An Investigation of Short-Term Gravimetric Sampling in Pig Farms and Bakeries

Abstract

Exposure to some workplace dusts can lead to occupational asthma through respiratory sensitization. It is thought that sensitization may be related to high exposures of short duration, thus requiring short-term exposure monitoring. In the United Kingdom there are presently no guidelines for taking short-term (15-minute) gravimetric samples. This investigation has evaluated the use of IOM and CIP 10 personal inhalable samplers for taking short-term samples in a series of field trials carried out in bakeries and pig farms. A direct-reading dust monitor (MIE Miniram) has also been used to provide time-resolved dust concentration levels. Uncertainties in measurements were dominated by the weight stability of the sample collection media used. The lower detection limits for the short-term samples were typically estimated at 3 mg m^-3 for the IOM sampler using a metal cassette, and 1.8 mg m^-3 with the CIP 10 sampler. IOM short-term samples were generally higher than concurrent CIP 10 short-term samples and exposure levels calculated from the Miniram data. This was thought to be due to particles greater than 100 μm in diameter (e.g., grains of sugar) entering the IOM under their own inertia and significantly biasing the calculated dust concentrations. The CIP 10 showed reasonable agreement with the Miniram at low dust concentrations, but the two diverged at higher dust concentrations, indicating that the Miniram gives semiquantitative results at best. Although many of the measured short-term exposures did not exceed the UK guideline limit of 30 mg m^-3, the continuous exposure record indicated the presence of peaks exceeding 500 mg m^-3 lasting for less than a minute. If these are real features, measured short-term exposure levels will be a direct function of the averaging or sampling time used.