Chromium (Hexavalent) Profile

METALS  KNOWN CARCINOGEN (IARC 1)

CAS No. 18540-29-9
IARC Monograph Vol. 49, 1990 (Group 1)
IARC Monograph Vol 100C, 2012 (Group 1)

Chromium (Hexavalent) Profile

QUICK SUMMARY

  • A naturally occurring element in the earth’s crust, and a product of industrial processes
  • Associated cancer: Lung cancer
  • Most important routes of exposure: Inhalation, skin contact
  • Uses: Found in stainless steel and other alloys, pigments, wood preservatives, and leather tanning and metal finishing (chrome plating)
  • Occupational exposures: Approx. 104,000 Canadians are exposed at work, primarily welders, machinists, and automotive technicians
  • Environmental exposures: Found in indoor and outdoor air, soil, surface water, and groundwater
  • Fast fact: Canada has not mined chromium ores since the early 1900s, although there are deposits across the country

General Information

Chromium is a naturally occurring element in the earth’s crust.[1] It has a number of different valence states, but typically occurs in its trivalent (chromium [III]) and hexavalent (chromium [VI]) forms.[1] Chromium [VI] compounds are most often products of industrial processes.[2] Common chromium [VI] chemicals include potassium chromate and dichromate, sodium chromate and dichromate, lead chromate, calcium chromate, and chromium trioxide.[2] A number of other hexavalent compounds exist; refer to Hazardous Substances Data Bank (HSDB) for more information.[3]

Hexavalent chromium has been classified by the International Agency for Research on Cancer (IARC) as Group 1, carcinogenic to humans, with a well established link to lung cancer.[4,5] Several epidemiological studies have also found increased risks of cancer in the nasal cavity and paranasal sinuses in workers exposed to chromium [VI],[2,5] and sinonasal cancer among workers engaged in chromate production, chromate pigment production, and chromium plating.[2] Compounds of chromium [III] and metallic chromium were classified as Group 3, not classifiable as to [their] carcinogenicity to humans.[4] This profile will focus on chromium [VI], since it is the known cancer-causing form of chromium.

Acute inhalation exposure to hexavalent chromium may irritate and damage the nose, throat, and lungs.[6] Dermal exposure to chromium [VI] may also cause allergic contact dermatitis and skin sensitization.[6]

Regulations and Guidelines

Occupational exposure limits (OEL) [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]

Canadian JurisdictionsCr [VI] compoundOEL (mg/m3)
Canada Labour CodeWater-soluble Cr [VI] compounds
Chromyl chlorideTert-butyl chromate
Lead chromate, as Cr
0.0002; 0.0005 [stel, dsen, rsen, i]
0.0001 ppm; 0.00025 ppm [stel, dsen, rsen, ifv]
0.1 [c]
0.0002; 0.0005 [stel, dsen, rsen, i]
AB, NB, ONWater-soluble Cr [VI] compounds
Insoluble Cr [VI] compounds
Tert-butyl chromate
Calcium chromate
Chromite ore processing
Lead chromate, as Cr
Strontium chromate
Zinc chromates
0.05
0.01
0.1 [c, sk]
0.001
0.05
0.012
0.0005
0.01
BCWater-soluble Cr [VI] compounds
Insoluble Cr [VI] compounds
Tert-butyl chromate
Calcium chromate
Chromite ore processing
Lead chromate, as Cr
Strontium chromate
Zinc chromates
0.025; 0.1 [c]
0.01
0.1 [c, sk]
0.001
0.05 [sk, dsen, rsen]
0.012 [dsen, rsen]
0.0005 [sk, dsen, rsen]
0.01 [sk, dsen, rsen]
MB, NL, NS, PEWater-soluble Cr [VI] compounds
Chromyl chlorideTert-butyl chromate
Lead chromate, as Cr
0.0002; 0.0005 [stel, dsen, rsen, i]
0.0001 ppm; 0.00025 ppm [stel, dsen, rsen, ifv]
0.1 [c]
0.0002; 0.0005 [stel, dsen, rsen, i]
NT, NU, SKWater-soluble Cr [VI] compounds
Insoluble Cr [VI] compounds
Tert-butyl chromate
Calcium chromate
Lead chromate, as Cr
Strontium chromate
Zinc chromates
0.05; 0.15 [stel]
0.01; 0.03 [stel]
0.1 [c, sk]
0.001; 0.003 [stel]
0.012; 0.036 [stel]
0.0005; 0.0015 [stel]
0.01; 0.03 [stel]
QCWater-soluble Cr [VI] compounds
Insoluble Cr [VI] compounds
Tert-butyl chromate
Calcium chromate
Chromite ore processing
Lead chromate, as Cr
Strontium chromate
Zinc chromates
0.05 [sen, em]
0.01 [sen, em]
0.1 [c, sk]
0.001 [em]
0.05 [em]
0.012 [em]
0.0005 [em]
0.01 [sen, em]
YTTert-butyl chromate
Chromic acid and chromate
Chromite ore processing
Lead chromate, as Cr
0.1 [c, sk]
0.1; 0.1 [stel]
0.1
0.05
Other JurisdictionCr [VI] compoundOEL (mg/m3)
ACGIH 2020 TLVWater-soluble Cr [VI] compounds
Chromyl chlorideTert-butyl chromate
Lead chromate, as Cr
0.0002; 0.0005 [stel, dsen, rsen, i]
0.0001 ppm; 0.00025 ppm [stel, dsen, rsen, ifv]
0.1 [c]
0.0002; 0.0005 [stel, dsen, rsen, i]
mg/m3 = milligrams per cubic
meterstel = short term exposure limit (15 min. maximum)
dsen = dermal sensitizer
rsen = respiratory sensitizer
ppm = parts per million
i = inhalable fraction
ifv = inhalable fraction and vapour
c = ceiling limit
sk = easily absorbed through the skin
sen = sensitizer
em = exposure must be reduced to the minimum
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value

Canadian environmental guidelines and standards*

JurisdictionLimitYear
Drinking Water Guidelines (Canada, BC, MB) and Standards (ON, QC, SK)0.05 mg/L (total chromium)2003-2020
[22,23,24,25,26,27]
BC’s Contaminated Sites Regulation, BC Reg 375/96Drinking water standard: 50 μg/L (hexavalent chromium)2019[28]
Ontario Ambient Air Quality Criteria**Annual: 0.00007 µg/m3 (Cr in PM10)
24-hour: 0.00035 µg/m3 (Cr in PM10)
Annual: 0.00014 µg/m3 (Cr in TSP)
24-hour: 0.0007 µg/m3 (Cr in TSP)
2016[29]
2012[29]
2012[29]
2012[29]
Ontario’s Air Pollution – Local Air Quality RegulationAnnual standard: 0.00014 µg/m(hexavalent chromium)2020[30]
Quebec’s Clean Air Regulation1 year limit: 0.004 µg/m3 (total chromium)2011[31]
Cosmetic Ingredient HotlistNot permitted for use2015[32]
*Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
**Chromium compounds (hexavalent forms) – Applies to pure Cr [VI] species or to the percentage of Cr [VI] species relative to total chromium
mg/L = milligrams per litre
µg/m3 = micrograms per cubic metre
PM10 = particulate matter 10 micrometers or less in diameter
TSP = total suspended particulate

Canadian agencies/organizations

AgencyDesignation/PositionYear
National Classification System for Contaminated SitesRank: “High hazard”2008[33]
Health CanadaDSL – low priority substance (already risk managed)*2006[34]
CEPASchedule 1, paragraphs ‘a’ and ‘c’2011[35]
Environment Canada’s National Pollutant Release InventoryReportable to NPRI if manufactured, processed, or otherwise used at quantities greater than 50 kg . Total of the pure element and the equivalent weight of the element contained in any compound, alloy or mixture.2016[36]
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
*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 guidelines, standards, or chemical listings reviewed.

Main Uses

Hexavalent chromium is used to manufacture stainless steel and other alloys, pigments, and wood preservatives and in leather tanning and metal finishing (chrome plating).[2,6] Chromium [VI] compounds are also used in smaller quantities in printer ink toners, textile dyes, drilling muds, and during water treatment and chemical production.[1,2]

Chromated copper arsenate (CCA) is a widely used wood preservative that contains hexavalent chromium.[37] The use of CCA-treated wood for residential purposes was voluntarily phased out by industry at the end of 2003.[37] Existing residential structures made with CCA-treated wood were not required to be removed. CCA is still used to preserve wood for industrial applications such as utility poles, pilings, and highway construction.[37]

Canadian Production and Trade

Canada has not mined chromium ores since the early 1900s, although there are deposits across the country. There has been recent interest in mining chromite ores in Northern Ontario.[38]

Production and rade

ActivityQuantityYear (ref)
Export18 t of chromium trioxide2015[39]
Import584 t of ‘chromium trioxide’ 2015[39]
Export22 t of ‘sodium dichromate’ 2015[39]
Import3,338 t of ‘sodium dichromate’ 2015[39]
t = tonne

Environmental Exposures Overview

Trace amounts of chromium [VI] occur naturally in unpolluted environments.[1,6] However, most chromium detected in the environment is released from anthropogenic sources.[6] Chromium [VI] is commonly found in indoor and outdoor air, soil, surface water, and groundwater.[6]

Surface water is contaminated with chromium [VI] in many parts of Canada.[1] Total chromium in Canadian drinking water is typically less than 5 µg/L.[1,6] 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].[1] Total chromium levels in unpolluted surface water are typically below 1 µg/g. CAREX Canada’s estimates indicate that chromium [VI] levels in drinking water may result in an increased risk of cancer at a population level (moderate data quality).

Average levels of chromium [VI] in air near industrial areas may be 10 – 45 times higher than those in non-industrial areas.[6] CAREX Canada estimates that exposures to chromium [VI] in outdoor air likely do not result in an increased risk of cancer (very low data quality). A data gap (moderate priority) was identified for chromium [IV] in indoor air.

Only monitoring data for total chromium concentration are available for soil. Total chromium levels in soil 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.[6] Soil near wood preservation plants, which use hexavalent chromium, had 25 times more total chromium content than uncontaminated soil.[1] Chromium [VI] may also leach into surrounding soil via treated wood structures such as building foundations, railroad ties, and decks.[6,37]

Searches of Environment Canada’s National Pollutant Release Inventory (NPRI) yielded the following results on current potential for exposure to hexavalent chromium in Canada:

NPRI reported releases

NPRI 2015[40]
Search Term:‘Hexavalent chromium (and its compounds)’
CategoryQuantityIndustry
Released into Environment2.36 tPower generation, pulp and paper,
metal plating, various manufacturing,
waste treatment (184 facilities)
Disposed of528 t
Sent to off-site recycling97 t
t = tonne

For more information, see the environmental exposure estimate for chromium [VI].

Occupational Exposures Overview

Inhalation and dermal contact are the most important routes of occupational exposure to chromium [VI].[2]

CAREX Canada’s estimates indicate that approximately 104,000 Canadians are occupationally exposed to chromium [VI]. Most exposures (87%) occur in the low exposure category. However, many workers are exposed to moderate or high levels of chromium [VI] in fabricated metal products, machinery, and transportation equipment manufacturing.

The industries with the largest numbers of exposed workers 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 when welding stainless steel), machinists, and automotive technicians.

For more information, see the occupational exposure estimate for chromium [VI].

Sources

Photo: Wikimedia Commons, Hi-Res Images of Chemical Elements

1. Government of Canada, Health Canada and Environment Canada. Priority Substances List assessment report (CEPA) for Chromium and its Compounds (1994)
2. National Toxicology Program (NTP). 14th Report on Carcinogens for Chromium Hexavalent Compounds (2016)
3. US National Library of Medicine. Hazardous Substances Data Bank entry for hexavalent chromium (2011) (Search term:’hexavalent chromium’)
6. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Chromium, 2012
12. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2018)
13. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2020) (PDF)
15. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
17. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
19. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
20. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2020) (PDF)
21. Occupational Safety and Health Administration (OSHA). Annotated PELs (2020)
22. Government of Manitoba, Manitoba Water Stewardship. Manitoba Water Quality Standards, Objectives, and Guidelines (2011) (PDF)
24. Government of British Columbia. Source Drinking Water Quality Guidelines (2020) (PDF)
25. The Canadian Legal Information Institute (CanLII). Regulation respecting the quality of drinking water, CQLR c Q-2, r 40 (2020)
27. The Canadian Legal Information Institute (CanLII). Ontario Drinking Water Quality Standards, O Reg 169/03 (2020)
28. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2019)
29. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2019)
31. Government of Quebec. Clean Air Regulation, Q-2, r. 4.1 (2020)
32. Health Canada. Cosmetic Ingredient Hotlist (2019)
33. Canadian Council of Ministers of the Environment. National Classification System for Contaminated Sites (PDF) (2008)
35. Environment and Climate Change Canada. CEPA List of Toxic Substances (2020)
39. International Trade Center. TradeMap (Free subscription required)
40. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Facility Search (2015) (Substance name: ‘chromium’)

     

Other Resources

  1. Agency for Toxic Substances and Disease Registry (ATSDR). ToxFAQ for Chromium (2008)
  2. US Environmental Protection Agency (EPA). Health assessment document for Chromium. Research Triangle Park, NC: Environmental (1984)

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