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1. Predicting groundwater contamination to protect the storm-exposed vulnerable

   https://doi.org/10.1016/j.crm.2023.100499  

   Hochard, Jacob; Abashidze, Nino; Bawa, Ranjit; Carr, Grace; Kirkland, Bailey; Li, Yuanhao; Matlock, Kayla; Siu, Wai Yan (March 2023, Climate risk management)

   Domestic wells provide drinking water to 44 million people nationwide. Many of these wells, which remain federally unregulated and rarely tested for pollutants, serve rural populations clustered near surface-contaminated sites (e.g., hazardous waste sites, animal agriculture operations, coal ash ponds, etc.). The potential for natural disasters to deteriorate drinking water quality is well documented. Less understood is whether opportunistic post-disaster sampling might underrepresent vulnerable populations. When disaster strikes, well water sampling campaigns offer a glimpse into the quality of water for exposed residents. We examined over 8,000 well water samples from 2016 and 2017 to measure Hurricane Matthew’s impact on the presence of indicator bacteria. Bacteria presence was predicted at the household level following Hurricane Matthew’s landfall. The residential addresses associated with birth records as well as clinically estimated dates of conception and birth dates were used to predict the likelihood of indicator bacteria in drinking water sources that were unsampled but likely to have served pregnant women. We estimate that opportunistic well water sampling captures the average predicted contamination rates among households with pregnant women. Our approach documents a distribution of contamination risk where 2.7% of the vulnerable sample (670 unsampled households) have a 75% likelihood of total coliform presence. The predicted likelihood of indicator bacteria is elevated for a small share of households nearby swine lagoons that experienced the most torrential rainfall. However, the gap between sampled and unsampled households cannot otherwise be explained by the storm event or proximity to surface-contaminated sites. Findings suggest that sophisticated and holistic water quality prediction models may support post-disaster sampling campaigns by targeting individual households within vulnerable groups that are likely to experience higher risks from groundwater contamination. 

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2. Patterns of sediment-associated fecal indicator bacteria in an urban estuary: Benthic-pelagic coupling and implications for shoreline water quality.

   O'Mullan, G.; Juhl, A.; Reichert, R.; Schneider, E.; and Martinez, N. (January 2019, Science of the total environment)

   Estuarine and coastal waterways are commonly monitored for fecal and sewage contamination to protect recreator health and ecosystem functions. Such monitoring programs commonly rely on cultivation-based counts of fecal indicator bacteria (FIB) in water column samples. Recent studies demonstrate that sediments and beach sands can be heavily colonized by FIB, and that settling and resuspension of colonized particles may significantly influence the distribution of FIB in the water column. However, measurements of sediment FIB are rarely incorporated into monitoring programs, and geographic surveys of sediment FIB are uncommon. In this study, the distribution of FIB and the extent of benthic-pelagic FIB coupling were examined in the urbanized, lower Hudson River Estuary. Using cultivation-based enumeration, two commonly-measured FIB, enterococci and Escherichia coli, were widely distributed in both sediment and water, and were positively correlated with each other. The taxonomic identity of FIB isolates from water and sediment was confirmed by DNA sequencing. The geometric mean of FIB concentration in sediment was correlated with both the geometric mean of FIB in water samples from the same locations and with sediment organic carbon. These two positive associations likely reflect water as the FIB source for underlying sediments, and longer FIB persistence in the sediments compared to the water, respectively. The relative representation of other fecal associated bacterial genera in sediment, determined by 16S rRNA gene sequencing, increased with the sequence representation of the two FIB, supporting the value of these FIB for assessing sediment contamination. Experimental resuspension of sediment increased shoreline water column FIB concentrations, which may explain why shoreline water samples had higher average FIB concentrations than samples collected nearby but further from shore. In combination, these results demonstrate extensive benthic-pelagic coupling of FIB in an urbanized estuary and highlight the importance of sediment FIB distribution and ecology when interpreting water quality monitoring data. 

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3. Ecological Analyses of Mycobacteria in Showerhead Biofilms and Their Relevance to Human Health

   https://doi.org/10.1128/mBio.01614-18  

   Gebert, Matthew J.; Delgado-Baquerizo, Manuel; Oliverio, Angela M.; Webster, Tara M.; Nichols, Lauren M.; Honda, Jennifer R.; Chan, Edward D.; Adjemian, Jennifer; Dunn, Robert R.; Fierer, Noah; et al (November 2018, mBio)

   ABSTRACT Bacteria within the genus Mycobacterium can be abundant in showerheads, and the inhalation of aerosolized mycobacteria while showering has been implicated as a mode of transmission in nontuberculous mycobacterial (NTM) lung infections. Despite their importance, the diversity, distributions, and environmental predictors of showerhead-associated mycobacteria remain largely unresolved. To address these knowledge gaps, we worked with citizen scientists to collect showerhead biofilm samples and associated water chemistry data from 656 households located across the United States and Europe. Our cultivation-independent analyses revealed that the genus Mycobacterium was consistently the most abundant genus of bacteria detected in residential showerheads, and yet mycobacterial diversity and abundances were highly variable. Mycobacteria were far more abundant, on average, in showerheads receiving municipal water than in those receiving well water and in U.S. households than in European households, patterns that are likely driven by differences in the use of chlorine disinfectants. Moreover, we found that water source, water chemistry, and household location also influenced the prevalence of specific mycobacterial lineages detected in showerheads. We identified geographic regions within the United States where showerheads have particularly high abundances of potentially pathogenic lineages of mycobacteria, and these “hot spots” generally overlapped those regions where NTM lung disease is most prevalent. Together, these results emphasize the public health relevance of mycobacteria in showerhead biofilms. They further demonstrate that mycobacterial distributions in showerhead biofilms are often predictable from household location and water chemistry, knowledge that advances our understanding of NTM transmission dynamics and the development of strategies to reduce exposures to these emerging pathogens. IMPORTANCE Bacteria thrive in showerheads and throughout household water distribution systems. While most of these bacteria are innocuous, some are potential pathogens, including members of the genus Mycobacterium that can cause nontuberculous mycobacterial (NTM) lung infection, an increasing threat to public health. We found that showerheads in households across the United States and Europe often harbor abundant mycobacterial communities that vary in composition depending on geographic location, water chemistry, and water source, with households receiving water treated with chlorine disinfectants having particularly high abundances of certain mycobacteria. The regions in the United States where NTM lung infections are most common were the same regions where pathogenic mycobacteria were most prevalent in showerheads, highlighting the important role of showerheads in the transmission of NTM infections. 

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4. The Importance of Including Non-Household Environments in Dengue Vector Control Activities

   https://doi.org/10.3390/v15071550  

   Peña-García, Víctor Hugo; Mutuku, Francis M.; Ndenga, Bryson A.; Mbakaya, Joel Omari; Ndire, Samwuel Otieno; Agola, Gladys Adhiambo; Mutuku, Paul S.; Malumbo, Said L.; Ng’ang’a, Charles M.; Andrews, Jason R.; et al (July 2023, Viruses)

   Most vector control activities in urban areas are focused on household environments; however, information relating to infection risks in spaces other than households is poor, and the relative risk that these spaces represent has not yet been fully understood. We used data-driven simulations to investigate the importance of household and non-household environments for dengue entomological risk in two Kenyan cities where dengue circulation has been reported. Fieldwork was performed using four strategies that targeted different stages of mosquitoes: ovitraps, larval collections, Prokopack aspiration, and BG-sentinel traps. Data were analyzed separately between household and non-household environments to assess mosquito presence, the number of vectors collected, and the risk factors for vector presence. With these data, we simulated vector and human populations to estimate the parameter m and mosquito-to-human density in both household and non-household environments. Among the analyzed variables, the main difference was found in mosquito abundance, which was consistently higher in non-household environments in Kisumu but was similar in Ukunda. Risk factor analysis suggests that small, clean water-related containers serve as mosquito breeding places in households as opposed to the trash- and rainfall-related containers found in non-household structures. We found that the density of vectors (m) was higher in non-household than household environments in Kisumu and was also similar or slightly lower between both environments in Ukunda. These results suggest that because vectors are abundant, there is a potential risk of transmission in non-household environments; hence, vector control activities should take these spaces into account. 

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5. Compromised Water Quality in Colonias of Nueces County, TX: A Vicious Cycle

   Rowles III, L. S.; Hossain, A. H.; Lawler, D. F.; Kirisits, M. J.; Araiza, I.; Saleh, N. B. (October 2019, University of North Carolina Chapel Hill Water & Health Conference)

   Colonias are self-built neighborhoods of mostly low-income families that lack basic infrastructure. While some funding from the state government has built roads and provided electricity, water and sewage systems are still lacking for many of the estimated 400,000 colonias’ residents in Texas. Of those that do have tap water, the supply is either inadequate or of questionable quality. Some colonias residents have access only to off-the-grid water supplies, and residents collect their water from community wells, or, if fortunate, from a personal well. Many of these wells are self-built and therefore shallow. In Nueces County, the groundwater in several colonias has been reported to contain arsenic, while poor sanitation practices (i.e., self-built septic systems) and heavy rainfall events in the region compromise the microbial quality of the groundwater. The naturally occurring arsenic in the aquifer and microbial contaminants from flooding events mean that the only available drinking water source in these colonias is contaminated throughout the year. In this research, datasets on water quality in nine colonias in Nueces County were collected both in wet (after a major rain/flooding event) and dry (no significant rainfall for four weeks) periods. The water quality analyses included traditional microbial quality assessment (total coliforms, Escherichia coli, and heterotrophs), pH, hardness, total dissolved solids, and a suite of metals that are relevant to human health (e.g., arsenic and lead). Microbial community analyses also were completed on select samples to assess the shifts in microbial ecology between wet and dry periods. Results reveal that water quality varies based on environmental conditions and presents a serious risk to human health. Water sampled during the wet period had extensive microbial contamination with elevated heterotrophs and total coliforms, and E. coli was identified in some samples. In the dry period, water from a number of colonias exhibited elevated levels of arsenic (above United States Environmental Protection Agency’s Maximum Contaminant Level of 10 µg/L). This study is one of the first to systematically investigate water quality in Texas colonias, and the results highlight how water quality in these communities is compromised year-round, going between microbial contamination in wet events and arsenic contamination in dry events. 

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