Scientists gathered Jan. 14-15 in Washington, D.C., to discuss the human microbiome, or the bacteria, viruses, and fungi that live in or on human bodies, and how it may serve as an intermediary between people and the environment. The workshop, “Environment and Health: What’s the Human Microbiome Have to Do with It?,” was convened by the National Academy of Sciences (NAS) Standing Committee on Use of Emerging Science for Environmental Health Decisions.
NIEHS grantees from various scientific disciplines were among the speakers (see sidebar), including chair Helmut Zarbl, Ph.D., from Rutgers University. The overarching importance of microbes in environmental health was neatly summarized by Maria Dominguez-Bello, Ph.D., of New York University. “We are not directly exposed to the outside, but rather we are exposed through our bacteria,” she said. “These bacteria form an integral part of our bodies.”
The microbiome has many roles
Andrew Patterson, Ph.D., from Pennsylvania State University, proposed that the human microbiome could be the missing link in our understanding of why people respond differently to the same exposures in the environment. He noted that microbes in the gut digest food and process foreign chemicals, such as drugs, pesticides, and metals.
Many speakers discussed how the microbiome may influence health. Stephanie Shore, Ph.D., of Harvard University, described her lab’s research into how responses to ozone, a common air pollutant, can differ, based on an individual’s gut microbiome. Knowing that obese mice are more likely to have respiratory irritation from ozone, Shore found that if she introduced gut bacteria from obese mice into lean mice, the lean mice also became sensitive to ozone, although they did not become obese.
The microbiome is established early in life
According to Bello, the microbiome begins to develop during the birth process. She said that the most important source of the infant microbiome is the birth canal, which has evolved to provide the baby with necessary microbial organisms. Bello has shown that babies born by cesarean section do not have the same profile of organisms in their microbiome as babies born vaginally, which may contribute to differences in health throughout life.
Researchers at Dartmouth College are also studying the development of the infant microbiome (see text box, JAMA Pediatrics). Margaret Karagas, Ph.D., and her colleagues found that the infant microbiome changed when pregnant mothers ingested low levels of arsenic from food or drinking water. They also found that the babies exposed to arsenic in the womb experienced a greater risk of infections during the first year of life, including respiratory symptoms, diarrhea, and fever, which Karagas hypothesized may be related to changes in the microbiome.
“The broad expertise gathered at this workshop is crucial to understanding the complexity of the microbiome and the role it plays in how people respond to the environment,” said NIEHS and National Toxicology Program Director Linda Birnbaum, Ph.D., who attended the event. The importance of the microbiome in human health was underscored by interest in the workshop expressed by scientists from across the National Institutes of Health (NIH).
Citation: Farzan SF, Li Z, Korrick SA, Spiegelman D, Enelow R, Nadeau K, Baker E, Karagas MR. 2015. Infant infections and respiratory symptoms in relation to in utero arsenic exposure in a U.S. cohort. Environ Health Perspect; doi:10.1289/ehp.1409282 [Online 11 September 2015].
(Virginia Guidry, Ph.D., is a technical writer and public information specialist in the NIEHS Office of Communications and Public Liaison.)