International Journal of Industrial Ergonomics, Volume 43, Issue 6, 2013, Pages 487-494, ISSN 0169-8141, https://doi.org/10.1016/j.ergon.2012.08.001.

^[6] Monica Lundh, Margareta Lützhöft, Leif Rydstedt, Joakim Dahlman, Working conditions in the engine department – A qualitative study among engine room personnel on board Swedish merchant ships, Applied Ergonomics, Volume 42, Issue 2, 2011, Pages 384-390, ISSN 0003-6870,  https://doi.org/10.1016/j.apergo.2010.08.009.

^[7] Jégaden D. Bruit à bord des navires: son retentissement sur la fonction auditive des marins de commerce. Arch Mal Prof 1984; 5: 345-9

^[8] Parker AW, Hubinger LM, Green S, Sargent BA, Boyd R. A survey of the health, stress and fatigue of Australian Seaafarers 1998, AMSA, Australie

^[9] Jégaden D, Marie Y. Exposition au bruit à bord des navires de pêche. Presented at 4th conference of SHMTA, Brest, 1990

^[10] Report on Fisheries: safety and causes of accidents (2000/2028(INI)) AF-0087/2001. European Parliament 12 March 2001. https://www.europarl.europa.eu/sides/getDoc.do?pubRef=-//EP//NONSGML+REPORT+A5-2001-0087+0+DOC+PDF+V0//EN&language=EN

^[11] Trécan F. Etude des atteintes auditives des marins français. A propos de 18000 marins. Université de Bretagne Occidentale 2006.

^[12] Neitzel R, Berna B, Seixas N. Noise Exposures Aboard Catcher/Processor Fishing Vessels. Am J Ind Med 2006; 49: 624-33

^[13] Tamura Y, Kawada T, Sasazawa Y. Effect of ship noise on sleep. Journal of Sound and Vibration 1997; 205 : 417-25

^[14] Tamura Y, Horiyasu T, Sano Y, Chonan K, Kawada T, Sasazawa Y et al. Habituation of sleep to a ship’s noise as determined by actigraphy and a sleep questionnaire. Journal of Sound and Vibration 2002; 250: 107-13

^[15] Rabat A, Bouyer JJ, Aran JM, Courtiere A, Mayo W, Le Moal M. Deleterious effects of an environmental noise on sleep and contribution of its physical components in a rat model.  Brain Research 2004: 88-97

^[16] Tirilly G, Foret J. Polyphasic sleep/wake strategy and alertness - observations in fishermen. Shiftwork International Newsletter 1999; 16 : 36

^[17] Smith A, Wellens B. Noise and occupational health and safety. Noiseatwork2007 First European Forum on Efficient Solutions for Managing Occupational Noise Risks. 3-5 July 2007

^[18] Poulton EC. Continuous intense noise masks auditory feedback and inner speech. Psychol Bull 1977; 84: 977-1001

^[19] Millar K, Steels BS. Sustained peripheral vasoconstriction while working in continuous intense noise. Aviation Space and environm Med 1990; 695-8

^[20] Tarter SK, Robins TG. Chronic noise exposure, high-frequency hearing loss, and hypertension among automotive assembly workers. J Occup Med 1990; 32: 685-9

^[21] Wu TN, Shen CY, Ko KN, Guu CF, Gau HJ, Lai JS et al. Occupational lead exposure and blood pressure. Int J Epidemiol 1996; 25: 791-6.

^[22] Garcia AM, Garcia A. Relationship between arterial pressure and exposure to noise at work. Med Clin (Barc) 1992; 11: 5-8

 [23] Garcia AM, Garcia A. Occupational noise as a cardiovascular risk factor. Schriftenr Ver Wasser Boden Lufthyg 1993; 88: 212-22

^[24] Nowak S. The influence of noise increased arterial blood pressure in workers during the work day. Pol Merkuriusz Lek 1996; 1: 389-93

^[25] Talbott EO, Gibson LB, Burks A, Engberg R, McHugh KP. Evidence for a dose-response relationship between occupational noise and blood pressure. Arch Environ Health 1999; 54: 71-8

^[26] Sokas RK, Moussa MA, Gomes J, Anderson JA, Achuthan KK, Thain AB et al. Noise-induced hearing loss, nationality, and blood pressure.

^[27] Knipschild P. Medical effects of aircraft noise. International Archives of Occupational and Rnvironmental Health 1977; 40: 185-204

^[28] Talijancic A, Mustac M. Arterial hypertension in workers exposed to occupational noise. Arh Hig Rada Toksikol 1989; 40: 415-20

^[29] Garcia AM, Garcia A. Occupational noise as a cardiovascular risk factor. Schriftenr Ver Wasser Boden Lufthyg 1993; 88: 212-22

^[30] Fogari R, Zoppi A, Vanasia A, Marasi G, Villa G. Occupational noise exposure and blood pressure. J Hypertens 1994; 12: 475-79

^[31] Pekkarinen J. Noise, impulse noise, and other physical factors- combined effects on hearing. Occup Med 1995; 10: 545-59

^[32] Tomei F, Papaleo B, Baccolo TP, Tomao E, Alfi P, Fantisi S. Chronic noise exposure and the cardiovascular system in aircraft pilots. Med Lav 1996; 87: 394-410.

^[33] Tomei F, Fantini S, Tomao E, Baccolo TP, Rosati MV. Hypertension and chronic exposure to noise. Arch Environ Health 2000; 55: 319-25.

^[34] Gomes LM, Martinho Pimenta AJ, Castelo Branco NA. Effects of occupational exposure to low frequency noise on cognition. Aviat Space Environ Med 1999; 70: 115-18

^[35] Jégaden D, Le Pluart C, Marie Y, Piquemal B. Contribution à l’étude des relations bruit-hypertension artérielle - A propos de 455 marins de commerce âgés de 40 à 55 ans. Arch Mal Prof 1986; 47: 15-20

^[36] Korotkov J. The noise and functional disturbances of the cardiovascular system in seamen. Bull Inst Marit Trop Med Gdynia 1985; 36: 29-35

^[37] Kontosic I. Noise as a risk factor for arterial hypertension in sailors. Ahr Hig Rada Toksikol 1990; 41: 187-99

^[38] Roodenko V.G, Oparina T.P., Demidova TV, Osadchook V.P., Choomachenko L.I. Arterial hypertension in seafarers and its link with occupational factors. Presented at 7th International Symposium on Maritime Health, Tarragona, Spain, 23-26 April 2003

^[39] Davies HW et al. Occupational exposure to noise and mortality from myocardial infarction. Epidemiology 2005; 16: 25-32

^[40] Zheng KC, Ariizumi M. Modulations of Immune Functions and Oxidative Status induced by Noise Stress. J Occup Health 2007; 49: 32-8

^[41] Sir Lionel was a British Member of Parliament, and the quotation comes from a speech he made in the House of Commons on 2 December 1955

^[42] Poulton, E. C. (1979). Composite model for human performance in continuous noise. Psychological Review, 86(4), 361–375. https://doi.org/10.1037/0033-295X.86.4.361

^[43] Poulton, E. C. (1981). Not sop Rejoinder to Hartley on masking by continuous noise. Psychological Review, 88(1), 90–92. https://doi.org/10.1037/0033-295X.88.1.90

^[44] Toppila E, Pyykkö I, Pääkkönen. Practical evaluation of the combined effect of noise and chemicals on hearing and accident risk. Noiseatwork2007 First European Forum on Efficient Solutions for Managing Occupational Noise Risks. 3-5 july 2007

^[45] Toppila E, Pääkkönen. Evaluation of increased accident risk due to noise in workplaces. Noiseatwork2007 First European Forum on Efficient Solutions for Managing Occupational Noise Risks. 3-5 july 2007

^[46] Manninen O. Studies of combined effects of sinusoidal whole-body vibration and noise of varying bandwidths and intensities on TTS² in men. Int Occup Environ Health 1983; 51: 273-88

^[47] Hamernik R, Ahroom W, Davis R, Axelsson A. Noise and vibration interactions – Effects on hearing. J Acoust Soc Am 1989; 86: 2129-37

^[48] Howarth H, Griffin M. Subjective response to combined noise and vibration – Summation and interaction effects. Journal of Sound and Vibration 1990; 143: 443-54

^[49] Okada A, Miyake H, Yamamura K, Minami M. Temporary hearing loss induced by noise and vibration. J Acoust Soc Am 1972; 51: 1240-8

^[50] Manninen O. Studies of combined effects of sinusoidal whole body vibrations and noise of varying bandwidths and intensities on TTS2 in men. Int Arch Occup Environ Health 1983; 51: 273-88

^[51] Pekkarinen J. Noise, impulse noise, and other physical factors: combined effects on hearing. Occupational Medicine (Philadelphia, Pa.). 1995 Jul-Aug;10(3):545-559. PMID: 8578418.

^[52] Pekkarinen J. Noise, impulse noise, and other physical factors- combined effects on hearing. Occup Med 1995; 10: 545-59

^[53] Morioka I, Miyai N, Yamamoto H, Miyashita K. Evaluation of combined effects of organic solvents and noise by the upper limit of hearing. Ind Health 2000; 38: 252-7

^[54] Sliwinska-Kowalska M. et al. Exacerbation of noise-induced hearing loss by co-exposure to workplace chemicals. Environmental Toxicology and Pharmacology 2005; 19: 547-53

^[55] Toppila E, Pääkkönen. Evaluation of increased accident risk due to noise in workplaces. Noiseatwork2007 First European Forum on Efficient Solutions for Managing Occupational Noise Risks. 3-5 july 2007

^[56] Starck J, Toppila E, Pyykko I. Smoking as a risk factor in sensory neural hearing loss among workers exposed to occupational noise. Acta Otolaryngo, 1999; 119: 302-5

^[57] Molvaer OI, Lehmann EH. Hearing acuity in professional divers. Undersea Biomed Res. 1985 Sep;12(3):333-49. PMID: 4060339.

^[58] Burr H, Lund S, Bügel Sperling B, Kristensen T, Poulsen O. Smoking and height as risk factors for prevalence and 5-year incidence of hearing loss – A questionnaire-based follow-up study of employees in Denmark aged 18-59 years exposed and unexposed to noise. In J Audiol 2005; 44: 531-9

E.10 Obesity

Details

Published: 09 January 2022

SUE STANNARD, TIM CARTER

Acute and Long Term Harm

Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. A body mass index (BMI) over 25 is considered overweight, and over 30 is obese^[1].

The health risks of being obese are well documented and include^[2]

• All-causes of death (mortality)
• High blood pressure (Hypertension)
• High LDL cholesterol, low HDL cholesterol, or high levels of triglycerides (Dyslipidemia)
• Type 2 diabetes
• Coronary heart disease
• Stroke
• Gallbladder disease
• Osteoarthritis (a breakdown of cartilage and bone within a joint)
• Sleep apnea and breathing problems
• Many types of cancer
• Low quality of life
• Mental illness such as clinical depression, anxiety, and other mental disorders4,5
• Body pain and difficulty with physical functioning

Risk assessment

Similar principles apply to these as for other health risks. The ‘Guidelines on the Medical Examination of Seafarers’^[3] state that BMI should be used as an indicator for further assessment, and this must include physical capability testing relevant to the position and job tasks to be performed on board. Examples include

• Handling mooring cables and fuel lines, especially dragging them and other manual handling tasks
• Entry and movement through narrow confined spaces
• Accessing all areas of the ship with breathing apparatus as part of the firefighting team

In addition, the increased likelihood of a medical incident associated with the conditions listed above must be calculated. This will not only include being overweight or obese but other risk factors such as the known presence of diabetes etc.

Risk management

Appropriate risk assessment at PEME should identify those seafarers thought to have a higher than acceptable likelihood of a medical incident over the next 2 years and the consequences of such an event based on factors including the seafarer’s position on board, trade routes, medical care available on board etc. In addition the seafarer needs to have the physical capabilities to perform routine and emergency duties. If the risk is not acceptable, with or without mitigating measures, the seafarer should not be given a medical certificate and an appropriate management plan should be instigated to encourage weight loss and an increase in fitness.

All seafarers on board, obese or not, should have access to an appropriate diet, exercise facilities and health promotion advice on these topics. Good collaboration between shore side management and cooks, purchasers etc is essential.

^[1] https://www.who.int/health-topics/obesity#tab=tab_1 Accessed November 14^th 2021

^[2] https://www.cdc.gov/healthyweight/effects/index.html Accessed November 14th 2021

^[3] https://www.ilo.org/sector/Resources/codes-of-practice-and-guidelines/WCMS_174794/lang--en/index.htm Accessed November 14th 2021