Endocrine Disruptors Flashcards
What is an endocrine disruptor?
An endocrine disruptor is an exogenous substance that causes adverse health effects in an intact organism or its progeny, subsequent to changes in endocrine function
Where does excess oestrogen come from?
In Britain approximate;y one in three sexually active women take the contraceptive pill
Contains synthetic oestrogen - ethinyl oestradiol
Excess oestrogen leaked into the sewage outlets
What has oestrogenic chemicals been linked to in humans?
Decreasing sperm counts (Carlsen et al. 1992)
Increasing testicular cancer
Increasing hypospadias (abnormal urethral opening)
Increasing cryptochidism (undescended testes)
What other endocrine disruptors are there?
DDt, DDD, DDE, Chlorlo-DDT
What effects did the 1980 chemical spill in Lake Apopka, Florida have on alligators?
90% decline in the population within the lake
surviving population had decline in thallus length, abnormal reproductive organs and disruption of the ratio of oestrogen and testosterone (Guillette et al, 1998)
Where can oestogenic compounds be found today?
contraceptive medication plastics detergents electronics paints pesticides food cans white fillings bottle tops water pipe linings printing ink on food cartons
What is the LOEC of ethinyl oestradiol?
the lowest observed effect concentration of ethinyl oestradiol is <1 nanogram per litre (0.0025g in 2.5million litres = 1ng/L)
What effects do endocrine disruptors have on fish?
Vitellogenin induction in male fish (essential protein in egg yolk nutrition)
Gonadal intersex (ovotestis)
Abnormal gametes (e.g. reduced sperm quality)
adverse effects on reproductive behaviour
Why are fathead minnows a good testing organism in this area?
Visible characteristics
easy to keep and breed
lay eggs on underside of shelters
effects can be measured in a number of ways; sexual characteristics, fecundity, GSI (size of gonads), vitellogenin
What act is in place to control certain endocrine disruptors?
environmental protection act 1816 is in place to control the use of nonylphenol and nonylphenol ethoxylate
What is DES?
diethylstilbestrol - affected 10 million women in the US and 300,000 in the UK
Banned for use in chickens and lambs in 1959 as workers suffered sterility and breast growth
1970 - 7 teenagers diagnosed with exceptionally rare type of vaginal cancer in Boston (Clear Cell adenocarcinoma)
1971 - link between DES and CCA established and DES banned
1979 - DES banned completley
What effects can DES have?
In the mother - Increased risk of breast cancer
In female offspring - high risk of pregnancies and miscarriage
Increased risk of CCA
Increased risk of infertility
Structural damage of reproductive organs
In male offspring - Increased risk of fertility
Structural damage to reproductive organs
What is TBT?
Tributyltin - marine anti-fouling paints lead to decline in oysters and whelks high incidences of imposex in dog whelks interferes with the enzyme aromatase anti-oestrogenic - masculinising effects
Points about Endocrine disruptors - taken from Tyler et al., 2008
- Been established that there is a wide variety of man-made chemicals capable of modulating or disrupting the endocrine system of animals
- Some mimic oestrogens others have masculising effects
- Although most endocrine disruptors are weak compared to their endogenous counterparts they can be present in significant concentrations in the environment
- Most have a strong tendency to bioaccumulate
- Some natural chemicals can mimic oestrogen effects (mycoestrogens from fungi and leguminous plants)
Additional Reading - Vitellogenin
Tyler et al., 2008
- excess vitellogenin may cause kidney and liver damage in fish
