endocrine disruptors and ddt
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DESCRIPTIONPresentation 5 in a series about pollution for Unit 4 VCE Environmental Science.
Endocrine Disruptors and DDT
Endocrine Disruptors, Phthalates and DDTVCE Environmental Science: Unit 4Area of Study 1: PollutionLast week Air Pollution What do you remember?APAHCECPDMFRLDKCSulphur dioxide What do you remember?APAHCECPDMFRLDKCEndocrine DisruptorsEndocrine disruptors are chemicals that interfere with endocrine (or hormone system) in animals, including humans. These disruptions can cause cancerous tumours, birth defects, and other developmental disorders. Known endocrine disrupting chemicals include:Pesticides (such as DDT)PCBs Bisphenol A (BPA)Polybrominated diphenyl ethers (PBDE)Pthalates and Alkylphenols
http://www.nacsetac.org/Shortcourse/shortcourse_2011.htmEndocrine DisruptorsThe critical period of development for most organisms is between the transition from a fertilized egg, into a fully formed infant. As the cells begin to grow and differentiate, there are critical balances of hormones and protein changes that must occur.Therefore, a dose of disrupting chemicals can do substantial damage to a developing fetus (baby). Whereas, the same dose may not significantly affect adult mothers.
Human Health EffectsSpecifically, they are known to cause learning disabilities, severe attention deficit disorder cognitive and brain development problems, deformations of the body (including limbs); sexual development problems, feminizing of males or masculine effects on females.
http://www.niehs.nih.gov/news/newsletter/2009/july/extramural-update.cfmPCBs Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings.Concerns about the toxicity of PCBs are largely based on compounds within this group that share a structural similarity and toxic mode of action with dioxin. Were used in transformers, capacitors, plasticizers, flame retardants, sealants and coolants now banned.
DichlorodiphenyltrichloroethaneDDT was first synthesized in 1874, but its insecticidal properties were not discovered until 1939. It was used with great success in the second half of World War II to control malaria and typhus among civilians and troops. After the war, DDT was made available for use as an agricultural insecticide and soon its production and use skyrocketed.
Farm workers in Central Valley being sprayed with pure DDT in 1956.Silent Spring by Rachel CarsonIn 1962, Silent Spring by American biologist Rachel Carson was published. The book catalogued the environmental impacts of the indiscriminate spraying of DDT in the US and questioned the logic of releasing large amounts of chemicals into the environment without fully understanding their effects on ecology or human health. The book suggested that DDT and other pesticides may cause cancer and that their agricultural use was a threat to wildlife, particularly birds. Its publication was one of the signature events in the birth of the environmental movement, and resulted in a large public outcry that eventually led to DDT being banned in the US in 1972Persistence in soilDDT is a persistent organic pollutant that is extremely hydrophobic and strongly absorbed by soil. Depending on conditions, its soil half-life can range from 22 days to 30 years. Routes of loss and degradation include runoff, volatilization, photolysis and aerobic and anaerobic biodegradation.
Persistence in waterWhen applied to aquatic ecosystems it is quickly absorbed by organisms and by soil or it evaporates, leaving little DDT dissolved in the water itself. Its breakdown products and metabolites, DDE and DDD, are also highly persistent and have similar chemical and physical properties
Effects on VertebratesDDT is toxic to a wide range of animals in addition to insects, including marine animals such as crayfish and prawns and many species of fish. It is less toxic to mammals, but may be moderately toxic to some amphibian species, especially in the larval stage.
DDT and DDE have been linked to diabetes, neurological problems, cancer and decreased fertility in males.Effect on BirdsMost famously, it is a reproductive toxicant for certain birds species, and it is a major reason for the decline of the bald eagle, brown pelican, peregrine falcon and osprey. Birds of prey, waterfowl and song birds are more susceptible to eggshell thinning than chickens and related species, and DDE appears to be more potent than DDT.
http://www.dolphinwatchnaturetours.com/edres/images/DDT.jpgPthalatesPhthalates (pronounced THAL-ates) are the most commonly used plasticisers in the world, and have been in use for about 50 years. They are primarily used to make polyvinyl chloride (PVC) flexible, but this group of industrial chemicals is used to confer softness, viscosity, transparency, flexibility and durability to a range of products including:
Toys and food packaging, Erasers and hosesRaincoats and shower curtains,Vinyl flooring and wall coverings,Pigments, lubricants, adhesives and wood finishes, Gelling and emulsifying agents,Waxes, solvents and detergents,PesticidesMedical products including catheters and transfusion devises. Nail polish, perfume, moisturisers, hair spray and shampoo
Characteristics of PthalatesPhthalates are a family of organic chemical substances produced from petroleum. They are esters of phthalic acid which are widely used as industrial compounds. When added to plastics, phthalates allow the long polyvinyl molecules to slide against one another. They are produced by reacting phthalic anhydride with an appropriate alcohol. Phthalates have:
low water solubilityhigh oil solubilitylow volatilitycolourlessodourlessliquids
Impacts of Pthalates:There have been a number of studies into the health impacts of phthalates. Some studies suggest they have a number of health impacts, including disrupting the endocrine system. Phthalates is one group of endocrine disrupting chemicals (EDCs) that affect the bodys hormones. The endocrine system is important in controlling hormones, which in turn balance several systems in the body including the reproductive system.
Impacts of Pthalates:As of 2004, manufacturers produced about 363 thousand metric tonnes of phthalates each year. By weight, they contribute 10-60% of plastic products.Phthalates can act as an oestrogen mimic, though knowledge of their impacts is still is slowly accruing.There is also considerable debate regarding their impacts, as different studies have arrived at conflicting conclusions, and while there has been some studies suggesting they pose considerable danger to some laboratory animals, there is debate as to whether this information can be extrapolated to humans.
Impacts of Pthalates:Some of the impacts attributed to phthalates include:premature birthsreduced sperm countsstructural abnormalities in the reproductive organs of male test animalsliver cancer
There has also been speculation they may cause:susceptibility to allergenspremature breast development in young girlsobesity and diabetes
Impacts of Pthalates:Although an expert panel has concluded that there is "insufficient evidence" that they can harm the reproductive system of infants, the state of California and the Europe Union have banned them from toys. In 2002, the US Food and Drug Administration (FDA) released a public report which cautioned against exposing male babies to DBP and DEHP. Although there are no direct human studies the FDA report states:
Exposure to DEHP has produced a range of adverse effects in laboratory animals, but of greatest concern are effects on the development of the male reproductive system and production of normal sperm in young animals. We have not received reports of these adverse events in humans, but there have been no studies to rule them out. However, in view of the available animal data, precautions should be taken to limit the exposure of the developing male to DEHP".
Transport mechanisms and sinksPhthalates are easily released into the environment because they can easily leach and evaporate into food, water or the atmosphere. As plastics age and break down, the release of phthalates accelerates. Phthalates in the environment are subject to biodegradation, photo-degradation, and anaerobic degradation therefore they do not generally persist in the outdoor environment.
PersistenceOutdoor air concentrations are higher in urban and suburban areas than in rural and remote areas. Indoor air concentrations are generally higher than outdoor air concentrations due to the nature of the sources. Phthalates can accumulate in some simple, aquatic organisms. However, most higher organisms (such as fish) are able to metabolise them and break them down. Therefore, biomagnification up the food chain does not usually occur. Inside the body, they break down and are excreted.
ExposurePeople are commonly exposed to phthalates. Exposure can be through direct use or indirectly through environmental contamination.
Phthalates can emanate from:Air: industrial air pollution Water: sewage sludge and treated water, tap water, industrial effluent Environment: agricultural landDirect contact with consumer products: adhesives, detergents, flooring, inks, paints and coatings, plastics, rubber, deodorant, fragrances, hand lotion, insect repellent, shampoo, soap, medical tubing.
IngestionIngestion is believed to be the main source of DEHP and other phthalates in the general population, with fatty foods such as milk, butter, and meats a major source. Low molecular weight phthalates such as DEP and DBP may be dermally absorbed. Inhalational exposure is also significant with the more volatile phthalates.Phthalates are also found in medications, where they are used to produce enteric coatings. Exposures from phthalate-contai