Breast cancer is one of the major female health problems worldwide. Although there is growing evidence indicating that air pollution increases the risk of breast cancer, there is still inconsistency among previous studies. Unlike the previous studies those had case-control or cohort study designs, we performed a nationwide, whole-population census study. In all 252 administrative districts in South Korea, the associations between ambient no 2 and particulate matter 10 (PM 10) concentration, and age-adjusted breast cancer mortality rate in females (from 2005 to 2016, N mortality = 23,565), and incidence rate (from 2004 to 2013, N incidence = 133,373) were investigated via multivariable beta regression. population density, altitude, rate of higher education, smoking rate, obesity rate, parity, unemployment rate, breastfeeding rate, oral contraceptive usage rate, and Gross Regional Domestic product per capita were considered as potential confounders. Ambient air pollutant concentrations were positively and significantly associated with the breast cancer incidence rate: per 100 ppb CO increase, odds Ratio oR = 1.08 (95% Confidence Interval CI = 1.06-1.10), per 10 ppb NO 2 , oR = 1.14 (95% CI = 1.12-1.16), per 1 ppb SO 2 , oR = 1.04 (95% CI = 1.02-1.05), per 10 µg/m 3 PM 10 , oR = 1.13 (95% ci = 1.09-1.17). However, no significant association between the air pollutants and the breast cancer mortality rate was observed except for PM 10 : per 10 µg/m 3 PM 10 , oR = 1.05 (95% CI = 1.01-1.09). Breast cancer is the most frequently diagnosed cancer among women worldwide 1 , and is rapidly increasing in industrialized countries and urban areas. In South Korea, breast cancer is the second most common after thyroid cancer and has annually increased by 6.1% from 1999 to 2014 2,3. Increased exposure to environmental female hormones is considered to affect the rise of breast cancer incidence. In addition, hormone-dependent cancer is increasing in industrialized countries 1,4. There is growing evidence indicating that air pollution is a risk factor for breast cancer. Nitrogen oxides (NO 2 and NO x) 5-9 , fine particulate matters (PM 10 and PM 2.5) 10,11 , and polycyclic aromatic hydrocarbons (PAHs) 12,13 are reported to associate with breast cancer incidence. The physiological mechanisms by which air pollutants affect breast cancer are largely explained in two ways. First, air pollutants may directly cause genetic mutations, as they are carcinogenic 14,15. Second, air pollutants may affect breast cancer incidence by increasing breast density, which is known to be a risk factor. Yaghjyan et al. reported an association between exposure to PM 2.5 , O 3 , and mammographic breast density 16. Female hormones affect breast density, and some air pollutants are known to exhibit endocrine-disrupting properties, including xenoestrogens 17. However, in the Danish Diet, Cancer and Health cohort (1993-1997) study, little evidence of association between traffic-related air pollution exposure and breast density was found 18. Hung et al. reported ...
For patients with chronic lower respiratory disease, hypobaric hypoxia at a high altitude is considered a risk factor for mortality. However, the effects of residing at moderately high altitudes remain unclear. We investigated the association between moderate altitude and chronic lower respiratory disease mortality. In particular, we examined the lower 48 United States counties for age-adjusted chronic lower respiratory disease mortality rates, altitude, and socioeconomic factors, including tobacco use, per capita income, population density, sex ratio, unemployment, poverty, and education between 1979 and 1998. The socioeconomic factors were incorporated into the correlation analysis as potential covariates. Considerable positive (R = 0.235; P <0.001) and partial (R = 0.260; P <0.001) correlations were observed between altitude and chronic lower respiratory disease mortality rate. In the subgroup with high COPD prevalence subgroup, even stronger positive (R = 0.346; P <0.001) and partial (R = 0.423, P <0.001) correlations were observed. Multivariate regression analysis of all available socioeconomic factors revealed that additional knowledge on altitude improved the adjusted R2 values from 0.128 to 0.186 for all counties and from 0.301 to 0.421 for counties with high COPD prevalence. We concluded that in the lower 48 United States counties, even a moderate altitude may pose considerable risks in patients with chronic lower respiratory disease.
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