Humans are missing out on almost three years of life expectancy on average because of outdoor air pollution, researchers have found.
However, the study reveals more than a year of life expectancy could be clawed back if fossil fuel emissions are cut to zero, while if all controllable air pollution is cut – a category that does not include particles from natural wildfires or wind-born dust – global life expectancy could rise by more than 20 months.
“This corroborates that fossil fuel-generated air pollution qualifies as a major global health risk factor by itself,” the authors write.
The study builds on the team’s previous research that confirmed about 8.8m early deaths a year worldwide, twice the figure from prior estimates, are caused by outdoor air pollution, with the new work examining the issue both for the world as a whole, and in detail for particular regions and countries.
“The loss of life expectancy from air pollution is much higher than many other risk factors, and even higher than smoking,” said co-author Prof Jos Lelieveld of the Max Planck Institute for Chemistry. “That was quite unexpected, I must say.”
As with the team’s previous work, the new study draws on a recently developed model of the impact of fine particulate matter known as PM2.5 on the body, as well as a model for the impact of ozone, levels of exposure to these pollutants, and population and mortality figures for 2015.
From this data, the team calculated the proportion of early deaths that could be attributed to outdoor air pollution across six categories, including unspecified non-communicable diseases – a category that encompasses conditions such as high blood pressure and diabetes.
The results reveal that, globally, 2.9 years of life expectancy on average are lost because of outdoor air pollution – a bigger toll than tobacco smoking (2.2 years lost), violence (0.3 years lost), HIV/Aids (0.7 years lost) and diseases spread by parasites and other vectors (0.6 years lost).
Should avoidable outdoor air pollution be cut, the team adds, more than 5.5m early deaths globally could be avoided every year.
However, there are variations between regions and countries: such a measure would save 2.4m early deaths a year in east Asia and regain three out of the 3.9 years of life expectancy lost because of outdoor air pollution. However, in Africa only 230,000 early deaths a year, and just over eight months of the 3.1 years of life expectancy lost, would be saved. In Australiathe gains would be even smaller.
That, the authors note, is down to a variety of factors, including Africa’s outdoor air pollution being dominated by wind-blown dust and Australia having stricter air pollution policies than many other countries to start with.
The team found the number of premature deaths owing to air pollution generally increased with age.However, for some regions, including Africa and south Asia, there is also a high number of premature deaths among very young children.
Coronary heart disease accounted for the largest number of extra deaths for any of the six categories, at almost 2.8m a year worldwide, and made up more than 28% of the loss in life expectancy. By contrast deaths from lung cancer, chronic obstructive lung disease and lower respiratory infections together made up about 2.6m early deaths from outdoor air pollution a year.
Prof Thomas Munzel, of the University Medical Centre Mainz in Germany and co-author of the study, said this was not surprising. “Even [though] the lung is the primary target of air pollution, causing inflammation and therefore pneumonia, there will be a transmigration of particles into the bloodstream and into blood vessels,” he said, noting that will cause inflammation and, over time, plaque will build up in the arteries.
Munzel said the findings underscore the importance of including air pollution as a risk factor for cardiovascular disease in official guidelines for such conditions.
However, the study has a number of limitations, including that it only looks at two air pollutants. and does not look at the chemical makeup of the particulate matter. Among other factors, the team note there may be diseases that should be associated with air pollution that are not currently, while the models are based on data from a limited number of countries.
As a result, the team say there are large uncertainties in the findings. Nonetheless, Munzel said, the study emphasises the need for governments to take action.
“We need lower emission levels – 91% of the [world’s] population breathes polluted air as defined by the [World Health Organization],” he said. “We have incredibly high limits for Europe: those need to be reduced markedly.”
The team note measures can include city planning and management, while improvements in healthcare can also improve life expectancy. Munzel added it was also important to conduct research into drugs that could mitigate the health impacts of air pollution.
Prof Kevin McConway, emeritus professor of applied statistics at the Open University, said the uncertainty in the figures means that is it not yet clear whether air pollution is a bigger killer than tobacco, but that it certainly rivals it. That, he said, is because although smoking a packet of cigarettes a day is more dangerous, a higher proportion of people inhale air pollution than tobacco smoke.
The work is published in the journal Cardiovascular Research.