Even little air pollution raises cancer risks

July 23, 2013 - 05:00

Air pollution, even in concentrations below EU limits, increases the risk of lung cancer.

Suspended dust is churned up when cars emit exhaust and plough up tiny bits of asphalt. A clear link exists between such dust and the risks of lung cancer. (Photo: Colourbox.com)

Researchers from the Norwegian Institute of Public Health and the University of Oslo have partaken in an international study comparing pollution levels and charting the health of over 300,000 persons.

The goal was to ascertain and calculate the risk of cancer from suspended dust that makes its way into our lungs.

A clear link was found between such ambient air pollution and cancer:

If you add 10 micrograms of suspended dust per cubic metre to the air long-term, the risk of lung cancer mounts by 22 percent. The risk of an adenocarcinoma type of lung cancer, not linked to smoking, increases by 50 percent.

The EU countries and Norway, a non-member state subject to many EU regulations, have set a ceiling on acceptable quantities of suspended particulate matter in the air, on any given day and on the average in a year.

The researchers found an increase in cancer risk even when air pollution increases by such a small amount, and from such a low level to start with, that it remains below maximum limits.

Large particles yielded the biggest risk

Particulate matter is common name given to particle pollution of various types. Such suspended dust is often split into two categories:

Particulate matter with an aerodynamic diameter of up to 10 micrometres, or 0.01 millimetres. Regulations stipulate that the concentration of such particles must not exceed 40 micrograms per cubic metre of air.

There is also a category for even smaller bits of dust, with an aerodynamic diameter of up to 2.5 micrometres.

These tinier particles make their way more easily into the lungs and our body tissues so the upper limit on them is even lower, at 25 micrograms per cubic metre.

It’s the larger type of particulate matter that gives a 22 percent bigger risk of lung cancer.

As regards the tinier type of air pollution the risk of lung cancer rose by 18 percent for every five extra milligrammes of dust, but this result was not statistically significant. Nor were all the results for risk increases below the accepted level.

A result is deemed statistically insignificant if the researchers tallied an affect but could not guarantee that it was due to unknown factors or random causes.

Risk is similar round the world

A recent study from the USA has calculated that 2.1 million people die annually as a direct result of excessive fine-grained particulate matter − most of them in the Orient and Southern Asia, where the air can be far more polluted than in Europe.

In Norway the contributor to the lung cancer research was the Oslo Health Study (HUBRO). The other countries involved were Sweden, Denmark, the Netherlands, Spain, Italy, Greece, Great Britain and Austria.

The researchers say none of these countries showed any distinction with particularly higher or lower cancer risks from air pollution when they were analysed individually.

Among some 312,000 participants in the study, 2,095 developed lung cancer in the course of the 12 years in which they were monitored.

The researchers made allowances for other cancer risk factors such as gender, age, smoking and occupations in their calculations.

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Read the Norwegian version of this article at forskning.no

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Translated by
Glenn Ostling