Threats to Human Health: Use of Chlorine, an Obsolete Treatment Technology - Global Drinking Water Management and Conservation - page 192

Table 9.1 Evidence of carcinogenicity as concluded by the IARC for some chemicals whose
main pathway of human exposure is through drinking water (Villanueva et al. 2014 )
Compounds Human

evidence

Animal
evidence

Overall
evaluation a

IARC
Monograph

DBPs:
Trihalomethanes
Chloroform Inadequate Suf cient 2B Vol. 73 (IARC

1999 )

Bromodichloromethane Inadequate Sufficient 2B Vol. 52 (IARC

1991 )

Dibromochloromethane Inadequate Limited 3 Vol. 52 (IARC

1991 )

Bromoform Inadequate Limited 3 Vol. 52 (IARC

1991 )

DBPs: Haloacetic
acids
Dichloroacetic acid Inadequate Sufficient 2B Vol. 106 (IARC
2013 )
Trichloroacetic acid Inadequate Suf cient 2B Vol. 106 (IARC
2013 )
Bromochloroacetic acid Inadequate Suf cient 2B Vol. 101 (IARC
2012 )
Dibromoacetic acid Inadequate Suf cient 2B Vol. 101 (IARC
2012 )
a Group 1 (the agent is carcinogenic to humans), 2A (the agent is probably carcinogenic to
humans), 2B (the agent is possibly carcinogenic to humans), 3 (the agent is not classifiable as to its
carcinogenicity to humans)

noncarcinogenic (IARC 1991 ). Moreover, all four primary HAA compounds are
classi cient evidence from

experimental animals for the carcinogenicity (IARC 2013 ). It should be noted that
the classi

ed as possible human carcinogens, and there is suf

cation of possible human carcinogens is extrapolated based on the data
that has come from research on animals (IARC 2010 ). Hence, there is inadequate
epidemiological evidence of carcinogenicity in humans for all DBPs compounds.
Furthermore, the USEPA ( 2003 ) has calculated the cancer potency factors for
the four THMs in mg of chemical per kg of body weight per day (expressed as mg/
kg/day). BDCM has the highest factor of 0.062 mg/kg/day, followed by Bromo-
form with 0.0079 mg/kg/day, and Chloroform with 0.0061 mg/kg/day, while
DBCM is considered noncancerous. The cancer potency factors have some foun-
dation in the study reported below.

9.2.1.1 Bladder Cancer

Cantor et al. ( 1987 ) summarized a number of case-control studies on the incidence
of cancer that have been undertaken in North America, such as Western Maryland,