Acute changes in serum immune markers due to swimming in a chlorinated pool

•Swimming in a chlorinated pool has been linked to health effects.•Modulation of the immune system by disinfection byproducts might play a role.•We measured exposure to disinfection byproducts due to swimming in a chlorinated pool.•We measured changes in immune markers in serum from before to after swimming.•We observed acute changes in immune markers after swimming.

BackgroundExposure to disinfectants and disinfection byproducts (DBPs) due to swimming in chlorinated water has been associated with allergic and respiratory health effects, including asthma.ObjectivesBiological mechanisms contributing to these associations are largely unknown. We hypothesized a potential pathway involving modulation of the immune system.MethodsWe assessed levels of immune markers (CCL11, CCL22, CXCL10, CRP, EGF, GCSF, IL-8, IL-17, IL-1RA, MPO, VEGF, Periostin) in serum collected from 30 women and 29 men before and after 40 min of swimming in a chlorinated pool. Exposure to DBPs was assessed by measuring bromodichloromethane, bromoform, chloroform, and dibromochloromethane in exhaled breath before and after swimming. Covariate data including information on physical activity was available through questionnaires and measurements. We assessed the association between indicators of swimming in a chlorinated pool and changes in serum immune marker concentrations using linear regression with bivariate normal distributions and adjusted for multiple comparisons by applying the Benjamini-Hochberg procedure.ResultsWe observed a significant decrease in serum concentrations of IL-8 (− 12.53%; q = 2.00e-03), CCL22 (− 7.28%; q = 4.00e-04), CCL11 (− 7.15%; q = 9.48e-02), CRP (− 7.06%; q = 4.68e-05), and CXCL10 (− 13.03%; q = 6.34e-14) and a significant increase in IL-1RA (20.16%; q = 4.18e-06) from before to after swimming. Associations with quantitative measurements of DBPs or physical activity were similar in direction and strength. Most of the observed associations became non-significant when we adjusted the effects of exposure to DBPs for physical activity or vice-versa.ConclusionsOur study indicates that swimming in a chlorinated pool induces perturbations of the immune response through acute alterations of patterns of cytokine and chemokine secretion. The observed effects could not be uniquely attributed to either exposure to DBPs or physical activity. Evidence in the literature suggests that observed decreases in immune markers are possibly due to an immunosuppressive effect of DBPs, while the increase in IL-1RA might be due to physical activity.