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Although all chromite ore processing residue (COPR) sites near residential neighborhoods in Jersey City, New Jersey have undergone remediation, recent studies found widespread, but low levels of hexavalent chromium (Cr(+6)) in house dust both in Jersey City and in communities with no known sources of Cr(+6). This study was designed as a follow-up to determine whether there is an association between current Cr(+6) levels in house dust and urinary chromium concentrations in young children. Dust samples (N=369) were collected from 123 homes. The median Cr(+6) concentration was 3.3 μg/g (mean±SD 5.2±7.5) and the median Cr(+6) loading was 1.1 μg/m(2) (1.9±3.1). These levels were not elevated compared with previously reported levels in background communities (median concentration=3.5 μg/g; median loading=2.8 μg/m(2)). Urinary chromium concentrations were measured in spot urine samples collected from 150 children, ages 3 months to 6 years. The median uncorrected urinary chromium concentration was 0.19 μg/l (0.22±0.16). Current urinary chromium concentrations were significantly lower than those previously reported before and during remediation (t-test; P<0.001). Urinary chromium concentrations were not significantly higher in homes with high (75th or 90th percentile) Cr(+6) dust levels (concentration or loading) compared with other homes. Multiple linear regression was used to examine the relationship between Cr(+6) levels (concentration and loading) in house dust and urinary chromium concentrations (uncorrected and specific gravity corrected). Contrary to pre-remediation studies, we did not find a positive association between Cr(+6) levels in house dust and urinary chromium concentrations. The findings indicate that current Cr(+6) levels in house dust are not positively associated with children's chromium exposure as measured by urinary chromium, and the children's exposure to Cr(+6) in house dust is below the level that could be identified by urine sampling.

Background: Hexavalent chromium (Cr(6+)) has long been recognized as an inhalation carcinogen. Useful data on its carcinogenicity by ingestion have been slower to develop. The 2008 NTP chronic bioassay of sodium dichromate dihydrate in drinking water found clear evidence of carcinogenicity in rodents and allows a generalizable estimate of the human ingestion cancer potency of Cr(6+)., Objectives: To estimate the human ingestion cancer potency of Cr(6+) and evaluate its relevance for human exposure., Methods: Tumors of the small intestine in male mice were selected as the critical endpoint, for the derivation of cancer potency. Following the 2005 USEPA Cancer Risk Assessment Guidelines, the point of departure in the dose-response data was defined using benchmark-dose modeling. Linear extrapolation was carried out from the point of departure and interspecies dose conversion was based on allometric scaling of body weight., Results: Small intestine tumor incidence in male mice provided a robust and nearly identical fit with most available dose-response models using benchmark-dose modeling. A human equivalent cancer slope factor of 0.5 (mg/kg/day)(-1) was derived based on linear extrapolation from the point of departure. Statistical and kinetic analysis carried out on the NTP data as well as data reported in other studies support that the carcinogenicity of Cr(6+) did not result from an exceedance of the reduction capacity of the mouse gastrointestinal tract at the doses in the NTP study., Conclusions: Mouse gastric emptying time and human Cr(6+) dosing studies strongly suggest that even at doses considerably lower than those in the NTP study, Cr(6+) escapes reduction in both the mouse and human stomachs due to kinetic competition from Cr(6+) absorption and gastric emptying. The cancer potency derived from the NTP data is, therefore, deemed to be relevant and applicable to human exposure. Cr(6+) is, therefore, identified as "likely to be carcinogenic to humans" in accordance with the USEPA's cancer characterization rubric., (Copyright © 2010 Elsevier Inc. All rights reserved.)

In contrast to Cr(+3), Cr(+6) is carcinogenic and allergenic. Although Cr(+6) can occur naturally, it is thought that most soil Cr(+6) is anthropogenic, however, the extent of Cr(+6) in the background environment is unknown. Cr(+6)-containing chromite ore processing residue (COPR) from chromate manufacture was deposited in numerous locations in Jersey City (JC), New Jersey. In the 1990's, significantly elevated concentrations of total Cr (Cr(+6)+Cr(+3)) were found in house dust near COPR sites. We undertook a follow-up study to determine ongoing COPR exposure. We compared Cr(+6) in house dust in JC to selected background communities with no known sources of Cr(+6). Samples were collected from living areas, basements and window wells. Cr(+6) was detected in dust from all JC and background houses. In the JC homes, the mean (+ or - SD) Cr(+6) concentration for all samples was 3.9 + or - 7.0 microg/g (range: non-detect-90.4 microg/g), and the mean Cr(+6) loading was 5.8 + or - 15.7 microg/m(2) (range: non-detect-196.4 microg/m(2)). In background homes, the mean Cr(+6) concentrations of all samples was 4.6 + or - 7.8 microg/g, (range, 0.05-56.6 microg/g). The mean loading was 10.0 + or - 27.9 microg/m(2) (range, 0.22-169.3 microg/m(2)). There was no significant difference between Cr(+6) dust concentrations in Jersey City and background locations. Stratification by sample location within houses and sampling method gave similar results. Samples exceeding 20 microg/g were obtained only from single wood surfaces in different homes. Lower concentrations in window well samples suggests transport from outside is not the major source of indoor Cr(+6). Landscaping and groundcover may influence indoor Cr(+6). There appears to be a widespread low level background of Cr(+6) that is not elevated in Jersey City homes despite its historic COPR contamination. It is possible that house dust, in general, is a source of Cr(+6) exposure with potential implications for persistence of chromium allergic contact dermatitis., (Copyright 2010 Elsevier B.V. All rights reserved.)

The recent article by Costa and Klein (2006) contains several inaccuracies about the federal drinking water standard for chromium. The federal drinking water standard for chromium is 100 ppb, not 50 ppb as stated by Costa and Klein, and it is based on non-carcinogenic effects, not a one in one million cancer risk level. The question of whether or not hexavalent chromium is carcinogenic via the oral route is the focus of much current interest and has major implications for regulation of chromium in drinking water and soil. The chronic drinking water study of hexavalent chromium currently being conducted by the National Toxicology Program will provide further information that will be useful in addressing this question. [ABSTRACT FROM AUTHOR]