We still have much to learn about the burden of illness imposed by environmental contaminants. We need a better understanding of the pathways, mechanisms, timing and nature of the effects of exposures on humans, including interactions, both among exposures and with other social and individual characteristics. We should monitor more systematically the exposure of entire populations to contaminants. Both those who deny the significance of environmental factors in illness, and those who argue that they are the major source of ill health must be more open to the existence of multiple causes. Finally, we must remind ourselves that social inequalities and global environmental changes also impose significant health impacts. As a society we should accept that there is an Environmental Burden of Illness (EBI) worth taking seriously, despite our uncertainties, and that, adhering to the precautionary principle, we should take whatever steps are feasible to reduce health impacts, while continuing to explore the links between human health and environmental contaminants.