IARC Monograph Vol. 84, 2004 (Arsenic in Drinking Water, Group 1)
IARC Monograph Vol 100C, 2011 (Group 1) (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 metals. 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 HSDB or IARC Monograph for more information.[4,5]
In both IARC Monograph Volumes 23 and 84, arsenic and its compounds were classified as Group 1, carcinogenic to humans. A recent IARC review of Class 1 carcinogens reaffirmed this classification. The evaluation applies to the whole group, not necessarily to each individual compound. Occupational epidemiology studies have established a strong association with inhalation exposure and the development of lung cancer, particularly in the smelting and mining industries. Long-term exposure to arsenic through ingestion (i.e. medicinal, drinking water) can cause skin cancer. Other cancer sites associated with arsenic exposure include the digestive tract, liver, bladder, kidney, prostate and lymphatic and hematopoietic systems.[2,32]
Discolouration and thickening of the skin on hands and feet are characteristic of chronic arsenic ingestion, often preceding malignancy. Neurological changes including peripheral neuropathies are also reported from low dose, chronic exposure. Because of its effectiveness as a poison, data on acute exposure resulting in death is well established and includes respiratory, kidney and cardiovascular damage, and haematological changes.
Although the major use for arsenic has been for chromated copper arsenate (CCA) in the wood preservation industry, use patterns have changed in recent years.
In December 2003, a voluntary agreement was made in the United States and Canada to stop using CCA in wood with 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. One use occurs in the metallurgical industry, for hardening copper and lead-antimony alloys; applications include ammunitions, solders, battery posts, bearings and lead shot. A second occurs in glassmaking, where arsenic is used as a bubble dispersant or colouring agent. Finally, in the semi-conductor industry, high-purity arsenic is used in several semiconductor applications, such as; solar cells, light emitting diodes, lasers, and integrated circuits.
Historically, arsenic has been included in agricultural chemicals, either directly of after conversion to arsenic acid, and was widely used as a pesticide and fertilizer. This is generally not allowed any longer, though arsenicals may be used in emergency situations (e.g. pine beetle infestation). Until the 1970s, arsenic was used in the treatment of leukemia, psoriasis, and asthma. In the 1990s, there was renewed interest in the use of arsenic for treatment of a specific type of leukemia.
Canadian Production and Trade
Historically, Canada produced refined arsenic trioxide in Ontario. The plant ceased smelting operations in 1961. The USGS reports that arsenic trioxide is still produced by Canada (250 tonnes per year as of 2007). The smelter in Trail, BC started producing gallium arsenide in 1981.
Canadian arsenic was also obtained from the treatment of arsenious gold in mines operated in Ontario and the Northwest Territories. In 1992, two mines were operational.
Production and Trade
Import: Mainly from the US
41 t of 'arsenic'
Canada did not export arsenic in 2010.
Inhalation and dermal contact are the most important routes of occupational exposure. The main occupations exposed include workers involved in mining, copper or lead smelting and the wood preservation industry.[2,3]
Consumption of arsenic in food is generally considered the primary route of exposure for the general population not living near a point source, although drinking water can also be a significant source in areas where arsenic is found in bedrock. Areas in Canada with arsenic-rich geologic deposits include the Yukon, Northern B.C., Nunavut Islands, the east coast, and few hot spots in Southern Ontario.
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,[24,25] intake of inorganic arsenic, considered to be more toxic, is estimated to be 25% of total arsenic intake. In Canada, sources of arsenic in food include shellfish, meat, poultry, grain and dairy products. In Ontario, 84% of the daily intake or arsenic was estimated to come from food, 15% from water, and <1% from soils/dusts and a negligible amount from skin contact. This trend is expected to be relatively similar across Canada.
Arsenic in pigments and paints may be ingested through contamination of hands, fingernails, food, cups, or cigarettes.
The average ambient air concentration in 11 Canadian cities and one rural site in 1990 was 0.001 µg/m3 (0.0005 – 0.017 µg/m3). Although weathering and erosion of arsenic-containing rocks and soils contributes to natural levels of arsenic in the environment, anthropogenic sources are the most significant contributors. Examples include base-metal mining and gold production; waste and coal burning; leaching from arsenic treated sawdust and wood or smoke from treated wood; and the applying of arsenic-based pesticides.
Monosodium Methanearsonate (MSMA), an arsenic-containing pesticide, was used in BC forests from 1995-2004 in an attempt to slow the pine beetle infestation. When arsenic accumulation in woodpeckers and other insect-feeding species became evident, MSMA was removed from BC markets.
Some Canadian sites with high arsenic levels from mining/smelting residues include Moira Lake, Ont., Yellowknife, NWT, Bathurst, NB, and Rabbit Lake, Saskatchewan. Samples taken recently near Sydney, Nova Scotia found 20% of background soil samples and 95% of tar pond soil samples were above Canadian health-based soil guidelines for arsenic.
Searches of environmental and consumer product databases yielded the following results on current potential for exposure to arsenic in Canada:
NPRI and US Household Products Database
Search term: 'arsenic'
Released into Environment
Mining, smelters, waste control, pulp and paper, oil refineries, power generation, and wood production (221 companies)
Lambert TW, Lane S (2004). 'Lead, arsenic, and polycyclic aromatic hydrocarbons in soil and house dust in the communities surrounding the Sydney, Nova Scotia, tar ponds,' Environmental Health Perspectives. Vol. 112, No. 1, pp. 35-41.