3 - International Joint Commission

chemicals in the lakes is also governed by the physicochemical characteristics
of the chemicals. These include solubility, volatility. hydrophobicity,
lipophilicity, the degree of partitioning onto suspended solids, and the
susceptibility to photo- and biodegradation. Once released to aquatic
ecosystems, some chemicals rapidly disappear by degradation or
volatilization to the atmosphere. Chemicals degradation can take place by a
variety of chemical and biological processes including hydrolysis, photolysis,
and bacterial or fungal dechlorination. Even short lived chemicals can be
highly toxic while they are in the water column.
1.2 MAIN CHEMICALS OF CONCERN
Concern about the contamination of the Great Lakes have focused on
persistent toxic chemicals. Toxic metals include lead, mercury, cadmium and
arsenic, and persistent toxic organic chemicals include chlorinated pesticides
such as DDT and mirex, chlorinated benzenes, chlorinated dioxins and
furans, and PCBs.
In 1983, the IJC published a comprehensive inventory of chemical
substances identified in the Great Lakes ecosystem. The 1986 working list
of chemicals in the Great Lakes basin (IJC Comprehensive Track chemicals)
was produced from this inventory. It contains 362 chemicals (IJC 1987b).
Of these chemicals, 11 critical pollutants were chosen by the IJC for its
Primary Track. Information used in deriving priority lists tends to include
chemical stability leading to persistence in the environment, the quantities
in use, the types of use, the tendency to accumulate in living organisms, and
the biological effects associated with acute or chronic exposure (Hamilton et
al., 1987). In this report, all of the Primary Track chemicals are discussed
as well as several of the Comprehensive Track chemicals.
In Canada, there are several sets of objectives and guidelines established
for concentrations of toxic chemicals in water. TWO of these are shown
in Table 2. When developing and using guidelines for the protection of
aquatic life, there should be complete information on the parameter of
concern, including its form and fate in the aquatic environment, quantitative
exposure/effect relationships, and its fate within organisms over awide range
of exposure concentrations. The relevant information base for a particular
chemical is rarely complete. In general, water quality guidelines used in