Rats retain chromium in tissues following chronic ingestion of drinking water containing hexavalent chromium

Humans have sometimes been exposed to as much as 10 ppm Cr(VI) in drinking water from contaminated wells. The risks to these individuals are not well understood because the digestive tract reduces some of the Cr(VI) to the less bioavailable Cr(III) prior to absorption, and the disposition of the remaining Cr(VI) has not been well studied. We determined tissue Cr concentrations in rats after chronic ingestion of Cr(VI) in drinking water at concentrations relevant to human exposure levels. Adult male and female Fischer 344 rats consumed ad libitum 0, 0.5, 3, or 10 ppm Cr(VI) as K₂CrO₄ in drinking water for 44 wk. Rats then were given deionized water 4–6 d prior to sample collection. Females given 3 or 10 ppm Cr(VI) consumed more Cr(VI) per unit of body weight than did males. Bone Cr concentrations were significantly elevated in rats that drink 10 ppm Cr(VI). Renal Cr concentrations were significantly elevated in male rats that drink 3 or 10 ppm Cr(VI) and in female rats dosed with 10 ppm Cr(VI). Female rats had elevated liver Cr concentrations after drinking 3 or 10 ppm Cr(VI). Testicular Cr concentrations were slightly elevated in rats that drank 10 ppm Cr(VI). Brain, ovarian, and whole-blood Cr concentrations were below detection limits in all exposure groups. Although tissue Cr accumulation may have resulted from absorption of Cr(III), it is poorly absorbed. Therefore, the increased tissue retention may also have resulted, in part, from increased absorption of Cr(VI) and its subsequent uptake from the systemic circulation.