as already noted, the risk (if any) is trivial compared to the benefits of swimming, so....keep swimming, don't worry about it
regarding the "new" study (part of a trilogy published September 2010)....
From the study...
"Swimming is not associated with DNA damage."
"Levels of disinfectant byproduducts in swimming pool water are not necessarily higher than those in drinking water."
"brominated DBPs are generally more genotoxic and carcinogenic than chlorinated DBPs"
(DBP = disinfectant byproducts)
Chlorination is not the problem according to the study (regarding statistically significant changes).
Bromination may be. Higher levels of exhaled brominated trihalomethanes were associated with increased numbers of micronucleated lymphocytes, but not in changes in micronucleated urinary tract lining cells. 'Urine mutagenicity" increased in association with higher levels of exhaled bromoform (determined by mutagenic effect of urine samples on the bacteria Salmonella).
May Be! Increasing cancer risk from indoor pools and absorption through the skin and lungs is HIGHLY speculative. Direct data does not exist...ie, data showing an increased cancer risk in cancer rates (vs a suspected biomarker effect from brominated compounds).
Study design, by the way, involved pre-swimming testing vs post-swimming testing, wherein swimming meant 40 minutes of undefined swimming in an indoor pool in Barcelona, Spain in 2007. Doing jumping jacks, pushups and situps, or merely sitting, near the pool for 40 minutes may have produced similar results!