Air pollution is classified as carcinogenic to humans given its association with lung cancer, but there is little evidence for its association with cancer at other body sites, researchers said.
In a large-scale study led by the Barcelona Institute of Global Health (ISGlobal) in Spain, researchers observed an association between some air pollutants and mortality from kidney, bladder and colorectal cancer.
The study, published in the journal Environmental Health Perspectives, included more than 600,000 adults in the US who were followed for 22 years (from 1982 to 2004).
Over 43,000 non-lung cancer deaths were registered among the participants. PM2.5 was associated with mortality from kidney and bladder cancer, with a 14 and 13 per cent increase, respectively, for each 4.4 micro-grammes per cubic metre (g/m3) increase in exposure.
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In turn, exposure to NO2 was associated with colorectal cancer death, with a six per cent increase per 6.5 parts per billion (ppb) increment.
No significant associations were observed with cancer at other sites, researchers said.
"This research suggests that air pollution was not associated with death from most non-lung cancers, but the associations with kidney, bladder and colorectal cancer deserve further investigation," she said.