Contamination of groundwater systems in the US and Canada by enteric pathogens, 1990-2013: a review and pooled-analysis.

BACKGROUND: Up to 150 million North Americans currently use a groundwater system as their principal drinking water source. These systems are a potential source of exposure to enteric pathogens, contributing to the burden of waterborne disease. Waterborne disease outbreaks have been associated with US and Canadian groundwater systems over the past two decades. However, to date, this literature has not been reviewed in a comprehensive manner. METHODS AND PRINCIPAL FINDINGS: A combined review and pooled-analysis approach was used to investigate groundwater contamination in Canada and the US from 1990 to 2013; fifty-five studies met eligibility criteria. Four study types were identified. It was found that study location affects study design, sample rate and studied pathogen category. Approximately 15% (316/2210) of samples from Canadian and US groundwater sources were positive for enteric pathogens, with no difference observed based on system type. Knowledge gaps exist, particularly in exposure assessment for attributing disease to groundwater supplies. Furthermore, there is a lack of consistency in risk factor reporting (local hydrogeology, well type, well use, etc). The widespread use of fecal indicator organisms in reported studies does not inform the assessment of human health risks associated with groundwater supplies. CONCLUSIONS: This review illustrates how groundwater study design and location are critical for subsequent data interpretation and use. Knowledge gaps exist related to data on bacterial, viral and protozoan pathogen prevalence in Canadian and US groundwater systems, as well as a need for standardized approaches for reporting study design and results. Fecal indicators are examined as a surrogate for health risk assessments; caution is advised in their widespread use. Study findings may be useful during suspected waterborne outbreaks linked with a groundwater supply to identify the likely etiological agent and potential transport pathway

Planning for the health impacts of climate change: Flooding, private groundwater contamination and waterborne infection – A cross-sectional study of risk perception, experience and behaviours in the Republic of Ireland

The frequency and severity of flooding events will increase over the coming decades due to global climate change. While close attention has typically been paid to infrastructural and environmental outcomes of flood events, the potential adverse human health consequences associated with post-event consumption from private groundwater sources have received minimal attention, leading to a poor understanding of private well users’ preparedness and the drivers of positive behavioural adoption. The current study sought to quantify the capacity of private well users to cope with flood-triggered contamination risks and identify the social psychological determinants of proactive attitudes in the Republic of Ireland, using a cross-sectional questionnaire incorporating two distinct models of health behaviour, the Health Belief Model and Risk-Attitude-Norms-Ability-Self Regulation model. Adoption of healthy behaviours prior to flooding was evaluated with respect to respondents’ risk exposure, risk experience and risk perception, in addition to systematic supply stewardship under normal conditions. Associations between adoption of protective behaviours and perception, experience and socio-demographic factors were evaluated through multinomial and multiple logistic regressions, while a multi-model inferential approach was employed with the predictors of health behaviour models. Findings suggest that floods are not considered likely to occur, nor were respondents worried about their occurrence, with 72.5% of respondents who reported previous flooding experience failing to adopt protective actions. Prior experience of well water contamination increased adoption of proactive attitudes when flooding occurred (+47%), with a failure to adopt healthy behaviours higher among rural non-agricultural residents (136%). Low levels of preparedness to deal with flood-related contamination risks are a side-effect of the general lack of appropriate well stewardship under normal conditions; just 10.1% of respondents adopted both water treatment and frequent testing, in concurrence with limited risk perception and poor awareness of the nexus between risk factors (e.g. floods, contamination sources) and groundwater quality. Perceived risk, personal norms and social norms were the best predictors of protective behaviour adoption and should be considered when developing future awareness campaigns

Summary statistics: a. Extracted Studies (n = 55), b. Extracted Records (n = 102), c. Extracted records associated with confirmed enteric pathogen presence (n = 74), d. Sampled well numbers (n = 52) and analysed groundwater sample numbers (n = 39).

<p>Summary statistics: a. Extracted Studies (n = 55), b. Extracted Records (n = 102), c. Extracted records associated with confirmed enteric pathogen presence (n = 74), d. Sampled well numbers (n = 52) and analysed groundwater sample numbers (n = 39).</p

Correlation matrix; fecal indictor organisms and total source contamination percentage (n = 25) (<i>Clostridium perfringens</i> and Heterotropic plate counts were excluded due to low record numbers).

<p>**Correlation is significant at the 0.01 level (2-tailed).</p><p>*Correlation is significant at the 0.05 level (2-tailed).</p

Review protocol employed throughout the current study, including results of literature identification, literature scans and data extraction processes.

<p>Review protocol employed throughout the current study, including results of literature identification, literature scans and data extraction processes.</p

Enteric pathogen records from included US and Canadian studies (1990–2013) (n = 102); record number, percentage of total records, record number with specified pathogen present, percentage of records with specified pathogen present.

1<p>Vero-toxigenic <i>Escherichia coli</i>.</p>2<p>Enteropathogenic <i>Escherichia coli</i>.</p>3<p>Small Round Structured Viruses.</p

Inclusion and exclusion criteria for literature screening.

<p>Inclusion and exclusion criteria for literature screening.</p