Low-level air pollution increases lung cancer risk

Densely populated areas and busy traffic increase risk. PA/Andy Butterton

Breathing in air pollution at a lower rate that prescribed EU limits for prolonged periods of time increases your risk of lung cancer, according to a new study published in the Lancet Oncology.

The study looked at the association between long-term exposure to ambient air pollution - the everyday pollution we breathe around us - and lung cancer in Europe.

Using information gathered from 17 cohort studies into the long-term effects of air pollution across nine European countries (nearly 313,000 people), the researchers looked at the effects of long-term exposure to nitrogen oxides, soot, and other particulate matter - solid and liquid matter suspended in the air.

They found that for every increase of five micrograms per cubic metre of PM2.5 pollution (fine particles that are small enough to travel in the gas exchange between the lungs), the risk of lung cancer rose by 18%. For every increase of 10 micrograms per cubic metre in PM10 pollution (breathable particles that can penetrate into deeper parts of the lung) the risk increased by 22%.

They also noted a stronger link to adenocarcinoma, one of the most common types of cancer found in the lung. It’s also the most common form of cancer found in people aged under 45 and the only one that develops in a substantial number of lung cancer sufferers who don’t smoke.

Among the participants, 2095 had developed lung cancer by a follow-up around 13 years later. The researchers said they applied further statistical modelling to separate the influence of other factors including smoking, diet (including low fruit intake) and socio-economic status.

EU limits aren’t enough

EU limits on air pollution did not protect people from the effects of long term exposure to particulate matter air pollution. “The association between particulate matter air pollution and the risk for lung cancer persisted also at concentrations below the existing European Union air quality limit values for PM10 (40 μg/m3) and PM2.5 (25 μg/m3),” the paper said. “We found no threshold below which there was no risk; the results showed a picture that ‘the more the worse, the less the better’.”

Causes of air pollution include traffic on the roads as well as industrial plants and factories. It can also be caused by domestic heaters in the home.

Lung cancer is the second most common cancer after breast cancer in England and Wales, with around 40,000 new cases diagnosed each year. Although it mainly affects older people - it’s rare in people aged under 40 - it’s commonly associated with smoking, which is linked to 85-90% of lung cancer and survival rates are low.

Air pollution risk

Air pollution is linked to higher risk of heart disease and respiratory conditions such as asthma and has been suspected as a cause for cancer.

However, a World Health Organisation study last year looked at people at higher risk from diesel exhaust fumes, such as miners and lorry drivers, and concluded that diesel exhaust was a definite cause of lung cancer.

Research published on Monday also showed higher levels of air pollution in northern China, mostly caused by burning free coal to heat homes in the winter, reduced life expectancy by around 5.5 years.

City locations

Most of those studied for the research lived in large cities or surrounding surburban or rural locations. They were located in countries including Sweden, the UK, Italy and Spain among others. People in the study who had lived at the same address throughout the follow-up showed the strongest associations with lung cancer.

“It’s not just a matter of busy roads. There were a range of locations - some had busy roads, some more in the background and some more suburban locations,” Ole Raaschou-Nielsen, from the Danish Cancer Society Research Centre and lead author of the report said. “Both traffic but also how densely populated and area is makes a difference.”

He added, “Long term effects look at years or decades rather than day-to-day impact. In this study we had a follow-up period of 13 years. Lung cancer can take years or decades to develop so this works well with a longer-term study.”

There is now a growing body of evidence linking air pollution with cancer but fewer longer term studies have led to a less definitive link than other conditions such as asthma.

Dr Francine Laden, from Harvard University’s School of Public Health, said: “There are a smaller number of studies that have looked at air pollution and cancer risk,” she said. “The reason why is because you need a much longer period of follow-up to look at the association. Cancer has a long latency, so there are fewer studies with the necessary number of years of data on the relevant air pollution exposures.”

In May, the UK government was judged to have breached its legal duty to reduce air pollution in cities. But with many of us now living in cities, how much air pollution can we really avoid?

We produce knowledge-based, ethical journalism. Please donate and help us thrive. Tax deductible.