Other health effects
Many in vitro and in vivo toxicological studies have provided evidence about genotoxic and cytotoxic effects induced by CBPs and the WHO International Agency for Research on Cancer acknowledges sufficient evidence for the carcinogenicity of chloroform and other widespread CBPs in animals75.
In humans, however, the epidemiologic evidence overall has generally been considered insufficient to declare CBPs to be carcinogenic, with bladder cancer presenting the most consistent evidence by providing the greatest likelihood of causality. It is worth noting that the majority of the studies evaluate the risk of cancer related to drinking water and not exposure in swimming-pools, so this lack of evidence should be considered with concern and not extrapolated. In fact, a recent study showed that for elite swimmers and their coaches, the levels of THMs in a Portuguese swimming-pool exceeded the limits for cancer risk76.
Regarding bladder cancer, several epidemiological studies have evaluated its risk in relation with CBPs, of which some are of sufficient quality to provide meaningful evidence towards causal inference, including meta-analysis77 and two pooled analyses78,79. While the majority were related to drinking water, there are also studies finding increased risk of bladder cancer related to showering, bathing, or swimming exposures to THM80-82.
Associations with other types of cancer have been suggested, namely melanoma risk associated with a history of swimming83and colorectal cancer risk with CBPs exposure in drinking water84.
Regarding reproductive effects, there is no clear evidence linking CBPs exposure to poor pregnancy outcomes, except for a slight association with fetal growth-related outcomes and sporadic associations with some categories of congenital anomalies85.
Potential impact of CBPs on male fertility has been much less studied and is of great concern given the remarkable permeability of the scrotal skin. Most studies have addressed mainly the risks related to drinking water, while one study addressed the exposure through swimming-pool water and found that adolescents having attended indoor chlorinated-pools for > 250 h before the age of 10 years or > 125 h before the age of 7 years were three times more likely to have an abnormally low serum inhibin B and ⁄ or total testosterone than their peers who never visited these pools and those who attended outdoor chlorinated-pools or a copper–silver pool86.