Air pollution: how many people does it kill?

"Air pollution is a killer, more of a killer than obesity or passive smoking before the smoking ban. It kills indirectly, through heart attacks, lung infections and cancers. No one questions its devastating impact — here, it is estimated to cause 29,000 early deaths per year."

The Guardian, 3 April 2014

As Saharan dust hit the headlines yesterday an editorial in the Guardian  focused on the health impact of air pollution, and how it compares to the impact of other public health problems. It said an estimated 29,000 deaths are caused by pollution every year.

But the researchers who produced the figure have said it's unlikely this is the number of people affected. They suggested that air pollution may have made a smaller contribution to the deaths of 200,000 people, and the number of years of life those people are estimated to have lost purely due to pollution is the equivalent of 29,000 deaths.

And differences in the conditions being measured and the year that the estimates were made makes it difficult to compare its impact to that of obesity or passive smoking.

Air pollution causes harm equivalent to about 29,000 deaths

This estimate comes from a 2010 report looking at the mortality effects of long term exposure to 'fine grain' pollution particles.

The report looks at mortality outcomes associated with 'PM2.5' pollution, which involves pollution particles that are 2.5 micrometres or less in size. There is some evidence to suggest that pollution in this category is more dangerous to health than pollution involving larger-sized particles.

Data from 2008 was used to estimate the life expectancy of the UK population if PM2.5 pollution were to be eliminated. Comparing this to actual life expectancy, it found the total number of years of life lost due to the pollution was 340,000 that year. It calculated that this was an effect on mortality equivalent to 29,000 deaths.

But this doesn't mean 29,000 people died solely due to air pollution. As the committee behind the report said in a press release:

"…the Committee considers it very unlikely that this represents the number of individuals affected. Instead it speculates that air pollution, acting together with other factors, may have made some smaller contribution to the earlier deaths of up to 200,000 people."

It's also important to note that the estimated number of deaths is based on pollution at 2008 levels. Since pollution levels have gone down since then this might have reduced the number of deaths.

30,000 deaths from obesity - maybe

Research carried out in 2001 by the National Audit Office found that approximately 30,000 deaths in 1998 were caused by obesity.

As Public Health England cautions, it isn't easy to assess how the number might have changed since then. That's because while the proportion of the population who are obese has risen, the number of people dying from all causes has fallen.

Passive smoking — as of 2005 — cost fewer years of life than air pollution

The claim refers to the level of mortality from passive smoking prior to the ban on smoking in public places that took effect in 2007. We couldn't find a comparison of passive smoking and pollution in terms of the number of deaths per year.

But in terms of the total lives lost, the Department of Health used 2005 data to estimate that if passive smoking was eliminated in 2005 the number of life years gained would be 13 million from 2005 up to the year 2110. The equivalent figure for elimination of man-made PM2.5 pollution was estimated at 39 million. Again, this was based on the higher pollution levels of 2005.