Contaminants, pathogenic bacterial/planktonic organisms. Regarding long term health studies, i'm not sure, but would expect that there is a monitoring system in place. I can only speak for Scotland.
Chlorine vs chloramine i think would basically come down to two things: cost and taste/odour. Chloramine hangs around longer, so less frequent use/lower amounts required and hence likely lower expenditure. Chloramine isn't as noticeable in water, chlorine can put some people off drinking water.
One of the things I heard about US water is that the number of polio cases (I think) dropped so drastically after they introduced chlorination that it was regarded as the greatest thing since sliced bread and no one really bothered to have a good look at possible downsides. Is it the case that chlorine will inhibit magnesium absorption, or in some way fuck with a person's magnesium levels?
They also put fluoride in US water. Sounds like a good idea except it helps aluminium get into the brain, and the US has a disproportionately high incidence of Alzheimers. Is aluminium sulfate connected somehow with chloramine water treatment? As an organic matter precipitant or something? If so, is it removed in some way?
