Consumption of Contaminated Lake Fish and Reproduction

In this issue, Buck et al1 report an association between time-to-pregnancy and the consumption of Lake Ontario fish by women who were attempting to become pregnant. Others have documented levels of lipophilic compounds such as dioxin, mirex, and polychlorinated biphenyls (PCBs) in fish from the Great Lakes, and these are among the toxic agents that might be responsible for the observed association. It can be determined from the plotted data for time-to-pregnancy that about 85% of the most heavily exposed group, ie, those with 7 or more years of consumption of Lake Ontario fish, became pregnant within the 1st year of trying. 1 While one must sympathize with parents who may have trouble conceiving or, ultimately, may not be able to conceive because of exposure to toxins in lake fish, there should also be concern for parents who successfully conceive and deliver infants who have been heavily exposed to these compounds. Jacobson et al have demonstrated that prenatal exposure to PCB can reduce visual recognition memory during infancy 2 and lower full-scale and verbal IQ scores at 11 years of age, especially in the domains of attention and memory. 3 The most heavily exposed children in their study 3 were several times as likely to have low average IQ scores and twice as likely to be 2 or more years behind in reading comprehension. Buck et al1 cite evidence that many sports fishermen claim to be unaware of the advisories against consumption of Lake Ontario fish by women of childbearing age. One wonders how many more are unaware of the evidence that such exposure could cause damage to their developing infants and children through mother’s consumption of lake fish. In addition to exposing the developing fetus during intrauterine life, these lipophilic compounds are also transmitted to the developing infant postnatally through consumption of mothers’ milk. Fortunately, the postnatal transfer of PCBs through human milk has not been associated with deficits in memory and attention during infancy nor at 11 years of age. 2,3 Nevertheless, serum PCB levels at 4 years of age, attributable to duration of breast feeding, were associated with reduced activity. 4 Clearly, milk from women who consume contaminated fish will expose the next generation to the effects of these environmental toxins, most of which are probably not known. As Buck and colleagues 1 note, there have been advisories against the consumption of Lake Ontario fish by women of reproductive age issued by New York State since 1976. Worldwide, human milk samples have shown a continual decline in polyhalogenated, aromatic hydrocarbons during the past decade. 5 Based on this evidence, the WHO working group concluded provisionally that current evidence did not warrant altering previous recommendations for promotion and support of breast feeding. 5 The Committee on Nutritional Status During Pregnancy and Lactation of the Food and Nutrition Board in the U.S. suggests that DDT, PCB, and mercury levels should be measured in mother’s milk and blood and that decisions to breast feed should be made on an individual basis. 6 Lake fish and human milk are excellent sources of dietary DHA, 7,8 an essential fatty acid in fetal and neonatal neurodevelopment. 9 Preterm infants fed experimental formulas with DHA have higher visual function 10–12 and appear to have more mature attentional development. 13,14 The latter evidence was obtained during administration of the same test used by the Jacobson et al2 to demonstrate poorer visual recognition memory in infants after intrauterine exposure to PCB. Diets that reduce brain DHA accumulation affect monoaminergic neurotransmission 15 and behavior. 16 Ironically, both sources of DHA are now thought to be undesirable for human consumption in some circumstances. In the long run, science may be able to offer some solutions to the problem of environmental contamination of the aquatic food chain and determine ways to reduce body burden of these compounds in women who have previously been exposed. In the meantime, however, additional efforts to increase public awareness of the problems associated with eating contaminated fish appear to be long overdue.

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