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Canada finalises environmental guideline for hexavalent chromium

(18.06.2018)


Background:

Chromium is a controversial element with important biological characteristics, depending on its different species. While chromium is considered essential in its trivalent form, the hexavalent species is classified as genotoxic and carcinogenic. Since toxicologist have found that ingestion of hexavalent chromium would be a health risk, the presence of this carcinogen cannot be tolerated in food and drinking water. For this reason, Canada has established guidelines, which are based on the toxicity or hazards of the substances covered. These guidelines are intended to serve three functions:

  • to aid in pollution prevention by providing targets for acceptable environmental quality;
  • to assist in evaluating the significance of concentrations of chemical substances found in the environment, as identified in biomonitoring; and
  • to serve as performance measures to determine the success of risk management activities.
The guidelines were developed as part of Canada's risk assessment and management of priority chemicals strategy identified in its Chemicals Management Plan (CMP) and other federal initiatives. They are voluntary unless incorporated into other regulations.


Canadian Federal Environmental Quality Guideline (FEQG) for hexavalent chromium

Chronic freshwater toxicity data were compiled from critical reviews (EU (2005), UKTAG (2007)) and recent publications (up to February 2016). Similar to UKTAG (2007) all toxicity results are expressed as the concentration of Cr(VI). Following the Canadian Water Quality Guideline protocol (CCME 2007) acceptable endpoints for 24 species were selected for developing the FWQG for Cr(VI). The toxicity values ranged from 5 to 3500 μg/L for various endpoints with no one group any more sensitive to Cr(VI) toxicity. Chronic toxicity to fish ranged from 10 μg/L for brook trout (Salvelinus fontinalis) to 3500 μg/L for medaka (Oryzias latipes) and guppy (Poecilia reticulata). Among invertebrates, the chronic toxicity effects ranged from 5 μg/L for water flea (Daphnia magna) to 1100 μg/L for brown hydra (Hydra oligactis). Among plant species, duckweed (Lemna minor) was most sensitive (EC10 of 7 μg/L), whereas blue-green alga (Microcystis aeruginosa) was most tolerant (NOEC of 500 μg/L).   

Each species for which appropriate toxicity data were available was ranked according to sensitivity and its position on the species sensitivity distribution (SSD) was determined. Several cumulative distribution functions (normal, logistic, extreme value and Gumbell) were fit to the data using regression methods and the model fit was assessed using statistical and graphical techniques. Based on goodness of fit, the log logistic model provided the best fit; the 5th percentile of the SSD plot is 5 µg/L, with lower and upper confidence limits of 4 and 7 µg/L, respectively.

The 5th percentile from the SSD (5 µg/L) is selected as the FWQG. The guideline represents the concentration below which one would expect either no, or only a low, likelihood of adverse effects on aquatic life.


Related information

Canadian Environmental Protection Act, 1999 Federal Environmental Quality Guidelines Hexavalent Chromium
U.S. EPA: Chromium in Drinking Water
EFSA: Scientific Opinion on the risks to public health related to the presence of chromium in food and drinking water

WHO: Chromium in Drinking-water - Background document for development of WHO  Guidelines for Drinking-water Quality


 Related EVISA Resources

 Link Database: Toxicity of hexavalent chromium (chromate)
Link Database: Human dietary chromium exposure
 Link Database: Industrial Use of chromate
 Link Database: Methods for chromium speciation analysis
Brief summary: ICP-MS: A versatile detection system for trace element and speciation analysis
Brief summary: LC-ICP-MS - The most often used hyphenated system for speciation analysis


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April 11, 2012: EPA calls for more study on hexavalent chromium in drinking water
December 27, 2011: EPA ruling on hexavalent chromium in water expected soon 
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November 24, 2010: Deemed Essential to Health for Decades, Chromium Has No Nutritional Effect, UA Researchers Show
October 7, 2010: US EPA offers chance to speak out against hexavalent chromium
November 15, 2009: Hexavalent chromium found in bread
May 17, 2007: Hexavalent Chromium in Drinking Water Causes Cancer in Lab Animals
April 24, 2007: Nutrigenomics: The role of chromium for fat metabolism revisited
June 8, 2006: Scientific journal adds fuel to ongoing chromium debate
November 23, 2004: Chromium (III) - not only therapeutic?


last time modified: June 18, 2018










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