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Various chemicals used in hydraulic fracturing have raised environmental and human health (EHH) concerns regarding water resources contamination, leading to the transition towards the use of chemicals with minimum EHH hazards. Chemical hazard screening and indexing approaches have been used to measure the chemical hazard of hydraulic fracturing, and each approach is associated with inherent advantages and limitations. In this study, the two chemical hazard assessment approaches were discussed, and an integrated chemical hazard screening and indexing system was developed to combine the strengths of the two approaches. The integrated system was applied to assess the EHH hazards of representative hydraulic fracturing chemicals used in British Columbia, Canada. The hazard screening results showed that more than half of the ingredients and additives were classified into high hazard groups. Moreover, the integrated system generated more critical hazard assessment results than two hazard indexing systems, revealing that using the individual hazard indexing approach could result in underestimated EHH hazards for chemicals. The integrated system can significantly improve the data confidence levels of hazard assessment results compared to a previously developed indexing system. The integrated system can also help formulate fracturing fluids with low EHH hazards by identifying ingredients of high hazard concerns. [ABSTRACT FROM AUTHOR]

• An integrated chemical hazard screening and indexing system was developed. • The existing chemical hazard screening and indexing approaches were discussed. • More than half of the assessed chemicals were screened into high hazard groups. • Individual hazard indexing systems could generate underestimated hazard results. Various chemicals used in hydraulic fracturing have raised environmental and human health (EHH) concerns regarding water resources contamination, leading to the transition towards the use of chemicals with minimum EHH hazards. Chemical hazard screening and indexing approaches have been used to measure the chemical hazard of hydraulic fracturing, and each approach is associated with inherent advantages and limitations. In this study, the two chemical hazard assessment approaches were discussed, and an integrated chemical hazard screening and indexing system was developed to combine the strengths of the two approaches. The integrated system was applied to assess the EHH hazards of representative hydraulic fracturing chemicals used in British Columbia, Canada. The hazard screening results showed that more than half of the ingredients and additives were classified into high hazard groups. Moreover, the integrated system generated more critical hazard assessment results than two hazard indexing systems, revealing that using the individual hazard indexing approach could result in underestimated EHH hazards for chemicals. The integrated system can significantly improve the data confidence levels of hazard assessment results compared to a previously developed indexing system. The integrated system can also help formulate fracturing fluids with low EHH hazards by identifying ingredients of high hazard concerns. [ABSTRACT FROM AUTHOR]

Abstract Water disinfection involves the use of different types of disinfectants, which are oxidizing agents that react with natural organic matter (NOM) to form disinfection by-products (DBPs). The United States Environmental Protection Agency (USEPA) has established threshold limits on some DBPs, which are known as regulated DBPs (R-DBPs). The human health risks associated with R-DBPs in drinking water distribution systems (DWDSs) and application of stricter regulations have led water utilities to switch from conventional disinfectant (i.e., chlorination) to alternative disinfectants. However, the use of alternative disinfectants causes formation of a new suit of DBPs known as unregulated DBPs (UR-DBPs), which in many cases can be more toxic. There is a growing concern of UR-DBPs formation in drinking water. This review prioritizes some commonly occurring UR-DBP groups and species in DWDSs based on their concentration level, reported frequency, and toxicity using an indexing method. There are nine UR-DBPs group and 36 species that have been identified based on recent published peer-reviewed articles. Haloacetonitriles (HANs) and haloacetaldehydes (HALs) are identified as important UR-DBP groups. Dichloroacetonitrile (DCAN) and trichloroacetaldehye (TCAL) are identified as critical UR-DBPs species. The outcomes of this review can help water regulators to identify the most critical UR-DBPs species in the context of drinking water safety and provide them with useful information to develop guidelines or threshold limits for UR-DBPs. The outcomes can also help water utilities in selecting water treatment processes for the mitigation of human health risk posed by UR-DBPs through drinking water. Graphical abstract Image 1 Highlights • Unregulated disinfection by-products in drinking water were comprehensively reviewed. • Commonly occurred unregulated disinfection by-products were prioritized. • Haloacetonitriles were identified as the most important group. • Dichloroacetonitrile and trichloroacetaldehyde were the most critical species. [ABSTRACT FROM AUTHOR]

Abrasion of tires on road surfaces leads to the formation of tire and road wear particles (TRWPs). Approximately 5.9 million tonnes/year of TRWPs are emitted globally, and 12–20% of emissions generated on roads are transmitted into surface waters, where they can release (i.e., leach) chemical compounds that adversely affect aquatic species. To better understand the ecological risk of TRWPs, an acute, probabilistic ecological risk assessment model was developed and applied. This was a screening-level, conceptual ecological risk assessment (ERA) based on secondary data from published scientific studies. The model was demonstrated using British Columbia (BC) Highway 97 (TRWP source) and Kalamalka Lake (receiving water) in Canada, considering two spatial scenarios with varied highway (HWY) lengths and lake volumes. TRWP-derived chemical leachates considered for ERA were aniline, anthracene (ANT), benzo(a)pyrene (B(a)P), fluoranthene (Fl), mercaptobenzothiazole (MBT), and zinc (Zn). An assumed 'total TRWP-derived leachate set' was also assessed, representing all compounds present in tire-derived leachate test solutions. The results indicated the risk to aquatic species in two spatial scenarios. In scenario 1, ecotoxicity risk was high from exposure to TRWP-derived zinc and the total TRWP-derived leachate set. Scenario 2 results indicated acute risk was high from all TRWP-derived chemicals examined, except MBT. This preliminary ecological risk screening provides an early signal that freshwater lakes adjacent to busy highways may be at risk from TRWP contamination, indicating a need for further research. This research is the first ERA of TRWPs in Canada, and the results and methodology provide a foundation for future research and solutions development. [Display omitted] • Tire and road wear particles (TRWPs) are a major source of micropolymer • Ecological risk assessment (ERA) was conducted to assess the risk of TRWPs. • Two scenarios were developed by considering lake spatial factors. • The risk quotients for both scenarios ranged from 4.3E-05 to 2.5E+02. • ERA results can assist in minimizing the impacts of TRWPs in surface waters. [ABSTRACT FROM AUTHOR]

A human health risk-based life cycle assessment (LCA) framework was developed for selecting low-impact water treatment systems with a focus on heavy metal(loids) removal. The framework comprises three phases, including pilot-scale water treatment, human health risk assessment (HRA), and LCA. The application of the framework was demonstrated by a case study. Two water treatment systems employing ozonation-greensand-ferric hydroxide-based sorbent (OGF) and Birm-ferric hydroxide-based sorbent (BF) processes were used to reduce arsenic and manganese concentrations in the source water of a small municipality in southwestern Canada. The heavy metal(loids) concentration as well as material and energy use data of the two systems were collected to perform HRA and LCA. The results showed that both systems can reduce arsenic and manganese concentrations; however, the removal efficiencies of OGF and BF processes decreased with the increase of treatment volume. At a constant inflow rate, the ferric hydroxide-based sorbent needed to be replaced every 31 and 25 days in the OGF and BF processes, respectively, to ensure that arsenic concentration in the effluent would not pose any significant human health risk. The LCA results indicated that the system using the OGF process generated lower life cycle environmental impacts than the system using the BF process throughout ten years' operation. It was also found that the arsenic removal process was the largest impact contributor in both systems. The manufacturing of ferric hydroxide-based sorbent and disposal of arsenic-contaminated treatment waste accounted for the highest impact in water treatment. Image 1 • A health risk-based LCA framework is proposed for assessing water treatment systems. • Two water treatment systems designed for arsenic and manganese removal are assessed. • Human health risk assessment determines acceptable adsorbent replacement frequency. • System using ozonation-greensand-ferric oxyhydroxide treatment shows lower impacts. • Arsenic removal process generates the highest life cycle environmental impacts. [ABSTRACT FROM AUTHOR]