China’s indoor air raises cancer risk for women

U. BUFFALO (US) — Breathing indoor air in some Chinese cities carries significant cancer risks, especially for women, new research shows.

While around 60 percent of Chinese men smoke, only about 4 percent of women in China smoke, however women’s rates of lung cancer are among the highest in the world—about 21 cases per 100,000.

Indoor air pollution generates levels of fine particulate matter that are at least double the maximum considered acceptable by World Health Organization guidelines, according to the study published in the journal Cancer Causes and Control. The study is the first to measure particulate matter (PM) levels inside the home and to link it with the incidence of lung cancer in Chinese women.


“Our results show that besides smoking, indoor air pollution contributes significantly to women’s lung cancer risk in China,” says lead author Lina Mu, assistant professor of social and preventive medicine in the School of Public Health and Health Professions at the University at Buffalo. “That’s why we wanted to find out how much indoor air pollution contributes to lung cancer risk among Chinese women. It has been suspected but not measured.”

Since women tend to be home for longer periods of time and to cook more frequently, housing-related exposure is more of a factor among women than men.

The case-control study includes 429 Chinese women: 197 who had lung cancer and 232 who were controls. Of the 197 with lung cancer, 164 were nonsmokers while there were 218 nonsmokers in the control group. The study was conducted in Taiyuan city, one of the top 10 air polluted cities in the world according to Asian Development Bank’s 2012 annual report. Taiyuan is a large industrial city in northern China, which is home to heavy industry, including steel, coal mining, and processing and electronics plants.

Among the nonsmokers, lung cancer was strongly associated with multiple sources of indoor air pollution, including exposure to tobacco smoke at work, frequent cooking, and the use of solid fuel, primarily coal, for cooking and heating.

A particle mass monitor was used to measure PM levels inside the homes—mostly apartments—of study participants.

“We found that the smallest type of particulate matter is the type associated with the higher risk of lung cancer among nonsmoking Chinese women,” Mu says.  “For every additional ten micrograms per square meter of fine particular matter, there is an associated 45 percent increased risk of lung cancer.”

Increased lung cancer risk among women was strongly attributed to the fine particles produced by coal combustion for heating and cooking, and from passive smoking. Kitchen ventilation systems, such as fans, are not common in China and people are reluctant to open windows because they want to keep heat in and pollution out.

Also, hot oil, a staple in traditional Chinese stir-frying and deep-frying, produces carcinogens, and is a key contributor.

“Women are at high risk because they are exposed to solid fuel emissions from heating and cooking as well as from passive smoking,” she says, adding that smoking is a key social ingredient in China. “Men tend to gather and smoke together, often in small, enclosed spaces, especially in offices.”

While in large cities, some restaurants have begun to segregate smokers, people smoke freely in most public places in China. Improvements will depend on significant changes, including a switch to clean energy sources, the installation of better ventilation systems, and public education about the benefits of keeping windows open and curbing passive smoking.

Researchers from the University of California, Los Angeles, Fudan University, the Taiyuan City Center for Disease Control and Prevention,  and Shanxi Tumor Hospital contributed to the study that was funded by the National Nature Science Foundation of China, the National Institutes of Health, and the Alper Research Center for Environmental Genomics at UCLA.

Source: University at Buffalo