Urinary Chromium as a Biological Marker of Environmental Exposure: What Are the Limitations?

Five welders working with high alloy Cr-Ni steel and one working with mild steel were followed during one work week. The chromium concentration in air was measured concomitantly with urinary chromium determinations. The water-soluble chromium concentrations in air exceeded 0.05 mg/m3 during welding with coated electrodes, but metal inert-gas (MIG) welding produced much lower concentrations. The proportion of water-soluble hexavalent chromium in the air was usually more than 50% of the total chromium concentration during welding with coated electrodes, whereas less than 10% of the chromium produced during MIG welding was in a water-soluble. Since water-soluble chromium (hexavalent) is the more important biologically, the determination of both water-soluble and water-insoluble chromium concentrations is emphasized instead of the measurement of the total concentration. The urinary chromium concentration proved to be a good indicator of short-term exposure to water-soluble chromium when exposure was above the current threshold limit value of 0.05 mg/m3, concentrations of more than 30 microgram/g of creatinine representing an exposure level higher than the threshold limit value.

Chromium is an essential nutrient required for normal sugar and fat metabolism. Insufficient dietary chromium is associated with maturity-onset diabetes and/or cardiovascular diseases. Dietary chromium intake in the U.S. and other developed countries is roughly half of the minimum suggested intake of 50 micrograms. Well controlled studies involving human subjects have demonstrated beneficial effects of supplemental chromium on fasting glucose, glucose tolerance, blood lipids, insulin binding, and hypoglycemic blood glucose values and symptoms. Since chromium is a nutrient and not a therapeutic agent, it will only benefit those people whose signs and symptoms are due to marginal or overt chromium deficiency. Stresses including high sugar diets, strenuous exercise, physical trauma, infection and certain diseases exacerbate the signs and symptoms associated with marginal intakes of dietary chromium. While excessive levels of chromium are usually limited to industrial settings, marginal dietary chromium intake is widespread in the general population and may lead to serious health problems.