Published online: April 5, 2019
Fine particulate matter, also known as particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5), has long been suspected to trigger asthma development and acute exacerbation. A few epidemiological studies have examined the associations of PM2.5 during pregnancy with childhood asthma; however, the existing studies generally used average concentrations of PM2.5 for the entire pregnancy or the three specific trimesters as exposure matrices. Lung development is a multi-stage process from conception to adolescent and early adulthood. For elucidating the plausible mechanism of PM2.5 and exploring vulnerable periods, studies with finer temporal resolution are required.
In a study recently published in The Journal of Allergy and Clinical Immunology (JACI), Jung and colleagues investigated the effects of weekly PM2.5 during pregnancy and infancy period on childhood asthma in a populous city in Taiwan with heavy air pollution. The authors used a birth cohort which recruited more than 180,000 children born from 2004 to 2011 and has been followed until the end of 2014. They applied a daily satellite-based hybrid model to estimate PM2.5 concentrations. A Cox proportional model with a distributed lag non-linear model (DLNM) was leveraged to examine the associations of asthma with PM2.5 during pregnancy and the first year after birth on a weekly basis.
The authors found that exposure to PM2.5 within gestational weeks 6–22 and within 9–46 weeks after birth was positively associated with the increased risk of asthma. They also examined the threshold of PM2.5 exposure for asthma. For the pregnancy period, the risk of asthma increased remarkably at PM2.5 above 93 µg/m3. The threshold of PM2.5 in the infancy period was much lower than in the pregnancy period. The risk of asthma remained significant and positive between PM2.5 of 26–72 μg/m3 and increased sharply at PM2.5 above 73 μg/m3.
The authors’ findings revealed that the vulnerable periods may be within the early- and mid-gestation, coinciding with the embryonic, pseudoglandular, and canalicular stages, and the first year after birth. They suggest that sensitive groups, pregnant women and infants, should stay indoors or avoid outdoor activities to reduce their health risks from exposure to particulate matter during these periods.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.