Hon Chun-Yip, Peters Cheryl E, Jardine Katherine J, Arrandale Victoria H
a School of Occupational and Public Health , Ryerson University , Toronto , Ontario , Canada.
b CAREX Canada , Simon Fraser University , Vancouver , British Columbia , Canada.
J Occup Environ Hyg. 2017 Jan;14(1):1-8. doi: 10.1080/15459624.2016.1207777.
Isocyanates such as toluene 2, 4-diisocyanate (TDI), methylene bisphenyl isocyanate (MDI), and hexamethylene diisocyanate (HDI) are known sensitizers and exposure to these chemicals can result in isocyanate-induced asthma-the leading cause of occupational asthma. A newly created exposure database was available containing occupational isocyanate measurements spanning 1981-1996 from Ontario and British Columbia (BC)-two of the largest provinces in Canada. The aim was to describe the historical measurements relative to exposure thresholds, ascertain differences in the data between provinces, and identify time trends. Descriptive statistics of the observations were summarized and stratified by isocyanate species and province. Chi-square tests and Student's t-test were performed to determine differences between provinces. To investigate time trends in the odds of a measurement exceeding the limit of detection (LOD) and time-weighted average (TWA), mixed effects logistic regression models were constructed. In total, 6,984 isocyanate measurements were analyzed, the majority of which were below the LOD (79%). Overall, 8.3% of samples were in excess of the 2014 TLV-TWA of 0.005 ppm. Comparing the two provinces, the proportion of samples exceeding the LOD and TLV-TWA was greater in BC for all isocyanate species. Differences in time trends were also observed between provinces-the odds of a sample exceeding the TLV-TWA decreased over time in the case of MDI (Ontario only), TDI (both Ontario and BC), and other isocyanates (BC only). Our finding that a majority of the exposure measurements was below the LOD is similar to that reported by others. Differences between provinces may be due the fact that isocyanates are classified as a designated substance in Ontario and must adhere to specific exposure control regulations. Limitations of the database, such as finite number of variables and measurements available until 1996 only, presents challenges for more in-depth analysis and generalization of results. An argument is made that a Canadian occupational exposure database be maintained to facilitate risk assessments as well as for occupational epidemiology research.
异氰酸酯，如甲苯2,4 -二异氰酸酯（TDI）、亚甲基双苯基异氰酸酯（MDI）和六亚甲基二异氰酸酯（HDI），都是已知的致敏剂，接触这些化学物质会导致异氰酸酯诱发的哮喘，这是职业性哮喘的主要病因。一个新创建的接触数据库可供使用，其中包含1981年至1996年期间来自安大略省和不列颠哥伦比亚省（BC）的职业性异氰酸酯测量数据，这两个省是加拿大最大的两个省份。目的是描述相对于接触阈值的历史测量数据，确定两省数据之间的差异，并识别时间趋势。对观测数据进行描述性统计，并按异氰酸酯种类和省份进行分层。进行卡方检验和学生t检验以确定两省之间的差异。为了研究测量值超过检测限（LOD）和时间加权平均值（TWA）的几率的时间趋势，构建了混合效应逻辑回归模型。总共分析了6984次异氰酸酯测量数据，其中大部分低于检测限（79%）。总体而言，8.3%的样本超过了2014年0.005 ppm的阈限值 - 时间加权平均值（TLV - TWA）。比较两省，所有异氰酸酯种类中，BC省超过检测限和TLV - TWA的样本比例更高。两省之间在时间趋势上也观察到差异 - 在MDI（仅安大略省）、TDI（安大略省和BC省）和其他异氰酸酯（仅BC省）的情况下，样本超过TLV - TWA的几率随时间下降。我们发现大多数接触测量值低于检测限这一结果与其他人报告的相似。两省之间的差异可能是由于异氰酸酯在安大略省被列为指定物质，必须遵守特定的接触控制法规。该数据库的局限性，如变量数量有限且仅提供到1996年的测量数据，给更深入的分析和结果的推广带来了挑战。有人认为应维护一个加拿大职业接触数据库，以促进风险评估以及职业流行病学研究。
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