The health Canada Great Lakes multigeneration study--summary and regulatory considerations

The Health Canada Multigeneration Study was initiated to determine the consequences in rodents consuming diets containing Lake Ontario (LO) or Lake Huron (LH) chinook salmon over successive generations. Following lyophilization, the contaminant levels in the salmon used in the formulation of the diets for this study exceeded a number of tolerances or guidelines established for contaminants in commercial fish and seafood products (PCBs, dioxin, mirex, chlordanes, mercury). Consumption of the fish diets by rats of two consecutive generations resulted in a variety of effects that can be described as adaptive responses or of limited biological significance. The two exceptions to this were (1) the suggestion of modification of working and reference memory in males of the high-dose groups 20% fish diets, which may have been related to decreases noted in neurotransmitters in several brain regions in these rats; and (2) an effect on thymus weights noted in the high-dose first generation (F1) reversibility study animals and an overall effect on T-helper/inducer lymphocyte subset numbers in the second generation (F2) male rats fed the LH diets compared to the LO diets. Relatively minor effects were observed in the rats consuming the 5% fish diets from either Great Lakes location (LH-5, LH-5), although their fish intake was approximately 16-fold greater on a daily basis than the average angler consuming Great Lakes sport fish (compared to a 60-fold greater intake in the 20% diet groups: LH-20, LO-20). Based on these study results with rats it would appear that for the average consumer of Great Lakes sports fish, the risk presented by the complex mixture of contaminants in chinook salmon collected from these two locations in the Great Lakes basin could be considered minimal, especially if sport fish consumption advisories are followed.