The most prevalent female cancer across the world is breast cancer. Current established breast cancer risk factors explain only a fraction of the breast cancer cases diagnosed, and for this reason, other environmental factors have been studied. Exposure to organochlorine compounds has been linked to an increased incidence of breast cancer, although not all data have been consistent. This study was designed to evaluate the relation between polychlorinated biphenyls (PCB) exposure and breast cancer risk in Mexican women. We recruited 140 women from the General Hospital. The cases were 70 newly diagnosed women. We collected environmental and reproductive information by questionnaire. Blood samples were taken for measurement of serum levels of 20 PCB congeners. Risk of breast cancer was found to be positively associated with heavy congeners, age, postmenopausal status, family history of breast cancer and living close to an industrial facility. When PCB were grouped by structure-activity relationships, the risk of breast cancer was positively associated with groups 2b (odds ratio, OR = 1.90, 95% confidence interval, CI, 1.25-2.88), 3 (OR = 1.81, 95% CI 1.08-3.04) and group 4 (OR = 1.57, 95% CI 1.20-2.07). Among postmenopausal women, PCB levels from groups 1a, 2b, and 4 and total PCB were higher in cases, and an association between risk of breast cancer with groups 1a (OR = 7.59, 95% CI 1.1-51.4), 2b (OR = 3.7, 95% CI 1.2-11.2) and 4 (OR = 1.8, 95% CI 1.1-3.1) was found in this group of women. This study showed an association between heavy and potentially estrogenic PCB congeners and breast cancer risk.

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The presence of these SNPs in patients with allergic rhinitis can lead to higher serum histamine, therefore to a higher risk of developing more severe symptoms or more associated allergic diseases, even if the serum IgE remains low.

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We suggest a synergistic association between HNMT and DAO functional polymorphisms and migraine; this hypothesis must be further confirmed by larger studies. However, the characteristics and ethnic differences between analysed populations should be considered when interpreting the results.