Publication project Cr vs. Cr(VI)

Status:

completed 02/2025

Aims:

In addition to nickel and manganese, the metallic elements most frequently analysed in industry include chromium and its compounds and chromium(VI) (hexavalent chromium) compounds. The ratio of chromium to chromium(VI) is not only dependent on the material used (e.g. the alloy); other possible influencing factors include the sector or activity, the presence of a collection or exhaust system and its mode of operation, the way sampling is performed (e.g. personal or static sampling), and the sampling system used.

To identify these possible influencing factors and recognize possible correlations between the workplace concentration of chromium and its compounds on the one hand and of chromium(VI) compounds on the other, two data records from the MEGA exposure database were to be analysed, for chromium and its compounds and for chromium(VI) compounds. These analyses were also to serve as a preliminary study for revision of the chromium report. The results of the study were to be published in an international journal.

Activities/Methods:

In the first step, data relating to chromium and its compounds and to chromium(VI) compounds was retrieved from the MEGA exposure database. The data was analysed by means of the IBM SPSS Statistics software.

From the complete data record of parallel concentration measurements of chromium and its compounds and chromium(VI) compounds, meaningful groups were to be formed (e.g. according to working activities) and various factors influencing the ratio were to be analysed and evaluated (e.g. the sampling method, presence of exhaust/collection systems and their mode of operation).

Based on the results of these analyses, relationships between the concentration ratios and influencing factors were to be determined. If possible, correlations were to be presented in the form of regression analyses.

Following approval by the German Social Accident Insurance Institutions, the results were to be compiled in an international publication and to serve as preparation for revision of the chromium report.

Results:

From the data retrieved from the exposure database MEGA exposure database on chromium and its compounds and on chromium(VI) compounds, 1,029 pairs of parallel measurements, i.e. of Cr(VI) and the total chromium content, were compiled with the aid of the IBM SPSS Statistics software.

To examine the influence of a number of activities on the concentration ratio and the individual measured values, the following working activity groups were formed: welding, grinding, cutting and electroplating. Within these groups, the ratio of Cr(VI) concentrations to the total chromium concentration was calculated and analysed, and various other factors influencing the ratio were studied. These included, for example, the form of sampling, the sampling system, the year in which sampling was performed, the grinding time fraction and the composition of the materials used in industrial processing. A uniform ratio as a function of the activity was not observed. The main influencing factors are the working temperatures (e.g. high temperature processing), the chromium content in the material and the grinding time fraction (where welding activities are performed simultaneously). The type of welding (e.g. manual arc welding or MAG welding) also has an influence on the concentration ratio.

A first draft for international publication was prepared. Once finalized, this will be submitted to an international journal (Annals of Work Exposure and Health or International Journal of Hygiene and Environmental Health).

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