Benchmark dose doses

In estimating the cumulative risk of a chemical in LCA, dose-response extrapolations can be based on toxicological benchmarks. Such a benchmark approach is considered more appropriate for use in comparative assessment contexts, such as in an LCA study. Benchmarks are an exposure measure associated with a consistent change in response, such as the 10% or even the 50% effect level. Regulatory-based measures do not necessarily provide a consistent risk basis for comparison, as they were often never developed for use in such a comparative context or to facilitate low dose-response extrapolation. Other data differences include the use of median, rather than extreme, data in the fate and exposure modeling, as well as the consideration of safety factors only as part of the uncertainty assessment and not as an integral part of the toxicological effects data. 

Instead of doing more or less doubtful extrapolations down to responses of 10 or 10 so-called benchmark values are sometimes determined. A dose-response regression line for the most appropriate endpoint is made. The dose producing 10% response and its 95% confidence interval are determined. The lower confidence limit is defined as the benchmark value (see Figure 10.2). This dose is then used to define a dose regarded as safe, by dividing it with an unsafety factor. 

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