Air pollution causes lung cancer. Yesterday this conclusion, which has already been reported in many scientific studies published in recent years, took a new turn after being declared by the World Health Organisation (WHO). In fact, the International Agency for Research on Cancer (IARC), the specialized cancer agency of the World Health Organization, whose mission is to investigate which substances cause this disease and how they may react, announced yesterday that environmental contamination had been classified as level 1, the highest on the scale, which includes substances that leave no doubt in scientific circles as to the danger they pose.

The research study described by the Agency, of which a summary is to be published in next week’s edition of The Lancet Oncology, notesthatin 2010 223,000 deaths worldwide from lung cancer were attributable to pollution.

The main causes of this “dirty air” are vehicles, energy production, industrial and agricultural emissions and residential heating systems. This is the first time that IARC, which produces the famous “encyclopaedia of carcinogens”, has studied and classified pollution in general. Previously, it had always concentrated on the individual substances that make up this dirty air that we breathe, especially in large cities, like the gas produced by diesel engines or metals.

“Although the composition of air pollution and levels of exposure can vary dramatically between locations, the conclusions apply to all regions of the world”, IARC stated yesterday in a press release. “Research shows that the risk of cancer increases with increased exposure. It’s a fairly linear relationship”, explains Esteve Fernàndez, epidemiologist with the Catalan Institute of Oncology and specialist in tobacco, who has helped write some of the Agency’s monographs.

“The risks are probably not as high as those linked to tobacco. In fact the risk for a smoker of contracting cancer is 20 times higher than a non-smoker. But far more people are exposed to air pollution”, he added.

“These studies take a long time, even up to a year, and scientists from all over the world help out, independently checking and editing all the works published about every subject”, he explained. In this case, IARC assures that it has checked over 1000 studies published in scientific reviews. The research analyses distinct elements present in environmental pollution, especially in the particles.

“The WHO had already classified diesel soot as carcinogenic in June 2012. If we bear in mind that in our cities the main cause of air pollution is road traffic, the WHO’s observation is perfectly consistent. Indeed, some components like polycyclic aromatic hydrocarbons (released by the combustion of fossil fuels and biomass), arsenic, cadmium and nickel have been regulated, in terms of their quantities in the air, by a European directive due to the fact that they are carcinogenic agents”, says Xavier Querol, pollution expert and researcher for the Spanish National Research Council.

“Now we know that atmospheric pollution is not only a general health risk, but also causes death from cancer”, states Kurt Straif, head of the IARC’s classification of carcinogens. “Our task has been to evaluate the quality of the air we breathe worldwide, instead of concentrating mainly on specific pollutants”.

“The effects of pollution on health are multiple. The most dangerous pollutants are ultrafine particles and ozone, although there are also other influential substances. The carcinogenic effect is one of the greatest risks, but there are others too: respiratory, cardiovascular and cerebrovascular problems “, explains Querol. IARC has suggested in one study that there is enough evidence to back up the theory of exposure to pollution as a cause of lung cancer and as another factor in the risk of developing bladder cancer. “Constantly breathing in these particles causes damage to the cells that cover our respiratory system, resulting in the accumulation of genetic failures which make the cells proliferate uncontrollably and, in the end, allow tumours to grow”.

“In my opinion, the WHO has sent a clear signal to politicians that the problem is serious and that they must act fast to improve air quality”, concludes Querol.