A new study by Spanish researchers suggests that short-term exposure to air pollution may be tied to increased antibiotic use in people experiencing respiratory symptoms.
The study, published last week in JAMA Network Open, found that increases of daily ambient air pollution in 11 Spanish cities over 7 years were associated with increased antibiotic consumption among people who sought care for acute respiratory symptoms on the day of exposure.
Exposure to air pollution has previously been tied to a variety of adverse health effects, among them increased risk of stroke, heart disease, and lung cancer. But the authors of the study say the identification of a link between ambient air pollution and heightened antibiotic use underscores the need to reduce exposure to toxic air.
"Our findings underscore the need for more comprehensive and ambitious policies to address ambient air pollution on a global scale," they wrote.
Key indicators of air pollution
For the study, a team led by researchers from Bellvitge University Hospital in Barcelona conducted a two-stage ecological time series analysis using data on daily ambient particulate matter and nitrogen dioxide (PM10, PM2.5, and NO2) concentrations from the 11 largest cities in Catalonia from June 23, 2012, to December 31, 2019.
PM10 (PM of 10 micrograms [μg] or less in diameter) and PM2.5 (2.5 μg or less in diameter) are the primary forms of inhalable PM derived from different emissions sources. Along with NO2, they are considered key indicators of air pollution that can have adverse effects on human health.
Our findings underscore the need for more comprehensive and ambitious policies to address ambient air pollution on a global scale.
The researchers defined the exposure day (day 0) as the day of exposure to an increase of 10 μg/m3 (cubic meter of air) of any of the three air pollutants. The main outcome was antibiotic consumption associated with primary care consultations for acute respiratory symptoms in the 30 days before and after dispensing of the antibiotic.
Among the nearly 2 million inhabitants of the 11 cities (median age, 48 years; 55% female), there were 8.4 million antibiotic dispensations during the study period. The median antibiotic consumption, measured as defined daily doses (DDD) per 1,000 inhabitants dispensed, was 12.26, ranging from 10.24 to 14.16 across the 11 cities. A total of 1.9 million antibiotic dispensations were associated with primary care consultations for acute respiratory symptoms.
The median concentration of PM10 across the 11 cities was 21.46 μg/m3, and the median concentration of NO2 was 30.00 μg/m3. In the two cities where daily measurements of PM2.5 were available, the median concentration was 12.70 μg/m3.
Pollution-induced respiratory irritation
The researchers found a significant correlation between increases of 10 μg/m3 in the concentration of all three pollutants studied and heightened antibiotic consumption on day 0 (PM10: relative risk [RR], 1.01; 95% confidence interval [CI], 1.01 to 1.02; PM2.5: RR, 1.03; 95% CI, 1.01 to 1.04; NO2: RR, 1.04; 95% CI, 1.03 to 1.05).
They also observed a delayed association between increases in PM2.5 concentration and antimicrobial consumption between day 7 (RR, 1.00; 95% CI, 1.00 to 1.01) and day 10 (RR, 1.00; 95% CI, 1.00 to 1.01) after exposure.
The study authors hypothesize that exposure to air pollution could increase antibiotic use in two ways. In one scenario, it induces immediate irritation of the respiratory tract, resulting in acute respiratory symptoms that prompt healthcare-seeking behavior, mis-diagnosis of respiratory tract infections, and subsequent antibiotic use. In the other, air pollution triggers an innate immune response in the respiratory system that could increase susceptibility to secondary bacterial infections that result in antibiotic use.
"In addition, the overlapping symptoms between pollution-induced irritation and acute respiratory tract infections may lead health care professionals to prescribe antibiotics even when the infection is likely viral or pollution induced, both immediately and later," they wrote.
The authors say further studies are needed to confirm and expand on the findings.
