Acute air pollution and temperature exposure as independent and joint triggers of spontaneous preterm birth in New South Wales, Australia: a time-to-event analysis

Tanya Singh; Bin Jalaludin; Shakoor Hajat; Geoffrey G Morgan; Katrin Meissner; John Kaldor; Donna Green; Edward Jegasothy

doi:10.3389/fpubh.2023.1220797

Acute air pollution and temperature exposure as independent and joint triggers of spontaneous preterm birth in New South Wales, Australia: a time-to-event analysis

Front Public Health. 2023 Nov 30:11:1220797. doi: 10.3389/fpubh.2023.1220797. eCollection 2023.

Authors

Tanya Singh^{1

2}, Bin Jalaludin^{3

4}, Shakoor Hajat⁵, Geoffrey G Morgan^{6

7

8

9}, Katrin Meissner^{1

2}, John Kaldor¹⁰, Donna Green^{1

2}, Edward Jegasothy^{6

7}

Affiliations

¹ Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia.
² Australian Research Council Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia.
³ School of Population Health, University of New South Wales, Kensington, NSW, Australia.
⁴ Ingham Institute for Applied Medical Research, University of New South Wales, Sydney, NSW, Australia.
⁵ Centre on Climate Change and Planetary Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.
⁶ School of Public Health, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia.
⁷ University Centre for Rural Health, Faculty of Medicine and Health, University of Sydney, Lismore, NSW, Australia.
⁸ Healthy Environments and Lives (HEAL) National Research Network, Australian National University, Canberra, ACT, Australia.
⁹ Centre for Air Pollution, Energy and Health Research (CAR), Glebe, NSW, Australia.
¹⁰ Kirby Institute, University of New South Wales, Sydney, NSW, Australia.

Abstract

Introduction: Exposure to high ambient temperatures and air pollution has been shown to increase the risk of spontaneous preterm birth (sPTB). Less clear are the effects of cold and the joint effects of air pollution and temperature.

Methods: Using a Cox proportional hazard regression model, we assessed the risk of independent and combined short-term exposure to ambient daily mean temperature and PM_2.5 associated with sPTB in the last week before delivery on overall sPTB (weeks 23-36) and three subtypes: extremely sPTB, very sPTB, and moderate-to-late sPTB for a birth cohort of 1,318,570 births from Australia (Jan 2001-Dec 2019), while controlling for chronic exposure (i.e., throughout pregnancy except the last week before delivery) to PM_2.5 and temperature. The temperature was modeled as a natural cubic spline, PM_2.5 as a linear term, and the interaction effect was estimated using a multiplicative term. For short-term exposure to temperature hazard ratios reported are relative to the median temperature (18.1°C).

Results: Hazard ratios at low temperature [5th percentile(11.5°C)] were 0.95 (95% CI: 0.90, 1.00), 1.08 (95% CI: 0.84, 1.4), 0.87 (95% CI: 0.71, 1.06), and 1.00 (95% CI: 0.94, 1.06) and greater for high temperature [95th percentile (24.5°C)]: 1.22 (95% CI: 1.16, 1.28), 1.27 (95% CI: 1.03, 1.57), and 1.26 (95% CI: 1.05, 1.5) and 1.05 (1.00, 1.11), respectively, for overall, extremely, very, and moderate-to-late sPTBs. While chronic exposure to PM_2.5 had adverse effects on sPTB, short-term exposure to PM_2.5 appeared to have a negative association with all types of sPTB, with hazard ratios ranging from 0.86 (95th CI: 0.80, 0.94) to 0.98 (95th CI: 0.97, 1.00) per 5 μg/m³ increase in PM_2.5.

Discussion: The risk of sPTB was found to increase following acute exposure to hot and cold ambient temperatures. Earlier sPTB subtypes seemed to be the most vulnerable. This study adds to the evidence that short-term exposure to ambient cold and heat and longer term gestational exposure to ambient PM_2.5 are associated with an elevated risk of sPTB.

Keywords: air pollution; ambient temperature; environmental epidemiology; environmental health; perinatal; preterm birth; survival analysis.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / adverse effects
Air Pollution* / analysis
Australia
Female
Humans
Infant, Newborn
New South Wales / epidemiology
Particulate Matter / adverse effects
Particulate Matter / analysis
Pregnancy
Premature Birth* / epidemiology
Premature Birth* / etiology
Temperature

Substances

Air Pollutants
Particulate Matter