Data from: Derivation of occupational thresholds of toxicological concern for airborne systemically-acting non-carcinogenic organic chemicals

Many substances in workplace do not have occupational exposure limits (OELs). The threshold of toxicological concern (TTC) principle is part of the hierarchy of approaches useful in occupational health risk assessment. The aim of this study was to derive occupational TTCs (OTTCs) reflecting the airborne concentrations below which no significant risk to workers would be anticipated. A reference dataset consisting of the 8-h threshold limit values -Time-Weighted Average (8-h TLV-TWA) for 280 organic substances was compiled. Each substance was classified into low (Class I), intermediate (Class II) or high (Class III) hazard categories as per Cramer rules. For each chemical, n-octanol:water partition coefficient and vapor pressure along with the molecular weight were used to predict the blood:air partition coefficient. The blood:air partition coefficient along with data on water solubility and ventilation rate allowed the prediction of pulmonary retention factor and absorbed dose in workers. For each Cramer class, the distribution of the predicted doses was analyzed to identify the various percentile values corresponding to occupational OTTC. Accordingly, for Cramer Classes I, II and III, the OTTCs derived in the present study correspond to 0.15, 0.0085 and 0.006 mmol/day at the 10th percentile level, while these values were 1.5, 0.09 and 0.03 mmol/day at the 25th percentile level. The proposed occupational TTCs are not meant to replace the traditional OELs, but can be used in data-poor situations along with exposure estimates to support screening level risk assessment and prioritization.

工作场所中的诸多物质尚未制定职业接触限值（occupational exposure limits, OELs）。毒理学关注阈值（threshold of toxicological concern, TTC）原则是职业健康风险评估常用方法体系中的组成部分。本研究旨在推导职业性毒理学关注阈值（occupational TTCs, OTTCs），该阈值对应可确保劳动者不会面临显著健康风险的空气传播浓度水平。本研究构建了一份参考数据集，收录了280种有机物质的8小时时间加权平均阈限值（8-hour threshold limit values-Time-Weighted Average, 8-h TLV-TWA）。依据克莱默分类法则（Cramer rules），每种物质被划分为低危险等级（I类）、中危险等级（II类）或高危险等级（III类）。针对每种化学物质，研究采用正辛醇-水分配系数、蒸气压与分子量，预测其血-气分配系数。结合血-气分配系数、水溶性及通风速率数据，可进一步预测劳动者的肺滞留因子与吸收剂量。针对每一类克莱默等级，研究对预测吸收剂量的分布进行分析，以确定与职业性毒理学关注阈值对应的各百分位数值。据此，在第10百分位水平下，本研究推导得到的I、II、III类克莱默等级对应的职业性毒理学关注阈值分别为0.15、0.0085和0.006 mmol/天；而在第25百分位水平下，对应数值则分别为1.5、0.09和0.03 mmol/天。本研究提出的职业性毒理学关注阈值并非旨在替代传统职业接触限值，而是可在缺乏相关限值数据的场景中，结合暴露估算结果，用于支持筛查级风险评估与优先级排序工作。