Integrating different tools and technologies to advance drinking water quality exposure assessments.

Contaminants in drinking water are a major contributor to the human exposome and adverse health effects. Assessing drinking water exposure accurately in health studies is challenging, as several of the following study design domains should be addressed as adequately as possible. In this paper, we identify the domains Time, Space, Data Quality, Data Accessibility, economic considerations of Study Size, and Complex Mixtures. We present case studies for three approaches or technologies that address these domains differently in the context of exposure assessment of drinking water quality: regulated contaminants in monitoring databases, high-resolution mass spectrometry (HRMS)-based wide-scope chemical analysis, and effect-based bioassay methods. While none of these approaches address all the domains sufficiently, together they have the potential to carry out exposure assessments that would complement each other and could advance the state-of-science towards more accurate risk analysis. The aim of our study is to give researchers investigating health effects of drinking water quality the impetus to consider how their exposure assessments relate to the above-mentioned domains and whether it would be worthwhile to integrate the advanced technologies presented into planned risk analyses. We highly suggest this three-pronged approach should be further evaluated in health risk analyses, especially epidemiological studies concerning contaminants in drinking water. The state of the knowledge regarding potential benefits of these technologies, especially when applied in tandem, provides more than sufficient evidence to support future research to determine the implications of combining the approaches described in our case studies in terms of protection of public health.

In vitro bioassays for monitoring drinking water quality of tap water, domestic filtration and bottled water.

BACKGROUND: Location-specific patterns of regulated and non-regulated disinfection byproducts (DBPs) were detected in tap water samples of the Barcelona Metropolitan Area. However, it remains unclear if the detected DBPs together with undetected DPBs and organic micropollutants can lead to mixture effects in drinking water. OBJECTIVE: To evaluate the neurotoxicity, oxidative stress response and cytotoxicity of 42 tap water samples, 6 treated with activated carbon filters, 5 with reverse osmosis and 9 bottled waters. To compare the measured effects of the extracts with the mixture effects predicted from the detected concentrations and the relative effect potencies of the detected DBPs using the mixture model of concentration addition. METHODS: Mixtures of organic chemicals in water samples were enriched by solid phase extraction and tested for cytotoxicity and neurite outgrowth inhibition in the neuronal cell line SH-SY5Y and for cytotoxicity and oxidative stress response in the AREc32 assay. RESULTS: Unenriched water did not trigger neurotoxicity or cytotoxicity. After up to 500-fold enrichment, few extracts showed cytotoxicity. Disinfected water showed low neurotoxicity at 20- to 300-fold enrichment and oxidative stress response at 8- to 140-fold enrichment. Non-regulated non-volatile DBPs, particularly (brominated) haloacetonitriles dominated the predicted mixture effects of the detected chemicals and predicted effects agreed with the measured effects. By hierarchical clustering we identified strong geographical patterns in the types of DPBs and their association with effects. Activated carbon filters did not show a consistent reduction of effects but domestic reverse osmosis filters decreased the effect to that of bottled water. IMPACT STATEMENT: Bioassays are an important complement to chemical analysis of disinfection by-products (DBPs) in drinking water. Comparison of the measured oxidative stress response and mixture effects predicted from the detected chemicals and their relative effect potencies allowed the identification of the forcing agents for the mixture effects, which differed by location but were mainly non-regulated DBPs. This study demonstrates the relevance of non-regulated DBPs from a toxicological perspective. In vitro bioassays, in particular reporter gene assays for oxidative stress response that integrate different reactive toxicity pathways including genotoxicity, may therefore serve as sum parameters for drinking water quality assessment.

Insights to estimate exposure to regulated and non-regulated disinfection by-products in drinking water.

BACKGROUND: Knowledge about human exposure and health effects associated with non-routinely monitored disinfection by-products (DBPs) in drinking water is sparse. OBJECTIVE: To provide insights to estimate exposure to regulated and non-regulated DBPs in drinking water. METHODS: We collected tap water from homes (N = 42), bottled water (N = 10), filtered tap water with domestic activated carbon jars (N = 6) and reverse osmosis (N = 5), and urine (N = 39) samples of participants from Barcelona, Spain. We analyzed 11 haloacetic acids (HAAs), 4 trihalomethanes (THMs), 4 haloacetonitriles (HANs), 2 haloketones, chlorate, chlorite, and trichloronitromethane in water and HAAs in urine samples. Personal information on water intake and socio-demographics was ascertained in the study population (N = 39) through questionnaires. Statistical models were developed based on THMs as explanatory variables using multivariate linear regression and machine learning techniques to predict non-regulated DBPs. RESULTS: Chlorate, THMs, HAAs, and HANs were quantified in 98-100% tap water samples with median concentration of 214, 42, 18, and 3.2 µg/L, respectively. Multivariate linear regression models had similar or higher goodness of fit (R2) compared to machine learning models. Multivariate linear models for dichloro-, trichloro-, and bromodichloroacetic acid, dichloroacetonitrile, bromochloroacetonitrile, dibromoacetonitrile, trichloropropnanone, and chlorite showed good predictive ability (R 2 = 0.8-0.9) as 80-90% of total variance could be explained by THM concentrations. Activated carbon filters reduced DBP concentrations to a variable extent (27-80%), and reverse osmosis reduced DBP concentrations ≥98%. Only chlorate was detected in bottled water samples (N = 3), with median = 13.0 µg/L. Creatinine-adjusted trichloroacetic acid was the most frequently detected HAA in urine samples (69.2%), and moderately correlated with estimated drinking water intake (r = 0.48). SIGNIFICANCE: Findings provide valuable insights for DBP exposure assessment in epidemiological studies. Validation of predictive models in a larger number of samples and replication in different settings is warranted. IMPACT STATEMENT: Our study focused on assessing and describing the occurrence of several classes of DBPs in drinking water and developing exposure models of good predictive ability for non-regulated DBPs.

Exposure to per- and Polyfluoroalkyl Substances and Markers of Liver Injury: A Systematic Review and Meta-Analysis.

BACKGROUND: Experimental evidence indicates that exposure to certain pollutants is associated with liver damage. Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals widely used in industry and consumer products and bioaccumulate in food webs and human tissues, such as the liver. OBJECTIVE: The objective of this study was to conduct a systematic review of the literature and meta-analysis evaluating PFAS exposure and evidence of liver injury from rodent and epidemiological studies. METHODS: PubMed and Embase were searched for all studies from earliest available indexing year through 1 December 2021 using keywords corresponding to PFAS exposure and liver injury. For data synthesis, results were limited to studies in humans and rodents assessing the following indicators of liver injury: serum alanine aminotransferase (ALT), nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, or steatosis. For human studies, at least three observational studies per PFAS were used to conduct a weighted z-score meta-analysis to determine the direction and significance of associations. For rodent studies, data were synthesized to qualitatively summarize the direction and significance of effect. RESULTS: Our search yielded 85 rodent studies and 24 epidemiological studies, primarily of people from the United States. Studies focused primarily on legacy PFAS: perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid. Meta-analyses of human studies revealed that higher ALT levels were associated with exposure to PFOA (z-score= 6.20, p<0.001), PFOS (z-score= 3.55, p<0.001), and PFNA (z-score= 2.27, p=0.023). PFOA exposure was also associated with higher aspartate aminotransferase and gamma-glutamyl transferase levels in humans. In rodents, PFAS exposures consistently resulted in higher ALT levels and steatosis. CONCLUSION: There is consistent evidence for PFAS hepatotoxicity from rodent studies, supported by associations of PFAS and markers of liver function in observational human studies. This review identifies a need for additional research evaluating next-generation PFAS, mixtures, and early life exposures. https://doi.org/10.1289/EHP10092.

Association of Local Variation in Neighborhood Disadvantage in Metropolitan Areas With Youth Neurocognition and Brain Structure.

Importance: Neighborhood disadvantage is an important social determinant of health in childhood and adolescence. Less is known about the association of neighborhood disadvantage with youth neurocognition and brain structure, and particularly whether associations are similar across metropolitan areas and are attributed to local differences in disadvantage. Objective: To test whether neighborhood disadvantage is associated with youth neurocognitive performance and with global and regional measures of brain structure after adjusting for family socioeconomic status and perceptions of neighborhood characteristics, and to assess whether these associations (1) are pervasive or limited, (2) vary across metropolitan areas, and (3) are attributed to local variation in disadvantage within metropolitan areas. Design, Setting, and Participants: This cross-sectional study analyzed baseline data from the Adolescent Brain and Cognitive Development (ABCD) Study, a cohort study conducted at 21 sites across the US. Participants were children aged 9.00 to 10.99 years at enrollment. They and their parent or caregiver completed a baseline visit between October 1, 2016, and October 31, 2018. Exposures: Neighborhood disadvantage factor based on US census tract characteristics. Main Outcomes and Measures: Neurocognition was measured with the NIH Toolbox Cognition Battery, and T1-weighted magnetic resonance imaging was used to assess whole-brain and regional measures of structure. Linear mixed-effects models examined the association between neighborhood disadvantage and outcomes after adjusting for sociodemographic factors. Results: Of the 11 875 children in the ABCD Study cohort, 8598 children (72.4%) were included in this analysis. The study sample had a mean (SD) age of 118.8 (7.4) months and included 4526 boys (52.6%). Every 1-unit increase in the neighborhood disadvantage factor was associated with lower performance on 6 of 7 subtests, such as Flanker Inhibitory Control and Attention (unstandardized Β = -0.5; 95% CI, -0.7 to -0.2; false discovery rate (FDR)-corrected P = .001) and List Sorting Working Memory (unstandardized Β = -0.7; 95% CI, -1.0 to -0.3; FDR-corrected P < .001), as well as on all composite measures of neurocognition, such as the Total Cognition Composite (unstandardized Β = -0.7; 95% CI, -0.9 to -0.5; FDR-corrected P < .001). Each 1-unit increase in neighborhood disadvantage was associated with lower whole-brain cortical surface area (unstandardized Β = -692.6 mm2; 95% CI, -1154.9 to -230.4 mm2; FDR-corrected P = .007) and subcortical volume (unstandardized Β = -113.9 mm3; 95% CI, -198.5 to -29.4 mm3; FDR-corrected P = .03) as well as with regional surface area differences, primarily in the frontal, parietal, and temporal lobes. Associations largely remained after adjusting for perceptions of neighborhood safety and were both consistent across metropolitan areas and primarily explained by local variation in each area. Conclusions and Relevance: This study found that, in the US, local variation in neighborhood disadvantage was associated with lower neurocognitive performance and smaller cortical surface area and subcortical volume in young people. The findings demonstrate that neighborhood disadvantage is an environmental risk factor for neurodevelopmental and population health and enhancing the neighborhood context is a promising approach to improving the health and development of children and adolescents.

Association of Outdoor Ambient Fine Particulate Matter With Intracellular White Matter Microstructural Properties Among Children.

Importance: Outdoor particulate matter 2.5 µm or less in diameter (PM2.5) is a ubiquitous environmental neurotoxicant that may affect the developing brain. Little is known about associations between PM2.5 and white matter connectivity. Objectives: To assess associations between annual residential PM2.5 exposure and white matter microstructure health in a US sample of children 9 to 10 years of age and to examine whether associations are specific to certain white matter pathways or vary across neuroimaging diffusion markers reflective of intracellular and extracellular microstructural processes. Design, Setting, and Participants: This cross-sectional study, the Adolescent Brain and Cognitive Development (ABCD) Study, was composed of 21 study sites across the US and used baseline data collected from children 9 to 10 years of age from September 1, 2016, to October 15, 2018. Data analysis was performed from September 15, 2020, to June 30, 2021. Exposures: Annual mean PM2.5 exposure estimated by ensemble-based models and assigned to the primary residential addresses at baseline. Main Outcomes and Measures: Diffusion-weighted imaging (DWI) and tractography were used to delineate white matter tracts. The biophysical modeling technique of restriction spectrum imaging (RSI) was implemented to examine total hindered diffusion and restricted isotropic and anisotropic intracellular diffusion in each tract. Hierarchical mixed-effects models with natural splines were used to analyze the associations between PM2.5 exposure and DWI. Results: In a study population of 7602 children (mean [SD] age, 119.1 [7.42] months; 3955 [52.0%] female; 160 [ 21.%] Asian, 1025 [13.5%] Black, 1616 [21.3%] Hispanic, 4025 [52.9%] White, and 774 [10.2%] other [identified by parents as American Indian/Native American or Alaska Native; Native Hawaiian, Guamanian, Samoan, other Pacific Islander; Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, or other Asian; or other race]), associations were seen between annual ambient PM2.5 and hemispheric differences in white matter microstructure. Hemisphere-stratified models revealed significant associations between PM2.5 exposure and restricted isotropic intracellular diffusion in the left cingulum, in the left superior longitudinal fasciculus, and bilaterally in the fornix and uncinate fasciculus. In tracts with strong positive associations, a PM2.5 increase from 8 to 12 µg/m3 was associated with increases of 2.16% (95% CI, 0.49%-3.84%) in the left cingulum, 1.95% (95% CI, 0.43%-3.47%) in the left uncinate, and 1.68% (95% CI, 0.01%-3.34%) in the right uncinate. Widespread negative associations were observed between PM2.5 and mean diffusivity. Conclusions and Relevance: The findings of this cross-sectional study suggest that annual mean PM2.5 exposure during childhood is associated with increased restricted isotropic diffusion and decreased mean diffusivity of specific white matter tracts, potentially reflecting differences in the composition of white matter microarchitecture.

Fine particulate matter exposure during childhood relates to hemispheric-specific differences in brain structure.

BACKGROUND: Emerging findings have increased concern that exposure to fine particulate matter air pollution (aerodynamic diameter ≤ 2.5 µm; PM2.5) may be neurotoxic, even at lower levels of exposure. Yet, additional studies are needed to determine if exposure to current PM2.5 levels may be linked to hemispheric and regional patterns of brain development in children across the United States. OBJECTIVES: We examined the cross-sectional associations between geocoded measures of concurrent annual average outdoor PM2.5 exposure, regional- and hemisphere-specific differences in brain morphometry and cognition in 10,343 9- and 10- year-old children. METHODS: High-resolution structural T1-weighted brain magnetic resonance imaging (MRI) and NIH Toolbox measures of cognition were collected from children at ages 9-10 years. FreeSurfer was used to quantify cortical surface area, cortical thickness, as well as subcortical and cerebellum volumes in each hemisphere. PM2.5 concentrations were estimated using an ensemble-based model approach and assigned to each child's primary residential address collected at the study visit. We used mixed-effects models to examine regional- and hemispheric- effects of PM2.5 exposure on brain estimates and cognition after considering nesting of participants by familial relationships and study site, adjustment for socio-demographic factors and multiple comparisons. RESULTS: Annual residential PM2.5 exposure (7.63 ± 1.57 µg/m3) was associated with hemispheric specific differences in gray matter across cortical regions of the frontal, parietal, temporal and occipital lobes as well as subcortical and cerebellum brain regions. There were hemispheric-specific associations between PM2.5 exposures and cortical surface area in 9/31 regions; cortical thickness in 22/27 regions; and volumes of the thalamus, pallidum, and nucleus accumbens. We found neither significant associations between PM2.5 and task performance on individual measures of neurocognition nor evidence that sex moderated the observed associations. DISCUSSION: Even at relatively low-levels, current PM2.5 exposure across the U.S. may be an important environmental factor influencing patterns of structural brain development in childhood. Prospective follow-up of this cohort will help determine how current levels of PM2.5 exposure may affect brain development and subsequent risk for cognitive and emotional problems across adolescence.