Masatoshi Morita
National Institute for Environmental Studies

During the last four decades, the management of hazardous chemicals has been one of the most critical problems facing mankind. The increase in the varieties and the total quantities of such chemicals, the enhancement of our knowledge of environmental chemistry, and the necessity of understanding the adverse impacts on human health and the natural environment have moved the issue to the top of the environmental agenda. Furthermore, a decade ago it was often assumed that only developed countries had to be concerned with chemicals management, but at present developing countries also have to tackle the issue because of their domestic industrialization and the global use of the chemicals. Consequently there is general agreement that hazardous chemicals management now constitutes a global issue.

There are cases where acute toxicity is seriously important and has resulted in episodes of poisoning in many countries, but in other cases chronic effects and the consequences for future generations caused by lower levels but prolonged exposure is considered most important. National and international regulation networks appear to cover a wide range of hazards. Persistent organic pollutants (POPs) are one example of the latter case, as they occur in high concentrations in human and other animal species though food chain magnification even after being diluted in the global environment.

Twelve chemicals in the first POPs list are all organochlorine compounds. Organochlorine compounds are generally resistant to biodegradation because of the lack of enzymatic systems that breakdown C-Cl bonds. The use of most of these chemicals was stopped in the early 1970s, and as a result their concentrations in the environment appear to have declined. We can see trends reflected in sediment samples and in samples from specimen banks. One may expect that computer calculations can simulate the distribution and future trends of chemical on the global scale. Examples will be discussed for several selected POPs chemicals including dioxins and furans.

There is clear evidence in several cases of effects on wildlife and of acute poisoning of humans, but questions still remain as to the chronic adverse effects of these POPs on the health of the general population. There are indications of relationships between exposure to POPs and specific cancer mortalities, adverse effects on reproduction, on neuro-brain development, on the immune system and other subtle effects, but the evidence is not strong. Further study is required for an understanding of the full biological implication of exposure to POPs.