Chromium status of tannery workers in relation to metabolic disorders.

Abstract

Chromium (Cr), being an excellent tanning agent, is widely used in the leather industry. In the process of leather production, tannery workers are exposed to either inorganic Cr(III) compounds or Cr bound to proteins (leather dust). The total Cr content in tannery air (1-54 microg m(-3)) is rather high in comparison to ambient air (4-6 ng m(-3)) but the amount of Cr in inhalable particles (<10 microm) is two to three orders of magnitude less (20-60 ng m(-3)). The total daily intake of Cr was estimated by the analysis of diet (24.3 +/- 4.0 microg Cr day(-1)), drinking water (0.3 +/- 0.1 microg Cr dm(-3)) and ambient air. The contribution of the latter was dominant for tannery workers and almost negligible (8%) for the unexposed population. Chromium is an essential nutrient required for sugar and fat metabolism. The normal dietary intake of Cr for the occupationally unexposed population is found to be suboptimal (<30 microg Cr day(-1)) whereas tannery workers receive on average 150-325 microg of supplemental Cr day(-1). Assessment of the Cr status of both populations was made on the basis of the Cr contents of their scalp hair, pre-shift urine and thermally induced sweat. The median Cr contents in these tissues and fluids were significantly higher (P<0.01) in tannery workers (hair: 4 microg Cr g (-1), urine: Cr/creatinine 1.7 microg Cr g(-1), sweat: 25 microg Cr dm(-3)) in comparison with the control group (hair: 0.16 microg Cr g(-1), urine: Cr/creatinine 0.13 microg Cr g (-1), sweat: 0.7 microg Cr dm(-3)). Tannery workers absorbed up to 13 times more Cr in comparison to controls, the amount varying considerably depending on the workplace and duration of exposure. The main route of Cr absorption appears to be through the gastrointestinal tract, where medium to large particles play a dominant role. The absorption of Cr from leather dust may be more efficient in comparison to inorganic Cr(III) compounds. Under normal circumstances sweat Cr losses represent at least 20% of urinary Cr excretion. The incidence of glucose intolerance and disturbed lipid metabolism was compared between the unexposed (control) population (n=150) and a population of tannery workers (n=138) from the same residential area. The percentage of glucose-intolerant subjects was significantly (P<0.01) lower in the older subgroup (age>48 years), who were even more obese, but not in the whole tannery population in comparison to controls. In the group of subjects displaying glucose intolerance, those from the control population showed a significantly higher body mass index (BMI) of 32.3 and a considerably larger proportion of females (86%) in comparison to subjects from the tannery population (28.2 and 60%, respectively). There was no significant difference in total serum cholesterol levels between the groups. Results of other lipid variables, such as high-density lipid (HDL) cholesterol, low-density lipid (LDL) cholesterol and triglycerides, are controversial: namely, the HDL/LDL ratio was higher for the controls, who showed in contrast significantly higher serum triglyceride levels in comparison to the older subgroup of tannery workers. The possible effects of other parameters on serum HDL-cholesterol level are outlined but the influence of Cr on lipid metabolism in tannery workers remains unclear.