Endocrine Disrupters: Effects on Wildlife

What Are Endocrine Disrupters? n The Endocrine System Regulates Numerous Biological Functions n The hormones secreted act like messengers within various cells or organs n These messages are extremely vital before birth for development of sexual differentiation and proper brain development

What are Endocrine Disrupters? n Cells have specifice receptor sites for specific hormones

Endocrine Disrupters n Endocrine disrupters are chemicals that can fit into these receptor sites n They can then interfere with hormone function n They can alter hormone synthesis, storage, release, secretion, transport, elimination, or binding action.

Environmental Estrogens (EEs) n Some substances in the environment can act like the hormone estrogen n Naturally occurring EEs are known as phytoestrogens u clover u soybeans, legumes u whole grains u fruits and vegetables

n Other EEs are man made: u pesticides: DDT, chlordane, methoxychlor, etc.. u plastics containing bisphenol A u pharmaceuticals:DES, birth control pills u detergents and surfactants u industrial chemicals:PCBs

Estrogen: What does it do? n Steroid hormone found in male and female sex organs n Females: regulates and sustains female sexual development and behavior, regulates reproductive cycles n Males: regulates fluid reabsorption in the tubules that carry sperm from the testis to the epididymis

Effects on Wildlife n Various wildlife studies have shown a direct relationship between exposure to endocrine disrupters and: u abnormal thyroid function u sex alteration u poor hatching success u decreased fertility and growth u altered behavior

Fish n England: fish found near a municipal sewage outlet known to dump several different chemicals including alkylphenols u had both male and female sex organs u male livers had produced a female egg-yolk protein normally found in females only u fish closest to the outlet showed more severe abnormalities

Fish n Mollusks have been found to exhibit a condition known as imposex: u male characteristics are imposed on genetic females u found in areas where tributyl tin is used as an “anti-fouling paint on ships”

Fish n 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: u concentrations could be as low as 5 parts per trillion (University of Wisconsin)

Fish n Female fish downstream from pulp and paper mills: u developed male sex organs u tried to mate with normal females or each other u males were “hypermasculinized”, exhibiting very aggressive mating behavior n Salmon in Great Lakes region have been found whit enlarged irregular thyroid glands

Alligators n Lake Apopka in Florida had DDT spill in 1980, alligator population declined severely over next 10 years n Mortality among eggs and newborns higher than normal n females had estrogen levels 2X normal level n males had lower testosterone levels and abnormal sex organs

Alligators n Other Florida lakes were found to have alligators with abnormal reproductive and thyroid hormones

Birds n DDT and softened eggshells n Gulls and terns in Great Lakes exhibit abnormal thyroid levels u supernormal egg clutches u female to female pairing u excessive chick mortality u birth defects u skewed sex ratios (excess of females)

Birds n Also exhibit suppression of immune system: u T-cell mediated immunity, probably caused by PCBs n Nesting Albatross in North Pacific, and Gulls in the Puget Sound also show contamination of DDTs and PCBs

Mammals n In the 1980s and 90s, several outbreaks of marine mammal epidemics were documented: u Russia ,000 seals died from a virus u United States bottlenose dolphins died u North Sea ,000 harbor seals died

Mammals u Mediterranean Sea ,000 striped dolphins washed up dead on shore u Diminished reproductive success in seals in the Netherlands has also been observed u Minke whales study shows increasing levels of PCBs in body

Mammals n Autopsies revealed PCBs present in animal bodies n PCBs are known to suppress immune system

Mammals n Studies were prompted to investigate: u US and Dutch conducted experiments that revealed suppressed immune systems in seals fed contaminated fish u T-cell responses were significantly below normal

Mammals n Reproductive hormones also affected: u populations of harbor, ringed and gray seals declining u high levels of PCB’s in body u beluga whales in St.. Lawrence River showing lower rate of pregnancy and fewer offspring produced

Amphibians n Frogs especially vulnerable to environmental contaminants because of permeable skin n Pesticides and PCBs are stored in frog’s fat and enter the bloodstream again during metamorphosis n Many scientists now believe that the commonly used chemical methoprene degrades in sunlight into an endocrine disrupter

Laboratory Experiments n University of Missouri: u female mice exposed to low doses of bisphenol A altered the reproductive organs of their male offspring n EPA in Research Triangle Park: u Direct link made between thyroid dysfunction and PCBs in rats

Effects on Humans n Wayne State University: u children whose mothers had eaten contaminated fish from Lake Michigan in the six years prior to pregnancy had significant deficits in intelligence and learning u mothers themselves however were not contaminated

Effects on Humans n Similar study in NY State: u measurable neurobehavioral deficits in the newborn children who’s mothers had eaten the equivalent of 40 pounds of Lake Ontario salmon in a lifetime. u children tended to have abnormal reflexes, shorter attention span and an intolerance to stress

Effects on Humans n Early exposure of males to endocrine disrupters (DES) causes major problems such as undescended testes, and increased incidence of testicular and prostate cancer n Sperm densities in the US are decreasing 1.5% every year

Conclusions n Thousands of chemicals need to be tested for endocrine disruption n October 1998: EPA unveils its strategy to start testing chemicals n No current plan to start testing common household products n On the cellular level, we are not very different from animals, if they are being affected by endocrine disrupters, so are we.