This study examined 184 legionellosis outbreaks in the United States reported to the Centers for Disease Control and Prevention's Waterborne Disease and Outbreak Surveillance System, from 2001 to 2017. Drinking water characteristics examined include source water type, disinfectant type, exposure setting, geographical distribution by U.S. Census Divisions, and the public water system size (population served). This study found that most of the reported drinking water-associated legionellosis outbreaks occurred in eastern United States, including 35% in the South Atlantic, 32% in the Middle Atlantic, and 16% in the East North Central Census Divisions were linked with building water systems in healthcare and hotel settings; and were associated with buildings receiving drinking water from public water systems serving >10,000 people. Targeted evaluations and interventions may be useful to further determine the combination of factors, such as disinfectant residual type and drinking water system size that may lead to legionellosis outbreaks.

Per-and polyfluoroalkyl substances (PFAS) in U.S. drinking water are currently a significant topic of public health concern. Data collection efforts have been undertaken to better understand PFAS occurrence, though limited data observed above reporting limits leaves considerable uncertainty. This work presents a hierarchical Bayesian model developed to estimate national PFAS occurrence in drinking water with a simple model structure and assumptions.Here the model is limited to the occurrence of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), and perfluoroheptanoic acid (PFHpA). This model estimates national PFAS exposure while capturing uncertainty, provides information on system-level PFAS co-occurrence, and creates an expandable foundation for generating future national estimates of PFAS occurrence. National estimates based on currently available data and model assumptions indicated population-weighted mean exposure to the sum of mean PFOS, PFOA, PFHpA, and PFHxS around 4.7-5.2 ppt while all four chemicals generally had moderate-to-strong correlations among system-level means.

During a cyanobacterial harmful algal bloom (HAB) event, drinking water treatment systems face the challenge of balancing acute and chronic health risks by treating the potentially toxin‐producing HAB and simultaneously managing for disinfection byproduct (DBP) formation. To explore the relationship between HAB events and DBP formation, a unique full‐scale study, including paired source water and finished water monitoring, was conducted at five drinking water utilities with HAB‐impacted source waters. Results confirm bench‐scale findings that HAB events in source water contribute to increases in DBP precursors. However, unlike results from laboratory studies, source water HAB‐related parameters and finished water DBPs were not consistently correlated at the five study utilities. These different outcomes suggest regulated DBP formation in utilities with HAB‐impacted source water is complex and influenced by a variety of site‐specific conditions, including source water conditions and data available for operational decision‐making, timing of treatment adjustments, and key operational choices.

Acanthamoeba keratitis (AK) is a painful, potentially blinding eye disease associated with contact lens use and corneal injury. AK, caused by the free-living amoeba Acanthamoeba, is ubiquitous in the environment and has been isolated from municipal water supplies. It can be tolerant of normal chlorine levels in drinking water. An AK outbreak investigated in 2003-2005 in five Illinois counties showed a lower AK age-standardized rate ratio in Cook County than in surrounding counties and was hypothesized to be due in part to reductions in residual disinfectant levels (RDLs) in drinking water. We evaluated RDLs in public water systems in the same five Illinois counties over eight years (2002-2009) using a multivariable model of water system RDL measurements. Fitted RDLs for each county were in the acceptable range by United States Environmental Protection Agency standards for the entire study period. After correcting for multiple testing, two of the surrounding counties had fitted RDLs that differed from Cook County for one year. This pattern differed from the epidemiologic pattern of cases observed in the AK outbreak. Our findings do not support the hypothesis that the development of AK was associated with changes in RDLs in the five Illinois counties.