Ugh, I really wish the CDC and WHO would issue a clarification of this - the studies being talked about in media outlets lately is solely based on COMMERCIAL/PUBLIC pools. It has NOTHING to do with residential pools except in the oblique manner that a pool of water that is not properly cared for can contain harmful disinfection byproducts (DBPs)....which is nothing more than a giant DUH!!!
DBP's are always a concern in public pools because the primary use of FC in that context is bather waste oxidation and control of pathogen transmission. Because the bather loads are very high in public pools, as well as the levels of bather waste including urine, there are going to be much higher levels dangerous DBPs in the water. This is why well controlled public facilities use secondary oxidation sources (UV, Ozone, peroxide, etc) as well as active filtration media (activated charcoal) to help keep DBPs to a minimum.
The fact that the reporter in this instance chose cyanogen chloride to focus on and breathlessly describes it as a compound often associated with chemical weapons just shows how the media is more interested in moronic click-bait than in reporting facts properly.
Just ignore it, it has no bearing on the methodologies we teach here.