Published in PLOS One on 2026-05-13, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: Allison R Sherris, Priscillah Wanini Edemba, Anne M Riederer, Judy Adhiambo, Lewis Olweywe, Prestone Owiti, Catherine J Karr, John Kinuthia, Barbra A Richardson, Christopher D Simpson, Christopher Zuidema, Elizabeth Maleche-Obimbo, Sarah Benki-Nugent
Source: PLOS One • DOI 10.1371/journal.pone.0347486
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) has been linked to lower birth weight (BW) and shorter gestational age (GA) at delivery. Most research has focused on populations in high-income countries, leaving low- and middle-income countries (LMICs) understudied. We examined associations between pregnancy urinary PAH metabolites and birth outcomes in a prospective cohort in Nairobi, Kenya. The study population was drawn from women and their newborn babies enrolled in a pregnancy cohort. Third-trimester urinary mono-hydroxylated PAH metabolites (OH-PAH) were measured and infant BW and GA were ascertained using medical record abstraction and self-report; BW-for-GA z-scores were computed. Linear and modified Poisson regression models were used to estimate the effects of five OH-PAHs on birth outcomes; Weighted Quantile Sum regression was used to explore OH-PAH mixture effects. Among 353 mother-infant pairs, the median infant BW was 3.2 kg and 7.6% were born preterm. All OH-PAH metabolites were present in urine of >99% of mothers. Individual OH-PAH concentrations were not associated with BW or BW-for-GA z-scores. One metabolite, 2-hydroxyphenanthrene, was associated with shortened gestation (RR = −1.6 day per doubling in concentration, 95% confidence interval: −3.1, −0.1). This association was attenuated after adjusting for self-reported exposure to household fuel and outdoor combustion and was strengthened among female infants, but not male infants, in sex-stratified analyses. Other metabolites and the OH-PAH mixture were not associated with birth outcomes. Our findings suggest that exposure to 2-hydroxyphenanthrene may have a modest adverse effect on pregnancy duration, with potential sex-specific differences in association. No associations were observed for markers of fetal growth. These results highlight need for further studies on sex-specific vulnerabilities and the role of environmental co-exposures in impacting birth outcomes in LMICs.
1. Introduction
Polycyclic aromatic hydrocarbons (PAHs) are a class of air pollutants originating from the burning of organic materials including biomass, fossil fuels, and tobacco products, as well as charred foods [1]. Exposure to PAHs may occur through inhalation of gaseous PAHs or those bound to ambient particulate matter (PM), ingestion of grilled or charred food, and contact with polluted surfaces [2–4]. PAHs are categorized into high molecular weight (HMW) and low molecular weight (LMW) compounds, which have different metabolization and biological impacts. Exposure to both classes of PAHs is well-documented in the general population and among pregnant individuals in the United States [5–7], though fewer studies have characterized exposure in low- and middle-income countries (LMICs). The health effects of PAHs are of concern in LMICs where household combustion of solid and liquid cooking fuels, waste burning, traffic emissions, and industrial activities can contribute to high levels of household and ambient air pollution [8–11].
Reading this evidence
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© 2026 Allison R Sherris, Priscillah Wanini Edemba, Anne M Riederer, Judy Adhiambo, Lewis Olweywe, Prestone Owiti, Catherine J Karr, John Kinuthia, Barbra A Richardson, Christopher D Simpson, Christopher Zuidema, Elizabeth Maleche-Obimbo, Sarah Benki-Nugent. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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