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Science & Policy Update October 2014: Toxics

By: Martha Dina Arguello, Executive Director

Every year, for the last three years, PSR-LA has worked alongside Black Women for Wellness, the Iris Cantor-UCLA’s Women’s Health Center, and other women’s health and reproductive justice groups in order to set a research, policy, and health education agenda that speeds the transfer of academic research into community driven solutions and policy efforts. Through this convening of community advocates, researchers, and health professionals, we seek to promote policies that are upstream and precautionary, that act on early warnings and prevent exposures, reducing the health disparities associated with environmental health hazards.

This month, the journal Environmental Research published an article discussing the relationship between exposure to polycyclic aromatic hydrocarbons (PAHs) and preterm birth, a key indicator of population health. The annual costs associated with preterm birth in the United States were estimated to be at least $26.2 billion in 2005, or $51,600 per infant born preterm. PAH’s are important components of PM2.5 and PM10, criteria pollutants present in outdoor air pollution. The article, “Exposure to airborne polycyclic aromatic hydrocarbons during pregnancy and risk of preterm birth” reveals a possible association between PAH exposure during the last six weeks of pregnancy and preterm birth occurring at 20-27 weeks.

Polycyclic aromatic hydrocarbons are chemicals typically found in groups of two or more – both man-made and naturally occurring – that are created during the incomplete combustion of products such as coal, oil, gas, and garbage. PAHs are considered ubiquitous in the environment. In mice, exposure to PAH’s at high levels is associated with tumor growth, birth defects, reproductive harm, and low birth weight. Many studies have found links between criteria pollutants and preterm birth, including one that suggested that more accurate air monitoring data could shed further light on the association.

This study examines ambient PAH’s that result in the environment from automobile exhaust and industrial emissions, evaluating the associations between exposure to these PAHs at certain points of pregnancy and preterm birth in Fresno, California between the years 2001 and 2006. Home to some of the worst air quality in the state and the nation, Fresno also has the dubious distinction of having the highest rates of preterm births in California. In 2010 that was 1,940 preterm births, or 13.2% of all live births in the city. Fresno is also ranks high in adverse health outcomes such as premature mortality and asthma.

Utilizing comprehensive spatio-temporal modeling of PAHs over the course of six years in a highly exposed region of the United States, the study looks at single births between 20 and 42 weeks gestation, and birth weight between 500 and 5000 grams. The exposure assessment was done by using a combination of data to put together a spatio-temporal model in order to indicate daily PAH exposure levels at the site of maternal residences. Covariates considered in the analysis include infant birth weight, maternal age, maternal race/ethnicity, maternal education, and prenatal care – all of which are important cofactors in preterm birth.

Though the authors note potentially confounding exposure misclassifications, the study shows an association between elevated levels of PAHs during the last six weeks of pregnancy and early preterm birth. The risk of preterm birth was also found to increase with greater exposure to PAHs.

The results of this study, along with many others preceding it, provide a clear warning that without aggressive steps taken to curb emissions from the burning of hydrocarbons, it will be very difficult to reduce the economic and human costs associated with preterm birth. As we develop policy recommendations for reducing the burden of preterm birth, we should also consider how improved regulation and enforcement of existing clean air laws are an important component of our strategy. When done right, environmental policy is also health policy.