Persistent organic pollutants (POPs) including PCBs and dioxins form an important issue in Europe. In Finland the main sources have been dioxins from forest industries due to chlorine bleaching of pulp and the production and use of chlorophenol fungicides.
Since air emissions of POPs are small in Finland, the animal forage and hence meat and dairy products are clean in contrast to e.g. Central Europe. In Finland fish causes almost all of the exposure to POPs. The challenge is to assess the total risks and benefits of fish consumption, including special groups such as fishermen and future mothers.
We have analysed POPs at abandoned industrial sites, hazardous waste dumps, and bottom sediments of rivers, lakes and the Baltic Sea. In human exposure studies we have analysed POPs in fish and milk products as well as human milk and tissues. In epidemiological studies, the levels of POPs in patients and controls are measured and correlated with the occurrence of various cancers and developmental defects.
Mechanistic studies exploit genetic differences in several strains of rats or mice. We have studied rat strains with mutations in their dioxin receptors and shown that dioxin toxicity can be divided into two types. This helps to understand the thousand-fold differences in toxicity between animal strains and species. It is crucial to know the relevance of these differences for human risk assessment. Early developmental effects may turn out to be the most important toxic endpoints.