An environmental assessor has to consider hazards and their associated risks to exposed persons and to all environmental media. This requires an appreciation of the hazard's effects, coupled with an ability to integrate this information with data on occupational exposure and adverse effects to air, soil and water. Once it is established that a substance may be toxic, that hazard then needs to be integrated with a measurement or a personal and professional observation to provide a risk assessment. Having achieved such an assessment, the risk then needs to be subjected to management techniques so as to reduce that risk in the most pragmatic manner for the system under consideration.; Measurement, or at least a qualitative assessment of the extent of the toxic insult caused by the substance or mixture of substances involved, is of importance when undertaking an environmental toxicology assessment. This text outlines some of the measurement techniques that have been developed during the early 1990s and provides examples of their application and use. Properly conducted animal experiments, coupled with generic measurements and epidemiological studies, provide a basis for establishing links between human health risks and environmental factors: from such associations public health and environmental policies can be progressed in both developed and underdeveloped countries so as to minimize the risks to current and future populations.