Trihalomethane concentrations in tap water as determinant of bottled water use in the city of Barcelona

Bottled water consumption is increasing worldwide, despite its huge economic and environmental cost. We aim to describe personal and tap water quality determinants of bottled water use in the city of Barcelona. This cross-sectional study used data from the Health Survey of Barcelona in 2006（N = 5417 adults）. The use of bottled water to drink and to cook was evaluated in relation to age, gender, educational level, district and levels of trihalomethanes（THMs）, free chlorine, conductivity, chloride, sodium, p H, nitrate and aluminium in municipal tap water using Robust Poisson Regression. The prevalence of bottled water use to drink and cook was 53.9% and 6.7%, respectively. Chemical parameters in water had a large variability（interquartile range of THMs concentrations： 83.2–200.8 μg/L）and were correlated between them, except aluminium. Drinking bottled water increased with educational level, while cooking with bottled water was higher among men than among women and decreased with age. After adjusting by these personal determinants, a dose–response relationship was found between concentrations of all chemicals except aluminium in tap water and bottled water use. The highest association was found for THMs,with a Prevalence Ratio of 2.00（95%CI = 1.86, 2.15） for drinking bottled water and 2.80（95%CI = 1.72, 4.58） for cooking with bottled water, among those with 〉 150 μg/L vs. 〈 100 μg/L THMs in tap water. Conclusion： More than half of Barcelona residents regularly drank bottled water, and the main determinant was the chemical composition of tap water,particularly THM level.

Gene expression changes in blood RNA after swimming in a chlorinated pool

Exposure to disinfection by-products（DBP） such as trihalomethanes（THM） in swimming pools has been linked to adverse health effects in humans, but their biological mechanisms are unclear. We evaluated short-term changes in blood gene expression of adult recreational swimmers after swimming in a chlorinated pool. Volunteers swam 40 min in an indoor chlorinated pool. Blood samples were drawn and four THM（chloroform,bromodichloromethane, dibromochloromethane and bromoform） were measured in exhaled breath before and after swimming. Intensity of physical activity was measured as metabolic equivalents（METs）. Gene expression in whole blood m RNA was evaluated using Illumina Human HT-12v3 Expression-Bead Chip. Linear mixed models were used to evaluate the relationship between gene expression changes and THM exposure. Thirty-seven before-after pairs were analyzed. The median increase from baseline to after swimming were： 0.7 to 2.3 for MET, and 1.4 to 7.1 μg/m^3 for exhaled total THM（sum of the four THM）.Exhaled THM increased on average 0.94 μg/m^3 per 1 MET. While 1643 probes were differentially expressed post-exposure. Of them, 189 were also associated with exhaled levels of individual/total THM or MET after False Discovery Rate. The observed associations with the exhaled THM were low to moderate（Log-fold change range：-0.17 to 0.15）. In conclusion, we identified short-term gene expression changes associated with swimming in a pool that were minor in magnitude and their biological meaning was unspecific. The high collinearity between exhaled THM levels and intensity of physical activity precluded mutually adjusted models with both covariates. These exploratory results should be validated in future studies.