To my knowledge this is the first extensive study which examined indoor pools in the USA .
It seems that finally attention is being paid on DBP's in order to protect public health.
For good reason the German regulation (DIN 19643) limits the amount of THM's at max. 20 microgram/l.
More and more European countries are adopting those tough German regulations ( which are already in effect
in Germany since the last 20 years or so ).
The study (23 Pools in the USA) found the average to be at 62 microgram/l.. . .
Recently ( last week) another study came out from Canada were 15 indoor pools were monitored and the average of
those were at 55 microgram/l - more or less in line with the US Pools.
Finally someone even took TOC readings as well (7.1 ppm average)
What is surprising is the fact that NSPF didn't really address this issue in their Pool and Spa Operator Hand Book
(edition 2009 - page 46). . It says . . ."Currently the risk to human health due to THM's in swimming pools is relatively low ".
Low ? Life guards, Pool personal, swimmers and everyone who is exposed to this environment have a much higher cancer rate
than the average population. THM in the water means THM in the air.
Perhaps NSPF should take a look at this study - NSPF also recommends ideal levels in pools should be between 2-4 ppm
(those levels are considered to be a "shock treatment " in Germany where the max. FAC is set at 0.60 ppm for public pools)
Again - there is (obviously) a link between high free chlorine levels and the formation of THM's.
Seems like there is some hope that Governments and Health Departments in North America start to wake up and set much tougher standards in the future for public pools.
Enjoy reading those 278 pages ->
http://etd.lib.clemson.edu/documents/12 ... _10627.pdf