Safety
of Drinking Water in Newfoundland and Labrador
Questions
and Answers
How
do the various levels of government in Newfoundland and Labrador ensure the
safety of drinking water?
Both provincial and municipal governments have some level of responsibility in
ensuring the safety of Newfoundland and Labrador�s drinking water.
The provincial government, in cooperation with municipal governments
protects source water quality through the watershed protection program.
Under a partnership program with municipal governments, the provincial
government monitors drinking water quality on a regular basis in order to ensure
compliance with the �Guidelines for
Canadian Drinking Water Quality� and to deal with emerging issues on a
pro-active basis. The Department of
Environment and Labour provide the drinking water quality data along with a
brief interpretation to municipal governments on a regular basis.
The Department is an active member of the Federal-Provincial Subcommittee
on Drinking Water (DWS) which is responsible for the development of the Guidelines
for Canadian Drinking Water Quality.
How
can I obtain a copy of the current Canadian drinking water quality guidelines?
Contact the Department of Environment and Labour or check Health
Canada�s web site //www.hc-sc.gc.ca/waterquality
for a summary table of the current guidelines.
Information on the development of these Guidelines can also be found on
Health Canada�s web site.
What
are chlorination disinfection by-products and how are they formed?
Chlorination disinfection by-products (CDBPs) are chemical compounds
that form when water containing natural organic matter (the decay products of
living things such as leaves, human and animal wastes, etc.) is chlorinated.
Chlorine disinfection of water can lead to the formation of a number of
chlorination by-products of which trihalomethanes (THMs) are only one subgroup. Among the many chlorination by-products, THMs are most often
present and in the greatest concentration in drinking water and as such are used
as indicators of total disinfection by-product formation.
Why
is drinking water chlorinated?
Chlorination is necessary for two reasons. First, almost all sources of surface water contain
microbiological organisms, which have to be removed in order to prevent the
outbreak of waterborne diseases such as typhoid fever and cholera.
Second, once the treated water leaves the treatment plant, it may travel
through water mains and pipes sometimes at significant distances, before it
reaches it�s destination. During
this time, it is necessary to maintain a residual level of disinfectant in the
water to ensure no possible regrowth of microorganisms.
Without adequate disinfection, the health risks from microorganisms far
outweigh the risks from THMs.
What
is the current Canadian drinking water guideline for THMs?
The current Canadian drinking water quality guideline for THMs is 100
parts per billion (ppb) or micrograms per litre (mg/l).
The guideline is based on an annual running average of quarterly samples
to account for seasonal variations. THM
levels are generally highest in the summer and lowest in the winter.
What
are the health effects associated with THMs?
The Federal‑Provincial Subcommittee on Drinking Water established
the current guideline for THMs in 1993. The
guideline is based on the risk of cancer reported in animal studies of
chloroform, the THM most often present and in greatest concentration in drinking
water. Since then, new
epidemiological (human) studies had been published which reported associations
between THMs and bladder and colon cancer, and adverse pregnancy outcomes
including miscarriage, birth defects and low birth weight.
In response to these new findings Health Canada, in its role as
Secretariat to the DWS, established a multi‑stakeholder task group in 1998
to oversee a comprehensive update of health risk information on THMs and to
develop recommendations for controlling the risks.
Which
public water supplies have the highest/lowest levels of THMs?
Levels of THMs are generally highest in treated water from sources with
high organic matter content, such as rivers and lakes.
Lower levels of THMs are usually found when the source water is
groundwater.
THM levels can vary within single water supply depending on the season,
water temperatures, amount of natural organic matter in water, pH, amount of
chlorine added, point of chlorination, time in distribution system, and other
factors such as treatment processes used.
What
are the alternate disinfectants?
Alternate disinfectants include chloramine, chlorine dioxide and ozone.
Each of these alternate disinfectants have their own advantages and
disadvantages regarding handling and storage, disinfection by-product formation
and cost. The use of chlorine is,
however, essential to maintain the required residual in the water distribution
system in order to ensure microbiologically safe water.
What
is being done to reduce the levels of THMs in municipal drinking water in
Newfoundland and Labrador?
The government of Newfoundland and Labrador in consultation with
municipal governments has developed a three-phase approach to deal with this
issue. The first phase is data
collection through THM surveys, the second phase deals with data assessment and
identification of remediation methods and the third phase will be the
implementation of mitigation measures where necessary.
It must be emphasized that any changes made to water treatment practices
must not compromise the effectiveness of disinfection.
The government of Newfoundland and Labrador is also actively
participating, with its provincial colleagues of the DWS in the Chlorinated
Disinfection By-Products Task Group that is overseeing a coordinated effort
to estimate the health risks from THMs and to develop risk management
recommendations.
Should
I stop drinking my tap water?
Tap water provided by municipal governments is generally safe and
regularly monitored by the provincial government for physical, chemical and
bacteriological quality. You do not
need to stop drinking tap water unless you are have been advised to do so by the
provincial or municipal governments.
Are
there risks from CDBPs through showering, bathing or swimming?
While showering, bathing or swimming in chlorinated water may result in
significant exposure to CDBPs through breathing in vapors and absorption through
the skin, the health risks of prolonged exposure to CDBPs from these sources are
currently unknown. Research is in
progress to better understand the contribution of inhalation and skin absorption
from showering in overall exposure to CDBPs.
How
can I reduce exposure to THMs?
Consumers wishing to reduce their exposure to
chlorination disinfection by-products can use a filter containing activated
carbon certified to the NSF Standard 53 for THM removal.
Blending and boiling the water will remove some THMs, but will not
eliminate or necessarily reduce the health risk from other disinfection
by-products that are not volatile (i.e., do not evaporate easily).
If a filter device is used it should be properly maintained because such
devices can become sources of bacterial contamination in water.
It should be noted, however, that no one method will eliminate all
disinfection by-products in drinking water.
Health Canada laboratories are currently
testing a range of carbon filters and other treatment methods to see if they are
able to remove most CDBPs. The
results will be made public within a year.
How
can I obtain information about my drinking water quality?
Contact your Town Council office or call the Department of Environment
and Labour at:
�
(709) 729-2563 (Eastern)
�
(709) 292-4285 (Central)
�
(709) 637-2367 (Western and Labrador)
Department
of Environment and Labour
January 9, 2000