It has been proposed that formaldehyde may influence the risk or severity of asthma through irritant effects by stimulating allergic responses (when linked with endogenous proteins) or by inhibiting bronchodilation, but findings of observational studies of childhood asthma and formaldehyde have been inconsistent. McGwin et al. conducted a systematic review and quantitative meta-analysis of seven peer-reviewed studies that included children with and without asthma and reported formaldehyde exposure levels and estimates of association. Pooled odds ratios (ORs) from both fixed-effects and random-effects models (that account for heterogeneity among studies) indicated positive associations for all studies combined [for a 10-µg/m3 increase in formaldehyde, fixed-effects OR = 1.03; 95% confidence interval (CI), 1.02–1.04; random effects OR = 1.17; 95% CI, 1.01–1.36] and for study subgroups classified according to a variety of characteristics. Results support an association between formaldehyde and childhood asthma, but the authors note that estimates are based primarily on cross-sectional studies without comprehensive individual exposure measurements, information on potential confounders, or diagnostic confirmation, and they conclude that well-designed prospective studies are needed to confirm these findings.
Related News Article: Formaldehyde Exposure among Children: A Potential Building Block of Asthma
Use of environmentally persistent polybrominated diphenyl ether (PBDE) flame retardants has been reduced because of concerns about health effects, but potential health effects of organophosphate (OP) flame retardants used as alternatives to PBDEs have not been extensively investigated, despite evidence of widespread human exposure. Meeker and Stapleton measured the OP flame retardants tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and triphenyl phosphate (TPP) in house dust samples collected from 50 male infertility clinic patients and estimated associations with serum hormone concentrations (luteinizing hormone, follicle-stimulating hormone, estradiol, prolactin, free thyroxine, total triiodothyronine, and thyrotropin) and semen quality parameters (concentration, motility, and morphology). The authors report that TDCPP and TPP were detected in 48 of 50 dust samples at widely varying concentrations. Models adjusted for potential confounders indicated that TDCPP and TPP were both positively associated with serum prolactin concentration, TDCPP was inversely associated with free thyroxine, and TPP was inversely associated with sperm concentration. The authors conclude that additional research to confirm these findings is warranted given evidence of potential effects and widespread exposure to these compounds.
Related News Article: Endocrine Damper? Flame Retardants Linked to Male Hormone, Sperm Count Changes
Associations between long-term exposure to ambient fine particulate matter [with aerodynamic diameter ≤ 2.5 µm (PM2.5)] and cardiovascular mortality have been reported by multiple studies, but associations with specific constituents of PM2.5 have not been examined. Ostro et al. used Cox proportional hazard models to estimate associations of PM2.5 and PM2.5 constituents [elemental carbon, organic carbon (OC), sulfates, nitrates, iron, potassium, silicon, and zinc] with all-cause, cardiopulmonary, ischemic heart disease (IHD), and pulmonary disease mortality in 44,847 participants in the prospective California Teachers Study (CTS). CTS participants were women who were predominantly white, nonsmoking, and U.S. born, with a median age of 54 years at enrollment in 1995. Participants in the present analyses were limited to women who lived within 30 km of a monitor that collected PM2.5 constituent data from June 2002 through July 2007. The authors report that interquartile range (IQR) increases in PM2.5 mass and all measured PM2.5 constituents were positively associated with all-cause, cardiopulmonary, and IHD mortality, and that IQR increases in OC, sulfates, and silicon were positively associated with pulmonary mortality. Associations were somewhat stronger but less precise when analyses were restricted to 7,888 women residing within 8 km of a monitor. Correlations among PM2.5 constituents prevented simultaneous adjustment for all individual constituents, but the authors report that constituents derived from combustion of fossil fuel (OC and sulfates) and crustal origin (Si), were associated with stronger relative risks.
Related News Article: Particulate Soup: Identifying the Most Toxic Constituents of PM2.5
Uterine leiomyomata (fibroids) are the most common indication for hysterectomies in the United States, but underlying causes of these hormonally responsive benign smooth muscle tumors have not been identified. D’Aloisio et al. hypothesized that early-life exposures that affect uterine development and hormone responses later in life might contribute to fibroid pathogenesis. The authors estimated associations between early fibroid diagnoses (diagnosed by health professional before 36 years of age) among 19,972 non-Hispanic white participants in the Sister Study who were 35–59 years old at enrollment. Early fibroid diagnoses were reported by 8% of study participants, consistent with previous estimates. Adjusted risk ratio estimates (from log-binomial regression models) indicated increased relative risks in association with being fed soy formula during infancy, maternal prepregnancy diabetes, low childhood socioeconomic status, and early birth (at least 1 month before the due date). In utero diethylstilbestrol (DES) exposure was also associated with early fibroid diagnosis, but only among women reporting probable (versus definite) DES exposure. The authors conclude that effects of early life exposures on uterine fibroid pathogenesis are biologically plausible, but note that findings need to be replicated in other study populations.
Related News Article: From One Womb to Another: Early Estrogenic Exposures and Later Fibroid Risk
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