A peer-reviewed open access journal published by the National Institute of Environmental Health Sciences

Telomeres are nucleoprotein structures that cap the end of chromosomes. They can consist of several thousands of tandem-repeated TTAGGG sequences.^1,2 With each cellular division, telomeres shorten. Telomere length (TL) has been associated with age-related diseases and mortality and is considered a marker of biological aging.^3-8 Telomere length is also associated with environmental and lifestyle factors that influence the oxidative stress and inflammatory status in humans, such as smoking,⁹ obesity,¹⁰ Mediterranean diet,¹¹ exposure to violence,¹² and life stress,¹³ which underscores the vulnerability of telomeres to reactive oxygen species (ROS). In a 2015 update of the Global Burden of Disease study, ambient particulate matter (PM) was ranked as the sixth most leading risk factor influencing public health worldwide.¹⁴ Increased oxidative stress and inflammation are proposed as underlying mechanisms through which PM may influence human health.^15,16 Exposure to air pollution during in utero life may have adverse effects on the fetus and neonate.^17-19 The ability of PM air pollution to generate ROS has led to the hypothesis that telomere attrition is influenced by air pollution exposure.²⁰ Occupational and population-based studies have described both positive and negative associations between different types of air pollution and TL in adults.^21-27 In general, long-term exposure to PM²⁵ and black carbon (BC)^24,26 are associated with shorter TL in adults. Because TL is highly variable at birth,^28,29 potential determinants, such as newborn sex,²⁸ paternal age,²⁸ maternal prepregnancy body mass index (BMI),²⁰ maternal stress,³⁰ maternal educational level,³¹ maternal smoking during pregnancy,³² and maternal residential proximity to a major road,³³ have recently been explored for explaining this phenomenon. In this regard, we hypothesized that exposure to PM air pollution during pregnancy may contribute to telomere setting at birth. Because in utero life is believed to be a critical time window in the early programming of diseases later in life,³⁴ unravelling the connection between prenatal air pollution exposure and TL at birth may help to gain new insights in the causes of diseases linked with telomere biological characteristics. In this study, we assessed the association between prenatal exposure to PM_2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) and TL at birth.

Objective: Studies on the association between short-term exposure to ambient air pollution and heart rate variability (HRV) suggest that particulate matter (PM) exposure is associated with reductions in measures of HRV, but there is heterogeneity in the nature and magnitude of this association between studies. The authors performed a meta-analysis to determine how consistent this association is. Data source: The authors searched the Pubmed citation database and Web of Knowledge to identify studies on HRV and PM. Study selection: Of the epidemiologic studies reviewed, 29 provided sufficient details to be considered. The meta-analysis included 18667 subjects recruited from the population in surveys, studies from patient groups, and from occupationally exposed groups. Data extraction: Two investigators read all papers and computerised all relevant information. Results: The authors computed pooled estimates from a random-effects model. In the combined studies, an increase of 10 μg/m³ in PM_2.5 was associated with significant reductions in the time-domain measurements, including low frequency (−1.66%, 95% CI −2.58% to −0.74%) and high frequency (−2.44%, 95% CI −3.76% to −1.12%) and in frequency-domain measurements, for SDNN (−0.12%, 95% CI −0.22% to −0.03%) and for rMSSD (−2.18%, 95% CI −3.33% to −1.03%). Funnel plots suggested that no publication bias was present and a sensitivity analysis confirmed the robustness of our combined estimates. Conclusion: The meta-analysis supports an inverse relationship between HRV, a marker for a worse cardiovascular prognosis, and particulate air pollution.