Global study linking PM2.5 and deaths leads to calls for tighter limits

Scientists have conducted the largest study yet into the impact that short-term exposure to air pollution has on death rates worldwide.

The study, led by scientists from China’s Fudan University, analysed data on air pollution and daily mortality in 652 cities across 24 countries and regions.

It found that short-term exposure to inhalable particulate matter (PM10) and fine particles (PM2.5), emitted from fires or vehicle exhausts, is directly linked to increases in total deaths across the world.

The study, published in the New England Journal of Medicine, has led to calls for air pollution guidelines to be tightened as the findings suggest that even the World Health Organisation (WHO)’s current guidelines are not sufficient to protect people from harm.

Professor Yuming Guo, co-author of the study and associate professor from Monash University’s School of Public Health and Preventive Medicine in Australia, said that even low-level exposure to air pollution can increase the risk of death.

‘The adverse health effects of short-term exposure to air pollution have been well documented, and known to raise public health concerns of its toxicity and widespread exposure,’ Professor Guo said.

‘The smaller the airborne particles, the more easily they can penetrate deep into the lungs and absorb more toxic components causing death.’

The scientists collected daily data on PM10 in 598 cities and on PM2.5 in 499 cities, including data on both pollutants in 445 cities in 16 countries or regions.

They also looked at a total of 59.6 million deaths in these cities including 20.1 million deaths from cardiovascular diseases and 5.6 million deaths from respiratory diseases.

The study found ‘positive and significant’ associations between PM10 and PM2.5 concentrations and overall mortality, as well as deaths specifically from respiratory and cardiovascular diseases. These associations were slightly stronger for PM2.5 which can enter the lungs more easily.

Links between PM exposure and deaths were also stronger in regions with higher temperatures and lower average exposure to PM air pollution.

The results echo previous findings in other cross-country studies, and suggest that even exposure to PM levels below the WHO’s current annual mean limits of 10 μg/m3 for PM2.5 and 20 μg/m3 for PM10 is hazardous to public health.

Dr Penny Woods, chief executive of the British Lung Foundation, said it is ‘not surprising’ the study found a link between PM and deaths from cardiovascular and lung disease, given the growing body of evidence around air pollution’s health impacts.

Dr Woods said: ‘We’ve seen lots of studies showing a link between outdoor air pollution and the development of some lung conditions. And we know if children are exposed to air pollution for a long period it stunts the development of their lungs – something that can potentially disadvantage them for life. What we’ve seen less of is effective action from government.’

The UK government has confirmed it will adopt the World Health Organisation’s limits on PM2.5 and PM10 in its forthcoming Environment Bill.

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