Guidelines for Canadian Drinking Water Quality - Advances in

35 Guidelines for Canadian Drinking Water Quality

Downloaded by LOUISIANA STATE UNIV on September 3, 2014 | http://pubs.acs.org Publication Date: December 15, 1986 | doi: 10.1021/ba-1987-0214.ch035

Peter Toft, Murugan Malaiyandi, and J. R. Hickman Bureau of Chemical Hazards, Environmental Health Directorate, Health Protection Branch, Health and Welfare Canada, Tunney's Pasture, Ottawa, Ontario, Canada, K1A 0L2 The

development

Quality

of Guidelines

is described.

guidelines published Information drinking

These

for Canadian guidelines

by the World

is included on drinking

water consumption

Health

Drinking

Water

are compared Organization

with

in 1984.

water quality in Canada and

habits of

Canadians.

AN ADEQUATE SUPPLY OF CLEAN, POTABLE WATER is one of the

primary requirements for good health. Traditionally, health hazards associated with water have been the classic waterborne diseases, namely, typhoid, cholera, and hepatitis. The advent, advancement, and practice of the science of bacteriology after the late 18th century led to the recognition of the causes and sources of these diseases, which resulted in the development of disinfection processes and in the recognition of the necessity to prevent public potable water sources from pollution from sewage and postdisinfection contamination. Following the introduction of disinfection to deal with the problem of bacterial contamination, little was done for many years to investigate other possible effects of disinfection and the link between health effects and drinking water quality. Perhaps the remarkable success in the minimization of the outbreaks of the epidemics just mentioned led to complacency and to a disregard of other potential health problems associated with disinfection processes. Considerable efforts, however, were directed toward reducing levels of specific substances such as iron and manganese and reduction of parameters such as color, turbidity, and hardness. Such efforts were more concerned with reducing the problems of corrosion and scale formation and making the potable water more aesthetically appealing than with health problems. 0065-2393/87/0214/0735$06.00/0 Published 1987 American Chemical Society

In Organic Pollutants in Water; Suffet, I., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1986.


736

O R G A N I C P O L L U T A N T S IN W A T E R

In recent years, advances in analytical methods such as gas chromatography-mass spectrometry and their application to the analysis of drinking water have uncovered a vast number of chemical compounds that had previously gone undetected, many of which are k n o w n to manifest toxic properties. Ironically, the discovery and recognition of certain chlorinated organic substances produced b y the disinfection process itself gave the stimulus for much of the current research on identification and minimization of organic contaminants in drinking water. A review committee set up under the auspices of the North Atlantic Treaty Organization in 1979 listed 744 chemical contaminants that had been identified in the drinking water of 14 countries (J). Since then, more have been found. H o w e v e r , it has been estimated that more than 80% of the total organic carbon in the drinking water still remains uncharacterized. This growing number of organic chemicals identified in drinking water supplies led to public concern and debate about the potential risks to health.

Jurisdictional Aspects of Drinking Water Supply According to the British North America Act of 1867, the Canadian legislative base for drinking water derives f r o m the constitutional distribution of powers between the federal and provincial governments. Although this act does not deal specifically with water resources and therefore drinking water supply, judicial interpretation over the years has resulted in a situation i n w h i c h d r i n k i n g water is a shared federal-provincial jurisdiction. Under the British North America Act, the ownership of natural resources, including water, is vested in the provinces that have exclusive jurisdiction over municipal institutions, local water works, and undertakings within the provinces. The municipal or equivalent acts in each of the provinces empower the municipalities to construct, operate, and maintain water systems including potable water supplies. It is apparent, then, that the legal framework for regulating drinking water in Canada differs f r o m that in the United States. There is no Canadian legislation that corresponds to the United States Safe Drinking Water A c t . The Department of National Health and Welfare Act gives reponsibility to this department to investigate and conduct programs related to public health. The Minister of National Health and Welfare has the authority to prescribe, b y regulation, standards for foods (and, consequently, water). Although standards have been prescribed for bottled (mineral and spring) waters, standards have not been prescribed for tap water because of the major role traditionally assumed b y the provinces. It w o u l d appear, therefore, that the federal and provincial jurisdic-



35.

T O F T E T AL.

Canadian

Drinking

Water Quality

737

tions overlap to a considerable degree in regard to drinking water. However, in practice, any action taken has often involved both levels of government, and efforts are complementary rather than overlapping. Generally, the provinces play a lead role in providing an adequate and safe supply of drinking water, whereas the Federal Government of Canada provides leadership in conducting research and in developing standards and guidelines for drinking water quality to protect human health. There are a few specific cases in which the Federal Government of Canada is solely responsible for drinking water. These include administering the potable water regulations for common carriers (transportation crossing Canadian interprovincial and international bor ders) and on Canadian coastal and shipping vessels, as well as ensuring an adequate and safe drinking water supply in the Territories, Indian reservations, and military bases.

Drinking Water as a Vehicle for Exposure to Contaminants The box on page 738 shows the various sources of chemicals to which we may be exposed from our drinking water (2). Drinking water is a major route whereby humans are exposed to many of these contaminants. Table I shows average values for the levels of these contaminants obtained from various national surveys undertaken by the Department of National Health and Welfare. Some water supplies showed sig nificantly higher concentrations of these substances than those in Table I, and in these cases the contribution via water to the total daily intake would be proportionally greater. Levels for most metals and organics are well below the maximum acceptable concentrations (MAC) specified in Guidelines for the Canadian Drinking Water Quality (1978). However, the highest level of lead found in some localities is higher (79.7 μg/L) than the M A C (50 Mg/L). To evaluate the actual contribution to the total exposure from contaminants via tap water, two general factors have to be considered: (1) the quantity of water consumed per person per day and (2) water-use habits. Under ordinary circumstances, an average adult consumes about 2-5 L of water per day, and this requirement is partly filled by ingesting liquids such as beer, soft drinks, etc. Furthermore, age, activity, and climatic conditions influence the amount of tap water ingested. As mentioned earlier, information on water quality at the treatment plant is inadequate to assess human exposure to various contaminants. The corrosion of plumbing fixtures and the type of construction materials also contribute to the levels of contaminants in treated water. Although cooking processes at high temperatures accelerate corrosion



738

ORGANIC POLLUTANTS IN WATER

Chemicals Commonly Occurring in Drinking Water and Their Sources Substances influencing the source quality (raw water) 1. Naturally occurring substances: compounds leached from the earth's crust (calcium, heavy metals) and leachates from soils and sediments (humic and fulvic acids). 2. Pollutants from point sources: domestic sewage (detergents), industrial effluents (synthetic organics, metal cyanides, metals, caustic chemicals), landfill waste disposal (metallic ions, chloride, nitrate, nitrite, sulfate, and synthetic organics). 3. Pollutants derived from nonpoint sources: run-off from agricultural lands (fertilizers, pesticides, humic materials), run-off from urban areas (salt, polyaromatic hydrocarbons [PAHs], asbestos), atmospheric fallout (particulates containing sulfate, nitrate, heavy metals, PAHs, and chlorinated organics). Substances added intentionally 1. Disinfectants: chlorine, ozone, chloramine, chlorine dioxide, and their byproducts. 2. Coagulants and coagulant aids: iron and aluminum sulfates, activated silicates, alginates, synthetic polyelectrolytes and their impurities, silica, and aluminum electrolyte monomers. 3. pH adjusters: technical grade chemicals and their impurities. 4. Fluoridation agents: fluorides. 5. Corrosion inhibitors: filming amines and their impurities (dicyclohexylamine, N-nitroso compounds). 6. Softeners: Calgon products, suds, etc. Contaminant byproducts 1. Impurities in water treatment chemicals: halogenated hydrocarbons in chlorine, oxides of nitrogen from ozonators, chlorates and chlorites from chlorine dioxide, acrylamide monomers. 2. Disinfection byproducts: trihalomethanes from chlorination, epoxides from ozonation. 3. Substances released from distribution systems and synthetic coatings. 4. Asbestos, metals, and vinyl chloride monomers from certain types of poly(vinyl chloride) piping and PAHs from coal-tar coatings. 5. Substances arising from plumbing fixtures and water treatment devices: metals such as chromium, cadmium, copper, and antimony from plumbing fixtures and bacteria from carbon filters used as water treatment devices.

of the utensils and lead to elevated levels of metallic contaminants, reduced levels of volatile organic contaminants such as trihalomethanes ( T H M s ) will be achieved. Water-softening devices could contribute to increased levels of sodium ions, a factor that may have some deleterious effects on individuals on salt-restricted diets. Hardness is considered to be both an aesthetic and a health parameter. Some epidemiological



35.

TOFT ET AL.

739

Canadian Drinking Water Quality

evidence suggests an inverse correlation between water hardness and cardiovascular disease; the incidence of cardiovascular disease is higher in soft-water communities than in hard-water areas (3). T o obtain relevant Canadian data on tap water consumption and use patterns, a survey was undertaken in 1977-78 (4). The average daily consumption was found to be 1.34 L/person/day, and this figure agrees w e l l with similar studies conducted in The Netherlands (5) and in Great Britain (6). Table II shows the volume of tap water consumed b y Canadians according to age and sex group. Only 32.3$ of the people surveyed ingested amounts in the range of 1-1.5 L/day. T w e l v e percent consumed quantitites of tap water exceeding 2 L/day, and about 2? consumed more than 3.9 L/day. Practically no difference was observed in tap water consumption between the sexes. O f particular interest is the consumption of tap water by the young and the elderly, w h o are likely to be more susceptible to the potential health effects of contaminants (4). Table II shows that children consumed less water than adults d i d . However, when body weight is taken into account, the amount of water (and hence the quantity of contaminants) consumed is significantly higher i n children than i n adults. This finding is important not only because the dose of contaminants Table I. Concentration of Contaminants in Canadian Drinking Water Supplies Concentration Contaminant

Median

Inorganics ^0.02 ^2.0 ^2.0 10 Mg/L, particularly during the summer. C h l o r o f o r m concentrations were usually >10 Mg/L i n treated water and again were generally highest i n summer. T h e values for total T H M s were always less than the Canadian M A C of 350 Mg/L, but these results suggest there m a y b e difficulties i n meeting the recommended W H O limit. (The W H O limit relates to chloroform, whereas the existing Canadian guideline is for total T H M s ) . Benzene and toluene occurred quite frequently at levels >1 Mg/L; occasionally levels >10 μg/L· were detected i n the corresponding r a w and treated water samples f r o m particular treatment plants. Benzene is of concern because of its ability to cause leukemia i n humans. A level

Table III. Comparison of Proposed W H O Limits for Certain Organics and Their Observed Levels in Canadian Drinking Waters Treated Water Proposed

^ddence in 30 City Surveys

Concentration

(Mg/L)

WHO Limits

Contaminant 1,1 -Dichloroethy lene 1,2-Dichloroethane Chloroform Benzene Monochlorobenzene 1,2-Dichlorobenzene 1,4-Dichlorobenzene Trichloroethylene Tetrachloroethylene

(ne/L) 0.3 10 30 10 10 1 1 30 10

Raw Water (60 samples)

Treated Water (90 samples)

Mean

Maximum

0 10 28 32 3 nd

1 25 87 55 16 nd 6 51 39

Guidelines for Canadian Drinking Water Quality - Advances in

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