Exposure factors (e.g., ingestion volume and frequency) are required to establish risk-based treatment requirements (i.e., log₁₀ reduction targets (LRTs)) for enteric pathogens using quantitative microbial risk assessment (QMRA). However, data to characterize nonpotable exposure factors are sparse. We calculated graywater and wastewater nonpotable LRTs (corresponding to 10^–4 infections per person per year) for uses missing detailed exposure data (including showering and decorative fountain) and across a range of exposure factors. The LRTs decreased linearly toward zero as the log₁₀ transformed volume or the frequency of reuse decreased. When nonroutine exposure was included, representing either accidental ingestion from misuse or cross-connection between potable and nonpotable waters, the LRTs remained high, even as the routine ingestion volume decreased. Therefore, uses with small anticipated routine ingestion volumes (i.e., roughly <10^–5 L), e.g., domestic indoor or decorative fountain uses, share common LRTs, and further refinement of the routine exposure is of limited value. Additional data to characterize nonroutine exposures and uses with high routine ingestion, e.g., showering, remain valuable to better estimate LRTs. These results will assist regulators in the selection of LRTs for nonpotable uses that lack detailed exposure factor characterizations.

中文翻译：

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尽管接触数据有限，但非饮用水回用的肠道病原体治疗要求

需要使用定量微生物风险评估（QMRA）来确定肠道病原体基于风险的治疗要求（例如，log ₁₀减少目标（LRTs）），需要接触因子（例如摄入量和摄入频率）。但是，表征非饮用水暴露因子的数据很少。我们针对缺少详细暴露数据（包括淋浴和装饰喷泉）以及各种暴露因素的使用情况，计算了灰水和废水非饮用水LRT（相当于每人每年^10–4感染）。随着对数_10的变化，轻轨数量线性减少至零转换量或重用频率降低。当包括非常规暴露时，代表误用或饮用水与非饮用水之间的交叉连接引起的误食，即使常规摄入量减少，LRT仍然很高。因此，预期的日常摄入量较小（即，大约<10 ^–5 L）的用途（例如，家用室内或装饰性喷泉用途），共用普通的LRT，并且进一步完善日常暴露的价值有限。表征非常规暴露的额外数据以及经常性摄入较多的用途（例如淋浴），对于更好地估算轻轨时间仍然很有价值。这些结果将有助于监管机构为缺乏详细暴露因子特征的非饮用水用途选择轻轨。