By Shana R. Spindler, PhD
How can you protect yourself and others from harmful substances? Some answers are obvious, like don’t swim in industrial waste. Beyond that, it becomes complicated. Should you wear sunscreen to protect your skin from UV rays, or avoid chemicals that make sunscreen effective? How about plastics? Fragrances? Flame-retardants?
Dr. Germaine M. Buck Louis has worked on this problem—specifically the role of environmental influences on reproduction—for 30 years. For the past two decades, she has focused on endocrine disruptors and currently serves as a senior investigator and Director of the Division of the Intramural Population Health Research. She began the NICHD Exchange meeting, “The Impact of Environmental Exposures on Human Health,” with a sampling of research in the field.
“Endocrine disruptors are an equal opportunity exposure,” Dr. Louis quipped. “Exposures are low…but they’re chronic and continual.”
To understand endocrine disruptor impacts, researchers measure these chemicals in each person and correlate chemical levels with disease presence or pregnancy outcomes. “A lot of the research is very new, and some of it is very crude,” cautioned Dr. Louis. For example, the estrogen-related disease Endometriosis has received a lot of attention from the research community, but the findings have been confusing and sometimes conflicting.
While it’s tempting to think about the effect of endocrine disruption on pregnancy as a female issue, Dr. Louis spent a significant portion of her talk convincing the audience that males play a role too. The LIFE study (Longitudinal Investigation of Fertility and Environment) has provided evidence that males serve as a driving factor in time-to-pregnancy. For example, male lead exposure is a factor of comparable magnitude to female age in relation to a woman’s ability to become pregnant. The work highlights the need to ensure both genders are represented in population-based fertility studies.
Dr. Dave Siegel, Program Director for Biodefense Research in the Obstetric and Pediatric Pharmacology and Therapeutics Branch, continued the meeting with his presentation: “Overview of the effects of select toxin exposure on the developing fetus and child.”
The growing fetus is exposed to many of the same environmental toxins as the mother, and changes in mom’s metabolism during pregnancy can affect toxin levels in the body. Once the baby is born, the child’s smaller size reduces the amount of toxin exposure required for an effect. Combined, these factors may have important outcomes. For example, children have an increased risk of Autism Spectrum Disorder (ASD) and Developmental Delay (DD) when living near farms applying organophosphate pesticides.
Nerve agents, such as those used during chemical warfare, are chemically similar to organophosphate pesticides. Following chemical attacks with a probable nerve agent in Moadamyah, Syria, researchers found increased miscarriage rates with head and spinal cord defects in the baby. Those findings underscore the importance of understanding environmental effects during pregnancy, when underlying physiological events may amplify the effects of chemical exposure.
In the final presentation of the event, Dr. Regina Bures of the NICHD Extramural Program examined measurement issues when assessing environmental impact on reproduction and developmental health. In her talk, “Moving targets: Population considerations of measuring environmental exposures,” she emphasized the ethical issues and complicating factors that impact the field.
Dr. Bures highlighted how researchers must remain sensitive to intentional dosing versus observation. For example, if a study offers a reward for living near pesticides, would the family have participated in the study without the reward? Environmental exposure studies, therefore, must turn to natural experiments, such as an economic recession, policy changes, and man-made or natural disasters.
Other complicating factors include the reality that human environments vary and people are mobile—potentially moving several times over the course of a study. Taking into account these naturally occurring variables is essential for accurate interpretation of data. To learn more about current population-based longitudinal studies, check out the Panel Study of Income Dynamics (PSID), the National Longitudinal Survey NLSY79, and the Fragile Families and Child Well-being study.
What was the take-away from the event? Research findings give cause for concern, and are cautionary but not yet conclusive. The main message being: do what you can to limit one's toxin exposure. A few practical tips offered during the question and answer session included: don’t microwave in plastic; be cognizant of potential heavy metals in your environment; and stay up-to-date with current research.
Awareness and materials change are not foolproof though: for those of you who look for 'BPA-Free' labels on your plastics, its replacement, BPS, may be far more toxic.