Guidelines for Canadian Drinking Water Quality – Summary Tables – Canada.ca
Aluminum (2021)
2.9
OG: 0.1
Naturally occurring; aluminum salts used as coagulants in drinking water treatment; leaching from cement-based materials; dissolution of activated alumina media (where applicable);
Health basis of MAC: Neuromuscular effects (hind- and fore-limb grip strength, foot splay), urinary tract effects and general toxicity.
The MAC and OG apply to all drinking water supplies (including groundwater) and are to be applied as locational running annual averages. The OG value is established to minimize the potential for the accumulation and release of metals in the distribution system and to avoid other operational and aesthetic issues. It takes treatment achievability into consideration.
I
Ammonia (2013)
None required
None
Naturally occurring; released from agricultural or industrial wastes; added as part of chloramination for drinking water disinfection
Levels of ammonia, either naturally present in the source water or added as part of a disinfection strategy, can affect water quality in the distribution system (e.g., nitrification) and should be monitored.
A guideline value is not necessary as it is produced in the body and efficiently metabolized in healthy people; no adverse effects at levels found in drinking water.
To help prevent nitrification, limit excess free ammonia entering the distribution system to below 0.1 mg/L, and preferably below 0.05 mg/L, measured as nitrogen. Nitrification can lead to the formation of nitrite/nitrate, decreased chloramine residual and increased bacterial count.
I
Antimony (1997)
0.006
None
Naturally occurring (erosion); soil runoff; industrial effluents; leaching from plumbing materials and solder
Health basis of MAC: Microscopic changes in organs and tissues (thymus, kidney, liver, spleen, thyroid)
MAC takes into consideration analytical achievability; plumbing should be thoroughly flushed before water is used for consumption.
I
Arsenic (2006)
0.010
ALARA
None
Naturally occurring (erosion and weathering of soils, minerals, ores); releases from mining; industrial effluent
Health basis of MAC: Cancer (lung, bladder, liver, skin) (classified as human carcinogen)
Other: Skin, vascular and neurological effects (numbness and tingling of extremities)
MAC based on treatment achievability; elevated levels associated with certain groundwaters; levels should be kept as low as reasonably achievable.
I
Asbestos (1989, 2005)
None required
None
Naturally occurring (erosion of asbestos minerals and ores); decay of asbestos-cement pipes
None
Guideline value not necessary; no evidence of adverse health effects from exposure through drinking water.
P
Atrazine (1993)
0.005
None
Leaching and/or runoff from agricultural use
Health basis of MAC: Developmental effects (reduced body weight of offspring)
Other: Potential increased risk of ovarian cancer or lymphomas (classified as possible carcinogen)
MAC applies to sum of atrazine and its N-dealkylated metabolites – diethylatrazine, deisopropylatrazine, hydroxyatrazine, diaminochlorotriazine;
Persistent in source waters.
I
Barium (2020)
2.0
None
Naturally occurring; releases or spills from industrial uses
Health basis of MAC: Kidney effects
MAC is for total barium and takes into consideration exposure estimates from all sources.
O
Benzene (2009)
0.005
None
Releases or spills from industrial uses
Health basis of MAC: Bone marrow (red and white blood cell) changes and cancer (classified as human carcinogen)
Other: Blood system and immunological responses
MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing.
O
Benzo[a]pyrene (2016)
0.000 04
None
Leaching from liners in water distribution systems
Health basis of MAC: Stomach tumours (classified as human carcinogen)
None
I
Boron (1990)
5
None
Naturally occurring; leaching or runoff from industrial use
Health basis of MAC: Reproductive effects (testicular atrophy, spermatogenesis)
Other: Limited evidence of reduced sexual function in men
MAC based on treatment achievability.
DBP
Bromate (2018)
0.01
None
Contaminant in hypochlorite solution; by-product of drinking water disinfection with ozone
Health basis of MAC: Tumours of the testicular mesothelium (classified as a possible human carcinogen)
Efforts to reduce bromate concentrations must not compromise the effectiveness of disinfection. Bromate is difficult to remove from drinking water once formed. The recommended strategy is controlling the ozonation process; use of certified treatment chemicals and; appropriate handling and storage of hypochlorite. Quarterly monitoring of raw water bromide is recommended to allow correlation to bromate or brominated DBPs.
P
Bromoxynil (2022)
0.03
None
Leaching or runoff from agricultural use
Health basis of MAC: Increased clinical signs (panting, salivation, liquid feces, pale gums) and liver weight, as well as both decreases in body weight and body weight gain
None
I
Cadmium (2020)
0.007
None
Leaching from galvanized pipes and solders; industrial and municipal waste
Health basis of MAC: Kidney damage
Other: Bone effects (decreased bone density)
MAC is for total cadmium and takes into consideration exposure estimates from all sources. Sampling should be done at the tap to reflect average exposure similar to sampling done for lead. The contribution of cadmium in drinking water is generally from the galvanized steel used in pipes and well components. The best approach to minimize exposure to cadmium from drinking water is to replace galvanized steel and components. Drinking water treatment devices are also an effective option.
I
Calcium (1987, 2005)
None required
None
Naturally occurring (erosion and weathering of soils, minerals, ores)
No evidence of adverse health effects from calcium in drinking water.
Guideline value not necessary; calcium contributes to hardness.
O
Carbon tetrachloride (2010)
0.002
None
Industrial effluents and leaching from hazardous waste sites
Health basis of MAC: Liver toxicity
Other: Kidney damage; liver tumours (classified as probable carcinogen)
MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing.
D
Chloramines (2020)
None required
None
Monochloramine is used as a secondary disinfectant; formed in drinking water when chlorine is added in the presence of ammonia
Guideline value not necessary due to low toxicity at concentrations found in drinking water
Chloramine residuals in most Canadian drinking water distribution systems are typically below 4 mg/L
DBP
Chlorate (2008)
1
None
By-product of drinking water disinfection with chlorine dioxide; possible contaminant in hypochlorite solution
Health basis of MAC: Thyroid gland effects (colloid depletion)
As chlorate is difficult to remove once formed, its formation should be controlled by respecting the maximum feed dose of 1.2 mg/L of chlorine dioxide and managing /monitoring formation in hypochlorite solutions.
I
Chloride (1979, 2005)
None
AO: ≤ 250
Naturally occurring (seawater intrusion); dissolved salt deposits, highway salt, industrial effluents, oil well operations, sewage, irrigation drainage, refuse leachates
A guideline value is not necessary as health effects are not of concern at levels found in drinking water.
Based on taste and potential for corrosion in the distribution system.
D
Chlorine (2009)
None required
None
Used as drinking water disinfectant
A guideline value is not necessary due to low toxicity at concentrations found in drinking water
Free chlorine concentrations in most Canadian drinking water distribution systems range from 0.04 to 2.0 mg/L.
D
Chlorine dioxide (2008)
None required
None
Used as drinking water disinfectant (primary disinfection only)
A guideline value for chlorine dioxide is not required because of its rapid reduction to chlorite in drinking water
A maximum feed dose of 1.2 mg/L of chlorine dioxide should not be exceeded to control the formation of chlorite and chlorate.
DBP
Chlorite (2008)
1
None
By-product of drinking water disinfection with chlorine dioxide
Health basis of MAC: Neurobehavioural effects (lowered auditory startle amplitude, decreased exploratory activity), decreased absolute brain weight, altered liver weights
Chlorite formation should be controlled by respecting the maximum feed dose of 1.2 mg/L of chlorine dioxide and managing /monitoring formation in hypochlorite solutions.
P
Chlorpyrifos (1986)
0.09
None
Leaching and/or runoff from agricultural or other uses
Health basis of MAC: Nervous system effects (cholinesterase inhibition)
Not expected to leach significantly into groundwater.
I
Chromium (2018)
0.05
None
Naturally occurring (erosion of minerals); releases or spills from industrial uses
Health basis of MAC: Hyperplasia of the small intestine from chromium (VI).
Other: No definitive evidence of toxicity to Chromium(III).
MAC protects against both cancer and non-cancer effects from Chromium (VI) and is established for total chromium.
T
Colour (1979, 2005)
None
AO: ≤ 15 TCU
Naturally occurring organic substances, metals; industrial wastes
A guideline value is not necessary as health effects are not of concern at levels found in drinking water.
May interfere with disinfection; removal is important to ensure effective treatment.
I
Copper (2019)
2
AO: 1
Naturally occurring; leaching from copper piping
Health basis of MAC: Gastronintestinal effects (short-term), liver and kidney effects (long-term).
Water samples should be taken at the tap. MAC is for total copper and protects against both short_term and long_term exposures. AO is based on taste and water discolouration (resulting in staining of laundry and plumbing fixtures).
I
Cyanide (1979, 1991)
0.2
None
Industrial and mining effluents; release from organic compounds
Health basis of MAC: No clinical or other changes at the highest dose tested
At the levels seen in Canadian waters, cyanide is not a concern as it can be detoxified to a certain extent in the human body.
O
Cyanobacterial toxins (2018)
0.0015
None
Naturally occurring – released from populations of cyanobacteria (planktonic blooms and benthic mats)
Health basis of MAC: Liver effects
MAC is for total microcystins (intra- and extra-cellular) Note that infants can ingest a significantly larger volume of water per body weight. As a precautionary measure, where levels of total microcystins in treated water are detected above a reference value of 0.4 µg/L, the public in the affected area should use an alternate suitable source of drinking water (such as bottled water) to reconstitute infant formula.
P
Dicamba (2022)
0.11
None
Leaching or runoff from agricultural or other uses
Health basis of MAC: Liver effects
Readily leaches into groundwater.
O
1,4-Dichlorobenzene
Table 2 footnote
2 (1987)
0.005
AO: ≤ 0.001
Releases or spills from industrial effluents; use of urinal deodorants
Health basis of MAC: Benign liver tumours and adrenal gland tumours (classified as probable carcinogen)
AO based on odour; levels above the AO would render drinking water unpalatable.
O
1,2-Dichloroethane (2014)
0.005
None
Releases or spills from industrial effluents; leachate from waste disposal
Health basis of MAC: Cancer of the mammary gland (classified as probable carcinogen)
The MAC protects against both cancer and non-cancer effects and takes into consideration all exposures from drinking water, which include ingestion as well as inhalation and dermal absorption during showering and bathing.
O
1,1-Dichloroethylene (1994)
0.014
None
Releases or spills from industrial effluents
Health basis of MAC: Liver effects (fatty changes)
None
O
Dichloromethane (2011)
0.05
None
Industrial and municipal wastewater discharges
Health basis of MAC: Liver effects (liver foci and areas of cellular alteration).
Other: Classified as probable carcinogen
The MAC protects against both cancer and non-cancer effects and takes into consideration all exposures from drinking water, which include ingestion as well as inhalation and dermal absorption during showering and bathing.
P
2,4-Dichlorophenoxy acetic acid (2,4-D) (2022)
0.1
None
Leaching and/or runoff from agricultural and non-cropland use
Health basis of MAC: Kidney effects
High potential to leach into groundwater
P
Dimethoate and omethoate (2022)
0.02
None
Leaching and/or runoff from agricultural and non-agricultural use
Health basis of MAC: Nervous system effects (cholinesterase inhibition)
MAC is for dimethoate. An additive approach should be taken in which the sum of the detected concentrations of dimethoate and omethoate (expressed as a dimethoate equivalent value) does not exceed the MAC for dimethoate.
I
1,4-Dioxane (2021)
0.050
Generally not detected in Canadian water supplies, but there have been contaminations of drinking water supplies near landfills and industrial sites
Basis of MAC: liver effects that occur before the development of cancer
1,4 Dioxane is difficult to remove using conventional drinking water treatment. Treatment technologies such as advanced oxidation processes and synthetic adsorbents need to be considered. Reverse osmosis membranes may be capable of removing 1,4-dioxane at both the municipal and residential scale.
P
Diquat (2022)
0.05
None
Leaching and/or runoff from agricultural use; added directly to water to control aquatic weeds
Health basis of MAC: Cataract formation
Unlikely to leach into groundwater.
O
Ethylbenzene (2014)
0.14
AO: 0.0016
Emissions, effluents or spills from petroleum and chemical industries
Health basis of MAC: Effects on the liver and pituitary gland.
Other: Tumour formation at various sites in animals, including kidney, lung, liver and testes.
MAC protects against both cancer and non-cancer health effects. MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing. AO is based on odour.
I
Fluoride (2010)
1.5
None
Naturally occurring (rock and soil erosion); may be added to promote dental health
Health basis of MAC: Moderate dental fluorosis (based on cosmetic effect, not health)
Beneficial in preventing dental caries.
DBP
Formaldehyde (1997)
None required
None
By-product of disinfection with ozone; releases from industrial effluents
A guideline value is not necessary as health effects are not of concern at levels found in drinking water.
A guideline value is not necessary, as levels in drinking water are below the level at which adverse health effects may occur.
P
Glyphosate (1987, 2005)
0.28
None
Leaching and/or runoff from various uses in weed control
Health basis of MAC: Reduced body weight gain
Not expected to migrate to groundwater.
DBP
Haloacetic acids – Total (HAAs)
Table 2 footnote
3 (2008)
0.08
ALARA
None
By-product of drinking water disinfection with chlorine
Health basis of MAC: Liver cancer (DCA); DCA is classified as probably carcinogenic to humans
Other: Other organ cancers (DCA, DBA, TCA); liver and other organ effects (kidney and testes weights) (MCA)
Refers to the total of monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), monobromoacetic acid (MBA) and dibromoacetic acid (DBA); MAC is based on ability to achieve HAA levels in distribution systems without compromising disinfection; precursor removal limits formation.
T
Hardness (1979)
None required
None
Naturally occurring (sedimentary rock erosion and seepage, runoff from soils); levels generally higher in groundwater
Although hardness may have significant aesthetic effects, a guideline has not been established because public acceptance of hardness may vary considerably according to the local conditions; major contributors to hardness (calcium and magnesium) are not of direct public health concern
Hardness levels between 80 and 100 mg/L (as CaCO3) provide acceptable balance between corrosion and incrustation; where a water softener is used, a separate unsoftened supply for cooking and drinking purposes is recommended.
I
Iron (1978, 2005)
None
AO: ≤ 0.3
Naturally occurring (erosion and weathering of rocks and minerals); acidic mine water drainage, landfill leachates, sewage effluents and iron-related industries
No evidence exists of dietary iron toxicity in the general population.
Based on taste and staining of laundry and plumbing fixtures
I
Lead (2019)
0.005 ALARA
None
Leaching from plumbing (lead service lines, lead solder and brass fittings)
Health basis of MAC: Reduced intelligence in children measured as decreases in IQ is the most sensitive and well established health effect of lead exposure. There is no known safe exposure level to lead.
Other: Possible effects include behavioural effects in children. Reduced cognition, increased blood pressure, and renal dysfunction in adults are also possible;.classified as probably carcinogenic to humans
MAC is for total lead. Lead levels should be kept as low as reasonably achievable. Sampling should be done at the tap to reflect average exposure. The most significant contribution of lead in drinking water is generally from the lead service line that supplies drinking water to the home. The best approach to minimize exposure to lead from drinking water is to remove the full lead service line. Drinking water treatment devices are also an effective option.
I
Magnesium (1978)
None required
None
Naturally occurring (erosion and weathering of rocks and minerals)
No evidence of adverse health effects from magnesium in drinking water, therefore a guideline value is not necessary.
No additional comments
P
Malathion (1986, 2005)
0.19
None
Leaching and/or runoff from agricultural and other uses
Health basis of MAC: Nervous system effects (cholinesterase inhibition)
Not expected to leach into groundwater.
I
Manganese (2019)
0.12
AO: ≤ 0.02
Dissolution of naturally occurring minerals commonly found in soil and rock. Other sources include industrial discharge, mining activities and leaching from landfills
Health Basis of MAC: Effects on neurological development and behaviour; deficits in memory, attention, and motor skills.
Other: Formula-fed infants (where water containing manganese at levels above the MAC is used to prepare formula) may be especially at risk
AO based on minimizing the occurrence of discoloured water, consumer complaints and staining of laundry.
I
Mercury (1986)
0.001
None
Releases or spills from industrial effluents; waste disposal; irrigation or drainage of areas where agricultural pesticides are used
Health basis of MAC: Irreversible neurological symptoms
Applies to all forms of mercury; mercury generally not found in drinking water, as it binds to sediments and soil.
P
2-Methyl-4-chlorophenoxyacetic acid (MCPA) (2022)
0.35
None
Leaching and/or runoff from agricultural and other uses
Health basis of MAC: Kidney effects (increased absolute and relative weights, urinary bilirubin, crystals and pH)
Other: Systemic, liver, testicular, reproductive/developmental and nervous system effects
Can potentially leach into groundwater.
O
Methyl tertiary-butyl ether (MTBE) (2006)
None
AO: ≤ 0.015
Spills from gasoline refineries, filling stations and gasoline-powered boats; seepage into groundwater from leaking storage tanks
The AO is lower than levels associated with potential toxicological effects, it is considered protective of human health. Studies on toxic effects remain inconclusive.
AO based on odour; levels above the AO would render water unpalatable.
P
Metribuzin (2021)
0.08
None
Leaching and/or runoff from agricultural use
Health basis of MAC: Liver effects (increased ornithine carboxytransferase, increased incidence and severity of mucopolysaccharide droplets, hepatic necrobiosis)
Leaching into groundwater depends on topography, precipitation and site-specific soil characteristics, such as organic matter content and soil pH.
I
Nitrate (2013)
45 as nitrate; 10 as nitrate-nitrogen
None
Naturally occurring; leaching or runoff from agricultural fertilizer use, manure and domestic sewage; may be produced from excess ammonia or nitirification in the distribution system
Health basis of MAC: Methaemoglobinaemia (blue baby syndrome) and effects on thyroid gland function in bottle-fed infants
Other: Classified as possible carcinogen under conditions that result in endogenous nitrosation
Systems using chloramine disinfection or that have naturally occurring ammonia should monitor the level of nitrate in the distribution system. Homeowners with a well should test concentration of nitrate in their water supply.
I
Nitrilotriacetic acid (NTA) (1990)
0.4
None
Sewage contamination
Health basis of MAC: Kidney effects (nephritis and nephrosis)
Other: Classified as possible carcinogen
MAC is based upon exposure mainly attributable (80%) to drinking water with 20% of exposure attributable to food.
I
Nitrite (2013)
3 as nitrite; 1 as nitrite-nitrogen
None
Naturally occurring; leaching or runoff from agricultural fertilizer use, manure and domestic sewage; may be produced from excess ammonia or nitirification in the distribution system
Health basis of MAC: Methaemoglobinaemia (blue baby syndrome) in bottle-fed infants less than 6 months of age
Other: Classified as possible carcinogen under conditions that result in endogenous nitrosation
Systems using chloramine disinfection or that have naturally occurring ammonia should monitor the level of nitrite in the distribution system. Homeowners with a well should test concentration of nitrite in their water supply.
DBP
N-Nitroso dimethylamine (NDMA) (2010)
0.000 04
None
By-product of drinking water disinfection with chlorine or chloramines; industrial and sewage treatment plant effluents
Health basis of MAC: Liver cancer (classified as probable carcinogen)
MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing. Levels should be kept low by preventing formation during treatment.
A
Odour (1979, 2005)
None
Inoffensive
Biological or industrial sources
Not applicable
Important to provide drinking water with no offensive odour, as consumers may seek alternative sources that are less safe.
O
Pentachlorophenol (1987, 2005)
0.06
AO: ≤ 0.03
By-product of drinking water disinfection with chlorine; industrial effluents
Health basis of MAC: Reduced body weight, changes in clinical parameters, histological changes in kidney and liver, reproductive effects (decreased neonatal survival and growth)
AO based on odour; levels above the AO would render drinking water unpalatable.
O
Perfluorooctane Sulfonate (PFOS) (2018)
A draft technical document is available for public consultation from February 11, 2023 to April 12, 2023.
0.0006
Synthetic chemical used in consumer products and fire-fighting foams for their water and oil repellant properties.
Health basis of MAC: Adverse effects in the liver. Additional effects at low doses include thyroid and immune effects and changes in serum lipid levels.
Additive effects with PFOA were considered. The sum of PFOS and PFOA concentrations in drinking water divided by their respective MAC should not exceed 1.
O
Perfluorooactanoic Acid (PFOA) (2018)
A draft technical document is available for public consultation from February 11, 2023 to April 12, 2023.
0.0002
Synthetic chemical used in consumer products and fire-fighting foams for their water and oil repellant properties.
Health basis of MAC: Adverse effects in the liver. Additional effects at low doses include delay in mammary, estrogenic and developmental effects.
Additive effects with PFOS were considered. The sum of PFOA and PFOS concentrations in drinking water divided by their respective MAC should not exceed 1.
T
pH (2015)
None
7.0-10.5
Table 2 footnote
4
Not applicable
Not applicable
The control of pH is important to maximize treatment effectiveness, control corrosion and reduce leaching from distribution system and plumbing components.
I
Selenium (2014)
0.05
None
Naturally occurring (erosion and weathering of rocks and soils) and release from coal ash from coal-fired power plants and mining, refining of copper and other metals.
Health basis of MAC: chronic selenosis symptoms in humans following exposure to high levels
Other: Hair loss, tooth decay, weakened nails and nervous system disturbances at extremely high levels of exposure
Selenium is an essential nutrient. Most exposure is from food; little information on toxicity of selenium from drinking water. Selenium can be found in non-leaded brass alloy where it is added to replace lead.
I
Silver (1986, 2005)
None required
None
Naturally occurring (erosion and weathering of rocks and soils)
Not applicable
Guideline value not required as drinking water contributes negligibly to an individual’s daily intake.
I
Sodium (1979)
None
AO: ≤ 200
Naturally occurring (erosion and weathering of salt deposits and contact with igneous rock, seawater intrusion); sewage and industrial effluents; sodium-based water softeners
For persons on strict sodium reduced diets applying to all sources, levels in drinking water should be below 20 mg/L
Based on taste; where a sodium-based water softener is used, a separate unsoftened supply for cooking and drinking purposes is recommended.
I
Strontium (2019)
7.0
Naturally occurring (erosion and weathering of rocks); effluents from mining or other industries
Health basis of MAC: Bone effects (adverse effects on bone formation in infants as well as rickets, osteomalacia)
MAC is protective of the most sensitive sub-population, infants.
I
Sulphate (1994)
None
AO: ≤ 500
Industrial wastes
High levels (above 500 mg/L) can cause physiological effects such as diarrhoea or dehydration
Based on taste; it is recommended that health authorities be notified of drinking water sources containing sulphate concentrations above 500 mg/L.
I
Sulphide (1992)
None
AO: ≤ 0.05
Can occur in the distribution system from the reduction of sulphates by sulphate-reducing bacteria; industrial wastes
Not applicable
Based on taste and odour; levels above the AO would render water unpalatable.
A
Taste (1979, 2005)
None
Inoffensive
Biological or industrial sources
Not applicable
Important to provide drinking water with no offensive taste, as consumers may seek alternative sources that are less safe.
T
Temperature
(1979, 2005)
None
AO: ≤ 15°C
Not applicable
Not applicable
Temperature indirectly affects health and aesthetics through impacts on disinfection, corrosion control and formation of biofilms in the distribution system.
O
Tetrachloroethylene (2015)
0.01
None
Spill or other point source of contamination
Health basis of MAC: Neurological effects (colour confusion) in humans
Other: Classified as probably carcinogenic to humans, based on sufficient evidence in experimental animals and limited evidence in humans
Primarily a concern in groundwater, as it volatilizes easily from surface water; MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing.
O
Toluene (2014)
0.06
AO: 0.024
Emissions, effluents or spills from petroleum and chemical industries
Health basis of MAC: Adverse neurological effects, including vibration thresholds, colour discrimination, auditory thresholds, attention, memory and psychomotor functions
Other: Insufficient information to determine whether toluene is carcinogenic to humans.
MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing. AO is based on odour.
A
Total dissolved solids (TDS) (1991)
None
AO: ≤ 500
Naturally occurring; sewage, urban and agricultural runoff, industrial wastewater
Not applicable
Based on taste; TDS above 500 mg/L results in excessive scaling in water pipes, water heaters, boilers and appliances; TDS is composed of calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, sulphate and nitrate.
O
Trichloroethylene (2005)
0.005
None
Industrial effluents and spills from improper disposal
Health basis of MAC: Developmental effects (heart malformations)
Other: Classified as probable carcinogen
MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing.
O
2,4,6-Trichlorophenol (1987, 2005)
0.005
AO: ≤ 0.002
By-product of drinking water disinfection with chlorine; industrial effluents and spills
Health basis of MAC: Liver cancer (classified as probable carcinogen)
AO based on odour; levels above the AO would render drinking water unpalatable.
DBP
Trihalomethanes)
Table 2 footnote
3 (THMs) (2006)
0.1
None
By-product of drinking water disinfection with chlorine; industrial effluents
Health basis of MAC: Liver effects (fatty cysts) (chloroform classified as possible carcinogen)
Other: Kidney and colorectal cancers
Refers to the total of chlorodibromomethane, chloroform, bromodichloromethane and bromoform; MAC based on health effects of chloroform. MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing. Utilities should make every effort to maintain concentrations as low as reasonably achievable without compromising the effectiveness of disinfection. Recommended strategy is precursor removal. The separate MAC for BDCM was rescinded in April 2009.
I
Uranium (2019)
0.02
None
Naturally occurring (erosion and weathering of rocks and soils); mill tailings; emissions from nuclear industry and combustion of coal and other fuels; phosphate fertilizers
Health basis of MAC: Kidney effects
Based on challenges and operational cost impacts for some private wells and small systems; MAC is for total uranium and is protective in relation to both chemical and radiological hazards.
O
Vinyl chloride (2013)
0.002 ALARA
None
Industrial effluents; degradation product from organic solvents in groundwater; leaching from polyvinyl chloride pipes
Health basis of MAC: Liver cancer (classified as human carcinogen)
Other: Raynaud’s disease, effects on bone, circulatory system, thyroid, spleen, central nervous system
Based on analytical achievability. MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing. Leaching from polyvinyl chloride pipe is not expected to be significant.
O
Xylenes (total) (2014)
0.09
AO: 0.02
Emissions, effluents or spills from petroleum and chemical industries
Health basis of MAC: Adverse neuromuscular effects
Other: Insufficient information to determine whether xylenes are carcinogenic to humans.
MAC takes into consideration all exposures from drinking water, which include ingestion, as well as inhalation and dermal absorption during showering and bathing. AO is based on odour.
I
Zinc (1979, 2005)
AO: ≤ 5.0
Naturally occurring; industrial and domestic emissions; leaching may occur from galvanized pipes, hot water tanks and brass fittings
Zinc is an essential element and is generally considered to be non-toxic, however levels above the AO in water would render it unpalatable.
AO based on taste; water with zinc levels above the AO tends to be opalescent and develops a greasy film when boiled; plumbing should be thoroughly flushed before water is consumed.
