Air pollution may be linked to heightened mouth

High levels of air pollutants, especially fine particulate matter (PM2.5) and ozone, can be linked to a risk of developing cancer, suggests the first study of its kind, published online in the Journal of Investigative Medicine.

The number of new cases, and deaths from, mouth cancer is increasing in many parts of the world. Known risk factors include smoking, drinking, human papilloma virus, and parts of South East Asia, the chewing of betel quid ('paan'), a mix of ingredients wrapped in betel leaf.

Exposure to heavy metals and emissions from petrochemicals 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.

To find out if air pollutants might have a role in the development of cancer mouth, the researchers mined national cancer, health, insurance, and air quality databases.

They are associated with air pollutants (sulfur dioxide, carbon monoxide, ozone, nitrogen monoxide, nitrogen dioxide, and varying particle size), measured in 2009 at air quality monitoring stations across Taiwan.

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

The diagnosis of oral cancer was then linked to local area readings for air pollutants taken in 2009.

In 2012-13, 1617 cases of oral cancer were diagnosed among men. Unsurprisingly, smoking and frequent betel quid chewing were significantly associated with heightened risk of a diagnosis.

But so too were high levels of PM2.5. After increasing the incidence of influenza, increasing levels of PM2.5 were associated with an increased risk of oral cancer.

When compared with levels below 26.74 ug / m3, those above 40.37 ug / m3 were associated with a 43 percent heightened risk of a mouth cancer diagnosis.

A significant association was also observed for ozone levels below 28.69-30.97 parts per billion.

This is an observational study, and as such, can not establish cause. And there are some caveats to consider, say the researchers. These include the lack of data on PM2.5 enters the mouth, or on this pollutant.

It is possible that they could contribute to cancer, they acknowledge, and further research would be needed to delve further into this.

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

And the smaller diameter, of larger area, of PM2.5 means that it can be easily absorbed while at the same time.

"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," they conclude.

Explore further:
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More information:
Yu-Hua Chu et al, Association between fine particle and oral cancer among Taiwanese men, Journal of Investigative Medicine (2018). DOI: 10.1136 / jim-2016-000263