Data suggests there may also be a link with bladder cancer.
Dr Kurt Straif, from IARC, said: "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 Research UK said it was not a surprise.
Dr Julie Sharp, the head of health information at the
charity, said: "It's important that people keep the risk from air
pollution in perspective.
"Although air pollution increases the risk of developing lung
cancer by a small amount, other things have a much bigger effect on our
risk, particularly smoking."
Dr Rachel Thompson, head of research interpretation at the
World Cancer Research Fund International, said: "This latest evidence
confirms the need for government, industry and multinational bodies to
urgently address environmental causes of cancer.
"But there's also a lot we can do as individuals to lower our
chances of developing the disease such as being more physically active
and adopting a healthier diet."