Chromium is a naturally occurring element in the earth’s crust. Chromium has a number of different valence states, but typically only occurs in its trivalent form (chromium [III]) and hexavalent form (chromium [VI]) naturally. Chromium [VI] compounds are most often products of industrial processes. Common chromium [VI] chemicals include potassium chromate and dichromate, sodium chromate and dichromate, lead chromate, calcium chromate, and chromium trioxide. A number of other hexavalent compounds exist; refer to HSDB for more information.
Hexavalent chromium has been classified by IARC as Group 1, carcinogenic to humans, with a well established link to lung cancer.[7,22] Several epidemiological studies have also found increased risks of cancer in the nasal cavity and paranasal sinuses in workers exposed to chromium [VI],[4,22] and sinonasal cancer among workers engaged in chromate production, chromate pigment production, and chromium plating. Compounds of chromium [III] and metallic chromium were classified as Group 3, not classifiable as to its carcinogenicity to humans. The current profile will focus on chromium [VI], which is the most carcinogenic species of chromium.
Acute inhalation exposure to hexavalent chromium may cause irritation and damage to the nose, throat and lungs. Dermal exposure to chromium [VI] may also cause allergic contact dermatitis and skin sensitization.
*This designation applies to a number of different chromium [VI] compounds, including chromium trioxide and various chromic acid (chromate) compounds.
Hexavalent chromium was not included in other Canadian government chemical listings reviewed.
Hexavalent chromium is used in the manufacturing of stainless steel and other alloys, pigments, wood preservatives and in leather tanning and metal finishing (chrome plating).[4,5] Chromium [VI] compounds are also used in smaller quantities in printer ink toners, textile dyes, drilling muds, and during water treatment and chemical production.[3,4]
Chromated copper arsenate (CCA) is a widely used wood preservative that contains hexavalent chromium. The use of CCA-treated wood for residential purposes was voluntarily phased out by the industry at the end of 2003. Existing residential structures made with CCA-treated wood were not required to be removed. CCA is still used in wood preservation in industrial applications such as utility poles, pilings, and highway construction.
Canadian Production and Trade
Canada has not mined chromium ores since the early 1900s, although there are deposits across the country. Recent exploration has taken place in Manitoba, Quebec and Newfoundland.
One Canadian producer of lead chromate remained in 1995; Dominion Colour in Ontario produced chrome yellow and molybdate orange pigments. No chromic acid is manufactured in Canada.
Production and Trade
Export: Mainly to US
116 t of ‘chromium trioxide’
Import: Mainly from Turkey
954 t of 'chromium trioxide'
Import: Mainly from China
459 t of 'chromate of zinc and lead'
Import: Mainly from US
3,814 t of 'sodium dichromate'
Import: Mainly from US
138 t of 'chromates and dichromates of metals not otherwise classified'
*No import or export of zinc and lead chromate was recorded for 2007-2010
Inhalation and dermal contact are the most important routes of occupational exposure to chromium [VI]. CAREX Canada’s estimates indicate that approximately 104, 000 Canadians are occupationally exposed to chromium (VI). Most exposures (87%) are occurring in the low exposure category. However, many workers are exposed to moderate or high levels of chromium (VI) in fabricated metal product, machinery, and transportation equipment manufacturing.
The industries with the largest numbers of exposures are automotive maintenance and repair, and printing and support activities. Other industries with larger numbers of workers exposed to chromium (VI) include saw mills and wood preservation, commercial and industrial machinery repair, and structural metal manufacturing.
In terms of occupation, the groups with the largest number of exposures to chromium (VI) are welders (who are exposed during the welding of stainless steel), machinists and automotive technicians.
Trace amounts of chromium [VI] occur naturally in unpolluted environments.[3,5] However, most chromium detected in the environment is released from anthropogenic sources. Chromium [VI] is commonly found in indoor and outdoor air, soil, surface water and groundwater.
Surface waters in many parts of Canada are contaminated with chromium [VI]. Water samples from the Great Lakes had median concentrations of total chromium (including hexavalent chromium) ranging from 0.08 – 0.77 µg/L. Later analysis showed that nearly all the chromium in the water samples was chromium [VI]. Mean or median total chromium concentrations from rivers and streams in British Columbia, Alberta, Ontario and Quebec were found to be between 4 – 7 µg/L, with 10 – 60% of the chromium as chromium [VI]. Total chromium levels in unpolluted surface water are typically below 1 µg/g. Total chromium in Canadian drinking water is typically less than 5 µg/L.[3,5] CAREX Canada’s estimates indicate that chromium [VI] levels in drinking water may be resulting in an increased risk of cancer to Canadians (moderate data quality).
One air monitoring study in southwestern Ontario found levels of chromium [VI] in indoor and outdoor air ranged from 0.1 – 1.6 ng/m3. Average air chromium [VI] levels in industrial areas may be 10 – 45 times higher than those in non-industrial areas. CAREX Canada estimates that exposures to chromium [VI] in outdoor air is likely not resulting in lifetime excess cancer risks greater than 1 per million people (very low data quality).
Only total chromium concentration monitoring data are available for soil. Soil total chromium levels vary widely from 5 – 1,500 mg/kg, depending on the type of rock from which the soil formed and the presence of nearby industrial activities. Soil near wood preservation plants, which uses hexavalent chromium, was found to have 25 times more total chromium content than uncontaminated soil. Chromium [VI] may also leach from treated wood structures such as building foundations, railroad ties, and decks into surrounding soil.[5,15]
No household products with hexavalent chromium as an ingredient were listed in the Household Products Database from the United States. However, several ‘portland cement’ products indicated that they may contain trace amounts of hexavalent chromium.
A search in the NPRI database yielded the following results on current releases of hexavalent chromium in Canada:
NPRI Reported Releases
’hexavalent chromium (and its compounds)'
Released into Environment
Power generation, pulp & paper, metal plating, various manufacturing, waste treatment (177 facilities)
Sent to off-site recycling
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 chromium in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at email@example.com.