The International Agency for Research on Cancer (IARC), a research branch of the World Health Organization (WHO), officially classified air pollution as a carcinogen Thursday, according to the press release.

"The air we breathe has become polluted with a mixture of cancer-causing substances," Dr. Kurt Straif, Head of the IARC Monographs Section said in the 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."

Staif's statement applies to all regions of the world, even if some are more polluted than others.

The IARC previously classified only one element of air pollution, diesel fumes, as air pollutants, according to Nature World News. Both diesel fumes and air pollution are group 1 carcinogens, the most dangerous group, as per cancer.org.

"Our task was to evaluate the air everyone breathes rather than focus on specific air pollutants," Dr. Dana Loomis, Deputy Head of the Monographs Section said. "The results from the reviewed studies point in the same direction: the risk of developing lung cancer is significantly increased in people exposed to air pollution."

Air pollution is most associated with lung cancer, but can also cause bladder cancer, according to the IARC. Research has already proven a link between heart and respiratory diseases. 

Over 220,000 people died of lung cancer in 2010, IARC reported. That number will rise if air quality continues to deteriorate. Solving the problem of air pollution would be best handled by preventative measures rather than medical procedures, CNN reported.

"We can't treat ourselves out of this cancer problem," said Chris Wild, who heads the WHO's cancer research wing, the International Agency for Research on Cancer.

The major sources of air pollution include transportation, stationary power generation, industrial and agricultural emissions, and residential heating and cooking, according to the IARC.

Air pollution's admittance as a group 1 carcinogen can be seen as a negative and a positive.

"Classifying outdoor air pollution as carcinogenic to humans is an important step," IARC Director Dr Christopher Wild said. "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."