Residential ultraviolet radiation and breast cancer risk in a large prospective cohort.

BACKGROUND: Ambient ultraviolet (UV) radiation has been increasing due to climate change. While this may result in adverse health consequences such as an increased incidence of skin cancer, UV radiation is also a source of vitamin D, which has been hypothesized to be protective for breast cancer risk. METHODS: Using a spatiotemporal kriging model, we estimated residential UV exposure levels for the enrollment addresses (2003-2009) of breast cancer-free women aged 35-74 years participating in the Sister Study and living in the contiguous United States (N = 48,450). Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the risk associated with UV exposure levels (mW/m2) categorized in quintiles. We examined the association for breast cancer overall (invasive and ductal carcinoma in situ) and by estrogen receptor (ER) status of the tumor. We considered effect modification by regular (≥4 times/week) vitamin D supplement use. RESULTS: Over a median of 10.5 years of follow up, 3,510 incident breast cancer diagnoses were reported. We found no evidence of an association between living in areas with higher levels of UV radiation and overall breast cancer risk (HRQ5 vs. Q1 = 1.00, 95% CI: 0.90, 1.11). Higher UV levels were inversely associated with the risk of ER- breast cancer (HRQ5 vs. Q1 = 0.73, 95% CI: 0.55-0.99), but not ER+ (HR Q5 vs. Q1 = 1.04, 95% CI: 0.92-1.18). For ER- breast cancer, the inverse association was only evident in women who did not regularly take vitamin D supplements (HRQ5 vs. Q1 = 0.52, 95% CI: 0.33-0.81) compared with those who did regularly take vitamin D supplements (HRQ5 vs. Q1 = 1.02, 95% CI: 0.68-1.54; p-for-heterogeneity = 0.12). CONCLUSIONS: The findings from this study support a role for UV exposure and vitamin D in the etiology of ER- breast cancer.

Outdoor air pollution and anti-Müllerian hormone concentrations in the Sister Study.

BACKGROUND: Anti-Müllerian hormone (AMH) concentrations are a marker of ovarian reserve and are indicative of a woman's reproductive lifespan. Exposure to tobacco smoke has been associated with lower AMH concentrations; however, less is known about the association between ambient air pollution and ovarian reserve. METHODS: For 883 premenopausal Sister Study participants recruited between 2003 and 2009 in the United States, adult residential annual average concentrations of PM2.5, PM10, and NO2 were estimated using validated universal kriging models incorporating land-use regression. We estimated the distance in meters to the nearest major road for both adult enrollment and childhood residences. Serum AMH was measured using an ultrasensitive ELISA assay. Samples with AMH concentrations below the detection limit were analyzed using a picoAMH ELISA assay. Multivariable-adjusted linear regression was used to estimate the percent change in AMH in relation to ambient residential air pollution, categorized in quartiles and per interquartile range increase, and distance to a major roadway. RESULTS: Overall, we observed little to no evidence of associations between AMH and air pollution concentrations or proximity to roadways. Women in the highest quartile of NO2 exposure, a traffic-related pollutant, had higher estimated AMH concentrations (Q4 vs. Q1, 42.9%; 95% CI = -3.4, 111.4) compared with the lowest quartile. However, lower mean AMH concentrations were observed for women living closer to a major roadway (<50 m to nearest roadway vs. ≥200 m = -32.9%; 95% CI = -56.1, 2.6). CONCLUSIONS: We saw little consistent evidence to support an association between outdoor air pollution and diminished ovarian reserve in US women ages 35-54.

Air pollution and breast cancer risk in the Black Women's Health Study.

BACKGROUND: Air pollution contains numerous carcinogens and endocrine disruptors which may be relevant for breast cancer. Previous research has predominantly been conducted in White women; however, Black women may have higher air pollution exposure due to geographic and residential factors. OBJECTIVE: We evaluated the association between air pollution and breast cancer risk in a large prospective population of Black women. METHODS: We estimated annual average ambient levels of particulate matter <2.5 µm (PM2.5), nitrogen dioxide (NO2) and ozone (O3) at the 1995 residence of 41,317 participants in the Black Women's Health Study who resided in 56 metropolitan areas across the United States. Cox proportional hazards regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for an interquartile range (IQR) increase in each pollutant. We evaluated whether the association varied by menopausal status, estrogen receptor (ER) status of the tumor and geographic region of residence. RESULTS: With follow-up through 2015 (mean = 18.3 years), 2146 incident cases of breast cancer were confirmed. Higher exposure to NO2 or O3 was not associated with a higher risk of breast cancer. For PM2.5, although we observed no association overall, there was evidence of modification by geographic region for both ER- (p for heterogeneity = 0.01) and premenopausal breast cancer (p for heterogeneity = 0.01). Among women living in the Midwest, an IQR increase in PM2.5 (2.87 µg/m3), was associated with a higher risk of ER- (HR = 1.53, 95% CI: 1.07-2.19) and premenopausal breast cancer (HR = 1.32, 95% CI: 1.03-1.71). In contrast, among women living in the South, PM2.5 was inversely associated with both ER- (HR = 0.74, 95% CI: 0.56-0.97) and premenopausal breast cancer risk (HR = 0.75, 95% CI: 0.62-0.91). DISCUSSION: Overall, we observed no association between air pollution and increased breast cancer risk among Black women, except perhaps among women living in the Midwestern US.

Adolescent use of hair dyes, straighteners and perms in relation to breast cancer risk.

Hair products can contain hormonally active and carcinogenic compounds. Adolescence may be a period of enhanced susceptibility of the breast tissue to exposure to chemicals. We therefore evaluated associations between adolescent hair product use and breast cancer risk. Sister Study participants (ages 35-74 years) who had completed enrollment questionnaires (2003-2009) on use of hair dyes, straighteners/relaxers and perms at ages 10 to 13 years (N = 47 522) were included. Cox proportional hazards regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for associations between hair products and incident breast cancer (invasive cancer or ductal carcinoma in situ), with consideration of heterogeneity by menopausal status and race/ethnicity. Over an average of 10 years of follow-up, 3380 cases were diagnosed. Frequent use of straighteners and perms was associated with a higher risk of premenopausal (HR = 2.11, 95% CI: 1.26-3.55 and HR = 1.55, 95% CI: 0.96-2.53, respectively) but not postmenopausal breast cancer (HR = 0.99, 95% CI: 0.76-1.30 and HR = 1.09, 95% CI: 0.89-1.35, respectively). Permanent hair dye use during adolescence was uncommon (<3%) and not associated with breast cancer overall (HR = 0.97, 95% CI: 0.78-1.20), though any permanent dye use was associated with a higher risk among black women (HR = 1.77, 95% CI: 1.01-3.11). Although frequency of use of perms (37% non-Hispanic white vs 9% black) and straighteners (3% non-Hispanic white vs 75% black) varied by race/ethnicity, associations with breast cancer did not. Use of hair products, specifically perms and straighteners, during adolescence may be associated with a higher risk of premenopausal breast cancer.