Prioritization and Risk Ranking of Regulated and Unregulated Chemicals in US Drinking Water.

Drinking water constituents were compared using more than six million measurements (USEPA data) to prioritize and risk-rank regulated and unregulated chemicals and classes of chemicals. Hazard indexes were utilized for hazard- and risk-based chemicals, along with observed (nondetects = 0) and censored (nondetects = method detection limit/2) data methods. Chemicals (n = 139) were risk-ranked based on population exposed, resulting in the highest rankings for inorganic compounds (IOCs) and disinfection byproducts (DBPs), followed by semivolatile organic compounds (SOCs), nonvolatile organic compounds (NVOCs), and volatile organic compounds (VOCs) for observed data. The top 50 risk-ranked chemicals included 15 that were unregulated, with at least one chemical from each chemical class (chromium-6 [#1, IOC], chlorate and NDMA [#11 and 12, DBP], 1,4-dioxane [#25, SOC], PFOS, PFOA, PFHxS [#42, 44, and 49, NVOC], and 1,2,3-trichloropropane [#48, VOC]). These results suggest that numerous unregulated chemicals are of higher exposure risk or hazard in US drinking water than many regulated chemicals. These methods could be applied following each Unregulated Contaminant Monitoring Rule (UCMR) data collection phase and compared to retrospective data that highlight what chemicals potentially pose the highest exposure risk or hazard among US drinking water, which could inform regulators, utilities, and researchers alike.

Degradation of polyethylene glycols and polypropylene glycols in microcosms simulating a spill of produced water in shallow groundwater.

Polyethylene glycols (PEGs) and polypropylene glycols (PPGs) are frequently used in hydraulic fracturing fluids and have been detected in water returning to the surface from hydraulically fractured oil and gas wells in multiple basins. We identified degradation pathways and kinetics for PEGs and PPGs under conditions simulating a spill of produced water to shallow groundwater. Sediment-groundwater microcosm experiments were conducted using four produced water samples from two Denver-Julesburg Basin wells at early and late production. High-resolution mass spectrometry was used to identify the formation of mono- and di-carboxylated PEGs and mono-carboxylated PPGs, which are products of PEG and PPG biodegradation, respectively. Under oxic conditions, first-order half-lives were more rapid for PEGs (<0.4-1.1 d) compared to PPGs (2.5-14 d). PEG and PPG degradation corresponded to increased relative abundance of primary alcohol dehydrogenase genes predicted from metagenome analysis of the 16S rRNA gene. Further degradation was not observed under anoxic conditions. Our results provide insight into the differences between the degradation rates and pathways of PEGs and PPGs, which may be utilized to better characterize shallow groundwater contamination following a release of produced water.

Succession of toxicity and microbiota in hydraulic fracturing flowback and produced water in the Denver-Julesburg Basin.

Hydraulic fracturing flowback and produced water (FPW) samples were analyzed for toxicity and microbiome characterization over 220 days for a horizontally drilled well in the Denver-Julesberg (DJ) Basin in Colorado. Cytotoxicity, mutagenicity, and estrogenicity of FPW were measured via the BioLuminescence Inhibition Assay (BLIA), Ames II mutagenicity assay (AMES), and Yeast Estrogen Screen (YES). Raw FPW stimulated bacteria in BLIA, but were cytotoxic to yeast in YES. Filtered FPW stimulated cell growth in both BLIA and YES. Concentrating 25× by solid phase extraction (SPE) revealed significant toxicity throughout well production by BLIA, toxicity during the first 55 days of flowback by YES, and mutagenicity by AMES. The selective pressures of fracturing conditions (including toxicity) affected bacterial and archaeal communities, which were characterized by 16S rRNA gene V4V5 region sequencing. Conditions selected for thermophilic, anaerobic, halophilic bacteria and methanogenic archaea from the groundwater used for fracturing fluid, and from the native shale community. Trends in toxicity echoed the microbial community, which indicated distinct stages of early flowback water, a transition stage, and produced water. Biota in another sampled DJ Basin horizontal well resembled similarly aged samples from this well. However, microbial signatures were unique compared to samples from DJ Basin vertical wells, and wells from other basins. These data can inform treatability, reuse, and management decisions specific to the DJ Basin to minimize adverse environmental health and well production outcomes.

Assessment of temperature and ultraviolet radiation effects on sunburn incidence at an inland U.S. Beach: A cohort study.

BACKGROUND: Increases in outdoor temperature may lead to increases in sunburn, outdoor exposure, and skin cancer in human populations. OBJECTIVE: This study aimed to quantify sunburn incidence and risk for Ohio beachgoers exposed to varying outdoor conditions. METHODS: Sunburn incidence data were obtained through a prospective cohort study at East Fork Lake (Cincinnati, Ohio, USA). Recruitment occurred over 26 weekend days. Beach interviews and follow-up telephone interviews obtained exposure and health information. New sunburns were self-reported 8-9 days post-enrollment. Survey data were paired with ultraviolet radiation (UVR) index and temperature data for statistical analysis. RESULTS: Among 947 beachgoers, new sunburns were reported in 18% of swimmers. Sunburn incidence was associated with temperature (odds ratio = 1.2; 95% CI: 1.1 - 1.4) and UVR index (odds ratio = 1.6; 95% CI: 1.0 - 2.5) in models adjusted for water exposure, arrival time, and beach visit frequency. Some evidence of a temperature+UVR interaction was observed. LIMITATIONS: Exposure and sunburn data were self-reported without clinical diagnosis and date of onset. The follow-up period enabled sunburns to be reported from a variety of days rather than only the beach visit day thereby limiting interpretation. Sun protection behaviors were not evaluated. CONCLUSIONS: Temperature and UVR influence sunburn frequency. Temperature, however was more strongly associated with sunburn in beachgoers than the nearest measured UVR index, suggesting future investigations are needed to better understand how temperature effects sunburn development. Interventions for decreasing sunburn are needed.

Evaluating UV-C LED disinfection performance and investigating potential dual-wavelength synergy.

A dual-wavelength UV-C LED unit, emitting at peaks of 260 nm, 280 nm, and the combination of 260|280 nm together was evaluated for its inactivation efficacy and energy efficiency at disinfecting Escherichia coli, MS2 coliphage, human adenovirus type 2 (HAdV2), and Bacillus pumilus spores, compared to conventional low-pressure and medium-pressure UV mercury vapor lamps. The dual-wavelength unit was also used to measure potential synergistic effects of multiple wavelengths on bacterial and viral inactivation and DNA and RNA damage. All five UV sources demonstrated similar inactivation of E. coli. For MS2, the 260 nm LED was most effective. For HAdV2 and B. pumilus, the MP UV lamp was most effective. When measuring electrical energy per order of reduction, the LP UV lamp was most efficient for inactivating E. coli and MS2; the LP UV and MP UV mercury lamps were equally efficient for HAdV2 and B. pumilus spores. Among the UV-C LEDs, there was no statistical difference in electrical efficiency for inactivating MS2, HAdV2, and B. pumilus spores. The 260 nm and 260|280 nm LEDs had a statistical energy advantage for E. coli inactivation. For UV-C LEDs to match the electrical efficiency per order of log reduction of conventional LP UV sources, they must reach efficiencies of 25-39% or be improved on by smart reactor design. No dual wavelength synergies were detected for bacterial and viral inactivation nor for DNA and RNA damage.