Abstract 3428: Domestic livestock exposure and lung cancer risk among non-smoking women in Xuanwei, China
Authors: Seow Wei Jie , Hu Wei , Vermeulen Roel , Downward George , Li Jihua , Xu Jun , He Jun , Wei Fusheng , Wu Guoping , Rothman Nathaniel , Chapman Robert S. , Lan Qing 
Published: July 2016

Abstract
Background: Lung cancer rates of women in Xuanwei and Fuyuan, rural counties located in the Yunnan Province, are among the highest in China, even though most women there are non-smokers. The unusually high lung cancer rates are mainly attributed to smoky (i.e. bituminous) coal exposures. Many households there and in other rural parts of China have raised animals such as pigs, cows, horses, chickens and ducks in close proximity to their homes. It is hypothesized that contact with animals increases the risk of infection with potentially carcinogenic pathogens. However, findings on the association between livestock and poultry exposures and lung cancer risk, mostly from occupational studies, have been inconsistent.
Objective: To investigate the association between livestock and poultry exposures and lung cancer risk in a general population of non-smoking women who lived in close proximity to livestock and poultry in a rural area in China.
Methods: A hospital-based case-control study among non-smoking women was conducted in Xuanwei and Fuyuan counties in China between March 2006 and July 2013. A total of 1,074 lung cancer cases and 977 hospital-based cancer-free controls were enrolled. Exposure to livestock and poultry, including the animal type (pigs, cows/horses, chickens, ducks) and total number of years an individual was exposed to each animal type, was obtained by questionnaire. Reference groups for the analysis were either never-exposed, or never-exposed combined with those with less than the median years of exposure, depending on the prevalence of exposure to each animal. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of the association between livestock and poultry exposures and lung cancer risk with adjustment for potential confounders, such as lifetime amount of smoky coal used and passive smoking.
Results: Individuals with above the median number of years of exposure to pigs (OR = 1.61, 95% CI = 1.19-2.17) and chickens (OR = 1.49, 95% CI = 1.12-1.99) had increased lung cancer risk, compared to those who had less than the median years of exposure. Compared to those who were never exposed, the risk of lung cancer increased with longer duration of exposure to cows/horses (&lt;median years of exposure: OR = 1.33, 95% CI = 1.00-1.77; ≥median years of exposure: OR = 1.38, 95% CI = 1.03-1.86). The significant associations for pigs and cows/horses persisted after adjusting for other animal exposures in the same model.
Conclusions: Exposure to certain animals was significantly associated with increased lung cancer risk, suggesting that infectious agents may play a role in the etiology of lung cancer among non-smoking women in this region. However, due to the fact that this study was conducted in an area with a high risk of lung cancer due to the use of solid fuels for heating and cooking, we cannot rule out residual confounding.
Citation Format: Wei Jie Seow, Wei Hu, Roel Vermeulen, George Downward, Jihua Li, Jun Xu, Jun He, Fusheng Wei, Guoping Wu, Nathaniel Rothman, Robert S. Chapman, Qing Lan. Domestic livestock exposure and lung cancer risk among non-smoking women in Xuanwei, China. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3428.