Daily exposure to ozone pollution in cities across the world is associated with an increased risk of death, the largest study of its kind claims today.
Based on data from the Multi-City Multi-Country Collaborative Research Network, which examined 406 cities in 20 countries across the world between 1985 and 2015, the report shows that more than 6,000 deaths each year would have been avoided in those cities if countries had implemented stricter air quality standards.
The international research team derived 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 extra deaths attributable to ozone.
The study, published in The BMJ, analysed the 45,165,171 deaths in the cities, concluding that a 10 µg/m3 increase in ozone during the current and previous day was associated with a 0.18% increased risk of death.
This suggests evidence of a potential causal association, say the researchers, and equates to 6,262 extra deaths each year (or 0.2% of total mortality) that could potentially have been avoided if countries had implemented stricter air quality standards in line with the WHO guideline, which stands at 100 µg/m3.
They also found that smaller, but still substantial, mortality impacts were found even for ozone concentrations below WHO guideline levels.
Although this observational study did not include areas such as South America, Africa, and the Middle East, the researchers say their results suggest that ozone-related mortality “could be potentially reduced under stricter air quality standards”.
“These findings have important implications for the design of future public health actions; particularly, for example, in relation to the implementation of mitigation strategies to reduce the impacts of climate change,” they conclude.
The project was led by the Institute of Social and Preventive Medicine, Bern, Switzerland.
Vicedo-Cabrera AM, Sera F, Liu C et al. Short term association between ozone and mortality: global two stage time series study in 406 locations in 20 countries. BMJ 11 February 2020
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