Examining the factors related to bacteriological testing of private wells in Southern Ontario

Private groundwater contamination and risk management: A comparative scoping review of similarities, drivers and challenges across two socio-economically developed regions

Consolidation of multi-domain risk management research is essential for strategies facilitating the concerted government (educational) and population-level (behavioural) actions required to reduce microbial private groundwater contamination. However, few studies to date have synthesised this literature or sought to ascertain the causal generality and extent of supply contamination and preventive responses. In light of the Republic of Ireland (ROI) and Ontario's high reliance and research focus on private wells and consequent utility for empirical comparison, a scoping review of pertinent literature (1990-2022) from both regions was undertaken. The SPICE (Setting, Perspective, Intervention, Comparison, Evaluation) method was employed to inform literature searches, with Scopus and Web of Science selected as primary databases for article identification. The review identified 65 relevant articles (Ontario = 34, ROI = 31), with those investigating well user actions (n = 22) and groundwater quality (n = 28) the most frequent. A markedly higher pooled proportion of private supplies in the ROI exhibited microbial contamination (38.3 % vs. 4.1 %), despite interregional similarities in contamination drivers (e.g., weather, physical supply characteristics). While Ontarian well users demonstrated higher rates of historical (≥ 1) and annual well testing (90.6 % vs. 71.1 %; 39.1 % vs. 8.6 %) and higher rates of historical well treatment (42.3 % vs. 24.3 %), interregional levels of general supply knowledge were analogous (70.7 % vs. 71.0 %). Financial cost, organoleptic properties and residence on property during supply construction emerged as predictors of cognition and behaviour in both regions. Review findings suggest broad interregional similarities in drivers of supply contamination and individual-level risk mitigation, indicating that divergence in contamination rates may be attributable to policy discrepancies - particularly well testing incentivisation. The paucity of identified intervention-oriented studies further highlights the importance of renewed research and policy agendas for improved, targeted well user outreach and incentivised, convenience-based services promoting routine supply maintenance.

Classification of sub-populations for quantitative risk assessment based on awareness and perception: A cross-sectional population study of private well users in Ontario

Private well users in Ontario are responsible for protective actions, including source maintenance, treatment, and submitting samples for laboratory testing. However, low participation rates are reported, thus constituting a public health concern, as risk mitigation behaviours can directly reduce exposure to waterborne pathogens. The current study examined the combined effects of socio-demographic profile, experience(s), and "risk domains" (i.e., awareness, attitudes, risk perceptions and beliefs) on behaviours, and subsequently classified private well users in Ontario based on cognitive factors. A province-wide online survey (n = 1228) was employed to quantify Ontario well owners' awareness, perceptions, and behaviours in relation to their personal groundwater supply and local contamination sources. A scoring protocol for four risk domains was developed. Two-step cluster analysis was used to classify respondents based on individual risk domain scores. Logistic regression was employed to identify key variables associated with cluster membership (i.e., profile analysis). Overall, 1140 survey respondents were included for analyses. Three distinct clusters were identified based on two risk domains; groundwater awareness and source risk perception. Profile analyses indicate "low awareness and source risk perception" (Low A/SRP) members were more likely male, while "low awareness and moderate source risk perception" (Low A/Mod SRP) members were more likely female and bottled water users. Well users characterised as "high awareness and source risk perception" (High A/SRP) were more likely to report higher educational attainment and previous well water testing. Findings illustrate that socio-cognitive clusters and their components (i.e., demographics, awareness, attitudes, perceptions, experiences, and protective actions) are distinct based on the likelihood, frequency, and magnitude of waterborne pathogen exposures (i.e., risk-based). Risk-based clustering, when incorporated into quantitative microbial risk assessment, enables the development of effective risk management and communication initiatives that are demographically focused and tailored to specific sub-groups.

Impacts of COVID-19 lockdown on private domestic groundwater sample numbers, E. coli presence and E. coli concentration across Ontario, January 2020-March 2021: An interrupted time-series analysis

Approximately 1.5 million individuals in Ontario are supplied by private water wells (private groundwater supplies). Unlike municipal supplies, private well water quality remains unregulated, with owners responsible for testing, treating, and maintaining their own water supplies. The COVID-19 global pandemic and associated non-pharmaceutical interventions (NPIs) have impacted many environmental (e.g., surface water and air quality) and human (e.g., healthcare, transportation) systems over the past 15-months (January 2020 to March 2021). To date, the impact of these interventions on private groundwater systems remains largely unknown. Accordingly, the current study aimed to investigate the impact of a province-wide COVID-19 lockdown (late-March 2020) on health behaviours (i.e., private domestic groundwater sampling) and groundwater quality (via Escherichia coli (E. coli) detection and concentration) in private well water in Ontario, using time-series analyses (seasonal decomposition, interrupted time-series) of a large-spatio-temporal dataset (January 2016 to March 2021; N = 743,200 samples). Findings indicate that lockdown concurred with an immediate (p = 0.015) and sustained (p < 0.001) decrease in sampling rates, equating to approximately 2200 fewer samples received per week post-interruption. Likewise, a slightly decreased E. coli detection rate was observed approximately one month after lockdowns began (p = 0.003), while the proportion of "highly contaminated" samples (i.e., E. coli > 10 CFU/100 mL) was shown to increase within one month (p = 0.02), followed by a sustained decrease for the remainder of the year (May 2020-December 2020). Analyses strongly suggest that COVID-19 interventions resulted in discernible impacts on both well user behaviours and hydrogeological mechanisms. Findings may be used as an evidence-base for assisting policy makers, public health practitioners and private well owners in developing recommendations and mitigation strategies to manage public health risks during extreme and/or unprecedented future events.

Drinking Water Consumption Patterns among Private Well Users in Ontario: Implications for Exposure Assessment of Waterborne Infection

Understanding the water consumption patterns within a specific population informs development of increasingly accurate, spatially specific exposure and/or risk assessment of waterborne infection. The current study examined the consumption patterns of private well users in Ontario while considering potentially influential underlying sociodemographics, household characteristics, and experiential factors. A province-wide online survey was circulated between May and August 2018 (n = 1,162). Overall, 81.5% of respondents reported daily well water consumption (i.e., tap water). Results indicate a mean daily well water consumption rate of 1,132 mL/day (SD = 649 mL/day) among well water consumers. Gender was significantly associated with well water consumption, with higher consumption rates found among female respondents. The experience of acute gastrointestinal illness (AGI) symptoms or diagnosis in the past 12 months did not impact the volume of water consumed, suggesting that experiencing previous AGI does not decrease consumption volumes, and therefore exposure over time. Significantly higher rates of well water consumption were found among respondents who reported previous testing or ongoing water treatment. Approximately 45.5% of survey respondents who stated that they do not consume well water selected bottled water as their primary household drinking water supply. Bottled water consumption was also not associated with previous AGI experiences. Findings will inform future quantitative microbial risk assessments associated with private well water use by providing spatially and demographically specific estimates of well water consumption.

Analysis of a large spatiotemporal groundwater quality dataset, Ontario 2010-2017: Informing human health risk assessment and testing guidance for private drinking water wells

Approximately 1.5 million individuals in Ontario are supplied by private water wells (private groundwater supplies). Unlike municipal supplies, private well water quality remains unregulated, with owners responsible for testing, treating, and maintaining their own water supplies. The primary goal of this study was to assess the effect of repeat sampling of private well water in Ontario and investigate the efficacy of geographically- and/or temporally specific testing recommendations and health risk assessments. The current study combines the Well Water Information System Dataset and the Well Water Testing Dataset from 2010 to 2017, inclusive. These two large existing province-wide datasets collated over an eight-year period were merged using an integrated spatial fuzzy logic and (next)- nearest neighbour approach. Provincial sampling data from 239,244 wells (702,861 samples) were analyzed for Escherichia coli to study the relationship between sampling frequency and Escherichia coli detection. Dataset variables were delineated based on hydrogeological setting (e.g. aquifer type, overburden depth, well depth, bedrock type) and seasonality to provide an in-depth understanding of Escherichia coli detection in private well water. Findings reveal differences between detection rates in consolidated and unconsolidated aquifers (p = 0.0191), and across seasons (p < 0.0001). The variability associated with Escherichia coli detection rates was explored by estimating sentinel sampling rates for private wells sampled three times, twelve times and twenty-four times per year. As sample size increases on an annual basis, so too does detection rate, highlighting the need to address current testing frequency guidelines. Future health risk assessments for private well water should consider the impact of spatial and temporal factors on the susceptibility of this drinking water source, leading to an increasingly accurate depiction of private well water contamination and the estimated effects on human health.