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Toxic Substances

Toxic Substances. Non-cumulative toxic substances do not increase in concentration in body over time Cumulative toxic substances continue to increase in concentration

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Toxic Substances

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  1. Toxic Substances • Non-cumulative toxic substances do not increase in concentration in body over time • Cumulative toxic substances continue to increase in concentration • Food chain magnification occurs when concentration of substance increases as toxic substance is passed from trophic level to trophic level. Only happens when special chemical conditions occur (e.g., solubility of toxic substance in a common substance such as fatty acids in consumer)

  2. Toxic Metals • Mercury - toxic when attached to short carbon-chain alkyl group (= methyl mercury), strongly neurotoxic, birth defects • Cadmium - from batteries, sewage, electroplating factories, effects on human kidney function, bone deformities • Lead - from batteries, paints, sewage, fuel additives, neurotoxic effects, mental development of children

  3. Pesticides, Herbicides • Designed to kill a variety of pests, principally arthropods such as mosquitoes, agricultural pests, but also plants • Targets are often non-specific, marine species also killed off • Pesticide toxicity often affects human health

  4. Some Pesticides, e.g. DDT • DDT - one of many chlorinated hydrocarbons • Used to kill Anopheles mosquito and other agricultural pests • Magnified up the marine food chain to vertebrates, owing to solubility in fatty tissue • Implicated in declines in 1970s of birds at apex of food web (marine-feeding bald eagles, osprey, brown pelicans, etc.) - strong effects on reproductive function, egg shell thickness • DDT banned in many countries, birds have increased in abundance, but still used in many developing countries to fight malaria • Pesticides used in USA today are less toxic (e.g., malathion)

  5. DDT and other Chlorinated Pesticides

  6. Other Carbon-based Toxic Substances • Polychlorinated Biphenyls (PCBs) - used as lubricants in industrial machinery, highly toxic - implicated in reproductive failures of marine mammals, human effects. Release in NE USA resulted in area closures to fishing, closures and health advisories. Current controversy over cleanups in Hudson River, other sites

  7. Other Carbon-based Toxic Substances 2 • Polycyclic Aromatic Hydrocarbons (PAHs) - derivatives from fossil fuels, coming from sewage, and other sources. Toxic effects on benthic invertebrates and fishes, effects on hormonal cycles and reproductive effects of fishes

  8. Oil Pollution - Sources • Leaks from terminals, loading pipes in harbors • Offshore drilling • Wrecks of oil tankers • Washout of oil into storm drains and direct washout to the shoreline

  9. Tanker accidents • Result in catastrophic release of oil • Associated with rough weather, making it difficult to clean up • Tanker traffic has increased with increasing use of petroleum around world • Tankers (e.g. large ones carry more than 200,000 tons) are not maneuverable, take several km to stop • New tankers are double skinned, have multiple holds, but older ones very vulnerable to puncture and breakup through imbalance of loads

  10. Tanker Accidents 2 • Torrey Canyon, off coast of U.K in 1967, released 80 tons of crude oil, tanker bombed to burn oil, use of detergents did much damage to marine life • Amoco Cadiz, spilled 200,000 tons near French coast in 1978, strong effects on marine life • BargeFlorida near Cape Cod, 1969, small spill of #2 diesel fuel oil, but toxic substances found in shellfish over a year later • Exxon Valdez, 1989, off coast of Alaska, 11 million gallons, strong effects on marine life, still evident in 2001. Hot water cleanup did much damage.

  11. 400 300 200 100 0 Density of amphipods per 1/4 square meter J F M A M J J Month in 1978 Change in abundance of amphipods following wreck of tanker Amoco Cadiz near Brittany coast

  12. Oil Mangroves Storm erosion Sediment Sea grasses Erosion Sediment Coral reef Onshore Offshore The cascading effects of oil derived from a 1986 spill along the shores of Bahia Las Minas in Panama

  13. Toxic Components of Oil • Crude oil generally less toxic than refined oil • Aromatic compounds (compounds with benzene rings) are more toxic - percent aromatics is a good indicator • Crude oil - < 5 % aromatics, Refined Oil - 40-50 % aromatics • Aromatics impair cell membrane function, neurotoxic and behavioral effects

  14. Oil - Effects on Seabirds • Contour feathers interlock and keep water from penetrating down feathers beneath • Oil coats contour feathers and collapses their interlock, seabirds lose insulation and die of hypothermia • Birds often ingest toxic oil while preening and feeding birds (e.g., puffins) are attracted to oil at surface

  15. Structure of a bird’s contour feather, showing how barbules are hooked together to seal spaces between barbs

  16. Birds covered with oil from a spill (above) are washed. Cleanup at this point often is futile

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