Does Air Pollution Lead to Increased Incidence of Breast Cancer? Naomi Schmidt ‘16 ES366: The Environment and Human Health, Environmental Studies Program, Colby College Air Pollution Chemicals and CarcinogenicityAir Pollution and Breast Cancer Many factors contribute to the development of breast cancer. It is hypothesized that one of these risk factors is exposure to air pollution. Correlative data supports the notion that breast cancer rates are significantly higher in industrialized countries, where there is more pollution. Within the US, breast cancer incidence is higher in urban areas. 3 However, correlation does not imply causation, and there could be a number of other factors that explain the changes in breast cancer incidence. NO 2 Concentration and Breast Cancer Incidence The chemicals in ambient air pollution, which are in large part due to motor vehicle emissions, were tested in three studies examining the link between pollution and breast cancer. A study done by Chen and Bina observed the trends in NO 2 detected in the environment and breast cancer incidence. It was found that they were correlated, but with a twenty year lag, which led the authors to the conclusion that if there is a link between NO 2 and breast cancer, there may be approximately twenty years between exposure and cancer formation. 1 Below is a graph of both NO 2 concentration and breast cancer incidence rates. Effect of Time of Exposure A study by Nie at al. collected data from women regarding where they had lived throughout their lives and determined how that information corresponded with time of breast cancer formation. The study found that pre-menopausal breast cancer was most likely in women who had lived in urban (or polluted) areas at the age of menarche, 2 which is likely due to the fact that that is when breast tissue is in development. It was also discovered that women who were exposed to pollutants during their first pregnancy were more likely to have post-menopausal breast cancer, 2 which is likely due to fragile hormonal changes during pregnancy, which are disrupted by toxic chemicals in pollution. The Clean Air Act Recognizing air pollution’s ill health effects, the federal Clean Air Act was passed in 1963, and was strengthened first in 1970, and then again in It is enforced by the EPA. 4 The graph below shows the concentrations of selected pollutants in the environment, all of which have had significant reductions. This is likely attributable to the clean air act. The graph below shows female breast cancer death rates by race. African-Americans women have by far the highest rate, 7 which could be attributed to the fact that a greater percentage of African-American women live in urban areas than other races. 15 In order to reduce this gap (and breast cancer death rates), public knowledge and actions towards cleaner air are necessary. Another explanation for these statistics could be that access to treatment varies by race. Works Cited These are small particles, such as dust or soot. They affect health by getting deep into the lungs and increasing the risk of heart and lung diseases. There is sufficient evidence that they are carcinogenic to the lungs. 9 Particulate Matter These molecules (NO2 and NO) are products of motor vehicle emissions. They react with ammonia and water to form small particles that get into the lungs. They have not been classified as carcinogens by the EPA,5 but are a focus of many breast cancer and air pollution studies. Nitrogen Oxides VOCs are present in the environment due to automobile emissions. They cause kidney, liver and CNS damage. Many have been shown to be carcinogenic to humans, especially in terms of lung cancer (e.g. formaldehyde). 8 Volatile Organic Compunds Social Justice Breast cancer incidence rates have followed a similar trend. Breast cancer was on the rise until the early nineties, when it began to level off, and has decreased in the last decade. 11 This could potentially be linked to the decreases seen air pollutants, showing the positive health effects of the clean air act. However, it is difficult to say, because the length of time between exposure to pollution and breast cancer is unknown, and is hypothesized by Nie et. al to be at least a decade 2, and by Chen in Bina to be twenty years. 1 Future Directions The Clean Air Act has made significant impacts on pollution, and so it logically follows that even stricter regulation of pollutants will lead to cleaner air and a healthier population. In addition the CAA, alternative forms of energy could lead to an ameliorated environment, since many air pollutants are derived from motor vehicle emissions. 1 Bina, W. F., & Chen, F. (). Correlation of white female breast cancer incidence trends with nitrogen dioxide emission levels and motor vehicle density patterns. Breast Cancer Research and Treatment,, Freudenheim, J. L., Nie, J., & Beyea, J. (). Exposure to traffic emissions throughout life and risk of breast cancer: the Western New York Exposures and Breast Cancer (WEB) study. Cancer Causes & Control,, Wei, Y., Davis, J., & William, B. (). Ambient air pollution is associated with the increased incidence of breast cancer in the US. International Journal of Environmental Health Research, 22, The Plain English Guide to the Clean Air Act. (2007, April 1). Environmental Protection Agency. Retrieved April 1, 2014, from 5 Nitrogen Dioxide Health. (2013, February 1). EPA. Retrieved April 1, 2014, from 6 An Introduction to Indoor Air Quality: Volatile Organic Compounds (VOCs). (2012, July 1). EPA. Retrieved April 1, 2014, from 7 Breast Cancer Rates by Race and Ethnicity. (2013, August 12). Centers for Disease Control and Prevention. Retrieved April 28, 2014, from 8 Indoor Air Quality Scientific Findings Resource Bankhttp:// (2014, January 1). Indoor Air Quality Scientific Findings Resource Bank : Indoor Volatile Organic Compounds (VOCs) and Health : Cancer. Retrieved April 28, 2014, from 9 Particle Pollution. (2013, January 1). State of the Air Retrieved April 28, 2014, from particle.html 10 SEER Stat Fact Sheet: Breast Cancer. (2012, January 1). Surveillence, Epidemiology and End Results Program. Retrieved April 28, 2014, from 11 Frey, W. (2011, May 1). Racial and Ethnic Changes in Metro America in the 2000s. Metropolitan Policy Program. Retrieved April 28, 2014, from Figure 1. Breast cancer death rates by race and ethnicity from 1999 until Figure 2. NO 2 concentrations reported from 75 monitoring sites, USA, and the incidence rate of breast cancer in white females. 1 Figure 3. NO 2, SO 2, CO and lead concentrations tested across the US from 1980 to