Metals and sulfate in air pollution mixture may contribute most to asthma hospitalizations

A recent study led by Harvard T.H. Chan School of Public Health has shed light on the components of fine particulate air pollution (PM2.5) that have the strongest association with asthma hospitalization. The study found that metals, particularly nickel and vanadium, along with sulfate particles, are the main contributors to the link between long-term exposure to air pollution and hospitalization among asthma sufferers.

According to Joel Schwartz, professor of environmental epidemiology and corresponding author of the study, the specific compounds in the PM2.5 mixture play a crucial role in exacerbating asthma symptoms. The study, published in the American Journal of Respiratory and Critical Care Medicine, identified various pollutants composing PM2.5 and examined their collective impact on asthma exacerbation.

Previous studies have mainly focused on the relationship between asthma and individual pollutants or PM2.5 as a whole. However, this study took a middle-ground approach by identifying compounds such as bromine, calcium, copper, elemental carbon, iron, potassium, ammonium, nickel, nitrate, organic carbon, lead, silicon, sulfate, vanadium, and zinc as the components of PM2.5. Machine learning algorithms were used to estimate the annual levels of each compound at a U.S. zip-code level.

The researchers analyzed data from state inpatient databases to determine the total number of asthma hospitalizations in 11 states between 2002 and 2016. Controlling for variables such as outdoor temperature and socioeconomic status, the study revealed that nickel, vanadium, sulfate, nitrate, bromine, and ammonium were the compounds that contributed the most to asthma hospitalizations.

Schwartz emphasized the importance of better controlling these sources of air pollution to reduce asthma hospitalizations. For example, nickel and vanadium are produced from burning fuel oil, while sulfates come from coal burning. Implementing measures such as scrubbers on coal combustion plants or switching to cleaner fuels can help reduce the harmful effects of these pollutants.

While the study focused on the impact of long-term exposure to the PM2.5 mixture, further research is needed to understand how specific particles in the mixture affect asthma hospitalizations after short-term exposure. The findings highlight the need for targeted control efforts to improve asthma outcomes and reduce the burden of air pollution on public health.

The study was co-authored by researchers from Harvard Chan School of Public Health, including Bryan Vu, Xinye Qiu, Yijing Feng, and Yaguang Wei. For more information, the study is available in the American Journal of Respiratory and Critical Care Medicine.