Health Canada 2006 - Arsenic drinking water guideline
Health Canada’s 2006 guideline technical document sets a maximum acceptable concentration (MAC) of 0.010 mg/L, or 10 ug/L, for arsenic in drinking water, based on municipal- and residential-scale treatment achievability. The document focuses on inorganic arsenic in drinking water and recognizes arsenic as a human carcinogen. Health Canada calculates that a concentration of 0.3 ug/L would correspond to an “essentially negligible” cancer-risk target, but sets the enforceable MAC at 10 ug/L because 0.3 ug/L was not considered technically and economically achievable for many small public systems and private wells. The guideline is therefore an ALARA source: arsenic should be kept as close as possible to the health-risk target even though the MAC is higher.
Key numbers
Guideline and cancer-risk values:
| Parameter | Value | Notes |
|---|---|---|
| Canadian drinking-water MAC for arsenic | 0.010 mg/L | Equivalent to 10 ug/L |
| Health-risk target concentration | 0.3 ug/L | Concentration associated with “essentially negligible” risk in this assessment |
| ALARA posture | yes | Every effort should be made to keep arsenic as low as reasonably achievable |
| Health Canada “essentially negligible” risk range | 10^-5 to 10^-6 over lifetime | One excess cancer per 100,000 to one per 1,000,000 |
| Unit risk for 1 ug/L arsenic in drinking water | 3.06 x 10^-6 to 3.85 x 10^-5 | Based on internal organ cancer endpoints |
| Upper-bound unit risk range | 6.49 x 10^-6 to 4.64 x 10^-5 | 95% upper bounds |
| Critical cancer endpoints | lung, bladder, liver | Kidney also discussed in the Taiwan evidence base |
| Source population for quantitative risk | Southwestern Taiwan | High-exposure artesian-well population; approximately 40,000 people |
| Taiwan exposure range noted | 350-1,140 ug/L | Much higher than Canadian guideline levels |
| IARC / Health Canada classification | Group 1, carcinogenic to humans | Arsenic classified as human carcinogen |
| EPA analytical PQL cited | 0.003 mg/L | 3 ug/L |
Estimated lifetime excess internal-organ cancer risk:
| Drinking-water arsenic concentration | Estimated lifetime excess internal-organ cancer risk |
|---|---|
| 0.3 ug/L | 0.09-1 x 10^-5 |
| 5 ug/L | 2-20 x 10^-5 |
| 10 ug/L (MAC) | 3-39 x 10^-5 |
| 25 ug/L | 8-97 x 10^-5 |
Canadian occurrence and exposure values:
| Dataset or exposure estimate | Reported arsenic values | Notes |
|---|---|---|
| Prince Edward Island groundwater supplies, 1986-2002 | 0.1-26.0 ug/L; >99% below 10 ug/L; average about 1.5 ug/L | Provincial monitoring |
| Quebec municipal treated surface water, 1990-2002 | 1.0-25.0 ug/L; >99% below 10 ug/L; annual average 1.6 ug/L | 523 communities |
| Quebec municipal treated groundwater, 1990-2002 | 1.0-60 ug/L; about 98% below 10 ug/L; annual average 2.0 ug/L | 562 communities |
| Ontario treated groundwater and surface water, 1997-2002 | 0.1-18 ug/L; >99% below 10 ug/L; annual average ⇐0.7 ug/L | 726 communities |
| Ontario private-lab raw/treated drinking water, 1999-2002 | <2.5-68 ug/L; average <2.5 ug/L | Higher values predominantly from wells |
| Saskatchewan municipal treated supplies, 1976-2002 | 0.5-105.0 ug/L; 97% ⇐10 ug/L; average 3.0 ug/L | 539 communities |
| Alberta treated groundwater and surface water, 1980-2002 | 0.1-1000 ug/L; about 99% below 10 ug/L; annual average 1.8 ug/L | 573 communities |
| Nova Scotia well samples, 1991-1997 | 9% above 25 ug/L | Environmental Chemistry Laboratory data |
| Nova Scotia seven-community well survey | 33%-93% of wells above 50 ug/L; 10% above 500 ug/L | 94 wells |
| Newfoundland public water supplies, 2002 | maximum 6-288 ug/L | 54 wells |
| Newfoundland school wells, 2002 | 1-368 ug/L; about 19% above 10 ug/L | 16 schools |
| British Columbia Bowen Island groundwater | maximum 580 ug/L | Groundwater samples |
| Typical adult drinking-water intake where water <5 ug/L | <7.5 ug/day | Assumes 1.5 L/day |
| Child drinking-water intake where water <5 ug/L | <3.5 ug/day | Ages 0.5-4 years, 0.7 L/day |
| Canadian adult total arsenic intake from food | 42 ug/day | Range 22.5-78.7 ug/day |
| Estimated inorganic arsenic from food | 10.5 ug/day | Assumes 25% of food arsenic is inorganic |
| Food prepared with arsenic-containing water | +10%-30% for most foods; +200%-250% for beans/grains | U.S. EPA estimate |
Analytical and treatment values:
| Topic | Value | Notes |
|---|---|---|
| Arsenic reliably measurable concentration cited | 0.005 mg/L | 5 ug/L |
| GHAA typical detection limit | 0.001 mg/L | 1 ug/L |
| EPA Method 200.8 ICP-MS MDL | 1.4 ug/L | Total arsenic |
| ICP-MS selective-ion monitoring MDL | 0.1 ug/L | Useful for chloride interferences |
| EPA Method 200.9 STP-GFAA MDL | 0.5 ug/L | Total arsenic |
| Standard Methods 3113B GFAA MDL | 1 ug/L | Total arsenic |
| Standard Methods 3114B GHAA MDL | 0.5 ug/L | Total arsenic |
| EPA Method 1632 speciation MDL | 0.002 ug/L | Direct drinking-water speciation; high skill requirement |
| Coagulation/filtration plus oxidation and ion-exchange polishing | 0.003-0.005 mg/L finished water | 3-5 ug/L |
| Lime softening | 0.001-0.003 mg/L finished water | 1-3 ug/L |
| Activated alumina | <0.01 mg/L in pilot studies; 95% removal efficiency | U.S. EPA best available technology |
| Ion exchange plus oxidation | as low as 0.003 mg/L finished water | Laboratory column studies as low as 0.002 mg/L from 0.021 mg/L influent |
| Reverse osmosis | up to 85% total arsenic removal | Requires pretreatment and reject brine management |
| Iron oxide-coated sand / granular ferric hydroxide | below 0.005 mg/L | Removes As(III) and As(V) in cited studies |
| Residential reverse osmosis | effective total arsenic removal | Amount removed depends on membrane |
| Residential distillation | virtually all arsenic removed | More complex than RO |
| NSF/ANSI 53, 58, and 62 arsenic challenge | 0.3 mg/L influent to 0.010 mg/L effluent | High-arsenic well-water scenario |
| Lower NSF/ANSI device challenge | 0.05 mg/L influent to 0.010 mg/L effluent | Lower-initial-concentration scenario |
Methods (brief)
This is a Health Canada guideline technical document, not a new field survey. It compiles Canadian provincial occurrence data, exposure estimates for water/food/air/soil, arsenic speciation and metabolism evidence, analytical-method performance, municipal and residential treatment technology, and cancer risk assessment. The guideline focuses on inorganic arsenic in drinking water and treats ingestion as the relevant exposure route; inhalation and dermal exposure from drinking water are considered insignificant.
Health Canada bases quantitative risk on human epidemiology rather than animal carcinogenicity because arsenic toxic effects and metabolism vary strongly across species. The risk calculation uses internal-organ cancer evidence from southwestern Taiwan and a Poisson model fit to the Morales et al. dataset with an external unexposed comparison population. Treatment achievability, the analytical PQL, and ALARA considerations then determine the final 10 ug/L MAC.
Implications
Certification: This source is a Canadian drinking-water regulatory anchor for arsenic and inorganic-arsenic context. It should not be pooled with food-occurrence data or with bottled-water market surveys. For water filters, its NSF/ANSI challenge values are device-performance comparators, not contamination values in finished products.
Courses: The guideline is useful for teaching the difference between a risk-derived target and a legally/practically achievable MAC. It is also a good example of why arsenic speciation matters: As(III) is harder to remove than As(V), and pre-oxidation is central to many treatment trains.
App: Use this source to explain that food is the main arsenic exposure source for most Canadians, but drinking water can dominate exposure near natural geological sources or contaminated wells. Consumer-facing guidance should preserve the ALARA posture and the private-well testing/treatment context.
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Verification notes
The PDF was read from the June 3 manual-fetch folder, including the guideline, executive summary, application, exposure, analytical methods, treatment technology, kinetics/metabolism, health effects, classification/risk assessment, and rationale sections, along with Tables 1 and 2. Page count is 38. No DOI is assigned. The canonical raw file raw/Manual Fetch Kimi /June 3 Folder/water-arsenic-eau-eng.pdf and duplicate file raw/Manual Fetch Kimi /June 3 Folder/water-arsenic-eau-eng 2.pdf are byte-identical with SHA-256 eb62f3177f0d1f01ff601ef670071f8220eee2023c649ba07019bcdbe213a5ce; the duplicate is recorded in the tracker as a duplicate rather than a second source.
Scope note: the source reports total arsenic analytical methods and a drinking-water arsenic MAC, while the risk assessment focuses on inorganic arsenic species. Frontmatter therefore includes both tAs and iAs; downstream routing must not use total arsenic as a substitute for inorganic arsenic in food matrices.
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.