Persistent organic pollutants have long been indicated to be potential endocrine disrupting substances (EDSs). The effects of PCB and DDT in various organisms from marine environments, especially in white-tailed sea eagles from the Baltic area, were studied already in the 1960's. "The debate regarding potential hazards related to hormone disrupting substances has been intense in recent years. There has been a great need among authorities for a solid knowledge basis in this field in order to direct actions against this group of compounds", says Titus Kyrklund of the Research Secretariat at the Swedish Environmental Protection Agency.
"Naturally, there has been a need to cover the specific environmental issues of Scandinavia and the Baltic Sea also with regard to hormone disrupting chemicals", he adds.
Several countries have published findings regarding effects on the estrogen system.The Swedish report, however, focuses on three hormonal systems, the sex hormones (estrogens, androgens and progestins), thyroid hormones and retinoids. Many of these systems may be affected by the same groups of chemicals. Their functions cannot be fully understood in isolation.
EDSs may induce changes in the normal development, cause different degrees of sex reversal and affect behaviour. Around the world, numerous incidences have been reported of humans or wildlife have been exposed to potential EDSs. For instance, in many parts of the world, including the Baltic Sea, it has been observed that gastropods develop imposex (the development of a penis in females) when exposed to tributyltin from antifouling paint on ships. This has led to a ban or restricted use in Sweden and other countries. Fish outside paper mills and sewage treatment plants have shown skewed sex ratios and decreased testosterone levels. Epidemiological studies of Swedish fishermen showed an increased low birth weight for infants among mothers with a consumption of fatty fish from the Baltic Sea.
"This is not a new problem. We know that hazardous substances are present in the environment and we know that they are disruptive. But we now need to go a step further and find out how these substances actually affect hormone signalling," says Per-Erik Olsson, associate professor of cellular and developmental biology at Umeå University and principal author of the report.
"More research is needed and the report is an appeal to politicians and authorities to support such further action. It is aimed as a basis for a Swedish research programme", he added.
New findings showing reduced sperm quality and increased cancer incidence in humans has sparked off the recent debate. However, there is no Swedish investigation into this, and the trends from the most comparable countries are highly different.
Testicular cancer and prostate cancer in men have been indicated to be increasing in the Nordic countries. The possible involvement of environmental endocrine disrupting chemicals in hormone related cancer is not known, but alterations in hormonal responses or in the metabolism of hormones have not been ruled out as a cause of hormone related cancers. The hypothesis that exposure to hormonally active chemicals would promote human breast cancer also remains to be verified.
It is uncertain to which extent humans and wildlife are exposed to levels high enough to cause adverse health effects. In Sweden, disturbed reproduction has been reported in fish, predatory birds and fish-eating mammals. The documented effects have in most cases been correlated to well-known contaminants such as DDT and PCB or to contaminants present in effluents from the pulp and paper industry.
According to the report, available data do not indicate a risk for adverse effects in the general Swedish population. However, safety margins for exposure depend on, for example, dietary habits. The interrelationships between the various hormone systems are not completely known and may have subtle effects not yet identified.
PCBs and DDT are banned in Sweden but are still present in the environment. The report calls for the study of substances which are still being spread to have priority, for instance, brominated flame retardants.
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