U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Environmental Factor

Environmental Factor

Your Online Source for NIEHS News

April 2018

Ferguson examines phthalate–preterm birth link in public webinar

NIEHS epidemiologists Kelly Ferguson and Amy Padula presented a free webinar exploring links between chemical exposures and preterm birth.

Kelly Ferguson Ferguson pairs epidemiological methods with mechanistic studies to reveal how an exposure may lead to an observed adverse birth outcome. (Photo courtesy of The University of Michigan)

NIEHS epidemiologist Kelly Ferguson, Ph.D., joined Amy Padula, Ph.D., from the University of California at San Francisco (UCSF) to present a free webinar March 1 for the Collaborative on Health and the Environment (CHE). Ferguson and Padula explored how phthalate and air pollution exposures, respectively, are linked to birth outcomes. The presentations emphasized that although the precise cause of preterm birth is unclear, increasing evidence implicates environmental contaminants.

Ferguson and Padula are two of 20 environmental health researchers named by CHE as pioneers to watch. CHE invites each researcher to present a public webinar, available free on the CHE website. With webinars and other educational activities, the nonprofit aims to eliminate environmental risks and protect the health of children, families, and communities.

Ferguson leads the Perinatal and Early Life Epidemiology Group. Padula is an assistant professor in the Program for Reproductive Health and the Environment at UCSF School of Medicine and a recipient of the National Institutes of Health Pathway to Independence award.

Maternal exposure to phthalates

Ferguson studies environmental factors that can affect the course of a pregnancy. “[Such factors are a] major public health priority for policymakers, and for gynecologists and obstetricians,” she said.

Focusing on a class of chemicals called phthalates, which are used to soften plastic and in other applications, Ferguson demonstrated a link between phthalate exposures and preterm birth. She used a technique called mass spectrometry to measure these compounds in urine samples from pregnant women.

Additional research focused on how oxidative stress resulting from phthalate exposure might be involved in preterm births. In future studies, she hopes to look at the exposure of mixtures of compounds.

Air pollution and preterm birth

Amy Padula Padula researches perinatal and environmental epidemiology, traffic-related air pollution exposure, endocrine-disrupting chemicals, adverse birth outcomes, social factors, and gene-environment interactions. (Photo courtesy of Amy Padula)

Padula addressed air pollution and preterm birth outcomes in California, especially exposures to carbon monoxide, nitrogen dioxide, and particulate matter. She looked at people in California who were exposed to high levels of air pollution and found that mothers with higher exposures were at higher risk for preterm birth.

She said she hopes to extend her studies by investigating whether there is a link between air pollution and diabetes and hypertension in pregnancy.

“Air pollution is regulated by the U.S. Environmental Protection Agency [EPA] and California EPA,” she pointed out. For more than 40 years, regulations under the Clean Air Act have set standards for acceptable levels of air pollutants. As scientific studies have demonstrated health effects at lower and lower levels, the standards and subsequent air pollution have been lowered.

Looking to the future

Following the presentation, there was an opportunity for viewers to ask questions. In answer to a question on why phthalates are more prominent in the U.S. versus other countries, Ferguson explained that there might be differences in exposure sources.

Padula was asked about the relationship between pesticides and preterm birth. She said her team did not find any associations but suggested that perhaps those who are exposed to pesticides did not get pregnant or had early loss.

Both speakers emphasized that reducing the risk of preterm birth is a difficult task that policy changes would help to achieve.

Ferguson KK, Chen YH, VanderWeele TJ, McElrath TF, Meeker JD, Mukherjee B. 2017. Mediation of the relationship between maternal phthalate exposure and preterm birth by oxidative stress with repeated measurements across pregnancy. Environ Health Perspect 125(3):488−494.

Ferguson KK, McElrath TF, Chen YH, Mukherjee B, Meeker JD. 2015. Urinary phthalate metabolites and biomarkers of oxidative stress in pregnant women: a repeated measures analysis. Environ Health Perspect 123(3):210–216.

Ferguson KK, McElrath TF, Ko YA, Mukherjee B, Meeker JD. 2014. Variability in urinary phthalate metabolite levels across pregnancy and sensitive windows of exposure for the risk of preterm birth. Environ Int 70:118–124.

Ferguson KK, McElrath TF, Meeker JD. 2014. Environmental phthalate exposure and preterm birth. JAMA Pediatr 168(1):61−68. (Summary)

Ferguson KK, McElrath TF, Pace GG, Weller D, Zeng L, Pennathur S, Cantonwine DE, Meeker JD. 2017. Urinary polycyclic aromatic hydrocarbon metabolite associations with biomarkers of inflammation, angiogenesis, and oxidative stress in pregnant women. Environ Sci Technol 51(8):4652−4660. (Summary)

Padula AM, Mortimer KM, Tager IB, Hammond SK, Lurmann FW, Yang W, Stevenson DK, Shaw GM. 2014. Traffic-related air pollution and risk of preterm birth in the San Joaquin Valley of California. Ann Epidemiol 24(12):888–895.e4.

Padula AM, Noth EM, Hammond SK, Lurmann FW, Yang W, Tager IB, Shaw GM. 2014. Exposure to airborne polycyclic aromatic hydrocarbons during pregnancy and risk of preterm birth. Environ Res 135:221–226.

(Salahuddin Syed, Ph.D., is an Intramural Research Training Award fellow in the NIEHS DNA Replication Fidelity Group.)

Back To Top