Can Indoor Swimming Alter Hormones in Boys?

Swimming is generally considered an excellent form of exercise, and indoor swimming is common, especially in winter. However, there is evidence that swimming in a chlori-nated indoor pool can cause respiratory irritation or genotoxicity in some people. A recent study suggests another possible consequence: altered levels of hormones in boys. 2 The study population consisted of 199 primarily white boys aged 14-18 years who swam regularly in indoor and/or outdoor chlorinated pools, and 162 similar boys who swam most frequently in an indoor pool disinfected with copper–silver ioniza-tion (but also swam at times in indoor or outdoor chlorinated pools). The authors compared serum levels of several testicu-lar hormone biomarkers between the two groups: inhibin B, total and free testosterone, sex hormone–binding globulin, luteinizing hormone, follicle-stimulating hormone, and dehydroepiandrosterone sulphate. The boys who swam the most in indoor chlorinated pools had concentrations of inhibin B and total testosterone about 20% lower than those of boys who swam in the pool disinfected with copper–silver ioniza-tion, and the former were about 3 times more likely than the latter to have abnormally low concentrations of these hormones. The effects were more pronounced for exposure before age 7 than before age 10 (after which no significant changes were seen), and adverse effects were associated with swimming as little as 30 minutes every 2 weeks. There were no significant hormonal changes in boys who swam in outdoor chlo-rinated pools. These were primarily backyard pools that study coauthor Alfred Bernard, a professor of toxicology at Catholic University of Louvain, says tend to be less prone than public pools to have elevated concentrations of urine and other organic matter. That means less chlorination by-products are formed. accounted for factors such as age, body mass index, time of day of blood sampling, smoking status, having been breastfed, consumption of tap or bottled water since babyhood, insecticide use, residential proximity to a busy road, and participation in certain other sports. There are several limitations to the study, such as the lack of many types of measurements of water quality and disinfec-tion by-products in the pools and the absence of data on testis size and other indicators of each boy's pubertal status. The clinical significance of the hormonal changes identified is therefore unclear. The authors speculate the hormonal changes may have occurred because of exposure to chlorination by-products that permeate the scrotum and affect the testes. The authors explain that the …