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Endocrine Disrupters: Effects on Wildlife What Are Endocrine Disrupters? The Endocrine System Regulates Numerous Biological Functions The hormones secreted act like messengers within various cells or organs These messages are extremely vital before birth for development of sexual differentiation and proper brain development What are Endocrine Disrupters? Cells have specifice receptor sites for specific hormones Endocrine Disrupters Endocrine disrupters are chemicals that can fit into these receptor sites They can then interfere with hormone function They can alter hormone synthesis, storage, release, secretion, transport, elimination, or binding action. Environmental Estrogens (EEs) Some substances in the environment can act like the hormone estrogen Naturally occurring EEs are known as phytoestrogens clover soybeans, legumes whole grains fruits and vegetables Other EEs are man made: pesticides: DDT, chlordane, methoxychlor, etc.. plastics containing bisphenol A pharmaceuticals:DES, birth control pills detergents and surfactants industrial chemicals:PCBs Estrogen: What does it do? Steroid hormone found in male and female sex organs Females: regulates and sustains female sexual development and behavior, regulates reproductive cycles Males: regulates fluid reabsorption in the tubules that carry sperm from the testis to the epididymis Effects on Wildlife Various wildlife studies have shown a direct relationship between exposure to endocrine disrupters and: abnormal thyroid function sex alteration poor hatching success decreased fertility and growth altered behavior Fish England: fish found near a municipal sewage outlet known to dump several different chemicals including alkylphenols had both male and female sex organs male livers had produced a female egg-yolk protein normally found in females only fish closest to the outlet showed more severe abnormalities Fish Mollusks have been found to exhibit a condition known as imposex: male characteristics are imposed on genetic females found in areas where tributyl tin is used as an “anti-fouling paint on ships” Fish Great Lakes trout extinction now thought to be due to high levels of dioxin in the fish which caused the developing trout within the egg to die: concentrations could be as low as 5 parts per trillion (University of Wisconsin) Fish Female fish downstream from pulp and paper mills: developed male sex organs tried to mate with normal females or each other males were “hypermasculinized”, exhibiting very aggressive mating behavior Salmon in Great Lakes region have been found whit enlarged irregular thyroid glands Alligators Lake Apopka in Florida had DDT spill in 1980, alligator population declined severely over next 10 years Mortality among eggs and newborns higher than normal females had estrogen levels 2X normal level males had lower testosterone levels and abnormal sex organs Alligators Other Florida lakes were found to have alligators with abnormal reproductive and thyroid hormones Birds DDT and softened eggshells Gulls and terns in Great Lakes exhibit abnormal thyroid levels supernormal egg clutches female to female pairing excessive chick mortality birth defects skewed sex ratios (excess of females) Birds Also exhibit suppression of immune system: T-cell mediated immunity, probably caused by PCBs Nesting Albatross in North Pacific, and Gulls in the Puget Sound also show contamination of DDTs and PCBs Mammals In the 1980s and 90s, several outbreaks of marine mammal epidemics were documented: Russia 1987- 10,000 seals died from a virus United States 1987- 700 bottlenose dolphins died North Sea 1988- 20,000 harbor seals died Mammals Mediterranean Sea 1990-93-1,000 striped dolphins washed up dead on shore Diminished reproductive success in seals in the Netherlands has also been observed Minke whales study shows increasing levels of PCBs in body Mammals Autopsies revealed PCBs present in animal bodies PCBs are known to suppress immune system Mammals Studies were prompted to investigate: US and Dutch conducted experiments that revealed suppressed immune systems in seals fed contaminated fish T-cell responses were significantly below normal Mammals Reproductive hormones also affected: populations of harbor, ringed and gray seals declining high levels of PCB’s in body beluga whales in St.. Lawrence River showing lower rate of pregnancy and fewer offspring produced Amphibians Frogs especially vulnerable to environmental contaminants because of permeable skin Pesticides and PCBs are stored in frog’s fat and enter the bloodstream again during metamorphosis Many scientists now believe that the commonly used chemical methoprene degrades in sunlight into an endocrine disrupter Laboratory Experiments University of Missouri: female mice exposed to low doses of bisphenol A altered the reproductive organs of their male offspring EPA in Research Triangle Park: Direct link made between thyroid dysfunction and PCBs in rats Effects on Humans Wayne State University: children whose mothers had eaten contaminated fish from Lake Michigan in the six years prior to pregnancy had significant deficits in intelligence and learning mothers themselves however were not contaminated Effects on Humans Similar study in NY State: measurable neurobehavioral deficits in the newborn children who’s mothers had eaten the equivalent of 40 pounds of Lake Ontario salmon in a lifetime. children tended to have abnormal reflexes, shorter attention span and an intolerance to stress Effects on Humans Early exposure of males to endocrine disrupters (DES) causes major problems such as undescended testes, and increased incidence of testicular and prostate cancer Sperm densities in the US are decreasing 1.5% every year Conclusions Thousands of chemicals need to be tested for endocrine disruption October 1998: EPA unveils its strategy to start testing chemicals No current plan to start testing common household products On the cellular level, we are not very different from animals, if they are being affected by endocrine disrupters, so are we.
