Drinking Water in Germany: A Case Study of High Quality Drinking Water - Global Drinking Water Management and Conservation - page 265

“ concentration action ” can lead to toxic effects of the total mixture, while the

“ does not result in toxic effects of the mixture. However, indi-

vidual action with different modes can lead to higher toxic effects of a chemical
mixture than the effects of an individual chemical (European Commission 2009 ).
Therefore, from a precautionary point of view, some emphasis must be placed on
“

individual action ”

as this would enhance safety (European Commission 2009 ).
As an example, in order to capture the cumulative risk of pesticides, the US EPA
has set both a common toxic effect of individual pesticides as well as the toxic effect
of a mixture of pesticides, called

concentration action, ”

(USEPA 2002 ). But in
general, this approach is not feasible for many other chemicals and their com-
pounds, as knowledge of the toxic effects of many compounds of chemicals found
in water is not yet available (Mons et al. 2013 ).

“ concentration action ”

12.5.2 Micropollutants in the USA

A study conducted in the USA by Kolpin et al. ( 2002 ) examined concentrations of
95 organic compounds (i.e. pharmaceuticals, antioxidants, phytosterols, biocides,
and flame retardants) in water samples from a network of 139 streams across 30

states between 1999 and 2000. They detected 82 of the 95 compounds in at least
one stream sample. To ensure drinking water safety, the USA has already regulated
Maximum Contaminant Levels for a number of chemical, microbiological, and
radiological parameters under the Safe Drinking Water Act (USEPA 1996 ).
Moreover, the US Environmental Protection Agency has released a Candidate
Contaminant List (CCL) in which the contaminants are known to be in drinking
water sources and should be regulated in the future. The drinking water utilities are
responsible for monitoring a number of unregulated and emerging contaminants
periodically under the Unregulated Contaminant Monitoring Rule (UCMR). The
new compounds are needed to determine whether they should be regulated and
included in the list based on the monitoring results. According to US EPA, the

rst
Candidate Contaminant List was issued in 1998 and the latest list was released in
2009 (USEPA 2009 ).
In the USA, there are no general target values used for the unregulated con-
taminants, but speci c health-based target values have been set for each contami-

nant. As compared with the Netherlands, Mons et al. ( 2013 ) pointed out that

the
Dutch Q21 approach differs from the US approach with the Contaminant Candidate
List where information on adverse health effects is essential in deciding whether or
not to regulate the speci

“

c compound. ” Furthermore, the Candidate Contaminant

“ ”

List is a which needs to be conducted for each

individual contaminant, while the target values, as a part of Q21 approach, can be
derived and applied to all substances (Mons et al. 2013 ). In addition, the US
approach

substance-speci c approach

does not provide guidance for situations where compounds are detected
in drinking water in concentrations below toxicological standards

“

” (Mons et al.

2013 ).