Abstract

Background:

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.

Objectives:

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.

Methods:

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.

Results:

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.

Discussion:

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

中文翻译：

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2002-2013 年亚特兰大的下水道溢流和胃肠道疾病：评估基础设施改善的影响

摘要

背景：

联合下水道溢流 (CSO) 将未经处理的污水排放到地表水和娱乐用水中，通常是在强降水之后。鉴于预计气候变化会导致降水频率和强度增加，了解 CSO 对健康的影响和污水处理系统的中介作用非常重要。

目标：

在这项研究中，我们估计了 CSO 事件与佐治亚州亚特兰大市居民因胃肠道 (GI) 疾病急诊 (ED) 就诊的关联，并探讨了这些关联如何随着污水处理系统的改善而变化。

方法：

我们使用泊松广义线性模型估计关联，控制时间趋势。我们根据溢出量对 CSO 进行分类，并在 1、2 和 3 周滞后的 ED 访问之前评估 CSO 事件的影响。同样，我们评估了在相同滞后时每周累积降水量大于第 90 个百分位数的影响。我们还使用交互项评估了邮政编码制表区 (ZCTA) 级贫困和基础设施改善期的影响修正。

结果：

前一周发生大量 CSO 与 GI 疾病的每日急诊就诊增加 9% 有关。我们确定了 ZCTA 级贫困的显着相互作用，在低贫困地区比高贫困地区 CSO-GI 疾病关联更强。在低贫困地区，我们在 1 周和更长的滞后时间观察到关联，发生在大型和低容量 CSO 事件之后。我们没有观察到基础设施改善期对 CSO 或降水与 GI 疾病关联的显着相互作用；但是，CSO 事件的数量从改进前的每周 2.31 次减少到改进后的每周 0.49 次。

讨论：

我们的研究结果表明，CSO 导致亚特兰大的急性胃肠道疾病负担，并且这种风险的程度在生活在低贫困地区的人群中可能更高。我们没有发现污水处理系统改进的保护作用。尽管如此，观察到的 CSO 频率降低可能会降低由这些事件引起的胃肠道疾病的绝对负担。https://doi.org/10.1289/EHP10399