Traffic air pollution and risk of death from breast and ovarian cancers in Taiwan: fine particulate matter (PM2.5) as a proxy marker

• Main Authors: Li-Ju Hung, 洪麗如
• Other Authors: Chun-Yuh Yang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/74171354019713812161

博士 === 高雄醫學大學 === 職業安全衛生研究所 === 101 === In Taiwan, breast cancer is the fourth leading cause of female cancer mortality, and ovarian cancer is the eighth. Only about one-third of new cases of breast cancer are attributable to known risk factors, and much of the etiology remains unexplained. Moreover, little is known about the etiology of ovarian cancer. Some studies have revealed that there is substantial geographic variation in female breast and ovarian cancer mortality within the country, which suggests an environmental risk may be involved. Therefore this thesis hypothesizes that environmental exposures may also contribute to breast and ovarian cancer risk. Air pollution from motor vehicle exhaust has been one of the most studied environmental factors. Exhaust from traffic is a complex mixture of many chemical compounds, including benzene, polycyclic aromatic hydrocarbons (PAHs) and benzo[a]pyrene (B[a]P). The International Agency for Research on Cancer (IARC) classified the emission of diesel engine exhaust compounds as probably carcinogenic (Group 2A) and gas engine exhaust compounds as possibly carcinogenic to humans (Group 2B). In Taiwan, the major source of PAHs is traffic exhaust. Most of the PAHs are in the particulate phase. Ninety to 95% of particulate phase PAHs are physically associated with particular matter which is less than 3.3 μm. These small particles are thought to have biological relevance because they can be inhaled and deposited in the lower respiratory tract. In this thesis, the relationship between breast and ovarian cancer mortality and air pollution was examined using an ecological design. The studied areas consisted of 61 municipalities in Taiwan. Air quality data for recorded concentrations of PM2.5 from studied municipalities within 2006–2009 were employed as a marker of traffic emissions and a proxy for PAHs exposure. Besides, age-standardized mortality rates for breast and ovarian cancer were calculated within 1999–2008. A weighted multiple regression model was adopted to calculate the adjusted risk ratio in relation to PM2.5 levels. Results have revealed that individuals who resided in municipalities with the highest PM2.5 were at an increased risk of death from breast and ovarian cancer. This study is the first to suggest that exposure to high levels of PM2.5 as a proxy measure of PAHs may be associated with an increased risk of death from breast and ovarian cancer. The present findings warrant further investigation into the role of air pollutants in the risk of breast and ovarian cancer.