International Joint Commission

elugawhalefood web, they haveto beconsidered asa possible aetiologicalfactorforthe high
frequency of tumors seen in this population. The occurrence of benzo(a)pyrene (BaP) adducts
in the DNA of the brains of three beluga whales provides incontrovertible evidence that these
particular animals had been exposed to BaP and had metabolized it to the carcinogenic form,
which subsequently became covalently bound to the DNA of brain tissue. DNAadducts are an
integral part of the process that culminates in overt malignancy.
The source of the organochlorine contaminants has been more difficult to locate,
however, the presence of Mirex in the whales indicated that a substantial proportion of the
organochlorinechemicals must originate from Lake Ontario since Mirex was manufactured by
Hooker Chemical at Niagara Falls, New York. The most likely vector for these organochlorine
chemicals is the American eel (Anguila rostrata), which seasonally migrates from the Great
Lakes, down the St. Lawrence Riverto the Gulf and out into the Sargasso Sea (Dutil et al. 1985;
Beland and Martineau, 1988). An initial indication that there were extremely high levels of
organochlorine contaminants in belugas was obtained in 1970 when a juvenile was collected
that contained 827 ppm DDTand 800 ppm PCB in the body fat (Sergent 1980). Since then many
samples have been analyzed that show that: a) males have higher levels than females, which
tend to lose organochlorinechemicalsthrough lactation, and b) organochlorine levels increase
with age (Martineau et al. 1987). These animals contained among the highest levels of these
pollutants ever recorded for cetacean samples taken anywhere in the world (Wagemann and
Muir, 1984; Martineau et al. 1987). Martineau et al. (1988) concluded that conditions such as
gastric ulcers, squamous metaplasia of mammary glands, histological evidence of activity in
the mammary glands of two immature animals and probable immunosuppression in three
animals are consistentwith chronic organochlorine toxicity. Consequently, it issuggested that
contamination by organochlorine compounds is contributory to diseases of the St. Lawrence
beluga whales, thus helping to explain the failure of the population to have recovered after the
end of commercial hunting a few decades ago.
The levels of PCBs in males collected in 1988-89 (107 71 mg/kg wet weight) were
significantly lower (p