Chemical process based reconstruction of exposures for an epidemiological studyIntroductionMethodsStudy sites and industrial hygiene data sourcesIndustrial hygiene records, retrieval, and development of exposure databaseResultsMonomer production operationsPolymer production operationsDiscussionAcknowledgmentsReferencesChemico-Biological Interactions 166 (2007) 277–284Chemical process based reconstruction of exposuresfor an epidemiological studyIII. Analysis of industrial hygiene samplesThomas A. Halla,∗, Nurtan A. Esmenb, Elizabeth P. Jonesa, Heather Basaraa,Margaret L. Phillipsa, Gary M. Marshc, Ada O. Youkc,Jeanine M. Buchanichc, Robin C. LeonarddaUniversity of Oklahoma Health Sciences Center, 801 NE 13th Street, CHB 413, Oklahoma City, OK 73190, USAbOccupational and Environmental Health Sciences, School of Public Health, University of Illinois at Chicago,2121 West Taylor Street, Chicago, IL 60612, USAcDepartment of Biostatistics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA 15261, USAdDuPont Safety Health Environment, Haskell Laboratory for Toxicology & Industrial Medicine, 1090 Elkton Road, Newark, DE 19714, USAAvailable online 16 September 2006AbstractAs part of an historical cohort study to investigate the mortality experience of industrial workers exposed to chloroprene (␤-CD)and other substances, all available industrial hygiene exposure monitoring data were collected and summarized. From discussionswith on-site industrial hygiene personnel, it was apparent that these data were not collected for epidemiological purposes and,therefore, their use in characterization of exposures was problematic as the data mostly pertained to samples collected to investigatethe performance of specific tasks. These data were, however, informative for validating the exposure modeling process used toestimate historical exposures. The data summarized below clearly indicate that exposures to ␤-CD were lowered across the timeperiod of this study. Typically, the exposures recorded were less than the occupational exposure limits of the periods in which theexposures were recorded. Additionally, exposure measurements recorded in the recent past do not represent the exposure actuallyexperienced by the worker as a strict personal protective equipment use program has been in place for the facilities studied sincethe mid-1980s.© 2006 Published by Elsevier Ireland Ltd.Keywords: Chloroprene; Cohort study; Industrial hygiene; Exposure1. Introduction␤-Chloroprene (2-chloro-1,3-butadiene) (␤-CD) is amonomer used exclusively for the production of syn-∗Corresponding author at: Department of Occupational and Envi-ronmental Health, College of Public Health, University of Oklahoma,Oklahoma City, OK 93041, USA. Tel.: +1 405 271 2070;fax: +1 405 271 1971.E-mail address: [email protected] (T.A. Hall).thetic rubber and latexes [1]. Because the chemicalstructure is similar to that of vinyl chloride, a knownhuman carcinogen, a concern arose in the 1960s thatchloroprene might have similar toxicologic properties[2]. Large-scale rodent bioassay and “in vitro” studieshave demonstrated that in these test systems ␤-CD is bothmutagenic and carcinogenic [3]. These studies indicatethat ␤-CD is genotoxic and can disrupt normal cellularreproduction. The question of its carcinogenic potentialin humans remains unanswered.0009-2797/$ – see front matter © 2006 Published by Elsevier Ireland Ltd.doi:10.1016/j.cbi.2006.09.004278 T.A. Hall et al. / Chemico-Biological Interactions 166 (2007) 277–284Early studies of the chloroprene production facili-ties in Louisville, Kentucky were not able to adequatelystudy the potential chronic health effects due to the shortperiod between first exposure and the follow-up time forthese studies [4,5].More recently, studies conducted in eastern Europeancountries have resulted in more questions than answersconcerning the carcinogenic potential of ␤-CD. Whileindicating some weakly positive relationships betweenliver and lung cancer with ␤-CD exposures, the expo-sure metrics used were at best speculative and probablyunreliable [6–8]. Recent reviews of these studies clearlydemonstrate the weaknesses of these studies [9,10].In 1999, the International Institute of Synthetic Rub-ber Producers (IISRP) initiated a four-plant, multi-national epidemiologic study of workers with potentialexposure to ␤-CD. As a component of this study, thehistorical industrial hygiene data from each plant werecollected and analyzed. These data were then used tovalidate the exposure assessment methodology used toassign exposures to each worker. The analysis of theavailable industrial hygiene measurements that wereused to validate the exposure assignment of ␤-CD is pre-sented here.2. Methods2.1. Study sites and industrial hygiene data sourcesThe study sites consisted of two plants located withinthe boundaries of the United States of America, one plantin Northern Ireland and one plant in southern France.The two U.S. plants were the DuPont/Dow ElastomersLLC (DDE) plants in Louisville, KY and Pontchartrain,LA. The plant in Northern Ireland was located in May-down and the French plant, Enichem Elastomers, wasnear Grenoble, France (FR). All four plants were inte-grated facilities in which ␤-CD monomer was producedfrom primary feedstocks and then polymerized to yieldpolychloroprene.At the two oldest facilities in this study, Louisvilleand Maydown, ␤-CD synthesis was initially carried outthrough the acetylene dimerization process. Louisvillesynthesized ␤-CD from 1942 until this process wasphased out during 1971–1976. The Maydown plantemployed a similar process from 1960 to 1980, whenthe acetylene dimerization process was replaced by aprocess that employed butadiene as the primary feed-stock. The Grenoble facility, which began operations in1966, was the first commercial-scale plant in the world toproduce chloroprene from butadiene. The Pontchartrainfacility began production of ␤-CD using the butadieneprocess in 1969. With the development of the butadieneprocess, Pontchartrain served as the primary monomersynthesis site in the United States, shipping ␤-CD to theLouisville facility by train car for further processing.2.2. Industrial hygiene records, retrieval, anddevelopment of exposure databaseEach of the study sites were visited by the indus-trial hygiene investigators at least two times, exceptfor the French plant which was visited once for