The hazards of breathing outdoor air in some Chinese cities have
been well-documented. Now a UB study confirms that breathing indoor
air also carries significant cancer risks, especially for Chinese
The UB study, published online this month in the journal Cancer
Causes & Control, found that indoor air pollution that
generates fine particulate matter is a key contributor to the high
rates of lung cancer among Chinese women, despite the fact that few
of them smoke.
The research found indoor particulate matter levels that are at
least double the maximum level considered acceptable by World
Health Organization guidelines. 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 Lina Mu, assistant professor of social
and preventive medicine in the School of Public Health and Health
Professions and lead author on the paper.
While around 60 percent of Chinese men smoke, Chinese women have
extremely low smoking rates—approximately 4 percent.
However, women’s rates of lung cancer in China are
among the highest in the world, approximately 21 cases per 100,000,
while smoking accounts for less than 20 percent of lung cancer
cases in Chinese women, says Mu.
“That’s why we wanted to find out how much indoor
air pollution contributes to lung cancer risk among Chinese
women,” says Mu. “It has been suspected but not
The paper notes that 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
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. A large industrial city in
northern China, Taiyuan is home to heavy industry, including steel,
coal mining and processing and electronics plants.
The study found that among the nonsmokers, lung cancer was
strongly associated with multiple sources of indoor air pollution,
which included exposure to tobacco smoke at work, frequent cooking
and the use of solid fuel, primarily coal, for cooking and
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 10 micrograms per square meter of fine particular
matter, there is an associated 45 percent increased risk of lung
The paper notes that 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.
Mu says that kitchen ventilation systems, such as fans, are not
common in China and that people are reluctant to open windows
because they want to keep heat in and prevent outdoor pollution
from coming inside.
She adds that hot oil, a staple in traditional Chinese
stir-frying and deep-frying, produces carcinogens and is a key
“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.”
Mu notes that while in large cities, some restaurants have begun
to segregate smokers, people smoke freely in most public places in
She says that improvements will depend on significant changes,
such as a switch to clean energy sources and the installation of
better ventilation systems, as well as public education about the
benefits of keeping windows open and curbing passive smoking.
UB co-authors with Mu are Yanli Li, graduate student; William
Scheider, research assistant professor; and Mya Swanson, data
manager; all in the UB Department of Social and Preventive
Medicine. Other co-authors are Shen-chih Chang and Zuo-Feng Zhang
of the Fielding School of Public Health, University of California,
Los Angeles; Jia Su and Shunzhang Yu of Fudan University; Li Liu,
Baozing Zhao and Jianping Shi of the Taiyuan City Center for
Disease Control and Prevention; and Rrungui Niu of Shanxi Tumor
The research 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.