Air pollution tied to survival odds for liver cancer patients

By Madeline Kennedy

(Reuters Health) – For people diagnosed with liver cancer, living in an area with heavy air pollution from industry, traffic or smoke is linked to lower odds of survival, a California study finds.

The association between levels of tiny particles known as PM 2.5 in the air and death from liver cancer or from any cause was strongest for people with the least advanced cancers, researchers report in the International Journal of Cancer.

“Our study suggests that liver cancer patients may be another susceptible group that could benefit from reductions in air pollution,” study co-author Sandrah Eckel of the University of Southern California in Los Angeles said by email.

The liver may be at a high risk because it is responsible for helping the body process toxic materials that enter from the outside, she added.

PM 2.5 pollution is made up of small particles and droplets less than 2.5 microns in diameter. These particles, which are tiny enough to enter the bloodstream through the lungs, are usually the product of combustion – including smoke and fumes from industrial sources and power plants, vehicle engines, wildfires or indoor cooking fires.

Air pollution has been shown to increase lung cancer risk, but it may affect other cancers as well, the study team writes.

The U.S. has standards to control air pollution, but some areas like Los Angeles still go above the allowed levels, Eckel noted. Globally, air pollution may be as much as 10 times the U.S. standard, she said.

To see if there is a link between air pollution and liver cancer survival, the researchers used data on over 20,000 patients with the most common form of liver cancer, hepatocellular carcinoma.

The researchers included all patients who were diagnosed between 2000 and 2009 and listed in the California Cancer Registry.

The research team also used air pollution measurements from the areas where patients lived based on data from the Environmental Protection Agency’s Air Quality System database.

They found that people who were exposed to higher levels of PM 2.5 pollution after being diagnosed were significantly more likely to die from liver cancer or any cause.

For people with localized liver cancer, higher levels of pollution exposure were tied to a 31 percent higher risk of death from any cause compared to people with the same stage cancer exposed to the least pollution. For those whose cancer had spread to nearby tissues, the increased risk associated with higher pollution exposure was 5 percent and for those whose cancer had spread further in their body, the added risk was 10 percent.

The risk differences were similar for death from liver cancer, the researchers note.

Researchers adjusted for factors that might influence the analysis, like the patients’ socioeconomic status, distance from the pollution monitoring station and the size of the city they lived in.

A strength of the study is having included all liver cancer patients in the state registry for a good representation of this population, the authors note. One limitation is that researchers didn’t have much information about patients’ personal details and behaviors, like weight, alcohol consumption and whether they had hepatitis A or B.

“There is increasing evidence that particulate air pollutants can lead to early death from cardiorespiratory disease as well as a range of cancers including liver cancer,” Neil Thomas of the University of Birmingham in the UK said by email.

People can try to reduce their exposure by using air filters, wearing masks and avoiding indoor pollution like burning candles, but the most important step is to put pressure on lawmakers to improve air quality, said Thomas, who was not involved in the study.

“Air pollution reduction should be the goal of everyone for their own health and that of future generations,” Thomas said.

“We generally recommend that people monitor their local air quality index,” said Eckel, noting that in the U.S., local data from the EPA’s air quality monitoring system can be found on the website. “On high pollution days, you might want to stay indoors, close the windows, and clean the air indoors using filters,” Eckel said, and drivers should roll up their windows on busy roads.

SOURCE: International Journal of Cancer, online June 7, 2017