title: Adsorption efficiency of respirator filter cartridges for isocyanates.
abstract: In some industries, the temperature and the humidity will vary greatly between different work places, such as outdoor work in arctic or tropical climates. There is therefore a need to test respirator filters at conditions that simulate conditions that are relevant for the industries that they are used in. Filter cartridges were exposed to controlled atmospheres of varying isocyanate concentration, air humidity, and temperature in an exposure chamber. For isocyanic acid (ICA) and methyl isocyanate (MIC), the exposure concentrations were between 100 and 200 p.p.b., monitored using a proton transfer reaction mass spectrometer. ICA and MIC were generated by continuous thermal degradation of urea and dimethylurea. The breakthrough was studied by collecting air samples at the outlet of the filter cartridges using impinger flasks or dry samplers with di-n-butylamine as derivatization reagent for isocyanates followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. For hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), the exposure concentrations were between 4 and 20 p.p.b. and were generated by wet membrane permeation. To reveal the profile of adsorption in different layers of the respirator filters, representative samples from each of the layers were hydrolyzed. The hydrolysis products hexamethylene diamine and isophorone diamine were determined after derivatization with pentafluoropropionic anhydride (PFPA) followed by LC-MS/MS analysis. The two filter types studied efficiently absorbed both ICA and MIC. There was no trend of impaired performance throughout 48-h exposure tests. Even when the filters were exposed to high concentrations (approximately 200 p.p.b.) of ICA and MIC for 96 h, the isocyanates were efficiently absorbed with only a limited breakthrough. The majority of the HDI and IPDI (>90%) were absorbed in the top layers of the absorbant, but HDI and IPDI penetrated farther down into the respirator filters during 120 h of exposure as compared to 16 h exposure.
authors.affiliation: Work Environment Chemistry, Stockholm University, 281 24 Hässleholm, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Gustavsson
authors.forename: Elinor
authors.initials: E
authors.lastname: Meiby
authors.forename: Daniel
authors.initials: D
authors.lastname: Gylestam
authors.forename: Jakob
authors.initials: J
authors.lastname: Dahlin
authors.forename: Mårten
authors.initials: M
authors.lastname: Spanne
authors.forename: Daniel
authors.initials: D
authors.lastname: Karlsson
authors.forename: Marianne
authors.initials: M
authors.lastname: Dalene
authors.forename: Gunnar
authors.initials: G
authors.lastname: Skarping
authors.forename: Björn Oscar
authors.initials: BO
authors.lastname: Tveterås
authors.forename: Age Engen
authors.initials: AE
authors.lastname: Pedersen
mesh_terms: D000327:Adsorption; D000395:Air Pollutants, Occupational / Q000032:analysis* / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry; D002853:Chromatography, Liquid; D003485:Cyanates / Q000032:analysis / Q000737:chemistry; D004780:Environment, Controlled; D004784:Environmental Monitoring / Q000295:instrumentation; D004867:Equipment Design; D005374:Filtration / Q000295:instrumentation* / Q000592:standards; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D006868:Hydrolysis; D017953:Isocyanates / Q000032:analysis* / Q000737:chemistry; D008422:Materials Testing / Q000379:methods; D016273:Occupational Exposure / Q000517:prevention & control / Q000706:statistics & numerical data; D012134:Respiratory Protective Devices / Q000592:standards*; D014508:Urea / Q000737:chemistry
chemical_list: D000395:Air Pollutants, Occupational; D003485:Cyanates; D017953:Isocyanates; D002606:Charcoal; D014508:Urea