Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, Washington, USA.
Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.
Environ Health Perspect. 2022 May;130(5):57009. doi: 10.1289/EHP10399. Epub 2022 May 17.
Combined sewer overflows (CSOs) discharge untreated sewage into surface and recreational water, often following heavy precipitation. Given projected increases in frequency and intensity of precipitation due to climate change, it is important to understand the health impacts of CSOs and mediating effects of sewerage systems.
In this study we estimate associations of CSO events and emergency department (ED) visits for gastrointestinal (GI) illness among City of Atlanta, Georgia, residents and explore how these associations vary with sewerage improvements.
We estimate associations using Poisson generalized linear models, controlling for time trends. We categorized CSOs by overflow volume and assessed effects of CSO events prior to ED visits with 1-, 2- and 3-wk lags. Similarly, we evaluated effects of weekly cumulative precipitation greater than the 90th percentile at the same lags. We also evaluated effect modification by ZIP Code Tabulation Area (ZCTA)-level poverty and infrastructure improvement period using interaction terms.
Occurrence of a large volume CSO in the previous week was associated with a 9% increase in daily ED visits for GI illness. We identified significant interaction by ZCTA-level poverty, with stronger CSO-GI illness associations in low than high poverty areas. Among areas with low poverty, we observed associations at 1-wk and longer lags, following both large and lower volume CSO events. We did not observe significant interaction by infrastructure improvement period for CSO- nor precipitation-GI illness associations; however, the number of CSO events decreased from 2.31 per week before improvements to 0.49 after improvements.
Our findings suggest that CSOs contribute to acute GI illness burden in Atlanta and that the magnitude of this risk may be higher among populations living in areas of low poverty. We did not find a protective effect of sewerage system improvements. Nonetheless, observed reductions in CSO frequency may lower the absolute burden of GI illness attributable to these events. https://doi.org/10.1289/EHP10399.
合流制污水溢流（CSO）将未经处理的污水排入地表和娱乐用水中，通常是在强降水之后。由于气候变化导致降水频率和强度预计会增加，因此了解 CSO 对健康的影响以及下水道系统的调节作用非常重要。
本研究旨在估计佐治亚州亚特兰大市居民中 CSO 事件与急诊科（ED）胃肠道（GI）疾病就诊之间的关联，并探讨这些关联如何随下水道系统改善而变化。
我们使用泊松广义线性模型进行估计，控制时间趋势。我们根据溢流量对 CSO 进行分类，并在 ED 就诊前 1、2 和 3 周的时间窗口内评估 CSO 事件的影响。同样，我们评估了在相同滞后时间内每周累积降水量超过第 90 百分位数的影响。我们还通过交互项评估了邮政编码区（ZCTA）级贫困和基础设施改善期的效应修饰作用。
上周发生大体积 CSO 与 GI 疾病每日 ED 就诊人数增加 9%有关。我们发现 ZCTA 级贫困存在显著的交互作用，低贫困地区的 CSO-GI 疾病关联更强。在低贫困地区，我们观察到大体积和低体积 CSO 事件后 1 周及更长时间滞后的关联。我们没有发现基础设施改善期对 CSO 或降水-GI 疾病关联的显著交互作用；然而，改进前每周 CSO 事件数量为 2.31 次，改进后减少到 0.49 次。
我们的研究结果表明，CSO 导致亚特兰大急性 GI 疾病负担增加，而生活在贫困地区的人群面临的这种风险可能更高。我们没有发现下水道系统改善的保护作用。尽管如此，观察到 CSO 频率的降低可能会降低归因于这些事件的 GI 疾病的绝对负担。https://doi.org/10.1289/EHP10399.
