Yup, disinfection byproducts in drinking water are monitored and regulated. A CDC primer on DBPs and current regulations can be found here.

Simple chlorination of water with lots of organic compounds creates trihalomethanes, which are regulated under the SDWA. Some cities switch to chloramine when they experience high THM levels from chlorine. Chlorine dioxide treatment can generate chlorites, discussed here.

Cheers,
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--Rick