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Swimming in a Chlorinated Pool is Associated with Changes in Levels of Metabolites in Blood

An international study led by ISGlobal, an institution supported by the “la Caixa” Foundation, identifies numerous molecular changes in blood after swimming 40 minutes in a chlorinated pool. The results of the study, published in Environment International, will help decipher the metabolic pathways involved in the association of disinfection by-products (DBP) exposure and adverse health outcomes.  

Chlorine used to disinfect water, including swimming pools, reacts with organic matter (like hair, saliva or perspiration) leading to the formation of numerous chemicals that are unwanted by-products of the disinfection (DBPs) such as trihalomethanes and haloacetic acids. Epidemiological and experimental studies indicate that exposure to DBPs may have adverse health outcomes, but the biological mechanisms remain poorly understood. 

The goal of this study – called PISCINA II and performed in Barcelona in the framework of the EXPOsOMICS project- was to investigate the short-term effects of DBP exposure on the metabolome (i.e. the complete set of small chemical molecules or metabolites in blood), and identify possible metabolic pathways linking DBP exposure and adverse health outcomes. 

The authors selected 60 healthy volunteers that swam during 40 minutes in an interior chlorinated pool. They collected blood samples from the volunteers before and two hours after swimming, and performed metabolic profiling (using liquid chromatography and high resolution mass spectrometry). In parallel, they measured for each person DBP levels in the swimming pool water and also in exhaled air and urine before and after swimming. They found that DBP levels in exhaled breath were significantly higher after the experiment and that uptake of DBP strongly correlated with the level of physical activity. They found 293 metabolic features associated with at least one DBP in exhaled breath. Twenty of these could be identified corresponding to 13 metabolites, including molecules involved in tryptophan metabolism.

The authors recognise the challenge of disentangling the negative effect of DBPs from the positive effect of physical activity. However, they point out that this is the first study to assess many DBPs in exhaled air, to include external exposures, and to accurately measure physical activity.

For Manolis Kogevinas, ISGlobal researcher and study coordinator, “this study can help identify molecular pathways affected by DBP exposure and eventually shed some light on the mechanisms underlying their toxicity”.


van Veldhoven K, Keski-Rahkonen P, Barupal DK, Villanueva CM, et al. Effects of exposure to water disinfection by-products in a swimming pool: A metabolome-wide association study. Environ Int. 2017 Nov 24;111:60-70. doi: 10.1016/j.envint.2017.11.017

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