Key Points

The study, published in the American Journal of Respiratory and Critical Care Medicine, showed that for each decile increase in the pollutant mixture, asthma hospitalisations increased 10.6 per cent among children and 8 per cent among adults ages 19 to 64.

Nickel, vanadium, sulfate, nitrate, bromine, and ammonium contributed the most weight to this association.

"If we want to reduce asthma hospitalisations, these are the sources that need to be better controlled -- which we know how to do," said corresponding author Joel Schwartz, professor of environmental epidemiology at Harvard T.H. Chan School of Public Health.

"Nickel and vanadium, for example, are produced from burning fuel oil, such as heating oil and heavier oils used by larger buildings. Sulfates come from coal burning. We can put scrubbers on coal combustion plants or replace coal with less polluting fuels, and we can remove metal contaminants from fuel oil," he added.

Most prior studies have examined the relationship between asthma and individual pollutants or fine particulate air pollution (PM2.5) as a whole.

The new study used previous studies and machine learning algorithms to identify bromine, calcium, copper, elemental carbon, iron, potassium, ammonium, nickel, nitrate, organic carbon, lead, silicon, sulfate, vanadium, and zinc as the compounds composing PM2.5's mixture of metals and organic compounds.

Controlling for variables such as outdoor temperature and socioeconomic status among those hospitalised, the researchers used a weighted quantile sum regression, a statistical method that assessed how each compound in the PM2.5 mixture contributed to the 469,005 asthma hospitalisations included in the study.

The team noted that further study is needed to assess how specific particles in the PM2.5 mixture impact asthma hospitalisations after short-term exposure.

- IANS