Risks, Rights and Regulation
Communicating about Risks
and Infant Feeding
CONSEQUENCES OF EXPOSURE
Breasts are the parts of women's bodies where toxins are most concentrated. But they are also the parts of women's bodies under most stringent surveillance because they have been identified as risk-laden sites of virtual pathology (Morgan 1998:90). Future work on contaminant exposure will need to examine semen and testicles as closely as breastmilk and breasts. The breastmilk of women in industrialized countries, including Canada, has concentrations of PCBs and dioxins (probable carcinogens) higher than that of women in developing countries (depending where women live and work). Women in Vietnam, Turkey, Japan, and Taiwan have experienced high exposure through food contamination as a result of industrial accidents, described earlier. Chemicals that are readily metabolised and eliminated in mother's faeces and urine are unlikely to be secreted in significant quantities in breastmilk (Schreiber 1997:96). Those that are eliminated slowly are more likely to be detected. Detailed studies on consequences of contamination come from the Netherlands and North Carolina.
Some of the most exhaustive studies of contaminants in breastmilk were conducted on the general Dutch population, a population exposed to the heaviest industrial pollution in Europe. Even the most careful toxicological studies acknowledge the difficulties of measurement and comparability in determining toxicity levels. In the Dutch studies, only 80 of 105 breastmilk samples could be measured with sufficient accuracy for PCB?dioxin. Prenatal exposure to toxins was measured by breastmilk toxins because "dioxins and dioxin?like PCBs could only be measured in human milk" (Koopman-Esseboom 1996:701). Using breastmilk as a proxy for prenatal
exposure further complicates the task of separating pre from post?
Since most studies examine contaminants in the fat in breastmilk, it is important to note that fat content changes during the process of lactation, during a feed and throughout day and night, and with the age of the baby. For example, in the Dutch PCB/Dioxin study, representative 24-hour breastmilk samples were collected two weeks after delivery (Koopman-Esseboom 1996:701). A second study using the same data, found that although greater amounts of PCBs and dioxins are transferred during breastfeeding than in utero through transplacental transfer, lactational exposure to dioxins was not found to influence neurological condition in 18 month old toddlers; the authors concluded that although transplacental PCB passage has a small detrimental effect on neurological development in toddlers, breastfeeding had only a beneficial effect on fluency of movement (Huisman et al 1995). However, later studies examining the immunological effects found subtle differences in the capacity of children to fight off infections. Children of women with the highest levels of PCB exposure were most affected, compromising the immunological benefits of breastfeeding (Weisglas-Kuperus et al 2000).
In another Dutch study, the effects of low level concentrations of dioxins passed in utero and through breastmilk were studied in newborns. These laboratory studies confirmed that the liver of the newborn is affected by postnatal exposure to dioxins, and both intrauterine and postnatal exposure to dioxins might have subclinical effects on newborns. However, the authors state that the clinical significance of their findings is unclear (Pluim 1994:586).
Patandin et al (1999) explored the relative risk of PCB/dioxin exposure during breastfeeding and through food intake in the pre-school years. However, the breastfeeding data is complicated by the fact that the children were not exclusively breastfed; thus the accumulation of toxins will also reflect toxic exposure through water, cow's milk, infant formula and food in addition to breastmilk. They found that the main source of PCB and dioxins among the pre-school children were dairy products, followed by processed foods and meats (Patandin et al 1999:49). Although more than 10% of the cumulative toxic equivalent intake (TEQ) from birth until 25 years of age is due to breastfeeding (non?exclusive), the authors do not suggest limiting the duration of breastfeeding because of the general advantages of breastfeeding on the development of children; instead, they suggest: "Strategies should be directed toward reducing PCB and dioxin intake through the food chain at all ages and by lowering the consumption of animal products and processed foods, and not by discouraging breastfeeding" (Patandin et al 1999:51).
In a paper summarizing their theses research on the effects of exposure to contaminants, Lanting and Patandin concluded that ".no adverse effects of PCB and dioxin exposure were described via breastmilk. We even found a small beneficial effect of breastfeeding on the quality of movements in terms of fluency. This is in line with several other studies which also reported an advantageous effect of breastfeeding on brain development" (WECF 1999:11). However, they do suggest that PCBs and dioxins may negatively influence human lactation, and therefore call for efforts to diminish these hazardous substances (WECF 1999:12).
North Carolina Studies
Rogan and associates have provided evidence that only extreme levels of contaminants in breastmilk represent more of a hazard than a failure to breastfeed. Recently, Rogan (1996) reviewed a much larger range of clinical and epidemiological literature on pollutants in breastmilk than reviewed here. Although he exhaustively reports every industrial accident that might have affected lactating women, he concludes that PCBs in breastmilk do not produce readily detectable damage to breastfed infants, but there are subtle effects on motor function and memory from transplacental exposure (Rogan 1996:988). Links to breast cancer are also considered in the article, since a relation has been shown between higher fat diets and breast cancer; lactation decreases the body burden of these pollutants, and thus lowers the risk of cancer among pre-menopausal women (Rogan 1996:987).
PCBs are less potent carcinogens than dioxins, but occur at higher concentrations than other pollutants. There have been few long-term studies of the consequences for breastfed children exposed to PCBs through breastmilk. Rogan reviews in particular studies in Michigan where mothers likely consumed Great Lakes fish; studies in North Carolina where women faced no special exposure; and the Dutch studies discussed above. In spite of Rogan's conclusion that contaminants in breastmilk do not seem to damage breastfed infants, Rogan and Steingraber both state that breastmilk, if regulated like infant formula, would often violate FDA levels for deleterious substances in food and could not be sold (Rogan 1996:981). According to Steingraber:
...by 1976, roughly 25% of all U.S. breast milk was too contaminated to be bottled and sold as a food commodity, or exceeded the legal limit above which commercial
formula is pulled from the shelves. (Steingraber 1997:238)
Most breastfeeding advocates warn against rapid weight loss during lactation; however, a recent study of exclusively breastfeeding women from California and North Carolina suggests that moderate weight loss among women with a low exposure to environmental contaminants such as PCB and DDT does not increase the contaminant concentration in breastmilk. A woman with greater fat reserves will have a lower concentration of contaminants in her fat than a leaner woman. Since lactation reduces the overall body burden of contaminants, we would expect lower concentrations in milk in later lactation than early postpartum (Lovelady et al 1999:308). The North Carolina women were recent Hispanic immigrants from Mexico where pesticides, including DDT, are heavily used. The California group who lost weight did not increase the contaminant exposure of their infants. In the North Carolina group, there were no significant correlations between change in contaminant concentration and change in body weight (Lovelady et al 1999:313).
Consequences of Exposure
All living beings contain traces of PCBs; contaminants will be in the breastmilk of women who have not had occupational or known exposure. Since contaminants are in the air, they are also absorbed through lungs and skin. It is hard to separate in utero effects from postnatal effects; however, since intrauterine contamination occurs at critical earlier stages of fetal development and is unavoidable, it is critically important to draw attention to this time period. Prenatal
exposure is the most significant problem, as developmental toxicities are associated with prenatal, not postnatal, exposure (Korrick 1998). Most women with residues in their breastmilk have been exposed for years to chemical contaminants, including during their pregnancy (Berlin and Kacew 1997:73). However, levels of many of the pollutants found in breastmilk are falling.
Who may be at special risk? Women living near a waste disposal site, particularly one involved in accidental industrial spills, women who work with or consume high amounts of fish from contaminated lakes, and women who work with volatile chemicals. Breastfeeding is not advised and rarely possible for women who are going through chemotherapy, food poisoning, or toxic shock syndrome. There is no contraindication to breastfeeding for women exposed to herbicides, pesticides, mercury, cadmium, or low levels of lead (Lawrence 1997).
At the international level, FAO/WHO committees provide reference standards for pesticide residues, veterinary drugs used in food?producing animals, food additives and environmental contaminants which ? intentionally or unintentionally ? become components of food. They establish the ADI (acceptable daily intake). However ADI is not applicable to neonates and infants up to 12 weeks of age, according to a WHO standard established in 1987. "This threshold of exclusion has been arbitrarily set and is not purely scientifically based" (GEMS 1998:3). Since thresholds cannot be found by experimenting on humans, the establishment of standards will always be somewhat arbitrary. Thus, even the UN regulatory agencies acknowledge that more research is needed before the consequences of exposure to contaminants is fully understood. However, Steingraber reminds us that the need for more research does not equate with adjournment of action (2001:55).
In summary, there is agreement that all our bodies carry heavy contaminant loads from man-made chemicals; there is agreement that breastfeeding is indispensable for human growth and development. There is not complete agreement on the health effects of contaminants in breastmilk on children. Through some mechanisms-known and unknown-breastfeeding always has a positive impact on child health, since breastmilk strengthens the immune system. However, heavy loads of environmental contaminants may threaten our capacity to repoduce immune-strengthening breastmilk. Most would probably agree with the Canadian policy: "Health professionals advise that the known benefits of breastfeeding outweigh the potential risk of exposing infants to PCBs in human milk" (Guidotti and Gosselin 1999:154).
Risks, Rights and Regulation: Communicating about Risks
and Infant Feeding