Evaluation of the use of an SKC button inhalable aerosol sampler with a Grimm aerosol monitor to determine air concentrations of subtilisin

Abstract

Study purpose Currently, there is no OSHA or NIOSH monitoring method for subtilisin. This study evaluated a personal aerosol monitoring method for detection and quantification of subtilisin. The ACGIH ceiling limit and NIOSH short term exposure limit (STEL) for subtilisin is 0.06 μg/m3 making it the lowest exposure limit established for any exposure by the organizations. This study specifically evaluated the use of an SKC Button inhalable aerosol sampler with a Grimm Aerosol Monitor for monitoring low concentrations of subtilisin particulates in air within a laundry detergent production facility. Methods Air samples of detergent with subtilisin were collected using a Button sampler containing a glass fiber filter concurrently with a Grimm model 1.109 Aerosol Spectrometer. Nineteen sampling events of four hours each were performed over a 7-week period, with three Button samplers operating simultaneously. Sampling locations included a detergent containing subtilisin (DCS) production area and a specially constructed enclosure where DCS was introduced in a controlledmanner. Sample analysis was conducted with a Konelab Arena 20 analyzer to quantify the amount of subtilisin collected on the filter of each air sample. Results A linear regression for the concentration of DCS aerosol measured in the enclosure by the Grimm was compared to the average concentration of DCS aerosol measured on the Button filter in the enclosure, which produced an R2 value of 0.64 (p = 0.006). The Pearson's correlation produced an r value of 0.8 (p = 0.006). The linear regression for the average concentrations of DCS aerosol measured on the Button filter media compared to the average subtilisin detected from the aerosol in the enclosure produced an R2 value of 0.66 (p = 0.004). The Pearson's correlation produced an r value of 0.81 (p = 0.004). Discussion The amount of subtilisin in all air samples in the DCS production area were below the limit of quantitation due to the subtilisin encapsulation at the DCS production area. This caused particles sizes to be greater than the inhalable fraction (100 μm), which is also the limit of the size selectivity of the Button inhalable sampler. Conclusion The results of the statistical evaluation from the aerosol monitoring results in the enclosure indicate the Button inhalable sampler compared with the results from the Grimm aerosol monitor may be a valid method for determining airborne subtilisin concentrations for aerosols with diameters less than or equal to the 25 μm particle size. However, due to all results below the limit of quantitation at the DCS production area, it is concluded that there are insufficient results to determine if the Button sampler with the Grimm aerosol monitor can be used in the workplace.