Chromate exposure during spray painting with spray cans

Status:

completed 12/2006

Aims:

In the 1970s, an employee had carried out paint-spraying work with coatings containing zinc chromate. In the 1990s, he contracted a squamous cell carcinoma in the main nasal cavity. In the course of the procedure for formal recognition of occupational diseases (BK), exposure was estimated mathematically at a cumulative dose of 10.8 to 55 mg/m³ x years (chromate years). For other paint-spraying workplaces, substantially lower chromate concentrations were measured in the same period in some cases. As a result, the validity of this particular calculation may be called into question. The objective of the project was to determine the exposure by simulation of the working method and by measurement, in order for the mathematically estimated exposure to be validated.

Activities/Methods:

In a closed room (a chamber with dimensions of 4 x 3.5 x 3 m (L x W x H)), paint-spraying was simulated of DIN A4 metal sheets with coatings containing zinc chromate from spray cans, and the chromate concentration arising in the atmosphere of the working area determined by measurement. Since the room conditions under which the employee had originally carried out the paint-spraying work could not be established clearly, a second series of tests was conducted of the exposure arising in a separate paint-spraying booth. For this purpose, a 2 x 2 m spraying area was divided off from the rest of the chamber.

Results:

Chromate concentrations of about 5 mg/m³ were measured in the breathing zone of the sprayer, respectively in the (unventilated) chamber atmosphere of approximately 3 to 4 mg/m³. If the test chamber is ventilated at 9 changes per hour, the chromate concentration in the chamber atmosphere stabilizes in the region of approximately 2 to 3 mg/m³. Slightly higher chromate concentrations (approx. 3.5 to 5 mg/m³) were measured in the spray booth with reduced dimensions. In consideration of the duration of exposure, a cumulative dose of approximately 1.3 to 2 mg/m³ chromate years was determined. This result differs considerably from that obtained by mathematical calculation, despite the fact that test conditions were selected which increase the chromate exposure. Note that the influence of sedimentation of the aerosol was not adequately considered in the analytical model.

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