Daily exposure to ground level ozone increases city residents' risk of early death, researchers warn.
Ground level ozone – commonly found in cities and suburbs – forms when pollutants react in sunlight.
New study findings suggest that thousands of ozone-related deaths "could be potentially reduced under stricter air quality standards," according to study co-author Ana Vicedo-Cabrera and her colleagues. She is with the Institute of Social and Preventive Medicine in Bern, Switzerland.
For the study, the researchers analysed data gathered between 1985 and 2015 from 406 cities in 20 countries. They concluded that thousands of deaths could have been avoided each year in those cities if their countries had stronger air pollution laws.
The investigators determined daily average ozone levels (above a maximum background level of 70 µg/m3), particulate matter, temperature, and relative humidity at each location to estimate the daily number of deaths attributable to ozone.
More than 45 million deaths were analysed. On average, a 10 µg/m3 increase in ozone during the current and previous day was associated with a 0.18% increased risk of death, suggesting evidence of a potential direct association, according to the researchers.
Current air quality thresholds (in micrograms per cubic meter of ambient air) are: 100 µg/m3 – World Health Organization (WHO); 120 µg/m3 – European Union directive; 140 µg/m3 – U.S. National Ambient Air Quality Standard; and 160 µg/m3 – Chinese Ambient Air Quality Standard.
Additional health benefits
The findings suggest that more than 6 260 deaths each year (or 0.2% of all deaths) in the 406 cities may have been prevented if countries had air quality standards in line with WHO guidelines, according to the authors. The study was published online in the BMJ.
Data suggest that 80% of the world's population in urban areas are exposed to air pollution levels above the WHO threshold, the study authors noted in a journal news release.
The study can't prove a direct cause-and-effect relationship. Still, reducing ozone pollution "would provide additional health benefits, even in regions that meet current regulatory standards and guidelines," the researchers noted.
"These findings have important implications for the design of future public health actions," particularly in relation to strategies to reduce the impacts of climate change, the study authors concluded.
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