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JUprinird Inmt AMERICAN lNDUSTRIAt. IIYCMENT. ASSOCIATION JOt'RNAI. Volume 30, Novcral>rr*rWtember, 1909 i Monitoring Exposures to Vinyl Chloride Vapor; Breath Analysis and Continuous Air Sampling EDWARD D. BARETTA.* RICHARD I>.STEWART, MJX* and JOHN E. MUTCHLERf Deportment of Emvhonmenlol Medicine, MerqmCIte School of Medicine, Mdtooukee, U'itconrin, end F-nvironmeotel HeoJlh Section. Bioehemieol Reteorck fjtkototarj. The Dow Chemieol Company, Afidland, Michigan f An environmental survey was conducted to dclernine the tune-wrightcd average exposure (TWA) o[ a croup of chemical plant workers to vinyl chloride ("Cl) vapor. This Surrey fcatu.-ed continuous multipoint air sampling and analysis mine infrared spectrophotom'trr. The inhalation exposure data were digitized and record ed on paper upe for subsequent computer analysis and derivation of daily TWA values for each worker. A breath sampling: program was conducted concurrently with the environmental survey, and a series of breath decay curves relating post exposure breath concentration to vapor exposure were derived from the data. To validate the brrath cut res derived from on-the-job data, postexposurc breath curves were also constructed from breath data obtained following experimental human exposures to carefully controlled concentrations of VC1 vapor. The dote agreement between postexposure breath concentrations at the corresponding TWA's obtained by each of the methods suggests that either continuous air monitoring or breath analysis is s-alid for est'niating the worker's individual daily exposure to VCI, and provides further evidence that breath analysis is a useful industrial hygiene technique for evaluating vapor exposure. Introduction The question that may arise following tin environmental survey is whethrr the chcmiral v.-qmr concentrations measured arc truly representative of the ex posure being experienced by (tic workmen. Evaluation of the ranges of atmospheric con centrations and estimates of time-weighted average concentration (TWA) arc all loo often liasrd on a few spot samples obtained under conditions which arc not representa tive of all phases of a given operation. A more rxaet measurement of vapor cxjiomiit would ltate to lie haetl on rontiuunus moni toring of air in the woikinan's breathing antu: during his entire stork shift. Obviously litis task is made sliflis tilt and often imjxissihle Hm* (U|q f m+n fttro+mird si (Itf trims. Si I sssim Mowaiii. \l it *,\latl|swhr Ss l>--! ,f M.iIuoh, M>lw.mUr 11S* Ilt4* msrtl MiJUmI. lotltMiitl |*ldl U'mp>in. by the Large number and variety of tasks per formed by today's modem chemical plant worker. Kerent improvements in automatic moni toring and data processing equipment have provided a means for a more satisfactory so lution. Sequential samplers and automatic analv/ers and recorders can now Ire used to rontinuously monitor srvrral locations or operations to provide more valid data on which to base estimates of rliemiral exposure. Computers can be miliml to manage tinlarge volume of data generated hv eontinutitit monitoring.' Meanwhile a technique has been under de velopment which more precisely defim-s the let el of individual exposure. The realization that the total body burden of a volatile chem ical is directly related to its roneenlration in rxpiied air led to the development of tcrliuiques lor rollcrting and analyzing hrealli samples useful in estimating llte mmv intli-