| A field study was executed to develop emission rates for dust exposure at a food processing facility. The processing area consisted of a series of four rooms, connected via a closed-loop ventilation system, housed within a larger warehouse-type facility. Workers were exposed to various fruit and vegetable dusts during the grinding, sieving, mixing and repackaging of freeze-dried products. Eight 2-hour periods were monitored over two days. Personal and area total dust samples were collected on 37mm PVC filters with 5μm pore size as dictated by NIOSH Method 0500. Filters were analyzed by gravimetric analysis. Ventilation data and production activity data were collected during air sampling. Personal dust exposures ranged from 0.33 mg/m3 to 102.71 mg/m3. Five out of eight of the worker time-weighted averages exceeded the Particulates Not Otherwise Classified (PNOC) Threshold Limit Value (TLV) of 10 mg/m3. Further, the TLV for PNOC may be inadequate to protect workers due to the irritant nature of the products, e.g. jalapeno peppers, aloe vera. Three mass balance models were used to develop emission rates. The first was an experimental mass balance model, with the mass of contaminant generated determined by air flow and concentration measurements at room exit and entry points. The second treated the work environment as a completely mixed space, utilizing ventilation and area concentration measurements. The third model assumed hemispherical diffusion of contaminant from a primary point source with a concentration gradient decreasing with distance from the source, no dominant air flow direction in the space of interest, and plume rise and surface deposition are neglected. Emission rates generated from the mass balance models ranged from 2.09 mg/min to 1018.90 mg/min for the various processing operations and food products. Process emission rates with production activity data allow estimation of dust exposure in similar facilities, and help direct development of exposure control strategies. |
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