Original articlesCooking oil fumes and risk of lung cancer in women in rural Gansu, China
Introduction
Chinese women experience high incidence and mortality rates of lung cancer, especially adenocarcinoma [1], [2]. Smoking may account for a relatively low percentage of the observed excess risk, since Chinese women tend not to smoke [3], [4], [5], [6]. Indoor air pollutants such as environmental tobacco smoke (ETS) or combustion by-products from coal burning have been hypothesized to explain some of this excess lung cancer [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]. Fumes emitted from vegetable cooking oils during stir- and deep-frying are important contributors to indoor air pollution, particularly for women. Oils are usually first heated to high temperatures in a wok (large metal pan with raised sides) to reduce noxious odors, resulting in large emissions of fumes.
Several epidemiological studies have reported significant positive associations between lung cancer and exposure to cooking fumes [4], [5], [6], [7], [8], [9], [10], [11], [12], [16], [17], [18], [19], [20], [21], [22]. Only two studies [4], [21] have investigated lung cancer risk in relation to specific types of vegetable cooking oils, with risk estimates ranging from 1.4 to 1.8 for use of rapeseed oil, as compared to soybean oil. These findings were supported by laboratory studies [23], [24], [25]. Volatile organic compounds (e.g. 1,3 butadiene, benzene, acetaldehyde and acrolein) and formaldehyde were detected in cooking fumes, with higher levels in unrefined rapeseed oil and lower levels in soybean and peanut oils [25], [26].
Most investigations of lung cancer risk among Chinese women have been conducted in large cities where commercially produced oils are used, mainly rapeseed, soybean, and peanut oils. We report here on an analysis of lung cancer risk in women who participated in a population-based case-control study of lung cancer that was conducted in Gansu Province, a rural, non-industrial area of North-western China. The purpose of the analysis was to evaluate cooking fumes and cooking practices in relation to lung cancer. In this area, cooking oils are made locally in workshops and small factories with no or limited refining, using mechanical filtration and chemical purification, and from a variety of locally grown seeds including linseed, rapeseed, and to a lesser extent, perilla seed and hempseed.
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Study subjects
Cases included female residents of Pingliang and Qingyang prefectures in Gansu Province, China, who were newly diagnosed with lung cancer between the ages of 30 and 75 years during the period January, 1994 through April, 1998. We ascertained cases retrospectively from January, 1994 to May, 1996, and prospectively from June, 1996 to April, 1998. Women with lung cancer were identified from local clinics, county and township hospitals, and county tuberculosis anti-epidemic stations. In addition,
Results
Table 1 shows the distribution of demographic characteristics of study subjects. Cases were more likely to have a higher level of income and education, own a color television, own fewer large animals, and live in standard above ground dwellings and apartments. These factors were significantly associated with the types of cooking oil used. There were very few cases (n=27) and controls (n=47) who had ever smoked cigarettes or pipes for more than 6 months (Odds Ratio (OR)=1.19, 95% confidence
Discussion
Our results suggested that women who ever-cooked with rapeseed oil, alone or in combination with linseed oil, experienced a statistically significant 67% increased risk of lung cancer compared to those who used linseed oil alone. We also observed a significant dose–response of increased risk with increased frequency of stir-frying among women who ever-cooked with either rapeseed or linseed oil. Risk also increased with total number of years cooking with either oil. We found an association
Conclusion
In summary, we found that women who stir-fried frequently, especially with rapeseed oil, had an increased risk of lung cancer. In addition, risk for lung cancer increased with total number of years spent cooking. There was also evidence that exposure to cooking fumes from linseed oil may have also contributed to this risk. Reports of eye/throat irritation associated with use of these oils also conferred a significantly increased risk of lung cancer in women.
Acknowledgements
We are grateful to Shouzhi Zhang, Shurong Zhang, Ying Xia, Bing Shang, Suwen Lei, Shujie Lei and Wenlan Wang of the Laboratory of Industrial Hygiene, Ministry of Public Health, Beijing, Peoples Republic of China, for data collection support; and Margaret Pacious and Regina Hur, Westat Inc., for data management and programming support. We thank Katherine Chen, National Cancer Institute (NCI), for recognizing the research potential of this uniquely exposed population and for bringing it to the
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