Study links air pollution to rising antibiotic resistance levels

Smoke stacks and white smoke

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A new study led by scientists in China and the United Kingdom suggests that curbing air pollution could help mitigate the impact of antibiotic resistance.

The modeling study, published yesterday in The Lancet Planetary Health, found a significant correlation between airborne particulate matter and aggregate antibiotic resistance levels, an association the researchers say is consistent across the globe and has grown stronger over time. In a scenario where countries implemented World Health Organization (WHO)-recommended policies to limit air pollution, the researchers estimate that premature deaths attributable to resistant bacteria could be reduced more than 20% by 2050.

Although the study authors acknowledge that more evidence is needed to verify the link, and that antibiotic overuse and misuse are still the main drivers of AMR, they say the findings provide more information on the role the environment plays in spreading resistant bacteria, and they suggest that controlling air pollution could present a new pathway for fighting antibiotic resistance.

"Until now, we didn’t have a clear picture of the possible links between the two, but this work suggests the benefits of controlling air pollution could be two-fold: not only will it reduce the harmful effects of poor air quality, it could also play a major role in combatting the rise and spread of antibiotic-resistant bacteria," lead study author Hong Chen, PhD, of Zhejiang University said in a Lancet press release.

Antibiotic resistance genes in polluted air

The study, conducted by Chen and colleagues from Zhejiang University and the University of Cambridge, builds on previous research that has identified the presence of antibiotic-resistance genes in source-specific and ambient air. Among the published research is a paper from 2018 that revealed the presence and abundance of 30 antibiotic-resistance gene subtypes in air samples from 19 cities in 13 countries. Other studies have found that the abundance of resistance genes in urban air is higher than resistance genes found in soil and river water.

Just as people can be exposed to resistant bacteria via food, water, and soil, Chen and his colleagues say this research suggests people can also be exposed to resistant bacteria trapped in airborne fine particulate matter (PM2.5), the most dangerous airborne pollutant. Inhalation of this bacteria could result in infections in the respiratory-tract system and other parts of the body, since PM2.5 can also penetrate the lung barrier and enter the blood system.

Although the underlying mechanism for how air pollution affects antibiotic resistance remains unclear, the study is the first to estimate the global associations between PM2.5 and clinical antibiotic resistance.

"Empirical evidence of the effects of PM2.5 on population-level antibiotic resistance that enable the global impact to be assessed is clearly needed," the authors wrote. "The air environment can cross regional boundaries and spread antibiotic resistance over long distances and on a large scale, which could be a crucial link between the dissemination of environmental and human antibiotic resistance."

For their analysis, the researchers used data collected from 116 countries from 2000 through 2018, including raw antibiotic resistance data on 11.5 million tested isolates covering nine bacterial pathogens and 43 types of antibiotic agents. In addition to air pollution, they also evaluated data on other factors that have been linked to rising antibiotic resistance levels, including antibiotic use, sanitation services, economics, healthcare spending, population, education, and climate.

The air environment can cross regional boundaries and spread antibiotic resistance over long distances and on a large scale, which could be a crucial link between the dissemination of environmental and human antibiotic resistance.

The analysis found that an increase in 1% of PM2.5 across regions was associated with increases in resistance ranging from of 0.5% to 1.9% in each of the nine pathogens. In addition, changes in PM2.5 concentration were linked to large increases in resistance since 2013. It also showed that the magnitude of the contribution of PM2.5 to aggregate antibiotic resistance is greater than factors like drinking water and healthcare expenditures. The researchers estimated that antibiotic resistance derived from PM2.5 caused an estimated 480,000 premature deaths in and 18.3 million years of life lost in 2018.

Limiting pollution could reduce resistance, attributable deaths

The researchers then modeled a set of scenarios to project how PM2.5 might affect antibiotic resistance and premature deaths in the future. If no policies to reduce air pollution were implemented and other factors were unchanged (the baseline scenario), they estimate that antibiotic resistance and premature deaths attributable to resistant pathogens would increase by 17% and 56.4%, respectively, by 2050, with the biggest impact seen in sub-Saharan Africa.

Several scenarios estimated that increasing healthcare spending, improving access to clean drinking water, and reducing antibiotic would significantly reduce levels of antibiotic resistance. In a scenario where countries implemented policies to limit the annual PM2.5 concentration to 5 micrograms per cubic meter, the researchers estimated a 16.8% decrease in global antibiotic resistance and 23.4% reduction in attributable deaths compared with the baseline, with countries in North Africa and west Asia benefitting the most.

"Together, these results suggest that, although measures of other drivers of antibiotic resistance are still needed, controlling PM2.5 could be a promising way to reduce global antibiotic resistance," Chen and his colleagues wrote.

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