The study by Yao et al.¹ in this issue of Environmental Health Perspectives advances our understanding of infant exposures to per- and polyfluoroalkyl substances (PFAS). They note that “it is essential to provide a national baseline of PFAS exposure in human milk … and to assess the risks of emerging and legacy PFAS exposure in exclusively breastfed infants.” It is impossible to argue with that point, and in fact for years my colleagues and I have made similar calls for national breast milk monitoring programs.² Although several countries have developed national programs to assess human exposures to environmental chemicals using blood and urine (among them the U.S. National Health and Nutrition Examination Survey, the Canadian Health Measures Survey, the European Human Biomonitoring Initiative, the China National Human Biomonitoring study, and the Korean National Environmental Health Survey), similar efforts around breast milk are lacking. Why is this and what does it mean for infants?

Why Are There No National Breast Milk Monitoring Programs?

Some breast milk monitoring programs have been undertaken to assess levels of persistent lipophilic chemicals (e.g., dioxins and furans).^3–6 These programs served important purposes such as assessing temporal and geographic variability and informing individual women about their breast milk chemical levels. However, most women did not—and do not—have access to programs such as these.

One obvious reason for not undertaking large-scale breast milk monitoring programs would be the cost and complexity associated with setting up and maintaining such an effort. But there are likely additional reasons. For example, the robust scientific evidence regarding breastfeeding-related benefits to both the mother and infant^7,8 makes it difficult to have a conversation about potential risks associated with chemicals in breast milk. The need for thoughtful communications regarding environmental chemicals in breast milk has been described.⁹ In fact, early in my research in this area I was admonished by lactation consultants and others working to improve breastfeeding rates for unintentionally using language that could scare women away from breastfeeding. I took this feedback seriously and modified how I communicate with mothers, physicians, risk and exposure scientists, and others.

Another factor that may be at play is our general inability to place the measured levels of chemicals into a risk-based context. Breastfeeding presents a unique exposure–risk situation in that exposures are of relatively short duration but occur during an exquisitely sensitive life stage. Available risk-based approaches do not generally offer guidance values specific to this circumstance. I would argue that this combination of factors has limited the will to create either national breast milk monitoring programs or on-request analyses of breast milk samples, at least in the United States.

What Does This Mean for Breastfeeding Infants?

Yao et al.¹ state that “further epidemiological studies are needed to demonstrate whether breastfeeding with contaminants has adverse health outcomes on newborns.” It is hard to disagree with the sentiment. For many legacy chemicals, we have several decades’ worth of epidemiologic studies on this subject.^10–13

However, in the case of PFAS and infant nutrition, the approach of waiting for robust epidemiological study results is unsatisfactory. Legacy PFAS have been detected in breast milk and drinking water at levels exceeding various guidance values^1,14,15; furthermore, emerging PFAS are commonly detected in breast milk.¹ The data are too sparse to make general statements about PFAS in infant formula. However, because some infant formulas require reconstitution with water, PFAS intakes above levels of concern cannot be ruled out. Thus, our current risk-based approaches already suggest that action—not waiting—is needed.

Monitoring and Guidance Values Are Needed Now

It has been noted time and time again that infants are our most vulnerable citizens. How can we in good conscience support waiting the many years it will take to complete epidemiological studies while being aware that risk-based approaches indicate that monitoring is needed for today’s generation of infants and children?

A PFAS monitoring program for infant nutrition is long overdue. In addition, we need health-based guidance values for infant PFAS exposures for the myriad of legacy and emerging PFAS—not just the four drinking water screening values that the U.S. Agency for Toxic Substances and Disease Registry has developed. At the very least, people should be aware of the levels of PFAS their children may be exposed to via breastfeeding, tap water, and infant formula to begin to make informed decisions.

We have known about lactational transfer of PFAS for over two decades and about the presence of PFAS in drinking water for just as long. How is it that we still cannot answer the most basic questions regarding PFAS and infant exposure and health? Although scientists—myself included—are trained to be circumspect and to wait for sufficient scientific information to give us confidence in the accumulated evidence before calling for action, we have waited long enough.