3 - International Joint Commission

tions of chemicals in water and suspended particulates can vary considerably
over short periods of time.
Much of the historical data on dissolved metals in water from the open
lakes have recently been questioned. Metals are ubiquitous and found in
sampling platforms such as boats, and in dust from laboratories. This
suggests that samples could have been contaminated, particularly with lead
and cadmium. The bottom sediment and most suspended solids chemical
data which follow are reliable. Sectioned, radiodated sediment cores have
shown long term trends in chemical inputs to the lakes. These trends can be
extended to pre-industrial and even pre-colonial periods. Bearing in mind
these problems, two types of chemicals are discussed in this report:
1) Toxic chemicals for which there is a reasonably extensive data base.
They include lead, mercury, cadmium, and arsenic, DDT and
metabolites, dieldrin, BHCs, HCB, dioxins, and PCBs .
2) Toxic chemicals for which there is a geographically restricted data
base. Such chemicals include: chlorobenzenes (e.g., Lake Ontario):
toxaphene (e.g., Lake Superior): octachlorostyrene (OCS)(e.g., Lake St.
Clair): mirex (e.g., St. Lawrence River): chlorinated volatile organics
(e.g., the lower Great Lakes and connecting channels): and PAHs (e.g.,
western Lake Erie).
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