Air pollutants linked to mouth cancer in new study

Exposure to heavy metals and emissions from petrochemical plants are also thought to be implicated in the development of the disease, while air pollution, especially PM2.5, is known to be harmful to respiratory and cardiovascular health.

For the study, the researchers mined national cancer, health, insurance, and air quality databases. They drew on average levels of air pollutants (sulfur dioxide, carbon monoxide, ozone, nitrogen monoxide, nitrogen dioxide, and varying sizes of fine particulate matter), measured in 2009 at 66 air quality monitoring stations across Taiwan.

In 2012-13, they checked the health records of 482,659 men aged 40 and older who had attended preventive health services and had provided information on smoking/betel quid chewing.

Diagnoses of mouth cancer were then linked to local area readings for air pollutants taken in 2009.

• When compared with PM_2.5<26.74 μg/m³, PM_2.5≥40.37 μg/m³ was significantly associated with an increased risk of oral cancer.


• Ozone (28.69≤O₃<30.97 ppb) was significantly associated with an increased risk of oral cancer.


• Smoking and frequent betel quid chewing were significantly associated with an increased risk of oral cancer.

"These results have increased knowledge regarding fine particulate pollution as a risk factor for oral cancer. However, there is a need for further research to investigate the association between oral cancer and PM_2.5, including lower exposure levels," write the authors.

This is an observational study, and as such, can't establish a cause. And there are certain caveats to consider, say the researchers. These include the lack of data on how much PM2.5 enters the mouth, or on long-term exposure to this pollutant.

But some of the components of PM2.5 include heavy metals, as well as compounds such as polycyclic aromatic hydrocarbons-known cancer-causing agents, they say.

And the smaller diameter, but the larger surface area of PM2.5, means that it can be relatively easily absorbed while at the same time potentially wreaking greater havoc on the body, they suggest.

"This study, with a large sample size, is the first to associate oral cancer with PM2.5...These findings add to the growing evidence on the adverse effects of PM2.5 on human health," conclude the authors.