Title: Food Contamination and Safety
1Food Contamination and Safety
- Concepts
- Persistent Organic Pollutants (POPs)
- E.g. PCBs
- Heavy Metals
- E.g. Mercury
2Food 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
3Concepts
- 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
4Bioaccumulation
5Concepts
- 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
6Biomagnification
7An extra link, on top of an already long food
chain
8Contamination Persistent Organic Pollutants
(POPs)
- Also called organochlorines
- An organic compound containing chlorine
- E.g. polychlorinated biphenyls (PCBs) common
pesticides, such as DDT or Dioxin
9Persistent 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
10Organochlorines
11Example 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
12Polychlorinated 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
13Levels of POPs in blood plasma
14Average intake of POPs/day
15Contamination 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
16Example 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
17Mercury
- 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
18Methyl Mercury
19Mercury 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
20Time trend of mercury concentration in blood
21Case 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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24James 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
25James 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
26James 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
27La Grande Rivière
28James 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
29James 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
30Mercury in fish in La Grande 2 reservoir
31Mercury in fish in La Grande 2 reservoir