Thursday, July 9, 2009

Endocrine Disruptors in the Chesapeake Bay Watershed

Chemicals are a fact of modern life they exist in pharmaceuticals, household products, personal care products, plastics, pesticides, industrial chemicals, human and animal waste; they are in short, all around us. There are some chemicals that can mimic, block, or otherwise alter animal hormone responses, sometimes affecting their reproduction, development, and behavior, this is actually, how some pest control treatments are designed to work. A diverse group of chemicals called endocrine disrupting chemicals (EDCs) come from a variety of sources. These chemical have vastly different molecular structures. These chemicals become of great concern when they are discovered to be human endocrine disruptors as DDT, dioxin, the drug DES and PCBs were in the past. Traces of endocrine disrupting chemicals are seemingly found in every part of our world, including dust, soil, water, air, food, manufactured products, wildlife, and even ourselves.

There are countless natural occurring phytochemicals so far thousands have been isolated from plants in addition there are estimated to be over 80,000 artificial chemicals in the world today. The structural diversity is enormous and it is not known which of these substances might adversely affect living things in subtle ways. Testing for new chemicals is for gross and acute impact, subtle impact is very difficult to identify. One thing is certain, the growing class of known endocrine disrupting chemicals can disturb a staggering range of hormonal processes. Like natural hormones, some EDCs bind directly with hormone receptors. The impostors can mimic or block hormone messages with the same, weaker, or stronger responses. Others are more subtle, they interfere with hormone maintenance to prevent or enhance hormones from being made, broken apart, or carried in the bloodstream.

When the USGS began looking into skin lesions on bass in the southern branch of the Potomac River, they found fish suffering from a variety of lesions. Some fish had bacterial lesions, some fungal lesions, and some fish had parasite. The USGS concluded that there was no specific cause of the lesions and that the fish appeared to be immunosupressed so that any pathogen in the water could attack the fish. A series of studies were performed over a period of years. During the investigation it was discovered that male fish had immature female egg cells in their testes and the females had lowered levels of an essential protein in the formation of eggs. The bass suffering from lesions were intersexed. It had previously been demonstrated that estrogen and estrogen mimicking compounds can cause intersex. The occurrence of intersex among the lesioned fish prompted further studies. How estrogen related compounds could be impacting the immune systems in these fish was studied by one group while several groups within the Fish and Wildlife Service and US Geological Survey studied the relationship between waste water treatment plants, other chemicals, and the impacted fish.

The study found the problem of endocrine disruption in fish to be widespread in the limited study area of a portion of the Chesapeake Water Shed, but increased in proximity to and downstream of the waste water treatment plants. Chemical sampling that took place along with the fish sampling found higher concentrations of waste water chemicals near the waste water plants. Pesticides currently used in agriculture were detected at all locations. Hormones were not detected in the samples, but analysis using yeast screening assays found estrogenic endocrine-disrupting chemicals at all locations their specific source is not yet known. Though they cannot identify a single chemical or group of chemicals responsible, the US FW and US GS have embarked on further study to gain greater understanding of the implications to the earth’s ecosystem.

The implications to the fish populations are apparent, but the waters where the study took place are part of the water supply for the region. The impact on human health and the ecosystem needs to be discovered. In addition to finding intersexed fish, the researchers have found male amphibians with ovaries and female frogs with male genitalia and frogs with six legs and other mutations. The endocrine system of fish is similar to the human endocrine system. The US FW and US GS research on the Potomac River poses some troubling questions for the 2 million people who rely on the Washington Aqueduct for their drinking water as well as the millions of people in other parts of the country with similar observed occurrences of endocrine disruption. The impact on human life is not known, but according to Dr. Robert Lawrence of the Johns Hopkins School of Public Health there is the potential to for humans to develop premature breast cancer, have problems with reproduction, and develop congenital anomalies of the male genitalia. These kinds of impacts are happening at a broad and low level in society so that the occurrence is not alarming to the general public or easily noted without detailed statistics.
In April of 2009 the US EPA issued the Final List of Initial Pesticide Active Ingredients and Pesticide Inert Ingredients to be Screened Under the Federal Food, Drug, and Cosmetic Act as potential endocrine disruptors. Pesticide runoff is a large contributor of known pollutants to the watershed. Water is the fluid of life. Do you know where your water’s been and what’s in it?

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