Food Contamination and Safety

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Food Contamination and Safety

• Concepts
• Persistent Organic Pollutants (POPs)
• E.g. PCBs
• Heavy Metals
• E.g. Mercury

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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

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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

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Bioaccumulation
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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

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

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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

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Organochlorines
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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

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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

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Levels of POPs in blood plasma
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Average intake of POPs/day
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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

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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

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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

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Methyl Mercury
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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
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Time trend of mercury concentration in blood
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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!

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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

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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

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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

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La Grande Rivière
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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

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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

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Mercury in fish in La Grande 2 reservoir
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Mercury in fish in La Grande 2 reservoir