Using disability-adjusted life years to set health-based targets: a novel use of an established burden of disease metric

Quantitative health risk assessment of microbial hazards from water sources for community and self-supply drinking water systems

In low and medium income countries (LMIC) drinking water sources (wells and boreholes) often contain a high number of pathogenic microorganisms, that can pose significant human and environmental health risks. In this study, a quantitative microbial risk assessment approach based on existing literature was conducted to evaluate and compare the quantitative health risks associated with different age groups using various drinking water supply systems. Results showed that both community-supply and self-supply modes exhibit similar levels of risk. However, the self-supply water source consistently showed higher risks compared to the community-supply one. Borehole water was found to be a more suitable option than well water, consistently showing between 5 and 8 lower health risks for E. coli and fecal coliform levels, respectively. The sensitivity analysis further showed the importance of prioritizing the reduction of E. coli concentration in well water and fecal coliform concentration in borehole water. This study offers a fresh perception on quantifying the impact of exposure concentration and age groups, shedding light on how they affect environmental health risks. These findings provide valuable insights for stakeholders involved in the management and protection of water sources.

Human rights in mental healthcare; A review of current global situation

The relationship between mental health and human rights is complex and bidirectional. Global mental health movements have been emphasizing the promotion of human rights in mental health care in accordance with the UN Convention on the Rights of Persons with Disabilities and the WHO QualityRights Initiative. The main objective of this review is to have an overview of the current global situation of human rights in mental health services by performing a review of scientific literature. The literature search and elimination process yielded a total of 26 articles focussing on human rights-related reports and tools. Further assessment of these articles clearly shows that despite significant improvements in mental health service delivery in the past decade, there is still substantial reporting of the continuing prominence of stigmatizing attitudes, and human rights violations and abuses in mental health settings. The human rights perspective requires society, particularly policymakers, to actively promote necessary conditions for all individuals to fully realize their rights. We suggest developing a more comprehensive model in mental health that integrates human rights into existing services and approaches. A model that recognizes that all people with mental health conditions and psychosocial disabilities are rights holders.

Quantitative microbial risk assessment with nasal/oral breathing pattern for S. aureus bioaerosol emission from aeration tanks and residual sludge storage yard in a wastewater treatment plant

A large number of pathogenic bioaerosols are generated during the treatment process of wastewater treatment plants (WWTPs), and they can pose potential risks to human health. Therefore, this study systematically analyzed the emission characteristics of Staphylococcus aureus bioaerosols released from an inverted umbrella aeration tank, a microporous aeration tank, and a residual sludge storage yard in a WWTP, and quantitatively evaluated the health risks of four kinds of exposed populations with nasal/oral breathing patterns under optimistic and conservative estimations. The results displayed that the bioaerosol concentration in inverted umbrella aeration tank was higher than that in microporous aeration tank and residual sludge storage yard. Aerosolization ratio in residual sludge storage yard was an order of magnitude lower than that in aeration tanks. Sludge workers were at higher health risks than the other three exposed populations. The health risks of nasal breathers (infection risk: 1.62 × 10^-5-2.56 × 10^-3 pppy; disease burden: 4.24 × 10^-8-6.72 × 10^-6 DALYs pppy) were 0.61-0.63 times higher than those of oral breathers (infection risk: 9.95 × 10^-6-1.59 × 10^-3 pppy; disease burden: 2.61 × 10^-8-4.18 × 10^-6 DALYs pppy). For female field engineers using oral breathing, laboratory technicians, and researchers without personal protective equipment (PPE), infection risk and disease burden had the opposite results, which indicated that satisfying one certain benchmark did not mean absolute safety. In addition, health risks of exposed populations were reduced by an order of magnitude after wearing PPE. This study can provide a reliable theoretical basis for the risk prevention of bioaerosols and supply data support for the strategies of health risk control perspectives for local sewage utilities.

Seasonal variation of quantitative microbial risk assessment for three airborne enteric bacteria from wastewater treatment plant emissions

Airborne E. coli, fecal coliform, and Enterococcus are all related to sewage worker's syndrome and therefore used as target enteric bioaerosols about researches in wastewater treatment plants (WWTPs). However, most of the studies are often inadequately carried out because they lack systematic studies reports bioaerosols emission characteristics and health risk assessments for these three enteric bacteria during seasonal variation. Therefore, quantitative microbial risk assessment based on Monte Carlo simulation was utilized in this research to assess the seasonal variations of health risks of the three enteric bioaerosols among exposure populations (academic visitors, field engineers, and office staffs) in a WWTP equipped with rotating-disc and microporous aeration modes. The results show that the concentrations of the three airborne bacteria from the rotating-disc aeration mode were 2-7 times higher than the microporous aeration mode. Field engineers had health risks 1.5 times higher than academic visitors due to higher exposure frequency. Health risks of airborne Enterococcus in summer were up to 3 times higher than those in spring and winter. Similarly, health risks associated to E. coli aerosol exposure were 0.3 times higher in summer compared to spring. In contrast, health risks associated with fecal coliform aerosol were between 2 and 19 times lower in summer compared to spring and winter seasons. Data further suggest that wearing of N95 mask could minimize health risks by 1-2 orders of magnitude. This research shed light on seasonal variation of health risks associated with bioaerosol emission from wastewater utilities.

Exploring static and dynamic relationships between burden of disease and research funding in the United States

Background

The relationship between burden of disease and research funding has been examined cross-sectionally, but temporal patterns have not been investigated. It is logical to assume that temporal improvements in disability-adjusted life-years (DALYs) reflect benefits from research funding; such assumptions are tempered by an unknown lag time for emergence of benefits from research.

Methods

We studied National Institutes of Health (NIH) research fund allocations and United States DALY estimates for overlapping disease categories (matched disease categories, MDC, N = 38). Using a general linear model, we separately analysed DALYs for MDCs in 2017 in relation to NIH research allocations in 2017 and 2007. We also examined how changes in DALYs were related to cumulative NIH research funding (2006–2017). After regressing DALY change on summed funding, we obtained model residuals as estimates of the discrepancy for each MDC between observed and expected change in burden, given funding.

Results

In 2017, there was a positive association between NIH research fund allocations and DALYs for the same year (F_1,36 = 16.087, p = 0.0002921; slope = 0.35020; model R² = 0.3088), suggesting proportionate allocation. There was a positive association between 2017 DALYs and 2007 NIH research allocation, implying a beneficial impact of research (F_1,36 = 15.754, p = 0.0003; slope = 0.8845; model R² = 0.3044). In contrast, there was a nonsignificant association between summed NIH funding and percent change in DALYs over 2006–2017 (F_1,36 = 0.199; p = 0.65; beta coefficient = −1.144). When MDCs were ordered based on residuals, HIV/AIDS ranked first. Mental, neurologic or substance abuse (MNS) disorders comprised most residuals in the lower half.

Conclusions

NIH fund allocation is proportional to DALYs for MDCs. Temporal changes in DALYs vary by MDCs, but they are not significantly related to cumulative research outlays. Further analysis of temporal changes in DALYs could help to inform research outlays for MDCs and to study the impact of research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12961-022-00837-y.

Burden of COVID-19: a preliminary analysis in the population of Saudi Arabia

Background

Coronavirus infection (COVID-19) has resulted in an unprecedented number of human deaths and economic losses. Analyzing the role of disease in different groups of people is useful for determining the burden of disease. As a result, the purpose of this study was to investigate the influence of COVID-19 on the Saudi Arabian population's quality of life, with a particular emphasis on the likely fall in their life expectancy.

Methods

A cross-sectional and retrospective analysis of 2,988 patients' databases was performed to assess COVID-19-induced mortality and complications in the community. The data was gathered from official websites that track the disease's impact daily between July and October 2021. On the acquired data, disability-adjusted life years (DALYs) and relative risk analysis were performed. The data was statistically analyzed using SPSS IBM 25. The Pearson's correlation test was used to examine the relationship between age and disease impact. The significance of the findings was determined by using a P value of less than 0.05.

Results

The data from the study indicated that the positive test rate, infection rate, and mortality rate in the population were 1.84% [+0.11/-0.39 of 95% confidence interval (CI)], 1.54% (+0.38/-0.52 of CI), and 1.59% (+0.4/-0.7 of CI), respectively. Highest percentage of mortality was observed in Riyadh (17%), followed by Jeddah (8.7%) and Makkah (7.5%). The DALYs/100,000 inhabitants increased progressively as the age of the population increased, and the highest value was found for those over 70 years old (25.73 ± 2.09). Similarly, the risk outcome (55%) increased significantly (p = 0.037) from 40 years onwards, and the maximum was observed at above 70 years (184%, p = 0.006). The correlation analysis indicated a significant association (p = 0.032) between age and COVID-19 induced mortality from the 40-year-old population onwards.

Conclusion

The current study found that the COVID-19 load in Saudi Arabia was comparable to that in nations that were said to have performed well during the pandemic. DALYs increased from 40 years to 60 years, although people over 60 years had a lower life expectancy and were more susceptible to infection. After 60 years, the occurrence of numerous co-morbid illnesses may have added to the population's burden of COVID-19. Further research in this area may yield a more precise estimate of the COVID-19-induced burden on the entire population.

[Transition of morbidity and mortality in Brazil: a challenge on the thirtieth anniversary of the SUS]

In 2020, the 30th anniversary of the publication of the Organic Laws of the Unified Health System was celebrated. Since then, the change in the profile of morbidity and mortality has been a challenge to management to ensure that the health services can attend the significant heterogeneity of approximately 6,000 municipalities. To achieve this, it is necessary to monitor the leading indicators of the country. The scope of this study was to present an overview of trends in mortality and morbidity in Brazil between 1990 and 2019. Data from the Study on the Global Burden of Disease was used to describe morbidity and mortality by major groupings (infectious diseases, chronic diseases, and external causes), according to gender and age groups. There was a reduction in morbidity and mortality in the period, irrespective of the cause or age group, albeit with a varied difference between the sexes depending on the cause. The contribution of chronic diseases increases with age, with a marked difference according to gender. The curves for mortality and years lost due to disability have a typical profile, with a different pattern of curves for men due to external causes, with marked excess mortality at young ages. The trend confirms the decline of indicators in a linear manner over the period.

Quantitative microbial risk assessment of bioaerosols in a wastewater treatment plant by using two aeration modes

Nonnegligible emission of bioaerosols usually occurs during aeration of wastewater in aerator tanks in wastewater treatment plants (WWTPs). Literature had shown that the respiratory and intestinal diseases of workers at WWTPs are related to bioaerosols. Thus, quantitative microbial risk assessment (QMRA) based on Monte Carlo simulation was utilized in this research to assess the health risks of Gram-negative bacteria bioaerosol (GNBB) and Staphylococcus aureus bioaerosol (SAB) among academic visitors and staffs. Results showed that the concentrations of GNBB and SAB in the inverted umbrella aeration mode were consistently higher than those in the microporous aeration mode under all six size distribution ranges of the Anderson six-stage impactor. Thus, GNBB and SAB can be highly threatening to the weasand and first bronchus (or alveoli and third bronchus) for the exposure populations. The health risks (annual probability of infection (P_y) and disease burden (DB)) of males were constantly higher than those of females for each certain exposure scenario. The health risks of staffs were higher than those of academic visitors when assessed by Monte Carlo simulation. The wearing of mask is an effective measure to minimize health risks through reducing the bioaerosol concentration intake. Especially, for the academic visitors and staffs exposed to GNBB, all their DB failed to meet the World Health Organization DB benchmark under various credible intervals when they were without a mask on. In a word, the results of health risk assessment in this research can be utilized as an educational tool and policy basis to facilitate the implementation of efficacious prevention measures to protect the public health from bioaerosol health threats in WWTPs.

Burden of disease at the same limit of exposure to airborne polycyclic aromatic hydrocarbons varies significantly across countries depending on the gap in longevity

Atmospheric polycyclic aromatic hydrocarbons (PAHs) disproportionately affect human health across the globe, and differential exposure is believed to drive the unequal health burden. Therefore, this study assessed and compared the burden of disease, in disability-adjusted life years (DALYs), at the same level (or limit) of exposure to atmospheric PAHs in nine countries. We calculated the DALYs per person-year per ng/m³ of benzo[a]pyrene from ten cancers and thirty-four non-cancer adverse outcomes using published toxicity information and country-specific disease severity. Exposure duration was averaged over 30 years and we adjusted for early-life vulnerability to cancer. The DALYs per person-year per ng/m³ of fifteen other individual PAHs was calculated using relative potency factors, and toxicity factors derived from quantitative structure-activity relationships. We found that even at the same level of exposure to PAHs, the incremental burdens of disease varied substantially across countries. For instance, they varied by about 2-3 folds between Nigeria and the USA. Countries having the lowest longevity had the highest DALYs per person-year per ng/m³ of each PAH. Kruskal-Wallis test (α = 0.05) showed that the variation across countries was significant. The post hoc tests detected a significant difference between two countries when the gap in longevity was >10 years. This suggests that countries having very low average life expectancy require more stringent PAH limit. Linear or exponential function of average longevity gave valid approximation of the DALYs per person-year per ng/m³ of benzo[a]pyrene or phenanthrene, respectively. Furthermore, we used global gridded surface benzo[a]pyrene concentrations and global population dataset for 2007, with spatial resolution of 0.1° × 0.1°, to calculate the contribution of differential exposures to the estimated DALYs per person-year. We found that in six out of nine countries, differential exposures to PAH contribute less to the estimated health loss than differential severities of the diseases. This indicates that the risk to health from PAHs may be underreported if the severities of the diseases in the countries are not considered.

Quantitative microbial risk assessment of Legionella pneumophila in a drinking water supply system in Israel

Legionella pneumophila cause human infections via inhalation of contaminated water aerosols, resulting in severe pneumonia. Legionella spp. prevalence was monitored in a drinking-water distribution system (DWDS) in Northern Israel. Five points (toilet faucets and showers) were sampled seasonally along a three years period. Toilet faucets and shower use, both generating aerosols, are known transmission routes for this pathogen and thus, present a potential health risk. Quantitative Microbial Risk Assessment (QMRA) was applied in order to assess the health risks posed by Legionella for these two exposure scenarios, while considering Legionella seasonality. The obtained results were compared with estimated tolerable risk levels of infection and of disease set by the USEPA and WHO. Both limits were expressed as Disability-Adjusted Life Years index (DALY) being 1 × 10^-4 and 1 × 10^-6, respectively. The QMRA revealed that the annual risk levels for both faucets and showers use exceeded the acceptable risk of infection with an average of 5.52 × 10^-4 and 2.37 × 10^-3 DALY'S per person per year, respectively. Annual risk levels were stable with no significant differences between the three years. Risk levels varied significantly between seasons by up to three orders of magnitude. Risk levels were highest during summer, autumn, and lowest during winter. The highest seasonal infection risk values were found in summer for both faucets and showers, which corresponded to 8.09 × 10^-4 and 2.75 × 10^-3 DALY'S per person per year, respectively. In conclusion, during summer and autumn there is a significant increase of the infection risk associated with exposure to Legionella-contaminated aerosols, in the studied water system. Public health assessment and prevention measures should focus on these seasons.

A Bayesian generalized log-normal model to dynamically evaluate the distribution of pesticide residues in soil associated with population health risks

Exploring better models for evaluating the distribution of pesticide residues in soil and sediment is necessary to assess and avoid population health risk. Frequentist philosophy and probability are widely used in many studies to apply a log-normal distribution associated with the maximum likelihood estimation, which assumes fixed parameters and relies on a large sample size for long-run frequency. However, frequentist probability might not be suitable for analyzing pesticide residue distribution, whose parameters are affected by many complex factors and should be treated as unfixed. This study aimed to implement a Bayesian generalized log-normal (GLN) model to better understand the distribution of pesticide residues in soil and quantify population risks. The Bayesian GLN model, including location, scale, and shape parameters, was applied for the first time to dynamically evaluate pesticide residue distribution in soil and sediments. In addition, a comprehensive human health risk assessment of exposure to lindane via soil was conducted using the lifetime cancer risk for carcinogenic effect, margin of exposure for non-carcinogenic effect, and disability-adjusted life year for health damage. The Bayesian posterior analysis results indicated that the distribution of the concentration of some pesticide was better fitted to a log-Laplace (e.g., the mode value of shape parameter for lindane is 1.079) or showed mixtures of distributions within the family of log-normal distributions (e.g., the mode value of shape parameter for p,p'-DDE is 2.395), which can better explain the long-tail phenomenon of pesticide residue distribution and dynamically evaluate distribution models. For lindane, the 95% uncertainty bounds on the 95th percentile computed from 95% highest probability density regions (credible intervals) of three parameters by using the Bayesian p-box method were [2.063, 1558.609] ng/g, which is several orders of magnitude larger than the computed frequentist 95% confidence interval of [4.690, 8.095] ng/g and indicates that the population could have cancer risk concerns. These uncertainty analysis results from the Bayesian GLN approach indicated a larger variation of Lindane soil residues, which might reflect the complex and unpredictable mechanism of pesticide residue distribution including both unfixed models and distribution parameters. In summary, Bayesian GLN model is more flexible for the dynamic evaluation of pesticide soil residue distribution, retains posteriors for future data analysis, and could better quantify the uncertainties in population health risks. Therefore, this study can provide a novel and dynamical perspective of pesticide residue distribution and help better quantify health risks.

Quantitative microbial risk assessment of Greywater on-site reuse

Recycle domestic greywater for on-site non-potable uses can lessen the demand on potable water and the burden on wastewater treatment plants. However, lack of studies to assess health risk associated with such practices has hindered their popularity. A Quantitative Microbial Risk Assessment was conducted to estimate the public health risks for two greywater reuse scenarios: toilet flushing and food-crop irrigation. Household greywater quality from three sources (bathroom, laundry and kitchen) was analyzed. Mathematical exposure rates of different scenarios were established based on human behavior using Monte-Carlo simulation. The results showed that, greywater from all three household sources could be safely used for toilet flushing after a simple treatment of microfiltration. The median range of annual infection risk was 8.8 × 10-15-8.3 × 10-11 per-person-per-year (pppy); and the median range of disease burden was 7.6 × 10-19-7.3 × 10-15 disability-adjusted life years (DALYs) pppy. In food-crop irrigation scenario, the annual infection risks and disease burdens of treated greywater from bathroom and laundry (2.8 × 10-8, 4.9 × 10-8 pppy; 2.3 × 10-12-4.2 × 10-12 DALYs pppy) were within the acceptable levels of U.S. EPA annual infection risk (≤10-4 pppy) and WHO disease burden (≤10-6 DALYs pppy) benchmarks, while kitchen greywater was not suitable for food-crop irrigation (4.9 × 10-6 pppy; 4.3 × 10-10 DALYs pppy) based on these benchmarks. The model uncertainties were discussed, which suggests that a more accurate risk estimation requires improvements on data collection and model refinement.

Why Public Health Researchers Should Consider Using Disability Data from the American Community Survey

The United States (US) federal government allocates hundreds of billions of dollars to provide resources to Americans with disabilities, older adults, and the poor. The American Community Survey (ACS) influences the distribution of those resources. The specific aim of the project is to introduce health researchers to Public Use Microdata Sample file from 2009 to 2011. The overall goal of our paper is to promote the use of ACS data relevant to disability status. This study provides prevalence estimates of three disability related items for the population at or over the age of 15 years who reside in one of the continental states. When population weights are applied to the 7,198,221 individuals in the sample under analysis, they are said to represent 239,641,088 of their counterparts in the US population. Detailed tabulations by state (provided as Microsoft Excel® spreadsheets in ACS output) clearly show disability prevalence varies from state-to-state. Because analyses of the ACS data have the ability to influence resources aiding individuals with physical mobility challenges, its use should be promoted. Particular attention should be given to monetary allocations which will improve accessibility of the existing built environment for the individuals with mobility impairment.

Greywater reuse - Assessment of the health risk induced by Legionella pneumophila

Greywater (GW), domestic wastewater excluding the streams generated by toilets and kitchens, can serve as an alternative water source. The main options for GW reuse are toilet flushing and garden irrigation, both generating aerosols. These may transmit inhalable pathogens like Legionella and present a potential health risk. This study quantified the health risk that may arise from inhalation of Legionella-contaminated aerosols due to non-potable GW reuse. Data on Legionella concentrations in potable water and GW was collected. Then, Quantitative Microbial Risk Assessment (QMRA) was performed for two possible exposure scenarios: garden irrigation and toilet flushing. This was performed while considering Legionella seasonality. In order to determine the safety of GW reuse regarding Legionella transmission, the obtained results were compared with estimated tolerable risk levels of infection and of disease. Both limits were expressed as Disability-Adjusted Life Years index (DALY) being 10^-4 and 10^-5, respectively. The QMRA revealed that the annual risk associated with reuse of treated and chlorinated GW for garden irrigation and toilet flushing was not significantly higher than the risk associated with using potable water for the same two purposes. In all studied scenarios, the health risk stemming from reusing treated and chlorinated GW was acceptable regarding Legionella infection. In contrast, reuse of untreated or treated but unchlorinated GW should not be practiced, as these are associated with significantly higher health risks.

Microbial health-based targets for drinking water: current state and Australian case study

Through the avoidance of a substantial health burden globally, access to safe drinking water is an important foundation of public health1. An emerging development in this regard is the use of public health metrics, such as disability-adjusted life years, to inform water safety planning2. This paper examines the hypothesis that confidence in the protection of public health, on the part of water suppliers, health regulators, and ultimately consumers is strengthened through the implementation of a health outcome target for the microbial safety of drinking water. A case study demonstrating the implementation of the target is presented.

Disability-Adjusted Life Years for Maternal, Neonatal, and Nutritional Disorders in Korea

Maternal and child health is an important issue throughout the world. Given their impact on maternal and child health, nutritional issues need to be carefully addressed. Accordingly, the effect of maternal, child, and nutritional disorders on disability-adjusted life years (DALYs) should be calculated. The present study used DALYs to estimate the burden of disease of maternal, neonatal, and nutritional disorders in the Korean population in 2012. For this purpose, we used claim data of the Korean National Health Insurance Service, DisMod II, and death data of the Statistics Korea and adhered to incidence-based DALY estimation methodology. The total DALYs per 100,000 population were 376 in maternal disorders, 64 in neonatal disorders, and 58 in nutritional deficiencies. The leading causes of DALYs were abortion in maternal disorders, preterm birth complications in neonatal disorders, and iron-deficiency anemia in nutritional deficiencies. Our findings shed light on the considerable burden of maternal, neonatal, and nutritional conditions, emphasizing the need for health care policies that can reduce morbidity and mortality.

Technical aspects of using human adenovirus as a viral water quality indicator

Despite dramatic improvements in water treatment technologies in developed countries, waterborne viruses are still associated with many of cases of illness each year. These illnesses include gastroenteritis, meningitis, encephalitis, and respiratory infections. Importantly, outbreaks of viral disease from waters deemed compliant from bacterial indicator testing still occur, which highlights the need to monitor the virological quality of water. Human adenoviruses are often used as a viral indicator of water quality (faecal contamination), as this pathogen has high UV-resistance and is prevalent in untreated domestic wastewater all year round, unlike enteroviruses and noroviruses that are often only detected in certain seasons. Standard methods for recovering and measuring adenovirus numbers in water are lacking, and there are many variations in published methods. Since viral numbers are likely under-estimated when optimal methods are not used, a comprehensive review of these methods is both timely and important. This review critically evaluates how estimates of adenovirus numbers in water are impacted by technical manipulations, such as during adenovirus concentration and detection (including culturing and polymerase-chain reaction). An understanding of the implications of these issues is fundamental to obtaining reliable estimation of adenovirus numbers in water. Reliable estimation of HAdV numbers is critical to enable improved monitoring of the efficacy of water treatment processes, accurate quantitative microbial risk assessment, and to ensure microbiological safety of water.

Assessment of Burden of Malaria in Gwanda District, Zimbabwe, Using the Disability Adjusted Life Years

Malaria is one of the highest contributors to morbidity and mortality in Zimbabwe. However, there is paucity of knowledge regarding disability adjusted life years (DALYs) as a measure of burden of malaria in affected communities. The DALYs metric was used to assess the burden of malaria in Gwanda District with the aim of contributing to a better understanding of the impact of disease on affected communities. Data was collected from health facility malaria registers and the District Health Information System (DHIS) to estimate DALYs at household and district levels respectively. The household DALYs included 130 malaria cases from 2013 to 2015 while the DALYs for the district included 719 confirmed malaria cases from 2011 to 2015. Households lost a total of 153.89 DALYs with the majority of the disease burden (65.55%) occurring in the most economically productive age group (15-45 years) with a mean loss of 1.18 DALYs per malaria case. At district level, 251.09 DALYs were lost due to malaria and the calculated average district DALY rate for 2011-2015 was 36.29 DALYs/100,000 persons per year. It is important to estimate malaria burden to assist policy makers in making informed decisions when channelling resources for control and prevention of the disease.

Evolution of regulatory targets for drinking water quality

The last century has been marked by major advances in the understanding of microbial disease risks from water supplies and significant changes in expectations of drinking water safety. The focus of drinking water quality regulation has moved progressively from simple prevention of detectable waterborne outbreaks towards adoption of health-based targets that aim to reduce infection and disease to a level well below detection limits at the community level. This review outlines the changes in understanding of community disease and waterborne risks that prompted development of these targets, and also describes their underlying assumptions and current context. Issues regarding the appropriateness of selected target values, and how continuing changes in knowledge and practice may influence their evolution, are also discussed.

Reevaluation of health risk benchmark for sustainable water practice through risk analysis of rooftop-harvested rainwater

Health risk concerns associated with household use of rooftop-harvested rainwater (HRW) constitute one of the main impediments to exploit the benefits of rainwater harvesting in the United States. However, the benchmark based on the U.S. EPA acceptable annual infection risk level of ≤1 case per 10,000 persons per year (≤10(-4) pppy) developed to aid drinking water regulations may be unnecessarily stringent for sustainable water practice. In this study, we challenge the current risk benchmark by quantifying the potential microbial risk associated with consumption of HRW-irrigated home produce and comparing it against the current risk benchmark. Microbial pathogen data for HRW and exposure rates reported in literature are applied to assess the potential microbial risk posed to household consumers of their homegrown produce. A Quantitative Microbial Risk Assessment (QMRA) model based on worst-case scenario (e.g. overhead irrigation, no pathogen inactivation) is applied to three crops that are most popular among home gardeners (lettuce, cucumbers, and tomatoes) and commonly consumed raw. The infection risks of household consumers attributed to consumption of these home produce vary with the type of produce. The lettuce presents the highest risk, which is followed by tomato and cucumber, respectively. Results show that the 95th percentile values of infection risk per intake event of home produce are one to three orders of magnitude (10(-7) to 10(-5)) lower than U.S. EPA risk benchmark (≤10(-4) pppy). However, annual infection risks under the same scenario (multiple intake events in a year) are very likely to exceed the risk benchmark by one order of magnitude in some cases. Estimated 95th percentile values of the annual risk are in the 10(-4) to 10(-3) pppy range, which are still lower than the 10(-3) to 10(-1) pppy risk range of reclaimed water irrigated produce estimated in comparable studies. We further discuss the desirability of HRW for irrigating home produce based on the relative risk of HRW to reclaimed wastewater for irrigation of food crops. The appropriateness of the ≤10(-4) pppy risk benchmark for assessing safety level of HRW-irrigated fresh produce is questioned by considering the assumptions made for the QMRA model. Consequently, the need of an updated approach to assess appropriateness of sustainable water practice for making guidelines and policies is proposed.