Air Pollution Accounts for Millions of Asthma ER Episodes

Ambient air pollution is major contributor to the global asthma burden, responsible for millions of emergency room (ER) visits, according to a new study.

Researchers at Dalhousie University (Halifax, NS, Canada), George Washington University (GW; Washington, DC, USA), the Stockholm Environment Institute (York, United Kingdom), and other institutions examined various national and regional ER visit rates, baseline asthma incidence and prevalence rates, and pollutant concentrations in order to estimate the number of asthma ER visits and new onset asthma cases globally that could be attributed to fine particulate matter (PM2.5), ozone, and nitrogen dioxide (NO2) concentrations.

The results showed that nine to 23 million annual asthma ER visits globally (8-20% of total global asthma ER visits) may be triggered by ozone, a pollutant generated when emissions from cars, power plants, and other combustion sources interact with sunlight; five to 10 million asthma ER visits (4-9% percent of total global asthma ER visits) were linked to PM2.5, small particles of pollutants that can lodge deep in the lung’s airways. The wide range of estimates reflects the application of central risk approximations from different epidemiological meta-analyses.

About half of the asthma ER visits attributed to dirty air were estimated to occur in South and East Asian countries, notably India and China. And although the air in the United States is relatively clean compared to South and East Asian countries, ozone and particulate matter were estimated to contribute 8-21% and 3-11% of asthma ER visits in the United States, respectively. The researchers suggest that countries like India and China may be harder hit by asthma burden because they have large populations and tend to have fewer restrictions on factories belching smoke and other sources of pollution.

Human-derived emissions were responsible for about 37% and 73% of ozone and PM2.5 asthma ER impacts, respectively. The remaining impacts were attributable to naturally occurring ozone precursor emissions, such as those from vegetation and lightning, and also due to PM2.5 factors such as dust and sea salt, although several of these sources are also influenced by humans. As reported, the largest ER impacts were found in China and India. The study was published on October 24, 2018, in Environmental Health Perspectives.

“We know that air pollution is the leading environmental health risk factor globally. Millions of people worldwide have to go to emergency rooms for asthma attacks every year because they are breathing dirty air,” said lead author Susan Anenberg, PhD, MSc, associate professor of environmental and occupational health at GW. “The range of global public health impacts from breathing dirty air is even more far reaching, and includes millions of asthma attacks every year. Policies aimed at cleaning up the air can reduce the global burden of asthma and improve respiratory health around the world.”

Asthma is the most prevalent chronic respiratory disease worldwide, affecting about 358 million people. It is characterized by variable, recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include episodes of wheezing, coughing, chest tightness, and shortness of breath, which may occur a few times a day or a few times per week. Diagnosis is usually based on the pattern of symptoms, response to therapy over time and spirometry.

Related Links:
Dalhousie University
George Washington University
Stockholm Environment Institute