Method for the measurement of lead in the vicinity of lead-glass furnaces

Status:

completed 12/2007

Aims:

Use of the standard measurement method for lead for the assessment of lead exposure often results in lower atmospheric concentrations being measured at workplaces in the vicinity of lead-glass furnaces and the associated retrieval and processing stages for the viscous glass, despite the internal exposure of the employees working in these areas more frequently reaching critical values. The BG for the ceramics and glass industry raised the issue of whether lead constituents in vapour form are also precipitated in full on the sample carrier when traditional filter sampling methods are used, or whether parts of the exposure pass the filter. The sampling method was to be examined with regard to this issue.

Activities/Methods:

For examination of the measurement method, a typical workplace was selected at which comparative measurements could be conducted using both the standard measurement method and alternative measurement methods. Measurements were performed in a glassworks in the vicinity of the pot furnace. On two measurement dates, the exposure was studied with two different blends containing lead in the melt. Since the measurements performed were comparative measurements for examination of the measurement method, measurement was performed statically in all methods. Three different sampling systems were employed in parallel: a standard measurement method involving a membrane filter, a combination of absorption bottles (containing dilute nitric acid) and filters, and double-filter systems. The results were to show whether the entire exposure to lead in these areas is recorded by the standard measurement method.

Results:

The comparability and consistency of all results obtained with the various sampling systems at all measuring points is satisfactory to good.
Contrary to expectations, the standard measurement method is also suitable for workplaces in hot areas. It returns measurement results which differ only marginally from those obtained with use of the double filters. No trend is observed in the minor deviations. Equally surprising is that the measurement results from the absorption bottle/double-filter combination are generally lower than those from the two other sampling systems.
Overall, all systems tested are suitable for atmospheric sampling. In the interests of ease of handling, the absorption bottle/double-filter combinations should not be employed. The two filter systems present no difficulties in handling; it is nevertheless recommended that double quartz-fibre filters be employed in future, owing to the high sensitivity of the membrane filters to heat (potential for destruction by sparks).
Altogether, the measurements showed that the high internal exposure of some employees at this or similar workplaces must in all probability be attributed in the first instance to oral exposure, and not in any way to the measuring methods.

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