Living in smog-filled cities raises mouth cancer risks by 40% for men, study suggests

October 11, 2018  19:16

Researchers say that being exposed to high levels of particles from power plants, exhaust systems and dust storms can drive up the risk by more than 40 percent.

The number of new cases of, and deaths from, mouth cancer has been rising in several countries, particularly in Southeast Asia.

Although known risk factors include smoking, drinking and the chewing of 'paan' - a mix of nuts and leaves - being exposed to heavy metals and chemical plant emissions are also thought to lead to the development of the disease.

But the team, from Quest Diagnostics Nichols Institute in California, says its findings are the first to link fine air particles to mouth cancer, and that high levels of ozone, the main component of urban smog, may be key.
For the study, the team looked at national air quality, cancer, health and insurance databases.

They analyzed the levels of various pollutants, including carbon monoxide, nitrogen monoxide, nitrogen dioxide, ozone, and sulphur dioxide, measured in 2009 at 66 monitoring stations in Taiwan.

Next, they examined the health records of more than 482,000 men aged 40 or older that attended preventive health services relating to quitting smoking or chewing paan between 2012 and 2013.

During that period, more than 1,600 mouth cancer diagnoses were made.

While smoking and paan chewing were identifiable risk factors, the researchers found that so were high levels of PM2.5, tiny particles that come from various sources including power plants, exhaust systems, airplanes, forest fires and dust storms.

Because of how small they are, PM2.5 particles stay in the air longer than heavy particles, increasing the risk of us inhaling them.

Additionally, due to their size, they can get deep into the lungs and potentially enter the circulatory system.

Studies have shown that exposure to fine particles can increase our risk of lung disease and heart disease as well as worsen chronic conditions including asthma and bronchitis.

Currently, the WHO estimates that, worldwide, seven million people die every year from exposure to such pollution with most deaths occurring in low- and middle-income countries, chiefly in Africa and Asia.

The concentration of an air pollutant is measured in micrograms (ug) per cubic meter air (m3).

Men who lived in areas where the levels were around 40 ug/m3 had a 43 percent higher risk of developing mouth cancer compared to men living in areas where the levels were approximately 27 ug/m3.

According to the US Environmental Protection Agency, 0 to 12 ug/m3 is viewed as little to no risk, 12.1 to 35.4 ug/m3 is moderate risk and above 35 ug/m3 is unhealthy.

The researchers also found a significant association when levels of ozone, the main component of urban smog, were above 28.69-30.97 parts per billion.

Currently, the Occupational Safety and Health Administration recommends no more than 0.10 parts per million for eight hours per day exposure - several times above the limit found in the study.

Because the study is an observational one, the authors note that cause cannot be established.

In addition, there are certain limitations to consider such as the absence of data on how much PM2.5 enters the mouth or the length of exposure to the pollutant.

However, the researchers say components of PM2.5 include known cancer-causing agents such as polycyclic aromatic hydrocarbons.

These organic compounds found in coal and tar deposits were linked in a June 2002 animal-model study from Sweden to bladder, liver, lung, skin and stomach cancers.

'This study, with a large sample size, is the first to associate oral cancer with PM2.5,' said author Dr Michael McPhaul, medical director of endocrinology and metabolism at Quest Diagnostics.

'These findings add to the growing evidence on the adverse effects of PM2.5 on human health.'

In August, a study from the University of Texas at Austin found that air pollution was shaving years off of the global life expectancy from an average of four months in the US and UK to two years in Egypt.

And in June, an essay by two Harvard scientists stated that environmental policy changes proposed by the Trump administration could lead to an extra 80,000 American deaths per decade.

David Cutler, a public-health economist, and Francesca Dominici, a biostatistician, wrote that rolling back the Clean Power Plan will lead to an estimated 36,000 deaths and a repeal of emission requirements for certain vehicles will lead to an estimated 14,000 deaths.

They argue that the changing policies could cause respiratory problems as well for more than one million people over a decade, many of them children.

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