No safe level of air pollution says US study

Two studies of tens of millions of Americans have determined there is no safe level of exposure to air pollution.

The research, published today in the British Medical Journal, found that there is no safe threshold for exposure to tiny particulate matter measuring 2.5 micrometres (less than the diameter of a human hair) and that exposure outside the World Health Organization’s (WHO) air quality guidelines carries significantly higher associations with hospitalisations.

Health data from more than 90 million health records was reviewed across the studies.

The first study (assessing 60m Americans aged over 65) found exposure to PM2.5 over three years was associated with increased hospital admission risk for a range of issues.

These included 7 types of cardiovascular disease.

Reducing PM2.5 to levels within the WHO guidelines could reduce hospital admissions by 29%, it found.

Lead author Yaguang Wei says stronger air quality protocols was an important measure for the US. However, the findings will also have benefits in other countries.

“The timing of our study couldn’t be more critical, and its implications are profound,” says Wei, who is a research associate in the US Department of Environmental Health and works out of Harvard University.

“Our findings quantify the benefits of implementing stricter air pollution control policies – even stricter than the Environmental Protection Agency’s new standards, which are considerably higher than the 5 micrograms per cubic meter standard set by the World Health Organization.”

The second analysis of 34m hospital and emergency department admissions found that any exposure, including to PM2.5 within the WHO limits, was associated with more hospital admissions than non-exposures.

The authors suggest “no safe threshold exists for overall cardiovascular health and that substantial benefits could be attained through adherence to WHO’s air quality guideline”.

Last year a separate study found air pollution from coal fired power stations caused 460,000 US deaths over two decades.

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