Applying Quantitative Microbial Risk Assessment Model in Developing Appropriate Standards for Irrigation Water

Abstract

This study aimed to apply a quantitative microbial risk assessment (QMRA) model to estimate the annual risk probability of Salmonella infection associated with the consumption of crops, which were irrigated with raw wastewater abstracted by farmers without official permission. Data generated from the model were used to propose realistic standards for Salmonella in irrigation water needed for safe crop production. Results demonstrated the presence of total coliforms, fecal coliforms, fecal streptococci, and Salmonella in wastewater samples. Salmonella was recorded on lettuce and spinach in 3 different harvesting events, although it was not found in data obtained for parsley plant. The QMRA scenario included surface irrigation, consumption of raw crops, and 1-day withholding period before harvest. The annual risk probability of Salmonella infection for consumers exceeded the target tolerable risk (7.7 × 10 −4 ) for investigated crops. The Pearson's correlation coefficient between different annual risk probabilities showed significant correlation (p < 0.05). The levels of risk posed from spinach and lettuce were roughly similar, although they tended to be higher for lettuce. The optimum concentrations of Salmonella in irrigation water needed to satisfy the World Health Organization guidelines of disease burden (disabilityadjusted life years 10 −6 ) per person per year ranged from 34 to 119 via multiple-tube fermentation technique/100 mL, for spinach and lettuce plants, respectively. The study concluded that unofficial reuse of wastewater in irrigation is a principle route for crop contamination. Water quality monitoring programs should be integrated with QMRA investigations for better estimation of risk level. The fit parameters used could be tailored to cover a wide array of local situations in different countries. Models applied for viruses, helminths, and bacteria other than Salmonella are encouraged in future studies. Integr Environ Assess Manag 2020;16:353-361. © 2019 SETAC

Sanitation By-Products Used for Lettuce (&lt;i&gt;Lactuca sativa&lt;/i&gt; L.) Production: Quantitative Microbial Risk Assessment

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“…Additionally, highest levels of bacterial contamination recorded to lettuce are probably as a result of increased D. Sangare et al surface area of leaves exposed to polluted irrigation water and soil (Ceuppens et al, 2014). Moreover, several studies reported that the highest risk of infection for lettuce than the raw consumption of other vegetables (Amha et al, 2015;Ezzat, 2019). In addition to the use of untreated greywater and the consumption of lettuce irrigated with untreated greywater, the contamination of soils has been…”

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Detection of SARS-CoV-2 RNA on contact surfaces within shared sanitation facilities

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