The International Agency for Research (IARC) on Cancer has announced that it has classified outdoor air pollution 'carcinogenic' to humans.

The agency added that it has reviewed data on the carcinogenicity of air pollution and found that there is sufficient evidence that it causes lung cancer. IARC has classified air pollution to be grade 1 carcinogen.

IARC is the cancer agency of the World Health Organization and is based in Lyon, France. Previously experts from the agency had classified a component of air pollution- diesel fumes as Group 1 carcinogens.

Now, health experts have classified particulate matter, another component of air pollution, as an independent risk factor for cancer.

"The air we breathe has become polluted with a mixture of cancer-causing substances," says Dr Kurt Straif, Head of the IARC Monographs Section, according to a press release. "We now know that outdoor air pollution is not only a major risk to health in general, but also a leading environmental cause of cancer deaths."

The report was based on data analysis of over 1,000 studies conducted in five continents. Researchers found that transportation, agricultural emissions, households and power stations were the main sources of air pollution.

"Classifying outdoor air pollution as carcinogenic to humans is an important step," stresses IARC Director Dr Christopher Wild. "There are effective ways to reduce air pollution and, given the scale of the exposure affecting people worldwide, this report should send a strong signal to the international community to take action without further delay."

Many studies have pointed out that air pollution can cause serious health problems. A related research had found that annually two million people die due to health complications from air pollution. Previous research by scientists at MIT, too, had found that more people in the U.K. die from air pollution than road accidents. Their study appeared in the journal Environment Science and Technology.