Chromium (Hexavalent)
Full Profile
General Information
Chromium is a naturally occurring element in the earth’s crust.[3] Chromium has a number of different valence states, but typically only occurs in its trivalent form (chromium [III]) and hexavalent form (chromium [VI]) naturally.[3] Chromium [VI] compounds are most often products of industrial processes.[4] Common chromium [VI] chemicals include potassium chromate and dichromate, sodium chromate and dichromate, lead chromate, calcium chromate, and chromium trioxide.[4] A number of other hexavalent compounds exist; refer to HSDB for more information.[6]
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.[4] Compounds of chromium [III] and metallic chromium were classified as Group 3, not classifiable as to its carcinogenicity to humans.[7] 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.[5] Dermal exposure to chromium [VI] may also cause allergic contact dermatitis and skin sensitization.[5]
How did CAREX choose this agent for review?
Regulations and Guidelines
Occupational Exposure Limits (OEL)
| Canadian Jurisdictions | OEL (mg/m3) |
|---|---|
| Canada Labour Code | 0.05 [water-soluble Cr compounds] 0.01 [insoluble Cr compounds] 0.1 [tert-Butyl chromate; c] 0.001 [calcium chromate] 0.012 [lead chromate, as Cr] 0.0005 [strontium chromate] 0.01 [zinc chromates] |
| AB, BC, ON, MB, NL, NB, NS, PE |
0.05 [water-soluble Cr compounds] 0.01 [insoluble Cr compounds] 0.1 [tert-Butyl chromate; c; sk] 0.001 [calcium chromate] 0.003 [stel; calcium chromate] 0.012 [lead chromate, as Cr] 0.036 [stel; lead chromate as Cr] 0.0005 [strontium chromate] 0.0015 [stel; strontium chromate] 0.01 [zinc chromates] |
| SK | 0.05 [water-soluble Cr compounds] 0.15 [stel; water-soluble Cr compounds] 0.01 [insoluble Cr compounds] 0.03 [stel; insoluble Cr compounds] 0.1 [tert-Butyl chromate; c; sk] 0.001 [calcium chromate] 0.012 [lead chromate, as Cr] 0.0005 [strontium chromate] 0.0014 [stel; strontium chromate] 0.01 [zinc chromates] 0.03 [stel; zinc chromates] |
| QC | 0.05 [water-soluble Cr compounds] 0.05 [water-insoluble Cr compounds] 0.1 [tert-Butyl chromate; c; sk] 0.012 [lead chromate, as Cr] 0.01 [zinc chromates] |
| YT | 0.1 [tert-Butyl chromate; sk] 0.1 [chromite acid and chroamtes, as CrO3 0.5 [soluble chromic chromous salts, as Cr] 0.1 [chromium metal and insoluble salts] 0.05 [lead chromate, as Cr] |
| NT, NU | 0.05 [water-soluble Cr compounds] 0.15 [stel; water-soluble Cr compounds] 0.05 [insoluble Cr compounds] 0.15 [stel; insoluble Cr componds] 0.1 [tert-Butyl chromate; c; sk] 0.05 [lead chromate, as Cr] 0.15 [stel; lead chromate, as Cr] 0.15 [zinc chromates] |
| Other Jurisdiction | OEL (mg/m3) |
| ACGIH 2010 TLV | 0.05 [water-soluble Cr compounds] 0.01 [insoluble Cr compounds] 0.1 [tert-Butyl chromate; c] 0.001 [calcium chromate] 0.012 [lead chromate, as Cr] 0.0005 [strontium chromate] 0.01 [zinc chromates] |
Canadian Environmental Guidelines
Hexavalent chromium was not included in Canadian government environmental guidelines reviewed.[8,9,14,16] A maximum allowable limit (MAC), set at 0.05 mg/L, is in place in the Canadian Drinking Water Guidelines for total chromium.[8]
Canadian Agencies/Organizations
| Agency | Designation/Position | Year |
|---|---|---|
| Health Canada | DSL – low priority substance (already risk managed)* | 2006[10] |
| CEPA | Schedule 1, paragraphs 'a' and 'c' | 2011[11] |
Hexavalent chromium was not included in other Canadian government chemical listings reviewed.[12]
Main Uses
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.[15] The use of CCA-treated wood for residential purposes was voluntarily phased out by the industry at the end of 2003.[15] 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.[15]
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.[13]
One Canadian producer of lead chromate remained in 1995; Dominion Colour in Ontario produced chrome yellow and molybdate orange pigments.[17] No chromic acid is manufactured in Canada.[18]
Production and Trade
| Activity | Quantity | Year (Ref) |
|---|---|---|
| Export: Mainly to US | 116 t of ‘chromium trioxide’ | 2010[19] |
| Import: Mainly from Turkey | 954 t of 'chromium trioxide' | 2010[19] |
| Import: Mainly from China | 459 t of 'chromate of zinc and lead' | 2006*[19] |
| Import: Mainly from US | 3,814 t of 'sodium dichromate' | 2010[19] |
| Import: Mainly from US | 138 t of 'chromates and dichromates of metals not otherwise classified' | 2010[19] |
Occupational Exposures
Inhalation and dermal contact are the most important routes of occupational exposure to chromium [VI].[4]
Workers involved in the following occupations/industries have the highest potential for exposure: manufacture of chromate compounds and pigments, stainless steel production, welding, chrome plating, production of ferrochrome alloys, wood preservation, and the leather tanning industry.[5]
Environmental Exposures
Trace amounts of chromium [VI] occur naturally in unpolluted environments.[3,5] Most chromium detected in the environment is released from anthropogenic sources.[5]
Chromium [VI] is commonly found in indoor and outdoor air, soil, surface water and groundwater.[5] The general public may be exposed to chromium [VI] through the inhalation of indoor and outdoor air, ingestion of drinking water, and dermal contact with water.
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.[5] Average air chromium [VI] levels in industrial areas may be 10 – 45 times higher than those in non-industrial areas.[5]
Surface waters in many parts of Canada are contaminated with chromium [VI].[3] Water samples from the Great Lakes had median concentrations of total chromium ranging from 0.08 – 0.77 µg/L.[3] Later analysis showed that nearly all the chromium in the water samples was chromium [VI].[3] 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].[3] Total chromium levels in unpolluted surface water are typically below 1 µg/g.
Total chromium (including hexavalent chromium) in drinking water is typically below 5 µg/L.[3,5]
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.[5] Soil near wood preservation plants, which uses hexavalent chromium, was found to have 25 times more total chromium content than uncontaminated soil.[3] Chromium [VI] may also leach from treated wood structures such as building foundations, railroad ties, and decks into surrounding soil.[5,15]
A Canadian government report published in 1994 concluded that hexavalent chromium is “entering or may enter the environment in a quantity or concentration or under conditions that are having or may have a harmful effect on the environment.”[3]
No household products with hexavalent chromium as an ingredient were listed in the Household Products Database from the United States.[20]
A search in the NPRI database yielded the following results on current releases of hexavalent chromium in Canada:
NPRI Reported Releases
| NPRI 2009[21] | ||
|---|---|---|
| Category | Quantity | Industry (# companies) |
| Released into Environment | 2.6 t | Power generation, pulp & paper, metal plating, various manufacturing, waste treatment (207 companies) |
| Disposed of | 131 t | |
| Sent to off-site recycling | 45.5 t | |
Sources
- Wikimedia Commons (2007) Photo of potassium chromate
- Wikimedia Commons (2007) Photo of potassium dichromate
- Health Canada Environment Canada (1994) Priority Substances List assessment report (CEPA) for Chromium and its Compounds
- NTP (2011) 12th Report on Carcinogens for Chromium Hexavalent Compounds
- ATSDR Toxicological Profile for Chromium, Hexavalent, Draft September 2008
- US National Library of Medicine (2011) Hazardous Substances Data Bank entry for hexavalent chromium (Search term: ‘hexavalent chromium’)
- IARC (1990) IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Volume 49: Chromium, Nickel and Welding
- Health Canada (2010) Guidelines for Canadian Drinking Water
- Health Canada (1987) Exposure Guidelines for Residential Indoor Air Quality
- Related Components of Categorization of the Domestic Substances List under CEPA (1999)
- Environment Canada (2010) Toxic Substances List – CEPA Schedule 1
- List of All Challenge Substances, Government of Canada Chemicals Management Plan (2009)
- Natural Resources Canada (1995) Canadian Minerals Yearbook, Chromium
- Health Canada (2010) Cosmetic Ingredient Hotlist
- Health Canada (2005) Fact Sheet on Chromated Copper Arsenate (CCA) Treated Wood
- Health Canada (2006) Food Additives Permitted for Use in Canada
- Camford Information Services (1995) CPI Product Profiles: Lead chromate
- Camford Information Services (1995) CPI Product Profiles: Chromic Acid
- TradeMap (Free subscription required)
- US Department of Health and Human Services (2011) Household Products Database
- Environment Canada (2009) The National Pollutant Release Inventory
- IARC (2009) Monograph Volume 100: A review of human carcinogens—Part C: metals, arsenic, dusts, and fibres
Other Resources
- ATSDR ToxFAQ for Chromium (2008)
- EPA (1984), Health assessment document for Chromium. Research Triangle Park, NC: Environmental