A comparison of the sampling efficiencies of a range of atmosphere samplers when collecting polymeric diphenylmethane di-isocyanate (MDI) aerosols.
Polymeric diphenylmethane di-isocyanate (PMDI) is a precursor or an intermediate in the manufacture of pure MDI and is used in many industrial applications. Potential health effects of diisocyanates are generally considered to include irritation and respiratory sensitization, dictating the need for low occupational hygiene standards and robust hygiene monitoring methods. A wide range of methods has been developed or adopted for this purpose but questions concerning their ability to accurately sample MDI aerosols in the occupational environment have often been raised. In order to provide such information, studies have been conducted to compare several MDI sampling systems: the Institute of Occupational Medicine (IOM) 25-mm open-faced inhalable dust sampler; the 13-mm Millipore Swinnex Cassette sampler; the 37-mm open-face Millipore cassette; the midget-impinger, the glass tube containing glass wool, and two direct reading paper tape monitors. The program was comprised of two phases, the first being a preliminary comparison of the collection efficiencies of the IOM, 13 mm and midget-impinger at a range of orientations to air flow, aerosol particle sizes, and sampling flow rates, using inert polyethylene glycol aerosols. The second phase compared all samplers operating according to each manufacturer's recommendations and sampling PMDI aerosols at a range of particle sizes and concentrations. All studies were conducted in a wind tunnel. All filter methods performed well in atmospheres containing small particles except impingers that required a filter backup. In general, the variability of all the samplers was high for larger particle size ranges. Direct reading monitors showed low efficiencies.