Microbial risk assessment of local handling and use of human faeces

Dry urine-diverting toilets may be used in order to collect excreta for the utilisation of nutrients. A quantitative microbial risk assessment was conducted in order to evaluate the risks of transmission of infectious disease related to the local use of faeces as a fertiliser. The human exposures evaluated included accidental ingestion of small amounts of faeces, or a mixture of faeces and soil, while emptying the storage container and applying the material in the garden, during recreational stays to the garden, and during gardening. A range of pathogens representing various groups of microorganisms was considered. Results showed that 12-months' storage before use was sufficient for the inactivation of most pathogens to acceptable levels. When working or spending time in the garden the annual risk of infection by Ascaris was still slightly above 10-4 in these scenarios, although the incidence rate for Ascaris is very low in the population in question. Measures to further reduce the hygienic risks include longer storage, or treatment, of the faeces. The results can easily be extended to other regions with different incidence rates.

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Quantitative Microbial Risk Assessment Models for Consumption of Raw Vegetables Irrigated with Reclaimed Water

Applied and Environmental Microbiology ◽

10.1128/aem.72.5.3284-3290.2006 ◽

2006 ◽

Vol 72 (5) ◽

pp. 3284-3290 ◽

Cited By ~ 158

Author(s):

Andrew J. Hamilton ◽

Frank Stagnitti ◽

Robert Premier ◽

Anne-Maree Boland ◽

Glenn Hale

Keyword(s):

Risk Assessment ◽

Reclaimed Water ◽

Quantitative Microbial Risk Assessment ◽

Risk Of Infection ◽

Worst Case ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

Risk Assessment Models ◽

Crop Type ◽

Annual Risk

ABSTRACT Quantitative microbial risk assessment models for estimating the annual risk of enteric virus infection associated with consuming raw vegetables that have been overhead irrigated with nondisinfected secondary treated reclaimed water were constructed. We ran models for several different scenarios of crop type, viral concentration in effluent, and time since last irrigation event. The mean annual risk of infection was always less for cucumber than for broccoli, cabbage, or lettuce. Across the various crops, effluent qualities, and viral decay rates considered, the annual risk of infection ranged from 10−3 to 10−1 when reclaimed-water irrigation ceased 1 day before harvest and from 10−9 to 10−3 when it ceased 2 weeks before harvest. Two previously published decay coefficients were used to describe the die-off of viruses in the environment. For all combinations of crop type and effluent quality, application of the more aggressive decay coefficient led to annual risks of infection that satisfied the commonly propounded benchmark of ≤10−4, i.e., one infection or less per 10,000 people per year, providing that 14 days had elapsed since irrigation with reclaimed water. Conversely, this benchmark was not attained for any combination of crop and water quality when this withholding period was 1 day. The lower decay rate conferred markedly less protection, with broccoli and cucumber being the only crops satisfying the 10−4 standard for all water qualities after a 14-day withholding period. Sensitivity analyses on the models revealed that in nearly all cases, variation in the amount of produce consumed had the most significant effect on the total uncertainty surrounding the estimate of annual infection risk. The models presented cover what would generally be considered to be worst-case scenarios: overhead irrigation and consumption of vegetables raw. Practices such as subsurface, furrow, or drip irrigation and postharvest washing/disinfection and food preparation could substantially lower risks and need to be considered in future models, particularly for developed nations where these extra risk reduction measures are more common.

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Characterizing the Risk of Infection fromMycobacterium tuberculosisin Commercial Passenger Aircraft Using Quantitative Microbial Risk Assessment

Risk Analysis ◽

10.1111/j.1539-6924.2008.01161.x ◽

2009 ◽

Vol 29 (3) ◽

pp. 355-365 ◽

Cited By ~ 23

Author(s):

Rachael M. Jones ◽

Yoshifumi Masago ◽

Timothy Bartrand ◽

Charles N. Haas ◽

Mark Nicas ◽

...

Keyword(s):

Risk Assessment ◽

Quantitative Microbial Risk Assessment ◽

Risk Of Infection ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

Passenger Aircraft

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Application of Microbial Risk Assessment to the Development of Standards for Enteric Pathogens in Water Used To Irrigate Fresh Produce

Journal of Food Protection ◽

10.4315/0362-028x-68.5.913 ◽

2005 ◽

Vol 68 (5) ◽

pp. 913-918 ◽

Cited By ~ 103

Author(s):

SCOTT W. STINE ◽

INHONG SONG ◽

CHRISTOPHER Y. CHOI ◽

CHARLES P. GERBA

Keyword(s):

Risk Assessment ◽

Irrigation Water ◽

Fresh Produce ◽

Enteric Bacteria ◽

Irrigation Event ◽

Risk Of Infection ◽

Probable Number ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

Annual Risk

Microbial contamination of the surfaces of cantaloupe, iceberg lettuce, and bell peppers via contact with irrigation water was investigated to aid in the development of irrigation water quality standards for enteric bacteria and viruses. Furrow and subsurface drip irrigation methods were evaluated with the use of nonpathogenic surrogates, coliphage PRD1, and Escherichia coli ATCC 25922. The concentrations of hepatitis A virus (HAV) and Salmonella in irrigation water necessary to achieve a 1:10,000 annual risk of infection, the acceptable level of risk used for drinking water by the U.S. Environmental Protection Agency, were calculated with a quantitative microbial risk assessment approach. These calculations were based on the transfer of the selected nonpathogenic surrogates to fresh produce via irrigation water, as well as previously determined preharvest inactivation rates of pathogenic microorganisms on the surfaces of fresh produce. The risk of infection was found to be variable depending on type of crop, irrigation method, and days between last irrigation event and harvest. The worst-case scenario, in which produce is harvested and consumed the day after the last irrigation event and maximum exposure is assumed, indicated that concentrations of 2.5 CFU/100 ml of Salmonella and 2.5 × 10−5 most probable number per 100 ml of HAV in irrigation water would result in an annual risk of 1:10,000 when the crop was consumed. If 14 days elapsed before harvest, allowing for die-off of the pathogens, the concentrations were increased to 5.7 × 103 Salmonella per 100 ml and 9.9 × 10−3 HAV per 100 ml.

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Improved methods for modelling drinking water treatment in quantitative microbial risk assessment; a case study of Campylobacter reduction by filtration and ozonation

Journal of Water and Health ◽

10.2166/wh.2008.066 ◽

2008 ◽

Vol 6 (3) ◽

pp. 301-314 ◽

Cited By ~ 19

Author(s):

P. W. M. H. Smeets ◽

Y. J. Dullemont ◽

P. H. A. J. M. Van Gelder ◽

J. C. Van Dijk ◽

G. J. Medema

Keyword(s):

Risk Assessment ◽

Drinking Water ◽

Rare Events ◽

Monitoring Data ◽

Average Risk ◽

Quantitative Microbial Risk Assessment ◽

Risk Of Infection ◽

Microbial Risk Assessment ◽

Microbial Risk

Quantitative microbial risk assessment (QMRA) is increasingly applied to estimate drinking water safety. In QMRA the risk of infection is calculated from pathogen concentrations in drinking water, water consumption and dose response relations. Pathogen concentrations in drinking water are generally low and monitoring provides little information for QMRA. Therefore pathogen concentrations are monitored in the raw water and reduction of pathogens by treatment is modelled stochastically with Monte Carlo simulations. The method was tested in a case study with Campylobacter monitoring data of rapid sand filtration and ozonation processes. This study showed that the currently applied method did not predict the monitoring data used for validation. Consequently the risk of infection was over estimated by one order of magnitude. An improved method for model validation was developed. It combines non-parametric bootstrapping with statistical extrapolation to rare events. Evaluation of the treatment model was improved by presenting monitoring data and modelling results in CCDF graphs, which focus on the occurrence of rare events. Apart from calculating the yearly average risk of infection, the model results were presented in FN curves. This allowed for evaluation of both the distribution of risk and the uncertainty associated with the assessment.

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Quantitative microbial risk assessment used to evaluate seasonal wastewater treatment limits: case study in Vacaville, CA

Water Science & Technology Water Supply ◽

10.2166/ws.2017.162 ◽

2017 ◽

Vol 18 (3) ◽

pp. 910-925 ◽

Cited By ~ 1

Author(s):

Edmund Seto ◽

Adam W. Olivieri ◽

Richard E. Danielson

Keyword(s):

Risk Assessment ◽

Wastewater Treatment ◽

Treatment Plant ◽

Enteric Viruses ◽

Secondary Effluent ◽

Quantitative Microbial Risk Assessment ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

Annual Risk ◽

Receiving Water

Abstract A quantitative microbial risk assessment (QMRA) was conducted to support renewal of the City of Vacaville wastewater discharge permit and seasonal (summer) filtration requirements. Influent and final disinfected effluent from the city's wastewater treatment plant, as well as 11 receiving water stations, were monitored for indicator organisms (i.e. total and fecal coliforms, Escherichia coli, Enterococcus, male-specific bacteriophage (MS2), and the Bacteroidales) and several pathogens (i.e. Giardia cysts, Cryptosporidium oocysts, infectious Cryptosporidium, and Norovirus GI and GII). QMRA annualized risks of infection for selected pathogens enteric viruses, Giardia and Cryptosporidium. Estimated median annualized risk for recreational exposure in either disinfected secondary and/or filtered disinfected secondary effluent is on the order of 1.1 × 10−3 per person per year (pppy) for enteric viruses and would be roughly one order of magnitude lower if local receiving water dilution of the treatment plant effluent was taken into account. Estimated median annual risk for recreation exposure in disinfected secondary effluent is 1.8 × 10−3 pppy for Cryptosporidium and 1 log10 less with filtration during the summer months. The estimated median annual risk for landscape exposure (e.g. golfing) to secondary disinfected effluent is 7.6 × 10−7 pppy for enteric viruses. Estimated median annualized risk is 1.7 × 10−7 pppy for enteric viruses and 3.0 × 10−5 to 3.6 × 10−6 pppy for parasites for use of secondary disinfected effluent with irrigated agriculture. Estimated annualized risks for recreational exposure to the local receiving waters were approximately 10 to 1,000 times greater than direct recreational exposure to the final filtered and disinfected effluent. All risk estimates associated with exposure to final treated plant effluent (i.e. secondary filtered and disinfected) were close to or lower than the California level of acceptable annual risk of infection of 10−4 pppy for recreational exposure. Risk estimates provide further evidence to support the use of seasonal treatment limits requiring summer filtration for public health protection.

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Quantification of Giardia and Cryptosporidium in surface water: a risk assessment and molecular characterization

Water Science & Technology Water Supply ◽

10.2166/ws.2019.059 ◽

2019 ◽

Vol 19 (6) ◽

pp. 1823-1830 ◽

Cited By ~ 1

Author(s):

M. O. Bataiero ◽

R. S. Araujo ◽

A. C. Nardocci ◽

M. H. Matté ◽

M. I. Z. Sato ◽

...

Keyword(s):

Risk Assessment ◽

Positive Impact ◽

18S Rrna Gene ◽

Rrna Gene ◽

Quantitative Microbial Risk Assessment ◽

Protection Measures ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

Contaminated Drinking Water ◽

Annual Risk

Abstract This study aimed to estimate the annual probability of Giardia and Cryptosporidium infection for a population supplied by contaminated drinking water sources. Parasites were quantified by the USEPA Method 1623.1/2012. Annual risk was estimated using the quantitative microbial risk assessment (QMRA) approach. Genotyping was performed using specific primers based on the 18S rRNA gene for Cryptosporidium and gdh gene for Giardia. Giardia was detected in 83.3% of the samples (<0.1 to 8.6 cysts/L) and Cryptosporidium in 37.5% (<0.1 to 2 oocysts/L). In general, annual risk values for Giardia were 1 log higher when compared with those obtained for Cryptosporidium. Giardia intestinalis A and B were present as well as C. hominis and C. parvum. The lack of protection measures for the water supply catchment point put the population's health at risk. The results provide data to support decision-makers to take actions to improve environmental quality resulting in a positive impact on consumers' health.

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Assessment of microbial infection risks posed by ingestion of water during domestic water use and full-contact recreation in a mid-southern African region

Water Science & Technology ◽

10.2166/wst.2004.0071 ◽

2004 ◽

Vol 50 (1) ◽

pp. 301-308 ◽

Cited By ~ 27

Author(s):

M. Steyn ◽

P. Jagals ◽

B. Genthe

Keyword(s):

Risk Assessment ◽

Quantitative Microbial Risk Assessment ◽

Risk Of Infection ◽

Single Exposure ◽

Domestic Water ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

E Coli ◽

Full Contact ◽

Contact Recreation

A customised Water-related Quantitative Microbial Risk Assessment (WRQMRA) process was used to determine risk of infection to water ingested by users in the south-eastern Free State, South Africa. The WRQMRA consisted of an observed-adverse-effect-level approach (OAELA) and a quantitative microbial risk assessment (QMRA). The OAELA was based on the occurrence of E. coli in the study waters to determine the possible risk of infection and the QMRA probable risk of infection by salmonellae. The WRQMRA was applied to recreational surface resource waters as well as waters from an unprotected spring and waters from the treated municipal supply that were stored in containers for domestic purposes. E. coli numbers were measured against expected infection levels expressed in water quality guidelines, while Salmonella counts were calculated to give the probable infection risk (Pi). Ingestion was based on intake volumes compiled for the various water uses. E. coli occurred in numbers <106 in the surface waters, while the untreated spring and treated supply water contained E. coli of <102 and <101 respectively. Salmonella occurred in numbers of <103 in recreational waters, and <10-1 in water used for domestic purposes. A single exposure to the mean (as well as 95th percentile) risk was calculated using a β-Poisson dose-response model at ingestion volumes of 100 mL (for full-contact recreation) and 1,318 mL (for domestic water use). Both the OAELA and the QMRA approaches indicated a risk of infection to recreational and domestic water users, even for a single exposure event, with the OAELA either over- or under-estimating the risk of infection for singular exposure events. This indicated that this method, used on its own, could not reliably predict a realistic risk of infection. It is recommended that the full WRQMRA process be used, and further developed to address several uncertainties that became evident during this study.

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Health Risk from the Use of Roof-Harvested Rainwater in Southeast Queensland, Australia, as Potable or Nonpotable Water, Determined Using Quantitative Microbial Risk Assessment

Applied and Environmental Microbiology ◽

10.1128/aem.00944-10 ◽

2010 ◽

Vol 76 (22) ◽

pp. 7382-7391 ◽

Cited By ~ 85

Author(s):

W. Ahmed ◽

A. Vieritz ◽

A. Goonetilleke ◽

T. Gardner

Keyword(s):

Risk Assessment ◽

Monte Carlo ◽

Threshold Value ◽

Monte Carlo Analysis ◽

Daily Basis ◽

Quantitative Microbial Risk Assessment ◽

Risk Of Infection ◽

Microbial Risk Assessment ◽

Microbial Risk ◽

Southeast Queensland

ABSTRACT A total of 214 rainwater samples from 82 tanks were collected in urban Southeast Queensland (SEQ) in Australia and analyzed for the presence and numbers of zoonotic bacterial and protozoal pathogens using binary PCR and quantitative PCR (qPCR). Quantitative microbial risk assessment (QMRA) analysis was used to quantify the risk of infection associated with the exposure to potential pathogens from roof-harvested rainwater used as potable or nonpotable water. Of the 214 samples tested, 10.7%, 9.8%, 5.6%, and 0.4% were positive for the Salmonella invA, Giardia lamblia β-giardin, Legionella pneumophila mip, and Campylobacter jejuni mapA genes, respectively. Cryptosporidium parvum oocyst wall protein (COWP) could not be detected. The estimated numbers of Salmonella, G. lamblia, and L. pneumophila organisms ranged from 6.5 × 101 to 3.8 × 102 cells, 0.6 × 10° to 3.6 × 10° cysts, and 6.0 × 101 to 1.7 × 102 cells per 1,000 ml of water, respectively. Six risk scenarios were considered for exposure to Salmonella spp., G. lamblia, and L. pneumophila. For Salmonella spp. and G. lamblia, these scenarios were (i) liquid ingestion due to drinking of rainwater on a daily basis, (ii) accidental liquid ingestion due to hosing twice a week, (iii) aerosol ingestion due to showering on a daily basis, and (iv) aerosol ingestion due to hosing twice a week. For L. pneumophila, these scenarios were (i) aerosol inhalation due to showering on a daily basis and (ii) aerosol inhalation due to hosing twice a week. The risk of infection from Salmonella spp., G. lamblia, and L. pneumophila associated with the use of rainwater for showering and garden hosing was calculated to be well below the threshold value of one extra infection per 10,000 persons per year in urban SEQ. However, the risk of infection from ingesting Salmonella spp. and G. lamblia via drinking exceeded this threshold value and indicated that if undisinfected rainwater is ingested by drinking, then the incidences of the gastrointestinal diseases salmonellosis and giardiasis are expected to range from 9.8 × 10° to 5.4 × 101 (with a mean of 1.2 × 101 from Monte Carlo analysis) and from 1.0 × 101 to 6.5 × 101 cases (with a mean of 1.6 × 101 from Monte Carlo analysis) per 10,000 persons per year, respectively, in urban SEQ. Since this health risk seems higher than that expected from the reported incidences of gastroenteritis, the assumptions used to estimate these infection risks are critically examined. Nonetheless, it would seem prudent to disinfect rainwater for use as potable water.

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