Outdoor air pollution has now been classed as carcinogenic (cancer causing) to humans, the International Agency for Research on Cancer (IARC) has confirmed.

According to the agency, which is part of the World Health Organisation (WHO), the decision was made following a thorough review of the latest scientific literature available. This led scientists to declare that there is ‘sufficient evidence that exposure to outdoor air pollution causes lung cancer'.

They also found an increased risk of bladder cancer.

Meanwhile, particulate matter, which is a major component of outdoor air pollution, was considered separately and it too was classified as carcinogenic to humans.

While levels of air pollution and levels of exposure can differ greatly depending on where you are, the IARC said that its warning applies to ‘all regions of the world'.

It noted that air pollution is already known to increase the risk of conditions such as heart and respiratory diseases, and exposure levels worldwide appear to be increasing, particularly in rapidly industrialising countries with big populations.

The most recent evidence available indicates that in 2010 alone, over 220,000 lung cancer deaths worldwide were due to air pollution.

"The air we breathe has become polluted with a mixture of cancer-causing substances. 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," commented Dr Kurt Straif of the IARC.

Meanwhile, according to IARC director, Dr Christopher Wild, this move ‘is an important step'.

"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," he said.