Exposures to substances hazardous to health and exposures to radiation (either ionising or non-ionising) share a number of features. Both may be responsible for acute and long-term health risks, the latter including genotoxic, carcinogenic and teratogenic effects. In both cases control of exposure to below a threshold level may prevent harm from some agents but for others some risk may arise from any level of exposure.

This chapter first reviews risks from substances that form cargoes and then from other uses and patterns of exposure to chemical substances on board. The term chemicals is taken to include not just defined compounds but all substances: natural products, mixtures, wastes etc. that include agents that can be harmful to health.  In this chapter properties such as flammability and effects of liquefaction on ship stability are not considered. The framework for risk management is also discussed. Later sections are concerned with ionising and with non-ionising radiation risks and their management.