Gardner Ron
Hawkes Associates, for the Energy Institute, 61 New Cavendish Street, London W1G 7AR, UK.
Ann Occup Hyg. 2012 Apr;56(3):326-39. doi: 10.1093/annhyg/mer098. Epub 2011 Dec 8.
This paper proposes a novel use of the reciprocal calculation procedure (RCP) to calculate workplace emergency action levels (WEALs) for accidental releases of hydrocarbon mixtures. WEALs are defined here as the concentration in air that area monitors should alarm at to provide adequate warning and be sufficiently protective of health to allow at least enough time to don respiratory protective equipment (RPE) and escape. The rationale for the approach is analysed, and ways of defining suitable substance group guidance values (GVs) for input into the RCP are considered and compared. WEAL GVs could be based on: 3× RCP GVs (i.e. using the 3× rule), the 5× RCP GVs (i.e. using the 5× rule for calculating ceiling values), emergency exposure limits, or immediately dangerous to life or health values (IDLHs). Of these, the method of choice is to base WEAL GVs on health-based IDLH values, which were developed for emergency situations in the workplace. However, IDLHs have only been set for 11 hydrocarbons, so the choice of GVs is also informed by comparison with possible GVs based on the other approaches. Using the proposed GVs, WEALs were calculated for various hydrocarbon mixtures, and the way they vary with the composition of the mixture was examined. Also, the level of health protection given by the current practice of setting emergency area alarms in the oil and gas industry at 10% of the lower explosive limit (LEL) was tested by comparing this with the WEAL. In the event of an accidental release, this comparison suggests that, provided that aromatics constitute <50% of the mixture, an alarm set at 10% LEL should provide adequate warning and be sufficiently protective of health to at allow at least enough time to don RPE and escape. In the absence of better information or specific acute toxicity concerns (such as the presence of hydrogen sulphide), it is proposed that the WEALs be used as a guide for assessing the adequacy of area alarm levels in respect of warning of an acute health risk. This work is exploratory (e.g. other rationales for setting GVs are possible) and the approach needs testing on further real-life samples. Although not explored here, the RCP approach may also lend itself to the calculation of in-house short-term exposure limits for hydrocarbon mixtures and other mixtures where the acute toxic end points of the components are similar.
本文提出了一种新颖的使用倒数计算程序（RCP）来计算碳氢化合物混合物意外释放时的工作场所应急行动水平（WEALs）的方法。此处将WEALs定义为区域监测仪应发出警报的空气中的浓度，以提供充分的预警并对健康有足够的保护作用，以便至少有足够的时间戴上呼吸防护设备（RPE）并逃生。分析了该方法的基本原理，并考虑和比较了为输入RCP而定义合适的物质组指导值（GVs）的方法。WEAL GVs可以基于：3×RCP GVs（即使用3倍规则）、5×RCP GVs（即使用5倍规则计算上限值）、应急暴露限值或立即威胁生命或健康的值（IDLHs）。其中，首选方法是将WEAL GVs基于基于健康的IDLH值，这些值是为工作场所的紧急情况而制定的。然而，仅为11种碳氢化合物设定了IDLHs，因此GVs的选择也通过与基于其他方法的可能GVs进行比较来确定。使用所提出的GVs，计算了各种碳氢化合物混合物的WEALs，并研究了它们随混合物组成的变化方式。此外，通过将其与WEAL进行比较，测试了石油和天然气行业目前将应急区域警报设定为爆炸下限（LEL）的10%的做法所提供的健康保护水平。在意外释放的情况下，这种比较表明，只要芳烃在混合物中所占比例小于50%，设定为10%LEL的警报应能提供充分的预警并对健康有足够的保护作用，以便至少有足够的时间戴上RPE并逃生。在缺乏更好的信息或特定的急性毒性问题（如存在硫化氢）的情况下，建议将WEALs用作评估区域警报水平在急性健康风险预警方面是否充分的指南。这项工作是探索性的（例如，设定GVs可能有其他基本原理），并且该方法需要在更多实际样本上进行测试。虽然此处未探讨，但RCP方法也可能适用于计算碳氢化合物混合物以及其他组分急性毒性终点相似的混合物的内部短期暴露限值。
