HONG KONG - Prolonged exposure to fine air pollutants is linked to a higher risk of dying by any cancer, a study that tracked more than 66,000 seniors in Hong Kong has found.
While studies have linked lung cancer with long-term exposure to fine particulate matter, the new study said that the risk of dying from any cancer could be raised.
"We suspected that these particulates could have an equivalent effect on cancers elsewhere in the body," said Dr Thuan Quoc Thach of the University of Hong Kong.
Dr Thuan is one of the main co-authors of the paper, along with Dr Neil Thomas, from the Institute of Applied Health at The University of Birmingham.
The paper was published by journal Cancer Epidemiology, Biomarkers & Prevention on Friday.
The study followed more 66,000 people above 65 in Hong Kong between 1998 and 2011.
The researchers used satellite data and fixed-site monitors to estimate the concentration of PM2.5 particles at their homes.
After accounting for other factors, such as whether the subjects smoked, the study found that the risk of dying from cancer rose by 22 per cent for every 10 micrograms per cubic metre of increased PM2.5 exposure.
The risk went up by up to 42 per cent for those dying of cancers in the digestive system, and by 80 per cent for breast cancer.
The team believe that the link between PM2.5 and cancer could be due to defects in DNA repair function, changes in the body's immune response or inflammation that triggers the growth of new blood vessels fuelling the spread of tumours.
"The implications for other similar cities around the world are that PM2.5 must be reduced to reduce the health burden," said Dr Thomas.
John Groopman, an environmental-health expert at Johns Hopkins Bloomberg School of Public Health, who was not involved in the study, told the Washington Post that the results of the study could be extrapolated to similar cities like Singapore and New York.
In Singapore, the one-hour PM2.5 pollutant reading reached a high of 471 micrograms per cubic metre in October last year, but experts were divided on how harmful that was to health.
While some said even a one-time event could be considered potentially hazardous, others believe that only prolonged exposure to high PM2.5 concentration levels should be a cause for concern.
PM2.5 refers to ambient fine particulate matter, or matter with an diameter of less than 2.5 micrometres.
Emissions from vehicles and factories are a main source of PM2.5 pollution.
The minute particles can be lodged deep in lungs or be absorbed into the bloodstream, and are thus considered more dangerous to health.