Is Urinary Chromium Specific to Hexavalent Chromium Exposure in the Presence of Co-exposure to Other Chromium Compounds? A Biomonitoring Study in the Electroplating Industry

OBJECTIVES

Electroplating processes are widely used in metal industries to improve the resistance properties of manufactured metal parts. Workers in this industry are potentially exposed both to hexavalent chromium (Cr(VI)) and to other chromium compounds [mostly trivalent chromium (Cr(III))], due to the use of chromic acid baths. The goal of this study was to validate urinary chromium as a Cr(VI) exposure biomarker in the presence of exposure to other chromium compounds.

METHODS

A biomonitoring study consisted in monitoring airborne chromium exposure and urinary chromium for one working week in 93 workers from nine electroplating companies. Chromium concentrations were measured in all urinations of each volunteer for the working week. Individual airborne soluble and insoluble Cr(VI) as well as Cr(III) concentrations were measured for all of the shifts of the week. The main statistical analysis consisted in modelling, in a Bayesian framework, the pre- and post-shift urinary chromium as a function of airborne Cr(III) and airborne Cr(VI), taking into account the day of the week and the time of collection of the urines (pre- or post-shift).

RESULTS

Preliminary descriptions showed an increase in pre-shift urinary chromium during the working week. The model showed an increase in urinary chromium over the shift related to the shift-specific airborne Cr(VI) concentration as well as an increasing trend over the week and a relationship with the mean weekly Cr(VI) thought to reflect chronic exposure. Taking into account the Cr(VI) exposure, there was no evidence of an effect of Cr(III) exposure on urinary chromium. A biological limit value (BLV) was derived from the French occupational exposure limit for Cr(VI) of 1 µg m-3 and was estimated at between 1.9 and 2.6 µg g-1 creatinine for a urinary sample collected at the end of the shift on the last working day of the week.

CONCLUSIONS

In the present context of mixed exposure to Cr(III) and Cr(VI) in electroplating, this study showed that urinary chromium depended only on airborne Cr(VI) concentrations, which justifies using a BLV for assessing workers' exposure. The estimated BLV was close to the recommended French BLV, which is 1.8 µg g-1 creatinine, in the electroplating industry.

Biological Monitoring of Occupational Exposure to Metals in Electric Steel Foundry Workers and Its Contribution to 8-Oxo-7,8-Dihydro-2'-Deoxyguanosine Levels

In this study, the urinary concentrations of selected metals in workers from an electric steel foundry in Tunisia were assessed and compared with existing biological limit values and general population reference values. Moreover, the association between oxidative DNA damage, measured as urinary 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG) and co-exposure to metals and polycyclic aromatic hydrocarbons (PAHs) was evaluated. Urinary levels of 12 metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS) in end-shift spot samples from 89 workers. The urinary levels of phenanthrene (U-PHE), as marker of exposure to PAHs, and 8-oxodG were also available. Median levels ranged from 0.4 µg/L (cobalt, Co, and thallium, Tl) to 895 µg/L (zinc, Zn). Only 1% of samples was above the biological limit values for Co, and up to 13.5% of samples were above limit values for Cd. From 3.4% (Co) to 72% (lead, Pb) of samples were above the reference values for the general population. Multiple linear regression models, showed that manganese (Mn), Zn, arsenic (As), barium (Ba), Tl, and Pb were significant predictors of 8-oxodG (0.012 ≤ p ≤ 0.048); U-PHE was also a significant predictor (0.003 ≤ p ≤ 0.059). The variance explained by models was low (0.11 ≤ R2 ≤ 0.17, p < 0.005), showing that metals and PAHs were minor contributors to 8-oxodG. Overall, the comparison with biological limit values showed that the study subjects were occupationally exposed to metals, with levels exceeding biological limit values only for Cd.

The reference values in the interpretation of toxicological data

The worldwide gradual expansion of industrialization has led to a dramatic increase in the production and use of chemical substances. This has resulted in a greater dispersion of these elements in the environment and in an increased exposure of the general population and workers. In this scenario, a thorough knowledge of exposure levels is needed in order to assess chemical risks in environmental and occupational settings. Biological monitoring is among the most useful tools for assessing exposure. However, in order to provide really effective guidance in the application/implementation of risk management measures, biomonitoring results need to be compared with appropriate references. Reference values (RVs) are an excellent resource since useful information for a correct interpretation of toxicological data can be obtained by comparing them with biomonitoring results. In the field of public health, this may enable us to identify potential sources of exposure, define the principal and most frequently exploited routes of exposure, and outline chemical absorption. Similarly, in occupational medicine, RVs can be used to give meaning to biomonitoring findings, especially when a biological limit value is not available for the chemical in question. Furthermore, these values are a valid tool for assessing exposure to chemical carcinogens. Therefore, by integrating reference values in an appropriate and complete system of guide values that also includes action levels and biological limit values, we could obtain both an adequate assessment of exposure and a better understanding of toxicological data.

Occupational exposure to beryllium in French industries

Beryllium (Be) is a metal mainly used in the form of alloys, with copper (Cu) and aluminium (Al) in the metal industry. Be is an extremely toxic element which must be handled under strictly controlled conditions to avoid health hazards to workers. Exposure to Be can be responsible for Chronic Beryllium Disease, a pulmonary disease preceded by sensitization to the element, and for lung cancer. The goals of the current study were to investigate Be exposure in France, to determine the airborne Be occupational exposure levels, the associated impregnation of employees through their urinary Be levels and the factors that might affect them, and finally to study a possible relation between biomonitoring and airborne data. Seventy-five volunteer subjects were thus atmospherically and biologically monitored in five French companies involved in Cu or Al casting, Al smelting, CuBe machining or AlBe general mechanical engineering. Airborne exposure was quite low with only 2% of measurements above the current French Occupational Exposure Limit (2 µg/m³); the population potentially most exposed was foundry workers. Impregnation with Be was also low with only 10% of quantified urinary Be measurements above the current German BAR value (0.05 µg/L). Using a Bayesian statistical modelling approach, the mean subject-specific urinary excretion of Be was found to increase significantly with the mean subject-specific exposure to airborne Be. From this relationship, and based on the current French OEL-8 hr, a Biological Limit Value of 0.08 µg/L (= 0.06 µg/g creatinine) could be proposed.