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Ireland’s Environment 2012
120
Clean Water and
Health
Drinking Water
Water is essential for life.
Approximately 60% of the average
adult human body, and 85% of the
human brain, is water. If deprived of
water, a person will die in a matter
of days. A daily intake of one to two
litres of water is recommended as
part of a healthy diet.
Most tap water in Ireland is drawn
from surface water sources (i.e. rivers
and lakes), with the remainder
originating from groundwater and
springs. For the majority of people
who live in urban areas the water
is supplied by the local authority
following extensive treatment.
Smaller communities use private
water schemes, while single houses
in rural areas tend to rely on
groundwater wells with little
or no water treatment.
The EU Drinking Water Directive sets
quality standards for water at the
tap. The most important indicator for
drinking water is the microbiological
content, in particular the bacterium
Escherichia coli
. The presence of
E. coli
in drinking water provides
a good indication that either the
source of the water has become
contaminated by faecal pollution or
the treatment process at the water
treatment plant is not operating
adequately.
The incidence of
E. coli
in drinking
water continues to decrease. In 2010
it was found in 0.01% of samples
from larger public water supplies
that serve a total of 3 million people
(EPA, 2011a). This figure is in line
with countries such as England and
Wales, Scotland and the Netherlands.
However, over 200,000 people
are served by private group water
schemes, where the microbiological
quality remains inferior to public
water supplies. Furthermore, little
is known about the quality of the
~200,000 private wells used in rural
areas as a source of drinking water
(EPA, 2011a and GSI, 1999).
Any contamination of drinking
water poses a health risk, especially
to children, older people and
those with compromised immune
systems. In 2007,
Cryptosporidium
contamination of the water supply
for Galway city led to widespread
illness in the community. The
outbreak highlighted the risks
to health associated with the
abstraction of surface waters for
drinking from poorly protected
reservoirs, and the need for modern
and well-managed water treatment
systems. Figure 9.1 shows the
number of cases of cryptosporidiosis
reported in Ireland between 2005
and 2010. Cryptosporidiosis
is caused by the parasite
Cryptosporidium
and the disease
can be contracted through contact
with infected animals or humans or
consumption of contaminated water
or food. Ireland had the highest rate
of cryptosporidiosis in the EU each
year from 2005 to 2009; comparison
figures for 2010 are not yet available
(HPSC, 2009, 2010, 2011; ECDC,
2011).
To protect public health, the EPA
adopts a risk-based and outcome-
driven approach to the enforcement
of the National Drinking Water
Regulations, focusing on issues that
present the greatest risk to health.
Significant investment in recent years
has resulted in increased treatment,
storage capacity and continuous
online monitoring for drinking
water. That effort is reflected in
the downward trend of public
supplies showing evidence of
E. coli
contamination in recent
years, as shown in Figure 9.2.
Compliance with chemical
standards (the safe amount of
different chemicals that can be
allowed in drinking water) is
generally very good in public
water supplies, with 99.2%
compliance in both 2009 and
2010. Trihalomethanes (THMs),
an unwanted by-product of
Figure 9.1
Reported Cases of Cryptosporidiosis in Ireland 2005–2010 (Source: HPSC, 2009, 2010, 2011)
0
100
200
300
400
500
600
700
2010
2009
2008
2007
2006
2005
Number of Reported Cases