Drinking Water in Germany: A Case Study of High Quality Drinking Water - Global Drinking Water Management and Conservation - page 263

In order to assure drinking water safety, the EU Drinking Water Directive ( 1998 )
has set a number of microbiological, chemical, and organoleptic parametric stan-
dards, and required drinking water in all member states to meet these minimum
requirements. 6 The Netherlands has regulated its own MCLs for a number of
parameters based on the Directive, some of which are even lower than those in the
Directive (Versteegh and Dik 2007 ) . Currently, the Netherlands has reached a high
quality in drinking water by using advanced water treatment technologies and
frequent water quality monitoring. As a result, bottled water consumption in the
Netherlands is the lowest among the EU Countries (The Dutch association of soft
drinks, waters, and juices 2009 and Geudens 2012 ). However, many emerging
contaminants have not been regulated in the Netherlands as well as in the other EU
countries, since toxicological information 7 for these contaminants (or compounds)
is unknown. Accordingly, the Dutch water utilities have developed a new approach
called Q21 (

) (Van Der Kooij
et al. 2010 ). To achieve an impeccable drinking water quality, as a part of the Q21,
target values (i.e. acceptable/tolerable concentrations) for those emerging contam-
inants have been proposed as an addition to the regulatory standards (Mons et al.
2013 ). The derivation of these target values is mainly based on the approach called
Threshold of Toxicological Concern (TTC), (Mons et al. 2013 ).

“ Drinking Water Quality for the twenty- rst Century ”

12.5.1.1 The Threshold of Toxicological Concern (TTC)

Frawley ( 1967 ), Rulis et al. ( 1989 ), and Munro ( 1990 ) examined 217 carcinogens
and found only a small chance (4 percent) that a new chemical would contribute a
higher risk for cancer. In a later paper, Munro et al. ( 1996 ) found higher thresholds
for 613 compounds tested for toxicity endpoints other than carcinogenicity. They
further divided these compounds into three structural

Higher
TTC values, up to 1800 mg per person per day are assigned to Cramer class I,
implying these compounds have signi

“ Cramer classes. ”

cant toxicity, namely substances of high
concern, while the lower values (90 mg per person per day) are put in Cramer class
III, showing simple chemical structures with ef

cient modes of metabolism (i.e.
substances of low concern). Substances of in-between concern are classi ed in

Cramer class II (Cramer et al. 1976 ). As a special case, organophosphates have a
lower TTC, i.e. 18 mg per person per day, which is below 90 mg per person per day
(or class III). Also recent reviews on low-dose compounds found effects at doses far
below those related to the Cramer class III (Macon et al. 2011 and Andrade et al.
2006 ). Thus, a TTC of 0.15 mg per person per day has been determined as a

6 As the EU Drinking Water Directive ( 1998 ) noted,

for the purposes of the minimum
requirements of this Directive, water intended for human consumption shall be wholesome and
clean if it is free from any micro-organisms and parasites and from any substances which, in
numbers or concentrations, constitute a potential danger to human health

“

.
7 Toxicological information reveals that the emerging substance is present in drinking water at a
concentration below the level that will threaten human health (Mons et al. 2013 ).

”