Quantitative assessment of infection risk from exposure to waterborne pathogens in urban floodwater (original) (raw)
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Microbial risks associated with exposure to pathogens in contaminated urban flood water
Urban flood incidents induced by heavy rainfall in many cases entail flooding of combined sewer systems. These flood waters are likely to be contaminated and may pose potential health risks to citizens exposed to pathogens in these waters. The purpose of this study was to evaluate the microbial risk associated with sewer flooding incidents. Concentrations of Escherichia coli, intestinal enterococci and Campylobacter were measured in samples from 3 sewer flooding incidents. The results indicate faecal contamination: faecal indicator organism concentrations were similar to those found in crude sewage under high-flow conditions and Campylobacter was detected in all samples. Due to infrequent occurrence of such incidents only a small number of samples could be collected; additional data were collected from controlled flooding experiments and analyses of samples from combined sewers. The results were used for a screening-level quantitative microbial risk assessment (QMRA). Calculated annual risks values vary from 5 106 for Cryptosporidium assuming a low exposure scenario to 0.03 for Giardia assuming a high exposure scenario. The results of this screening-level risk assessment justify further research and data collection to allow more reliable quantitative assessment of health risks related to contaminated urban flood waters.
Microbial risk assessment for urban pluvial flooding
sbe.hw.ac.uk
Public health risks of urban pluvial flooding have so far received little attention in technical discussions. In this paper, the results of pathogen measurements in the sewer system of Utrecht and an urban flooding experiment are presented and used in an application of Quantitative Microbial Risk Assessment, an existing risk analysis method for the quantification of infection probabilities. This method uses ingested doses of pathogenic organisms for the calculation of infection probabilities. Ingested dose estimations are based on pathogen measurements. These samples have been analysed for concentrations of Campylobacter, Cryptosporidium and Giardia. Dose-response relations from literature are used to calculate infection probabilities for flood events. The results show that mean probabilities of obtaining a Campylobacter or Giardia infection as a result of contact with urban flood water are 2.8% and 0.6% per event respectively for adults and at least 5.7% and 1.0% per event for children, respectively. Infection probabilities for Cryptosporidium are about 1000 times lower than for Giardia. The infection probabilities found indicate that the health risk of urban flooding is higher than that of swimming in recreational freshwater environments, based on a comparison to the values for 'acceptable risk' as defined by the WHO for bathing water.
Journal of Flood Risk Management, 2011
A quantitative microbial risk assessment of flooding and gastrointestinal illness was carried out using a combination of floodwater quality data from the existing literature on pathogen concentrations in the various floodwater components, the use of microcosms to determine pathogen die-off rates in floodwaters and opportunistic sampling of actual UK floodwaters. Two flood-related scenarios were examined in a hypothetical population to provide an assessment of the likely cases of gastrointestinal illness resulting from contact with floodwater. The results of the study suggest that significant numbers of people are at risk of illness (especially from viral gastroenteritis) during the clean-up process rather than during the inundation and withdrawal phases. Additional sampling during flood events of water and sediment would strengthen the empirical policy evidence base required for estimating the severity and range of health impacts using the risk assessment methodology developed in this paper.
2019
BackgroundClimate change is expected to increase the chance of extreme rainfall events in the Northern Hemisphere and herewith, there is an increased chance of urban pluvial flooding. Urban pluvial flooding often consists of street flooding and/or flooding of combined sewerage systems, leading to contamination of the floodwater with several gastrointestinal and/or respiratory pathogens. An increase in flooding events therefore pose a health risk to those exposed to urban floodwater. We studied the association between exposure to pluvial floodwater and acute gastroenteritis (AGE) and acute respiratory infection (ARI).MethodsWe performed a retrospective, cross-sectional survey during the summer of 2015 in 60 locations in the Netherlands with reported flooding. Two weeks after the flooding, questionnaires were sent to households in these locations, collecting data on self-reported AGE and ARI and information on floodwater exposure in the previous 2 weeks. Multivariable generalized esti...
Quantification of Waterborne Pathogens and Associated Health Risks in Urban Water
Environmental Science & Technology, 2015
Citizens are exposed to microbial hazards in urban waters. To quantify health risks associated with this exposure, pathogen concentrations in an urban river, lake, rainwater sedimentation pond, a pond in a park, and a wadi, were assessed. E. coli concentrations were variable in all locations, mean values ranging between 1.2×10 2 (lake) and 1.7×10 4 (sedimentation pond) cfu (colony forming units)/100mL. High concentrations of Campylobacter were found, being the lowest in the lake (4.2×10 1 gc (genomic copies)/L) and the highest in the wadi (1.7×10 4 gc/L). Cryptosporidium was not found in any sample. Low levels of adenovirus 40/41 were found in some samples in the river (1.8×10 1 gc/L) and lake (7.2×10 0 gc/L), indicating human faecal contamination. Legionella pneumophila was found in the sedimentation pond, with higher concentrations after rain events (1.3×10 2 gc/L). Cyanochlorophyll-a was found in the lake (7.0×10-1 µg/L), the sedimentation pond (1.1×10 0 µg/L) and the pond in the park (2.9×10 1 µg/L), where low levels of microcystin were found (2.1×10 0 µg/L). Campylobacter data were used to estimate gastrointestinal risks from recreational exposure. This revealed risks above the annual disease incidence of campylobacteriosis in The Netherlands, being highest in the wadi and river. Measures are proposed to reduce the health risks.
Epidemiology and Infection, 2015
Extreme rainfall events may cause pluvial flooding, increasing the transmission of several waterborne pathogens. However, the risk of experiencing clinically overt infections following exposure to pluvial floodwater is poorly estimated. A retrospective cross-sectional survey was performed to quantify the occurrence of self-reported gastrointestinal, influenza-like illness (ILI) and dermatological complaints, and the frequency of visits to the general practitioner (GP), during a 4-week observation period following pluvial flooding at seven locations in The Netherlands. Questionnaires were sent to 817 flooded households, 149 (17%) of which returned the questionnaire reporting information for 199 participants. Contact with floodwater was significantly associated with increased occurrence of gastrointestinal [odds ratio (OR 4•44)], ILI (OR 2•75) and dermatological (OR 6•67) complaints, and GP visits (OR 2•72). Having hand contact with floodwater was associated with gastrointestinal and dermatological complaints, whereas ILI complaints were associated with being engaged in post-flooding cleaning operations and having walked/cycled through floodwater. This study shows that floodwater-associated diseases occur in urban settings following extreme rainfall events in a high-income country. As pluvial floods are expected to escalate in the future due to global climate change, further research is warranted to determine the disease burden of pluvial flooding and to assess the effect of different interventions, including raising awareness among stakeholders.
Research Square (Research Square), 2022
Flooding increases with climate variabilities and results in health risk factors in urban settings with poor sanitation infrastructure. Expert previsions highlight that by 2030, climate change and change in land-use will increase waterborne disease transmissions. However, there are few assessments of the indirect impacts of ooding, such as waterborne pathogens and zoonoses. This research aimed at assessing ooding-related disease transmission patterns in two municipalities (Abobo and Cocody) of Abidjan in Côte d'Ivoire. The study applied a cross-sectional survey with 844 households. Overall, 200 samples of rainwater from ooded households and drainage streams were collected, followed by laboratory analyses. Giardia lamblia and Vibrio cholerae spp. concentrations were assessed using the Sodium Acetate Formalin (SAF) method and the most probable number (MPN) method, respectively. Blood and urine were sampled from 129 rodents captured in households, followed by a PCR analysis to detect Leptospira species. The results show no signi cant difference detected in household exposure to ooding associated with solid waste management. In ooded households, perceived malaria symptoms and diarrhoea are associated with education (OR = 0.8, 95% CI 0.7-0.8, p = 0.001) and waste disposal (OR = 1.4, 95% CI 1.2-1.6, p = 0.001). There was no V. cholerae detected in the ood water. A total of 77 cyst/ml of Giardia lamblia were found in the ood water in Abobo. Three species of rodents were identi ed (Mus musculus, Crocidura, Rattus), and there is no Leptospira spp. detected in water, blood and urine. The presence of waterborne pathogens associated with ood water highlighted mainly faecal contamination risk. Further interventions should focus on sanitation that reduce faecal contamination.
Building Services Engineering Research and Technology, 2006
Some microorganisms can grow in water while others merely survive. The use of the water may result in the creation of aerosols which can disseminate the products of microbial growth or the microorganisms themselves. In the home, toilets, sinks and showers can provide a reservoir for microorganisms to survive and grow. Intermittent use of disinfectants alone may not be adequate to control these microorganisms unless regular cleaning and brushing is practiced. Similar problems occur in hospitals, offices and public buildings. Here control is much more important. In these environments infections can potentially spread readily to large numbers of people from the creation of aerosols both in sanitary equipment and the sewerage system associated with it. Control is helped by regular cleaning but much more attention needs to be placed on proper construction, servicing and maintenance of the infrastructure. This article reviews the types of microorganisms associated with growth in water and...
Sustainability Science, 2011
Flooding and inundation are annual events that occur during the rainy season in Cambodia, and inundation has a strong relationship with human health. This study simulated the coliform bacteria distribution using a hydraulic model and estimated the impact of inundation on public health using a dose-response model. The model parameters were calibrated using field survey data from Cambodia and obtained good agreement with the coliform group count (CGC) distribution. The results suggest that the impact of inundation on human health is most noticeable in residential areas. The annual average risk of infection during medium-sized flood events is 0.21. The risk due to groundwater use ranges from 0.12 to 0.17 in inundation areas and reaches as high as 0.23 outside the inundation areas. The risk attributed to groundwater use is therefore higher than that for surface water use (0.02-0.06), except in densely populated areas at the city center. There is a high risk for infection with waterborne disease in residential areas, and the annual average risk during small flood events is 0.94. An assessment of possible countermeasures to reduce the risk shows that the control of inundation may bring more risk to public health in Cambodia. Shallower inundation water (< 0.3m) leads to a higher risk of infection, but if the depth is greater than 2m, the risk is low in residential areas. The simulated results explain the spatial distributions of infection risk that is vitally important for determining the highest priority places with relatively high risk and will be helpful for decision makers when considering the implementation of countermeasures.