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Food Contamination and Safety

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Pollutants move from soil and water into plants, and from there ... Feeding on caribou vs. marine mammals exposes humans to different levels of contaminants ... – PowerPoint PPT presentation

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Title: Food Contamination and Safety


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
Region Micro-grams mercury/liter whole blood
West. NWT 1.7
N-central NWT 3.5
Nunavik (N. Québec) 13.7
NW Greenland 19.8
N Sweden 1.6
N Norway 2.3
Iceland 2.9
Nikel, Russia 2.3
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
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23
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24
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

25
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

26
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

27
La Grande Rivière
28
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

29
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

30
Mercury in fish in La Grande 2 reservoir
31
Mercury in fish in La Grande 2 reservoir
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