Use Of Quantitative Microbial Risk Assessment Research Articles

Applications of Quantitative Microbial Risk Assessment to Respiratory Pathogens and Implications for Uptake in Policy: A State-of-the-Science Review.

Respiratory tract infections are major contributors to the global disease burden. Quantitative microbial risk assessment (QMRA) holds potential as a rapidly deployable framework to understand respiratory pathogen transmission and inform policy on infection control. The goal of this paper was to evaluate, motivate, and inform further development of the use of QMRA as a rapid tool to understand the transmission of respiratory pathogens and improve the evidence base for infection control policies. We conducted a literature review to identify peer-reviewed studies of complete QMRA frameworks on aerosol inhalation or contact transmission of respiratory pathogens. From each of the identified studies, we extracted and summarized information on the applied exposure model approaches, dose-response models, and parameter values, including risk characterization. Finally, we reviewed linkages between model outcomes and policy. We identified 93 studies conducted in 16 different countries with complete QMRA frameworks for diverse respiratory pathogens, including SARS-CoV-2, Legionella spp., Staphylococcus aureus, influenza, and Bacillus anthracis. Six distinct exposure models were identified across diverse and complex transmission pathways. In 57 studies, exposure model frameworks were informed by their ability to model the efficacy of potential interventions. Among interventions, masking, ventilation, social distancing, and other environmental source controls were commonly assessed. Pathogen concentration, aerosol concentration, and partitioning coefficient were influential exposure parameters as identified by sensitivity analysis. Most (84%, ) studies presented policy-relevant content including a) determining disease burden to call for policy intervention, b) determining risk-based threshold values for regulations, c) informing intervention and control strategies, and d) making recommendations and suggestions for QMRA application in policy. We identified needs to further the development of QMRA frameworks for respiratory pathogens that prioritize appropriate aerosol exposure modeling approaches, consider trade-offs between model validity and complexity, and incorporate research that strengthens confidence in QMRA results. https://doi.org/10.1289/EHP12695.

A scientometric study on quantitative microbial risk assessment in water quality analysis across 6 years (2016-2021).

Water contamination by microbes is a growing environmental challenge that has exacerbated the apparent scarcity of safe drinking water. To alleviate this challenge, it is important to screen water for pathogens to reduce the risk of contracting waterborne diseases among consumers. The use of the quantitative microbial risk assessment (QMRA) tool to approximate illness possibility from exposure to microorganisms using dose-response models between pathogens and their associated health impacts is, therefore, recommended. The aim of this study was to explore the use of QMRA in water quality assessment using a scientometric approach and data sourced from the Web of Science (WoS) database for the period between 2016 and 2021. Articles were searched in the WoS databases before downloading the content for a bibliometric analysis using the VOSviewer software. Additionally, Microsoft Excel was used to analyze the inter-relationships of the searched results. Journal articles had the highest results from the searched query at 90.6% compared to other forms of output. High-impact journals such as the Science of the Total Environment and Water Research had the highest number of publications at 11.056 and 7.5%, respectively. Keyword analysis showed the multidisciplinary nature of the search query based on the clustered themes. The USA and China showed greater publication output with a total of 51.7% of total publications compared to developing countries due to their high research potential and extensive collaborative networks. A similar trend was evident in the institutional analysis with the University of California, USA, and the Chinese Academy of Sciences being the highest research contributors with 8% of the searched output. The study highlighted the need to extend research inputs to developing countries of Africa and Asia to improve their research and development capacity, productivity and share knowledge on QMRA in water quality assessment.

The challenges of microbial source tracking at urban beaches for Quantitative Microbial Risk Assessment (QMRA)

Urban beaches are frequently impacted from multiple sources of fecal contamination. This along with high beach usage underscores the importance of appropriate management that protects swimmer health. The USEPA has enabled the use of QMRA as a tool for quantifying swimmer health risk and setting site-specific water quality objectives. This study illustrates the challenges associated with human and non-human source identification and how these challenges influence the decision of whether QMRA at typical urban beaches for water quality management is appropriate. In this study, a similar and correlated spatial relationship with elevated Enterococcus and avian-specific markers was observed, suggesting shorebirds as a primary source of FIB. However, human-associated markers were also detected frequently but at low concentrations. Ultimately, a QMRA was not conducted because pathogen loading from potential human sources could not be confidently quantified, having consequences for health risk in receiving waters where recreational contact occurs.

Using quantitative microbial risk assessment and life cycle assessment to assess management options in urban water and sanitation infrastructures: Opportunities and unresolved issues

Quantitative microbial risk assessment (QMRA) and life cycle assessment (LCA) are two distinct environmental management techniques that can provide complementary perspectives when assessing management options for urban water and sanitation infrastructure. While QMRA per definition concerns microbial risks, accounting for pathogens in LCA has received little attention. A few case studies, however, have explored the concurrent use of QMRA and LCA. These studies were motivated by the perceived need to address trade-offs between local health burdens associated with pathogens and global health burdens associated with other stressors at different spatial and temporal scales. Along with the LCA, the QMRA results were sought to provide the basis for addressing such trade-offs, rather than for deciding whether pathogen-related adverse effects experienced by specific individuals or populations are acceptable, or which scenario leads to the highest overall health burden for a given community, as is traditionally the case in QMRA. This paper highlights opportunities and unresolved issues related to the concurrent use of QMRA and LCA, such as assumptions in translating chemical and pathogen health impacts to a common metric or other mode structure and parameterisation aspects. Our aim is to facilitate more consistent design and transparent communication of future case studies of this type, and to highlight opportunities for QMRA experts to contribute to LCA method development so as to include pathogen health impacts. While most examples provided in this paper focus on water reuse, the findings apply more broadly and can also be extrapolated to other pathogen exposures in the context of urban water and sanitation systems as well as other contexts.

Estimating the burden of acute gastrointestinal illness due to Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus associated with private wells and small water systems in Canada.

Waterborne illness related to the consumption of contaminated or inadequately treated water is a global public health concern. Although the magnitude of drinking water-related illnesses in developed countries is lower than that observed in developing regions of the world, drinking water is still responsible for a proportion of all cases of acute gastrointestinal illness (AGI) in Canada. The estimated burden of endemic AGI in Canada is 20·5 million cases annually - this estimate accounts for under-reporting and under-diagnosis. About 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. There is evidence that individuals served by private systems and small community systems may be more at risk of waterborne illness than those served by municipal drinking water systems in Canada. However, little is known regarding the contribution of these systems to the overall drinking water-related AGI burden in Canada. Private water supplies serve an estimated 12% of the Canadian population, or ~4·1 million people. An estimated 1·4 million (4·1%) people in Canada are served by small groundwater (2·6%) and surface water (1·5%) supplies. The objective of this research is to estimate the number of AGI cases attributable to water consumption from these supplies in Canada using a quantitative microbial risk assessment (QMRA) approach. This provides a framework for others to develop burden of waterborne illness estimates for small water supplies. A multi-pathogen QMRA of Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus, chosen as index waterborne pathogens, for various source water and treatment combinations was performed. It is estimated that 103 230 AGI cases per year are due to the presence of these five pathogens in drinking water from private and small community water systems in Canada. In addition to providing a mechanism to assess the potential burden of AGI attributed to small systems and private well water in Canada, this research supports the use of QMRA as an effective source attribution tool when there is a lack of randomized controlled trial data to evaluate the public health risk of an exposure source. QMRA is also a powerful tool for identifying existing knowledge gaps on the national scale to inform future surveillance and research efforts.

Including pathogen risk in life cycle assessment: the effect of modelling choices in the context of sewage sludge management

Purpose: Recent attempts to include adverse effects of pathogens on human health in life cycle assessment (LCA) have focused on integrating results obtained through quantitative microbial risk assessment (QMRA) as an impact category in LCA. This study aimed to investigate whether the use of QMRA can be an adequate way of integrating pathogen impact potential in LCA and to quantify how pathogen impact potential is affected by choices regarding model structure and mathematical relationships used. Methods: This study was performed for the context of sewage sludge management and is based on pathogen concentrations in treated sludge reported in the literature. Eight reference pathogens were included in order to address important microbial groups. The pathogen impact potential associated with land application of sewage sludge was quantified based on a QMRA model for eight distinct exposure pathways. The modelling choices investigated were linearisation of dose-response and severity assessment and different modelling approaches and parameter choices in fate and exposure assessment. Results and discussion: The linearisation of effect and severity assessment had a minor impact on the results for exposure pathways where pathogen doses were low but had a major impact where pathogen doses were high. The assumptions regarding fate and exposure conditions, such as pathogen decay time, number of individuals exposed and frequency of exposure, had a significant effect on overall pathogen impact potential. If pathogen impact potential is to be integrated in LCA, a range of different parameterisations for each exposure event may be warranted rather than only the one with the highest risk per individual exposed as commonly reported for QMRAs. This is also in line with the ordinary LCA practice of focusing on average rather than extreme conditions. Conclusions: This study suggests that the use of QMRA can be an adequate way of integrating adverse effects of pathogens on human health in LCA. However, analysts should be careful when choosing model parameters such as the number of people exposed or the frequency of exposure, as LCA may require a different parameterisation than an ordinary risk assessment (RA). Therefore, a direct integration of the results of a QMRA study into LCA may be problematic. Also, in order to avoid potential bias, analysts should carefully consider whether or not pathogen impact potential and human toxicity potential need to be estimated based on a similar set of exposure pathways.