IARC Monograph Vol. 84, 2004 (Arsenic in Drinking Water, Group 1)
IARC Monograph Vol 100C, 2012 (Group 1)
Arsenic is a semi-metallic element. Although it is rare to find pure arsenic in nature, inorganic arsenic compounds are found in complex minerals containing copper, lead, iron, nickel, cobalt, and other elements. Most arsenic compounds are white powders with no odour. Of all commercially traded arsenic compounds, arsenic trioxide is the most important. There are numerous other synonyms and product names for arsenic; see the Hazardous Substances Data Bank (HSDB) for more information.[4,5]
In both Monograph Volumes 23 and 84 of the International Agency for Research on Cancer (IARC), arsenic and its compounds were classified as Group 1, carcinogenic to humans. IARC's Volume 100 review of Group 1 carcinogens in 2012 reaffirmed this classification. The evaluation applies to the whole group of arsenic compounds, not necessarily to each individual compound. Epidemiologic studies in occupational settings established a strong association between inhalation exposure to arsenic and lung cancer, particularly in smelting and mining industries. Long-term exposure to arsenic through ingestion (i.e. medicinally, via drinking water) can cause skin cancer. Other cancer sites associated with arsenic exposure include the digestive tract, liver, bladder, kidney, prostate, and lymphatic and haematopoietic systems.[2,6]
Chronic ingestion of arsenic is characterized by discoloured and thickened skin on hands and feet, which often precedes malignancy. Neurological changes including peripheral neuropathies are also reported from low dose, chronic exposure to arsenic. Because of its effectiveness as a poison, there is well established data on acute exposure to arsenic resulting in death; this includes respiratory, kidney, and cardiovascular damage, as well as haematological changes.
The major use for arsenic has been for chromated copper arsenate (CCA) in the wood preservation industry. In recent years, however, use patterns have changed.
In December 2003, a voluntary agreement was made in the United States and Canada to stop using CCA in wood for residential applications, including play structures, decks, fencing, and boardwalks. Prior to 2004, 90% of arsenic consumption in the US was for pressure treated wood; the figure reported for 2007 was 50%. Marine timbers, plywood flooring and roofing, utility poles, and glue-laminated beams can still be treated with CCA.
There are several other current uses of arsenic. In the metallurgical industry, arsenic is used to harden copper and lead-antimony alloys; applications include ammunitions, solders, battery posts, bearings, and lead shot. In glassmaking, arsenic is used to disperse bubbles or for colour. In the semiconductor industry, high-purity arsenic is used in applications such as solar cells, light emitting diodes, lasers, and integrated circuits.
Historically, arsenic has been included in agricultural chemicals, either directly or after conversion to arsenic acid, and was widely used as a pesticide and fertilizer. This is generally no longer permitted, though arsenicals may be used in emergency situations (e.g. pine beetle infestation). Until the 1970s, arsenic was used to treat leukemia, psoriasis, and asthma. In the 1990s, there was renewed interest in using arsenic to treat a specific type of leukemia.
Canadian Production and Trade
Arsenic is presently obtained as a byproduct of the smelting of copper, lead, cobalt, and gold ores.  In 2009, Hudson Bay Mining and Smelting was the base metal smelter with the largest emissions of arsenic in Canada accounting for 38% of emissions.  Other Canadian base metal smelters and refineries that produce and emit arsenic include: Vale Canada Ltd.-Copper Cliff, Vale Canada Ltd.-Thompson, Xstrata Copper-Horne, and Xstrata Copper-CCR. 
Production and Trade
58 t of 'arsenic'
t = tonne
Inhalation and dermal contact are the most important routes of occupational exposure.
CAREX Canada estimates that approximately 25,000 Canadians are exposed to arsenic at work; about half are exposed due to the use of arsenic in CCA wood preservatives. The industries with the highest number of exposed workers are foundation, structure, and building exterior contractors, as well as sawmills and wood preservation, and non-residential building construction. These workers are primarily exposed to arsenic through CCA treated wood. Workers are also exposed to arsenic in metal processing and manufacturing, oil and gas extraction, metal and ore mining, and water, sewage and other systems industries. Overall, larger numbers of exposed workers are employed in British Columbia and Quebec due to the large wood and wood product manufacturing industries in these provinces.
Consuming arsenic through food is generally considered the primary route of exposure for the general population, although drinking water can also be a significant source in areas where arsenic is found in bedrock (thus contaminating drinking water sources). Areas in Canada with arsenic-rich geologic deposits include the Yukon, Northern British Columbia (B.C.), Nunavut Islands, the Atlantic coast, and few hot spots in Southern Ontario. CAREX Canada's environmental estimates indicate that arsenic levels in Canadian drinking water result in higher risks of cancer at a population level (moderate data quality). Estimates for food and beverages show that arsenic exposure also results in an increased risk via this route (low data quality).
Quantifying the relative contribution of food and drinking water is difficult because arsenic uptake varies based on the form (i.e. organic or inorganic) and valence state of arsenic. Based on limited available research,[40,41] intake of inorganic arsenic, which is considered more toxic, is estimated at 25% of total arsenic intake. In Canada, sources of arsenic in food include shellfish, meat, poultry, grain, and dairy products. Arsenic has been found in bioaccessible forms (i.e. that can be readily absorbed) in Canadian wild plants and game, including berries, mushrooms, and hares. In Ontario, 84% of the daily intake of arsenic was estimated to come from food, 15% from water, less than 1% from soils/dusts, and a negligible amount from skin contact. This trend should be relatively similar across Canada. Arsenic in pigments and paints may be ingested through contaminated hands, fingernails, food, cups, or cigarettes.
The average arsenic concentration in ambient air in 11 Canadian cities and one rural site in 1990 was 0.001 µg/m3. Weathering and erosion of arsenic-containing rocks and soils contributes to natural levels of arsenic in the environment, however anthropogenic sources are the most significant contributors. Examples include mining base-metals and producing gold; burning waste and coal; leaching from arsenic treated sawdust and wood, or smoke from treated wood; and applying arsenic-based pesticides. Monosodium methanearsonate (MSMA), an arsenic-containing pesticide, was used in B.C. forests from 1995-2004 in an attempt to slow the pine beetle infestation. When arsenic accumulation and behavioural changes in woodpeckers and other insect-feeding species were observed, MSMA was removed from B.C. markets.
Some Canadian sites with high arsenic levels from mining/smelting residues include Moira Lake, ON, Yellowknife, NT, Bathurst, NB, and Rabbit Lake, SK. Samples taken recently near Sydney, NS found 20% of background soil samples and 95% of tar pond soil samples were above Canadian health-based guidelines for arsenic in soil .
Searches of Environment Canada's National Pollutant Release Inventory (NPRI) and the US Household Products Database yielded the following results on current potential for exposure to arsenic in Canada:
NPRI and US Household Products Database
Substance name: 'Arsenic'
Released into Environment
Foundries, Non-ferrous metal (except aluminum) production and processing, metal ore mining (272 facilities)
Sent to off-site recycling
US Household Products 2015
Gear and motor oils (4), cement colorant (1), pet care lotion(1)
t = tonne
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to arsenic on the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at firstname.lastname@example.org.