Two Critical Water Pollutants Affecting Human Health – Mercury and PCBs

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”)

MercuryVery rare in the Earth’s crustOnly metal that is liquid at room

temp.Uses: thermometers,

preservative in vaccines, dental fillings, mercury-vapour lamps……

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

Grassy Narrows, Ontario

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

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

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

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 …

Slow to break down – 2,000,000 tons produced – 10% remain in the natural environment

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

PCB storage site – South Etobicoke (Toronto)……notice in the background how close residential neighbourhoods are!

PCBsCan

bioaccumulate – can be found in Ontario lake fish

refer to The Guide to Eating Ontario Sport Fish for consumption advice.