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Two Critical Water Pollutants Affecting Human Health – Mercury and PCBs
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1. Heavy MetalsNaturally Occurring (in rock)Also released by human activitiesMercury (Hg), Lead (Pb), Cadmium
(Cd), Copper (Cu), Arsenic (As) + others
All are neurotoxinsAll can bioaccumulate (build up in
the tissues, not excreted)All can biomagnify (concentration
increases “up the foodchain”)
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MercuryVery rare in the Earth’s crustOnly metal that is liquid at room
temp.Uses: thermometers,
preservative in vaccines, dental fillings, mercury-vapour lamps……
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Example: Mercury (Hg)Minimata, JapanMercury from a chemical plant
released into the bay 1930s-1960s
About 2000 deaths and 10,000 ill1956 – “Minimata
disease”…..difficulty walking and speaking, convulsions
Cause was identified by 1958 – mercury in fish
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Grassy Narrows, Ontario
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Grassy Narrows - OntarioLate 1960sFirst Nations people experience
symptoms similar to Minimata (blurred vision, speech and hearing, tremors…)
Japanese doctors called in to helpSource: paper bleaching factory
(Dryden Pulp and Paper Company)Over 9000 kg of mercury was dumped
into the Wabigoon-English River system before ordered to stop in 1970
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http://archives.cbc.ca/environment/pollution/topics/1178/
http://www.cbc.ca/thenational/blog/2010/04/grassy-narrows-marred-by-mercury.html
http://www.cbc.ca/video/#/Shows/The_National/Environment/1290117620/ID=1461698083
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2. PCBsPolychlorinated BiphenylsUsed but never produced in
CanadaNot naturally occurring –
manufactured in U.S. 1929-1977
Versatile chemical – many usesResistant to acids and bases Resistant to heat
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Used as an insulating material in electric equipment, such as transformers and also in heat transfer fluids and in lubricants.
used in wide range of products such as plasticizers, surface coatings, inks, adhesives, flame-retardants, paints …
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Slow to break down – 2,000,000 tons produced – 10% remain in the natural environment
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Disposal – (e.g. decommissioned transformers) – must go to an approved storage site
23 sites in Ontario where they remain “in storage”
2011 – federal regulation is that by the end of this year, they are to be disposed of (probably by incineration)
Health effects – cancer, liver damage, nervous/immune system damage
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PCB storage site – South Etobicoke (Toronto)……notice in the background how close residential neighbourhoods are!
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PCBsCan
bioaccumulate – can be found in Ontario lake fish
refer to The Guide to Eating Ontario Sport Fish for consumption advice.
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