Canadian water quality guidelines for chromium

Abstract

Canadian Water Quality Guidelines (CWQG) are numerical or narrative limits that protect designated water uses. Development of CWQG is based on review of chromium's properties, uses, fate in the environment, ambient levels, accumulation in biota, and toxicity. Chromium's principal uses and entry into the environment include electroplating, production of paints and pigments, tanning, wood preservation, chromium chemicals production, metal smelting, and pulp and paper production. Concentrations of chromium in Canada range between 1 and 545,000 ng·m−3 in air, 0.001 and 0.165 mg·L−1 in water, nondetectable and 31,000 mg·kg−1 in sediments, 10 and 5000 mg·kg−1 in soils, 0.006 and 18 mg·kg−1 in plants, and 0.03 and 1.6 mg·kg−1 in animals. In nature, trivalent chromium sorbs to various ligands and forms insoluble entities becoming unavailable for uptake by biota. Hexavalent chromium forms many soluble salts that can enter body membranes and induce a toxic response. Estimates of toxicity of hexavalent chromium to aquatic life range from 0.0006 mg·L−1 (reduction in algal growth) to 1000 mg·L−1 (decrease in rest time of Chironomus tentans). For trivalent chromium the toxicity ranges from 0.002 mg·L−1 (reduction in filtering rate of Perna perna) to 937 mg·L−1 (48-h LC50 of Asellus aquaticus). Plants are affected by the concentrations of hexavalent chromium ranging from 0.16 mg·L−1 (growth reduction in lettuce) to 75 mg·L−1 (no effects in sweet orange). For trivalent chromium the toxicity ranges between 0.104 mg·L−1 (reduction in root growth of oats) and 50 mg·L−1 (stunted growth of corn and tomato). Terrestrial animals such as the beagle dog can be affected by concentrations exceeding 62.7 mg·L−1 (Cr VI). Mice can tolerate 100 mg·L−1 of hexavalent chromium. Trivalent chromium has adverse effects on rats and mice at 28.0 mg·L−1. For freshwater life, guidelines of 0.001 (Cr VI; full) and 0.008 (Cr III; interim) mg·L−1 are recommended. For marine life, guidelines of 0.001 (Cr VI; draft) and 0.05 (Cr III; interim) mg·L−1 are recommended. Irrigation guidelines are set at 0.008 (Cr VI) and 0.005 (Cr III). A guideline of 0.05 mg·L−1 is recommended for drinking and livestock waters. © 1997 by John Wiley & Sons, Inc. Environ Toxicol Water Qual 12: 123–183, 1997