Heatwaves and PM2.5: Sometimes-Surprising Associations with Preterm Birth

Abstract

Extreme heat is linked to higher mortality from a variety of causes ranging from heart disease to heat stroke. 1,2 Climate change is not only raising the global temperatures-with local areas experiencing extreme heatwaves-it may also cause a deterioration in air quality by altering the behavior of primary pollutants and the formation of secondary pollutants. 3,4 A retrospective cohort study published in Environmental Health Perspectives looked at the relationship between fine particulate matter (PM 2:5) combined with heatwaves and the risk of preterm birth in Guangzhou, China. 5 Heat and air pollution have each been independently associated with increases in the risk of preterm birth (fewer than 37 weeks of gestation). 6,7,8 Although findings have not been conclusive, some past studies showed that extreme heat and air pollution may work synergistically to increase mortality, particularly from cardiovascular and respiratory conditions. 9,10 However, the combined effects of heat and pollution on premature birth are even less certain. Complications of preterm birth are a leading cause of mortality among children under 5 years of age, especially in developing countries, causing approximately 1 million deaths in 2015. 11 Using birth registry data, the authors of the new paper looked at 215,059 singleton live births in Guangzhou that occurred during the warm season (May through October) in 2015, 2016, and Environmental Health Perspectives 094002-2 128(9) September 2020

Preterm Labor, a Syndrome Attributed to the Combination of External and Internal Factors

“…However, a number of studies showed that exposure to air pollution (PM2.5), ozone, and heat was associated with increased risk of preterm birth 9 . Heat and air pollution are independent risk factors of preterm birth 10,11 . Many chemical contaminants, such as nitrate, diisobutyl phthalate metabolites, bisphenol-S, and ethyl paraben have been found to be risk factors for sPTL, 12–14 while 2, 5-dichlorophenol is inversely correlated with overall PTL 14 …”

“…9 Heat and air pollution are independent risk factors of preterm birth. 10,11 Many chemical contaminants, such as nitrate, diisobutyl phthalate metabolites, bisphenol-S, and ethyl paraben have been found to be risk factors for sPTL, [12][13][14] while 2, 5-dichlorophenol is inversely correlated with overall PTL. 14…”