Y:X sperm ratio in boron-exposed men.

Several epidemiologic investigations have shown shifts in sex ratios at birth toward females in populations with relatively high boron exposure. To investigate the paternal origin of these shifts, we assayed sperm Y:X ratio in men exposed to a range of environmental and workplace boron. Participants included 63 workers in boron industry: 39 men living in an area of high environmental boron but not employed in boron industry, and 44 controls living in an area of low environmental boron. Total daily boron exposure was calculated as the sum of boron in 24-hour duplicate food and fluid intakes plus personal air sampling for workplace inhalable dust. Internal dose was measured in blood, urine, and semen. Sperm were analyzed by fluorescence in situ hybridization for Y- versus X-bearing cells. Potential confounders were identified using a questionnaire. Total exposure was correlated with internal dose (Pearson correlation for total exposure and boron in blood = 0.63, P < .0001; semen = 0.80, P < .001; and urine = 0.79, P < .0001). Linear regression of logged boron in biologic fluids on Y:X ratio was significant for blood P = .02, semen P = .0003, and urine P = .005. Additionally, when subjects were categorized by exposure group, decreased Y:X sperm ratio was found for boron workers compared with men in a high boron environment and controls (P < .0001). Exogenous environmental or workplace boron exposures were associated with decreases in Y- versus X-bearing sperm. This may explain earlier findings from us and others showing changes in offspring sex ratios at birth for men exposed to boron.