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Home ›› About Speciation ›› Speciation News

Canada finalises environmental guideline for hexavalent chromium

(18.06.2018)

Canada has finalised Federal Environmental Quality Guideline (FEQG) for hexavalent chromium.

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:

The final version of the Federal Environmental Quality Guideline (FEQG) for hexavalent chromium was published in June 2018.

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.

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