LAUSR

The infant diet is typically limited to breast milk and/or infant formula for the first months of life. Yet relatively little is known about the environmental chemicals present in these foods and their potential shortand long-term effects on health. In two systematic reviews published in Environmental Health Perspectives,12 Geniece Lehmann of the U.S. Environmental Protection Agency, Judy S. LaKind of LaKind Associates, LLC, and colleagues identified points where better-designed studies would help characterize infant exposures via breast milk and formula, as well as improve risk assessment. More than 40,000 chemicals are currently in use in the United States. Pregnant women and infants may be exposed to chemicals in their environment via oral, inhalation, or dermal routes; there is also some risk of transplacental chemical exposures. Even for the small subset of environmental chemicals that are well studied, the effects of early life exposures are often unclear. “There are substantial gaps in our understanding of what chemicals, as well as what levels of them, would be concerning [for infants],” says Suzan Carmichael, a perinatal and nutritional epidemiologist at Stanford University, who was not involved with the reviews. Most of what we suspect, she says, is extrapolated from animal and adult data. Breast milk is a dynamic mixture of fats, sugars, and proteins, with compositional changes occurring both throughout a single feeding and over the course of lactation. The complex chemistry of breast milk makes it especially difficult for scientists to study its load of environmental chemicals, says Benedikt Warth, an analytical food chemist at the University of Vienna, who also was not involved in the reviews. It becomes even more challenging when researchers move from targeted studies of samples, which measure levels of specific compounds, to untargeted chemical screening, which tries to determine all chemicals present. During lactation, a woman’s body mobilizes its adipose stores to produce fat-rich milk. That means that fat-soluble chemicals stored in the mother’s adipose tissue can be passed into her milk and on to her infant. Persistent organic pollutants, such as polychlorinated biphenyls, dioxins, and polybrominated biphenyl ethers (PBDEs), are especially likely to be transmitted this way, Lehmann says. But non–fat-soluble chemicals may still end up in breast milk. For example, perand polyfluoroalkyl substances