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 K. DETERMINATION OF AIRBORNE ISOCYANATE EXPOSURE by Robert P. Streicher, Ph.D., Christopher M. Reh, M.S., Rosa Key-Schwartz, Ph.D., Paul C. Schlecht, and Mary Ellen Cassinelli

CONTENTS:

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1. 2. 3. 4. 5.

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isocyanate Exposure Related Health Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exposure Criteria for Diisocyanates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air Sampling and Analytical Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . b. Derivatization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . c. Sampling: Collection plus Derivatization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . d. Sample Handling and Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . e. Separation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f. Identification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . g. Quantification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

115 116 118 119 121 121 123 123 125 126 128 130 132

1. INTRODUCTION A variety of air sampling and analysis methods for determining workers’ exposures to isocyanate-containing compounds have been published or are under development by NIOSH, OSHA, and others. The following chapter provides information on the health effects, exposure criteria, sampling considerations, and analytical considerations used at NIOSH to select isocyanate methods. The purpose is to provide information to the industrial hygienist, chemist, and client of laboratory services to make an informed decision on which isocyanate method is appropriate for a given exposure scenario. Summary tables of isocyanate exposure standards (Table I) and NIOSH and OSHA analytical methods for isocyanates (Table II) are included. Other discussions of air sampling methods and direct reading instruments have been published.1,2,3,4 Many material safety data sheets (MSDS) use isocyanate-related terms interchangeably. For the purpose of this discussion, terms are defined as follows. Diisocyanates (Monomers): The difunctional isocyanate species from which polyisocyanates and polyurethanes are derived (Figure 1a). Common examples of monomeric isocyanates include 1,6hexamethylene diisocyanate (HDI), 2,4- and/or 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), methylene bis(4-cyclohexylisocyanate (HMDI), isophorone diisocyanate (IPDI), and 1,5-naphthalene diisocyanate (NDI). Commercial-grade TDI is an 80:20 mixture of the 2,4- and 2,6- isomers of TDI, respectively. Polyisocyanates: Species possessing free isocyanate groups and derived from monomeric isocyanates either by directly linking these monomeric units (a homopolymer) or by reacting these monomers with

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NIOSH Manual of Analytical Methods