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Food Contamination and Safety

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  1. Food Contamination and Safety • Concepts • Persistent Organic Pollutants (POPs) • E.g. PCBs • Heavy Metals • E.g. Mercury

  2. Food Contamination and Safety • Northern plants and animals are exposed to contaminants that accumulate in the North • Pollutants move from soil and water into plants, and from there into animals • The carnivore diet of humans in the Arctic involves the consumption of species high up in the food chain  This results in a higher chance of poisoning • Feeding on caribou vs. marine mammals exposes humans to different levels of contaminants

  3. Concepts Bioaccumulation • The process by which a contaminant accumulates in the tissues of an individual organism • E.g. certain chemicals in food eaten by a fish tend to accumulate in its liver and other tissues – the chemicals are taken in faster than the individual can get rid of them • PCBs are stored in fat • Cadmium is stored in the kidneys • Mercury is stored in the liver

  4. Bioaccumulation

  5. Concepts Biomagnification • Increase in concentration of certain stable chemicals (for example, heavy metals or fat-soluble pesticides) in successively higher trophic levels of a food chain or web. • E.g. metals such as mercury, persistent organic pollutants (POPs) such as PCBs, pesticides, dioxins • Note: Not all contaminants biomagnify

  6. Biomagnification

  7. An extra link, on top of an already long food chain

  8. Contamination: Persistent Organic Pollutants (POPs) • Also called organochlorines • An organic compound containing chlorine • E.g. polychlorinated biphenyls (PCBs); common pesticides, such as DDT or Dioxin

  9. Persistent Organic Pollutants (POPs) • Highly toxic chemicals • Estimated that 400 million tons are produced annually worldwide • The “dirty dozen”  aldrin, chlordane, DDT, dieldrin, dioxins, furans, endrin, HCB, heptachlor, mirex, PCBs, toxaphene • Stored in fat and are persistent

  10. Organochlorines

  11. Example: Polychlorinated Biphenyls (PCBs) • No longer produced in North America, but are still produced in some developing countries • Were commonly used as lubricants in hydraulic fluid, transmission oil, and in electrical transformers • Considered a POP  they stay in the environment for a long time and travel long distances

  12. Polychlorinated Biphenyls (PCBs) • PCBs biomagnify • At low level in food  can affect the reproductive system and thyroid, may damage the immune and nervous system • Prenatal infants exposed to PCBs tend to have a higher incidence of upper respiratory-tract infections • Suspected to cause liver, skin, and intestinal cancers

  13. Levels of POPs in blood plasma

  14. Average intake of POPs/day

  15. Contamination: Heavy Metals • Minerals that are naturally present in rocks and soils in all parts of the world, including the bed rock and unconsolidated material of the Canadian Arctic • E.g. mercury, cadmium, lead • Cadmium and mercury are released as a by-product of mining and smelting  primary long-range transport is through the atmosphere • Significant quantities of mercury are also released as a result of the erosive and chemical actions that take place in reservoirs built to store water for large hydro-electric projects • Metal levels are highest in people who eat large amounts of organ meat

  16. Example: Mercury • Mercury is a natural element that occurs in terrestrial and aquatic ecosystems in the Arctic • Atmospherically deposited mercury is emitted from sources such as coal-fired electric utilities and waste incinerators in the south • Global levels of atmospheric mercury are increasing each year

  17. Mercury • Major source of mercury is through meat, in the form of methyl mercury • Highest in people who eat a lot of marine food • Methyl mercury is easily taken up through the intestinal wall • Major health concern is damage to the brain and nervous system, may also affect the immune system • Methyl mercury easily passes through the placenta and can affect the fetus  may cause neurological damage

  18. Methyl Mercury

  19. Mercury in Maternal Blood

  20. Time trend of mercury concentration in blood

  21. Case Study: James Bay Project • The construction of a series of hydroelectric power stations on the La Grande River in northwestern Québec • One of the largest hydroelectric systems in the world • Installed generating capacity of 16,000 megawatts  3x more power than the power station at Niagara Falls!

  22. James Bay Project • 1971: plans unveiled for the construction of several large hydroelectric power stations on the rivers flowing into James Bay • Environmental assessments were not required under Québec law at the time • Strong opposition to the project by the Crees of James Bay, the Inuit to the north, and several environmental groups • They believed the government was violating treaties and committing unlawful expropriation and destruction of traditional hunting and trapping lands • The Cree and Inuit were not informed of the project until after the construction of access roads had begun

  23. James Bay Project • 1975: the governments of Canada and Québec signed the James Bay and Northern Québec Agreement with the Cree and Inuit • Granted exclusive hunting and fishing rights to ~170,000 km2 of territory and 250 million dollars in financial compensation in return for the right to develop the project

  24. James Bay Project: Environmental Impact • Caniapiscau and Eastmain rivers were diverted into La Grande River watershed • 11,000 km2 of Boreal forest was submerged • Flow of La Grande River doubled

  25. La Grande Rivière

  26. James Bay Project: Mercury • Before the project, local levels of mercury in lakes and rivers were high due to atmospheric pollution and the natural geology of the region • When a reservoir is created the existing vegetation and soil is submerged, causing it to decompose and deplete oxygen from the water supply • Mercury that exists in a harmless inorganic form in the soil may be transformed by bacteria into methyl mercury once the soil is flooded • The toxic methyl mercury is lethal to the fish and can be absorbed and passed up the food chain

  27. James Bay Project: Mercury • Mercury concentrations in benthic insects, fish (which feed on benthic insects), and nestling tree swallows (which feed on fish) increased after flooding • Many native people in villages where fish are a main component of the diet have shown symptoms of mercury poisoning • Mercury concentrations in fishery resources of reservoirs may remain substantially elevated for decades after flooding

  28. Mercury in fish in La Grande 2 reservoir

  29. Mercury in fish in La Grande 2 reservoir