key: cord-0970976-u8rc48f4 authors: Ishaq, Sadia; Sadiq, Rehan; Farooq, Shaukat; Chhipi-Shrestha, Gyan; Hewage, Kasun title: Investigating the public health risks of low impact development at residential, neighbourhood, and municipal levels date: 2020-07-06 journal: Sci Total Environ DOI: 10.1016/j.scitotenv.2020.140778 sha: 92b30500f12eda440ae50444b333f3360710fcd5 doc_id: 970976 cord_uid: u8rc48f4 Abstract Low Impact Developments (LIDs) employ a series of vegetative techniques to retain rainfall close to the origin. Although LIDs offer sustainable runoff management, these infrastructures can be considered a risk to public health due to the presence of pathogens in the runoff and human exposure to contaminated water held in and transported by LIDs. The objective of this study is to examine the disease burden from exposure to LIDs at the residential, neighbourhood, and municipal levels. The authors conducted a meta-analysis of literature on three water features: (1) harvested rainwater obtained from LIDs, (2) surface water, and (3) floodwater. A set of 32 studies were systematically selected to collect values of risks of infection and expressed as the disease burden, i.e. disability adjusted life years (DALYs). The results showed that the percentage of GI illness exceeding the health guidelines were high for harvested rainwater, i.e. 22% of annual disease burden exceeded the WHO guidelines (0.001 DALYs/1000 persons), and 2% exceeded the US EPA guidelines (5.75 DALYs/1000 bathers). Among the six exposures for harvested rainwater, exposure to spray irrigation, exceeded US EPA guidelines whereas; five exposures, i.e. flushing, hosing, daily shower, spray irrigation, and children playing, surpassed the WHO guidelines. Considering LID treatment, the values of annual disease burden from all the selected barriers were below US EPA guidelines however, these values exceeded the WHO guidelines for three barriers i.e. water plaza, grass swale, and open storage ponds. These findings provide a broader perspective of the disease burden associated with LIDs and emphasise to consider the type of exposures and required treatment barriers for developing LID infrastructures in urban areas. J o u r n a l P r e -p r o o f requires consideration and management of human exposure to runoff water and reducing public health risks. The presence of pathogenic microorganisms in runoff water has been well documented (Albrechtsen H. J., 2002; Sakamoto et al., 2009; Selvakumar and Borst, 2006; Sidhu et al., 2012; van Heijnsbergen et al., 2014) . These pathogens entering the water system belong to various sources such as animal waste, (un)treated sewage, and solid waste mixing with rainwater when it flows over the urban surfaces (Arnone and Walling, 2007; Hofstra et al., 2011) . Exposure to water-borne pathogens during domestic use of water and recreational activities can cause mild health problems (e.g. gastrointestinal, respiratory, skin, ear, and eye infection) or more severe conditions (e.g. hepatitis and meningitis) (White et al., 2010) . The occurrence of health problems incur economic burden in terms of lost productivity, visits to healthcare, hospitalization, sequelae, and mortality. For example, in the US, recreational water-borne illness is estimated to cost a substantial economic burden of approximately USD 2.9 billion/year (Deflorio-Barker et al., 2018) . Since LIDs are meant to store and transport runoff water, the presence of pathogenic microbes can influence the risk of infection and investigations are needed to compare human exposure versus occurrence of disease and identify critical factors. A substantial amount of research shows the ability of water-borne pathogens to survive on leafy greens and enter the human body during consumption (Dicaprio et al., 2012; Esseili et al., 2012; Ethelberg et al., 2010; Hirneisen and Kniel, 2013; Warriner et al., 2003) . For example, zoonotic pathogens can persist and internalize leaves of lettuce or spinach foliage due to protection from solar irradiation and desiccation (Markland, 2015) . Similarly, leguminous tree and bryophytes are associated with a large number of facultative human pathogens, including Staphylococcus, Salmonella, and J o u r n a l P r e -p r o o f 6 residential and neighbourhood levels. Surface water includes urban tributaries, rivers, and lakes, which receive runoff and are mainly used for recreational purposes (Lim et al., 2015) . Floods include rainfallgenerated surface runoff, and/or from the flooded storm sewers, which contain a variety of microbial pathogens and pose risks to public health. The process of systematic review started with the identification of scientific literature on QMRA modeling of runoff water flowing through LIDs, surface water, and floods. For this purpose, a systematic literature search was performed using four electronic databases including Science Direct, PubMed, Engineering Village, and Google Scholar. The combinations of keywords used in this search included the following: "runoff"/"rainwater"/"surface water"/"stormwater"/"floods" and "low impact development"/"green infrastructure"/"water sensitive urban design" and "quantitative microbial risk assessment"/"public health risk"/" disease burden". To identify additional records, initially identified articles were searched for forward/reverse citation. All original articles referenced in reviews were retrieved including QMRA of Water Sensitive Urban Design (WSUD) and Green Infrastructure. The initial identification of articles was followed by the removal of duplicate records. The screening of articles was performed to determine the eligibility of the articles as per inclusion-exclusion criteria (Table 1 s; supplementary document -S2). The titles and abstracts of identified articles were reviewed for the selection of relevant records and, full-text PDFs were obtained for those articles, formatted with Adobe Acrobat X Pro® for text recognition. The selected articles were imported into Mendeley library to further proceed with the data extraction and analysis. The key output of this systematic review was a collection of peer-reviewed literature on QMRA modeling of runoff water flowing through J o u r n a l P r e -p r o o f 7 From each of the selected studies, the data on risk of infection estimated via QMRA modeling was extracted by a single reviewer. In the context of this research, the details of QMRA steps are as follows. The health hazards are the water-borne pathogens i.e. virus, bacteria, and protozoa, present in urban runoff; LID infrastructures e.g. rain barrels, grass swales, biofilters; surface water; and floodwater (step 1). During exposure assessment (step 2), all processes of human-water interaction are quantitatively described through the estimation of concentration of pathogens, volume of water ingested/inhaled, and annual exposure frequency (Ahmed et al., 2010) . Once an episode of humanwater interaction occurs at any of the selected water features, water-borne pathogens transmit into human body via mouth, nose, and/or skin and may cause an infection. In the case of harvested rainwater at residential level, human-water interaction may occur when rainwater is reused during irrigation and non-potable activities, such as toilet flushing, showering, etc. Regarding surface water, human-water interaction occurs via primary and/or secondary contact activities. Primary contact activities indicate that the whole body is submerged in water (e.g. swimming, bathing, diving, water skiing, etc.) and secondary contact activities indicate that only limbs of an individual is exposed to water (e.g. boating, rowing, fishing, sailing, etc.) (Dorevitch et al., 2012) . In dose-response assessment (step 3), mathematical models specific to the type of pathogen are used to calculate the probability of infection (Chhipi-Shrestha et al., 2017) . This research covered the complete suite of water-borne pathogens responsible for GI infection and the relevant equations for estimating the probability of infection are Beta-Poisson (Eq. 1) and Exponential (Eq. 2) dose-response models. Lastly, risk characterisation (step 4) involves the integration of exposure assessment and dose-response assessment for a specific pathogen and exposure route. Typically, the risk of infection is measured for a single-event (P inf ), followed by the estimation of annual risk (P inf(A) ) over a period of one year by using an annual exposure frequency for the exposure activity under consideration (Eq. Campylobacter, and Salmonella (Haas et al., 1999) . Exponential dose-response model used for Adenovirus (Vergara et al., 2016) , Norovirus (Schmidt, 2015) , and Cryptosporidium and Giardia (Robertson et al., 2005) . where P inf represents probability of infection to an individual exposed to a single pathogen dose "d"; d is the pathogen dose; P inf(A) refers to annual probability of infection from "n" exposures/ year due to a single pathogen dose "d"; "α" and "r" are parameters referring to pathogen infectivity constant which characterise dose-response relationships; N 50 is the median infective dose, i.e., the dose required to infect 50% of the exposed population. Following data extraction, geometric mean was calculated to estimate central tendency if the data on risk of infection were available as a set of more than one value. In addition to the risk of infection values, the record of review included the details of location of the study, water feature, sampling site, pathogen prevalence, detection method, recovery efficiency, pathogen concentration, exposure assessment, and dose-response model. Based on the estimation of annual risk of infection, the annual risk of illness (P ill ) and disease burden (DALY) were calculated as follows (Eq.4 and 5): J o u r n a l P r e -p r o o f 9 where P ill|inf refers to risk of disease given infection, i.e., morbidity. For the purpose of standardisation, the data were expressed as the burden of disease i.e. DALY (Eq. 4 and 5). DALY is the estimation of the number of healthy years lost due to disease or early death of an individual; a disease with higher values of DALYs indicates unhealthy impacts whereas lower values of DALYs are beneficial for population health (Murray and Lopez, 1996) . In this research, the risk is expressed in units of DALYs/1000 persons/year. This unit provides an estimate of the risk of illness or disease cases for a population of 1000 individuals in a year and offers a more accurate comparison of the disease cases and health targets. Often, the incidence of infection has been considered as the assessment endpoint of risk but, it may lead to over or underestimation of health risk. To overcome this discrepancy, DALYs measurement was used to represent the health risks from exposure to LIDs or related infrastructures. The conversion of risk of infection into DALYs requires three conversion factors, i.e. annual exposure frequency, infection to illness ratio, and DALYs loss per disease case (Table S2 ; Supplementary document-S2). The values of these conversion factors were obtained from the literature as given in Supplementary document-S2 (Table S3 , S4 and S5, respectively). For the purpose of analysis, the health risks from exposure to surface water during primary (e.g. swimming, bathing) and secondary (e.g. rowing, sailing) recreations were assumed comparable to LIDs present in neighbourhoods and municipalities in terms of water quality, exposure type, and pathogen. The data were analyzed for the disease burden exceeding the health targets, most critical pathogens, water features, exposure activity, and age groups. Two widely recognised health risk guidelines were used to examine the risk assessment outcomes, which includes 1) the acceptable disability-adjusted life The current research presents an attempt of examining the public health risks associated with LIDs at three levels i.e. residential, neighbourhood, and municipal. At the residential level, the use of cisterns and rain tanks is a common practice to overcome water scarcity in many parts of the world such as Australia, Pakistan, and India. Similarly, in urban communities, the development of grass swales, permeable pavement, and retention ponds are considered a sustainable solution to manage rainfall and runoff close to the site of origin thus reducing pollutant loading and stormwater quantity in the drainage system (Fletcher et al., 2015) . The water management benefits of LIDs are well recognised, but the assessments of public health risks associated with these infrastructures are scarce. Water-borne pathogens are an increasing public health concern and substantial research is available on quality management of drinking water and wastewater treatment systems. This study builds upon the previous work to determine whether or not the health risks from exposure to LIDs during recreational and nonpotable activities meet public health guidelines of the WHO and US EPA. A summary of the results from a systematic review are given in Tables 1 and 2 for 1) harvested rainwater, 2) surface water, and 3) floodwater). The information on geographical location of the articles included in this review is shown in Table 1 . The data on risk of infection and burden of disease were collected from 32 articles ( J o u r n a l P r e -p r o o f 11 data were most abundant for Cryptosporidium (n=12), followed by Giardia (n= 9), and Norovirus (n= 6). Regarding floodwater, the data were obtained from five articles and, QMRA analysis was mostly performed for Cryptosporidium and Campylobacter (n=4 for each of these pathogens), followed by Giardia (n= 2). Table 1 here>> << Please insert Table 2 here>> The comparison of cumulative probability of exceedance and the annual burden of disease from exposure to the selected water features is shown in Fig. 2 . In general, the percentage of diarrheal illness exceeding the two guidelines was highest for floodwater exposures, followed by recreational exposure in surface water, and non-potable exposures to harvested rainwater. In the case of harvested rainwater, almost 22% of annualised disease burden exceeded the WHO (0.001 DALYs/1000 persons), and approximately 2% exceeded the US EPA guidelines (5.75 DALYs/1000 bathers). The results of surface water revealed that the percentage of exceedance for recreational activities in surface water was considerably high, surpassing the WHO guidelines up to 73% of the time and US EPA guidelines up to 12.3% of the time. Considering floodwater, the probability of exceeding the two health guidelines was significantly high, and approximately 87% of the dataset exceeded the WHO guidelines and 22.5% exceeded the US EPA guidelines. These findings support the fact that microbial contamination is more pronounced in floodwater and so is the likelihood of GI illness during wet weather, thus the burden of GI illness or diarrheal problems needs to be considered while developing LIDs in urban settings. Previous studies have confirmed that microbial contamination of floodwater far exceeded the acceptable levels as given in guidelines pertaining to microbial quality of recreational water (Xiao et al., 2013) whereas, the harvested rainwater was reported to exhibit a lower level of microbial contamination that lies below the health guidelines (Ahmed et al., 2010) . Floodwater impacted by J o u r n a l P r e -p r o o f animal waste and human sewage exhibited the highest likelihood of GI illness during withdrawal and the clean-up of contaminated water (Fewtrell et al., 2011) . Similarly, surface water bodies were reported to receive a high concentration of water-borne pathogens from (un)treated sewage, defecation from animals, sewer overflows which could lead to the widespread occurrence of GI illness during recreational activities (Ahmed et al., 2005; Gannon and Busse, 1989; LeChevallier et al., 1998; Noble et al., 2006; Rajal et al., 2007) . In contrast, harvested rainwater was recorded to be less polluted as the sources of microbial pollution included bird/insects droppings, leaves in the gutter, and condition of the roof, piping, and storage (Brodie et al., 2007; Evans et al., 2006; Huston et al., 2009; Lye, 2009 ). The analysis of data of floodwater and surface water presented a worst-case scenario of the disease burden of GI illness, and harvested rainwater depicted the situation of least contamination of runoff water leading to less burden of GI illness. It is important to note that these results do not provide an exact measure of the burden of GI illness from LIDs. However, broadly, one can infer that the development of LIDs may negatively affect public health in urban neighborhoods. This study covered the complete suite of pathogens that were examined in the selected literature and can cause GI illness and Legionellosis. Figure 3 summarises the total annual burden disease of water-borne pathogens from exposure to the selected water features. From exposure to harvested rainwater, the total annual burden of disease, the sum of annual disease burden from each pathogen, was 67.72 DALYs/1000 persons. The pathogen with the highest burden was Adenovirus, with an estimated value of 48.69 DALYs/1000 persons/year, followed by Campylobacter, and Rotavirus. These three top-ranking pathogens accounted for 96% of the disease burden when harvested rainwater was used for non-potable activities (Fig. 3a) . J o u r n a l P r e -p r o o f 13 Considering surface water, the total annual burden of water-borne pathogens from exposure to this water feature was 448.9 DALYs/1000 persons. The pathogen with the highest burden was Giardia, with an estimated annual value of 89.1 DALYs/1000 persons, followed by Adenovirus, and Cryptosporidium. These three top-ranking pathogens accounted for 51.2% of GI illnesses when the population was exposed to surface water through primary or secondary contact recreational activities (Fig. 3b ). Regarding floodwater, the total annual disease burden from water-borne pathogens was alarmingly high, i.e., 980.2 DALYs/1000 persons. The pathogen with the highest burden was virus, having an estimated value of 804.9 DALYs/1000 persons, followed by Cryptosporidium, and Campylobacter. These three top-ranking pathogens accounted for 95.2% of the disease burden of water-borne diseases when the population was exposed to urban floods during clean-up and withdrawal of contaminated water (Fig. 3c) . Overall, it is found that the total annual burden of disease for water-borne pathogens vary greatly across the three water features. Another important finding was that the total annual disease burden was highest for the viral pathogens, followed by protozoal and bacterial pathogens (Fig. 3) . These << Please insert Fig. 3 here>> The comparison of disease burden at individual and population level is given in Fig. 4 . For the pathogens examined within the selected water features, Rotavirus stood out for having a high impact on individual health, whereas, two bacterial pathogens, Campylobacter and Salmonella, were identified to have a high impact on population health. Overall, viruses make a large contribution to the disease burden at the individual and population level in the selected water features. For prevention-orientated management of water-borne diseases from these water features, intervention strategies must focus to manage risks from viruses, Cryptosporidium, and Giardia. For harvested rainwater at the residential level, the results of annual disease burden in relation to exposure activity and pathogens are presented in Figure 5 . At this level, the analysis of six activities showed that the disease burden from all the exposures were below US EPA guidelines ( Considering LID treatment train in the neighborhood, the value of annual disease burden was below the US EPA guidelines for the selected treatment barriers but, it exceeded the WHO guideline for three LID barriers i.e. water plaza, grass swale, and open storage ponds (Fig. 7) (an analysis of annual disease burden in relation to LID treatment train, water-borne pathogens, and exposure activity is given in Fig. 1 s; supplementary document S1). These treatment LID barriers provide desirable habitat to birds and animals, which leads to contamination of water and infects the local population (Ahmed et al., 2010; Petterson et al., 2016) . On the other hand, the rainwater from biofilters met the WHO guidelines for use in toilets, showering, and crop irrigation (Fig. 7) . Toilet flushing using non-potable water is a common practice in many parts of the world. Generally, it involves aerosolisation of human waste and vomitus and limited human-water interaction makes the use of harvested rainwater safe in toilet flushing. Similarly, the disease burden of cold shower was far below the acceptable level of WHO guidelines. But, the social acceptance of using harvested rainwater for showering is argued due to close contact of water with the human body. Since rainwater flowing in neighbourhoods may contain a high concentration of zoonotic fecal and human fecal pathogens, appropriate treatment of water depending on the level of contamination is recommended before using for showering or other activities that involve close human-water interaction. Fig. 7 here>> J o u r n a l P r e -p r o o f 17 i.e. playing in water, jump, and fall ( Fig. 8 ) (an analysis of surface water annual disease burden in relation to water-borne pathogens and exposure activity is given in Fig. 2 s; supplementary document S1). These high values of disease burden can be attributed to the level of contamination, volume of ingested water during these contacts, exposure duration, and exposure frequency. Considering floodwater, the disease burden from one exposure activity, residents' withdrawal of floodwater, surpassed US EPA guidelines. The median values of disease burden from water splash were below WHO guideline whereas, these values for three exposures were above this guideline and included floods clean-ups, splash and play, and playing in floodwater ( Fig. 9 ) (an analysis of flood-based annual disease burden from flood water in relation to water-borne pathogens and exposure activity is given in Fig. 2 s; supplementary document S1). These findings were similar to the previously observed trends in surface water and can be associated with the high microbial concentration of floodwater and longer exposure duration of these activities. Overall, the burden of GI illness in relation to age groups and three water features has shown unevenness. The inconsistency of results for the surface water and floodwater can be attributed to the lack of data as number of data points for children was less than adults in these two water features. Considering adult population, the likelihood of developing sequelae or death is higher at old ages (Dumic et al., 2019) . Also, the disease burden of immune-compromised population cannot be neglected. Further research on the role of LIDs in developing GI infection among these groups would be beneficial for appropriate stormwater management. Fig. 10 here>> This research aimed to analyze the burden of respiratory illness from Legionella. There was a lack of information and data on the risk of Legionellosis from exposure to selected water features. Only a few data points were available from previous studies on harvested rainwater, and this discrepancy limited scientific understanding of Legionellosis from exposure to LIDs and related infrastructures. From the available literature, the risk of Legionellosis was reported from three exposure activities i.e. daily showering, hose irrigation, and children play in water plaza ( Fig. 5 and 6 ). These three activities are related to the generation of aerosols and inhalation of contaminated droplets that may cause respiratory infection. Overall, the burden of disease from Legionella seems to be low but the unavailability of dataset impedes an in-depth understanding of the burden of Legionellosis. More research is necessary to draw any conclusion about the burden of Legionellosis for the population exposed to LIDs in urban neighbourhoods. Journal Pre-proof J o u r n a l P r e -p r o o f The use of LIDs is becoming increasingly popular in urban stormwater management. Considering the water management benefits of LIDs, in many developed countries, stormwater management guidelines urge the development of LIDs for quantity and quality management of urban runoff. For example, the stormwater planning guidelines of British Columbia, Canada, state that total runoff volume should be 10% of rainfall and 90% must be returned to the natural hydrological cycle through percolation, evapotranspiration, and reuse (Finnie et al., 2002) . This means permeable cover should be 90% of the total watershed area. The availability of large amount of green spaces in urban settings combined with increased water retention would possibly offer the most suitable habitat to water-borne pathogens, thus increasing the risk of GI infection and subsequent disease burden. In Rotterdam, the Netherlands, Sales-Ortells & Medema (2015) reported the Campylobacter disease burden of 0.00041 DALYs pppy (i.e. 0.258 pppy) for kids playing in water plaza (an infrastructure that combines the storage of runoff with water recreational activities). In another study, Nguyen et al., (2017) reported the Campylobacter disease burden of 0.0008 DALYs pppy for children playing in floodwater. Based on these estimates, the authors assumed that during the rainy season, the disease burden of GI illness from exposure to a LID treatment train at neighbour level (i.e. green play areas, grass swales, interactive fountains, retention ponds) for all pathogens could be approximately 50% of the disease burden from floods. Considering this assumption, Figure 11 shows the annual disease burden of GI illness for children from exposure to neighbor level LIDs treatment train and expected probability of exceedance for GI illness against WHO and US EPA guidelines. The plot revealed that the percentage of exceedance was considerably high, i.e. 90.9%, for WHO guidelines whereas, US EPA guidelines was met all the time. Therefore, it can be deduced that the development of LIDs in urban communities is associated with the likelihood of GI infections and people exposed to these infrastructures may suffer water-borne GI illness. This research is the first attempt to estimate the disease burden of GI illness and Legionellosis from exposure to LIDs at the residential, neighbourhood, and municipal levels. The authors adopted a meta-analysis methodology and estimated the public health risks of these infrastructures. The review of literature showed a dearth of QMRA modeling for LIDs at neighbourhood and municipal levels, which was overcome by including surface water and floods from rains in the review process. However, understanding the risk of infection associated with LIDs at these two levels is necessary to obtain insights into the disease burden experienced by the exposed population. This study establishes the conceptual foundation of the effects of LIDs on public health and presents a wider perspective of the disease burden from exposure to LIDs. The results revealed that the probability of GI illness exceeding the WHO and US EPA guidelines was highest for floodwater, followed by recreation in surface water, and non-potable exposures to harvested rainwater. Among the various microbes, the most critical pathogens of concern were Adenovirus, Cryptosporidium, Campylobacter, and Giardia. Considering exposure activity, the most critical exposures of concern were hosing and spray irrigation from harvested rainwater at residential and neighbourhood levels. Considering LID treatment train in the neighbourhood, the estimated disease burden met the US EPA guideline for the selected treatment barriers, but it exceeded the WHO guideline for three LID treatment alternatives, i.e. water plaza, grass swale, and open storage ponds. Within the different population groups, it was found that children could ingest a larger amount of contaminated water and suffer more severe illness from exposure to harvested rainwater. Moreover, the likelihood of developing sequelae or death is also an important concern, particularly in elderly and immune-compromised individuals. When designing J o u r n a l P r e -p r o o f 22 future LID in the urban neighborhood, it is recommended to consider the type of exposure activity and LID treatment train. In future work, this research can be extended to assess the safety of these infrastructures in urban areas using modeling tools. In the long-term, an assessment of the disease burden from exposure to LIDs under the conditions of climate change is important to identify best practices that help to reduce negative health impacts. respectively. The horizontal lines identify the exceedance rate for these two guidelines. Legend'a' describes exposure activities and Legend'b' describes LID treatments. 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Thanks are extended to Ms. Anber Rana for assistance with the charts. The authors would also like to thank the editors and anonymous reviewers for their helpful and constructive comments that greatly contributed to improving the quality of this content analysis.