Threats to Human Health: Use of Chlorine, an Obsolete Treatment Technology - Global Drinking Water Management and Conservation - page 191

exceeding the maximum acceptable concentration. To date, there are a total of 18
DBPs for which the World Health Organization (WHO 2006 ), USA (USEPA
2006 ), European Union ( 1998 ), Canada (Health Canada 2012 ) and Japan (Japanese
Council on Public Welfare Science 2003 ) have set health-based guideline values
(Itoh et al. 2011 ). Yet, there is no guideline of the tolerable level of DBP that would
avoid developmental and reproductive toxicity (Itoh et al. 2011 ). DBPs are complex
mixtures, but current management practices focus on meeting the maximum con-
centration levels (MCLs) for individual DBPs. Therefore, current water quality
management is insuf

cient to reduce overall toxicity of DBPs (Villanueva et al.

2014 ).
In this chapter, we focus on exploring the long-term health effects of using
chlorine in untreated water. Section 9.2 reviews a select set of epidemiological
studies on some main areas of health impacts in humans from exposure to DBPs,
including cancer (mainly bladder cancer), adverse reproductive and developmental
outcomes, blood lead levels, as well as estrogenic effects. Section 9.3 discusses the
current management practices in some developed countries, including USA, Can-
ada, and some EU countries, such as Germany, Denmark, and the Netherlands.

9.2 Long-Term Health Effects of Using Chlorine

9.2.1 Chlorinated DBPs Exposure with Cancer Incidence

Chlorinated drinking water contains a complex mixture of chlorinated and bromi-
nated byproducts with mutagenic and carcinogenic properties; toxicologists have
known this for a long time. A number of studies have drawn an association between
the consumption of chlorinated drinking water and cancer due to the DBPs (i.e.
THMs and HAAs). The adverse effects of DBPs are not universally supported, partly
because the effects can vary in time and space (Villanueva et al. 2012 ). As a matter of
fact, the epidemiological studies of DBP exposures and health effects in humans
have focused on a small subset of the several hundred DBPs that may occur in public
water supplies (Richardson et al. 2007 ); they have focused primarily on THMs and
HAAs (Hinckley et al. 2005 , Hoffman et al. 2008 , and Righi et al. 2012 ).
An early WHO ( 2004 ) report was inconclusive although it did carry some evi-
dence of adverse health effects, particularly due to chloroform, one of the common
THMs. But more recent

findings suggest there is cause for concern. As summarized
in Table 9.1 , a series of research on potential carcinogens reviewed by the WHO
International Agency for Research on Cancer (IARC) indicated that there is evidence
on the carcinogenicity of DBP compounds in drinking water. First, as primary
THMs, Chloroform (IARC 1999 ) and bromodichloromethane (BDCM) (IARC
1991 ) are classi ed as possible human carcinogens, and have been linked to

reproductive defects in animal studies, while Dibromochloromethane (DBCM) and
bromoform are not yet so classi ed, indicating there is no evidence supporting these

two compounds as carcinogens, but there is insuf

cient evidence to classify them as