Health risk assessment along wastewater recovery and reuse systems in Kampala, Uganda and Hanoi, Vietnam

Background: Reuse and recovery of wastewater in agriculture and aquaculture has gained traction in the new millennium. In view of continued population growth, increasing scarcity of freshwater and other natural resources, the demand to boost food production and efforts to enhance wastewater reuse will increase in the years to come. Indeed, wastewater reuse and the recovery of water, nutrients and energy can generate promising business opportunities and support livelihoods in poor communities, particularly in urban and peri-urban areas of low- and middle-income countries (LMICs). Contact with untreated wastewater is associated with microbial and chemical hazards and thus might negatively affect human health. Standardised, quality-controlled methods to assess and manage health risks are available, such as those described in the World Health Organization (WHO) guidelines for the safe use of wastewater, excreta and greywater. However, the practicability and uptake of these methods have proved difficult in LMICs. There is a paucity of context-specific, quality-based environmental pollution data, epidemiological data and accurate disease burden estimates for highly dynamic environments along wastewater recovery and reuse systems in major urban settings, especially in Africa, Asia and Latin America. Moreover, discharge thresholds and health-based targets need to be reviewed to match the realities of LMICs. Objectives: This PhD thesis aims to generate evidence of health risks among people living and working along wastewater and faecal sludge management and reuse systems in Kampala, Uganda, a low-income African city, and in Hanoi, Vietnam, a lower-middle-income Asian city. By comparing relevant conditions in these two systems, the thesis seeks to: (i) generate evidence on microbial and chemical contamination and treatment capacities along wastewater management systems; (ii) assess prevalence and risk factors of intestinal parasitic infections in different population groups exposed to wastewater and faecal sludge; (iii) estimate the burden of gastrointestinal infections due to the exposure to wastewater; and (iv) discuss and compare risk assessment approaches and their potential for application along wastewater recovery reuse systems in selected LMICs. Research partnership: This PhD thesis is embedded in the “Resource Recovery and Reuse” (RRR) project, funded by the Swiss Agency for Development and Cooperation (SDC). Our main partner in this collaborating endeavour is WHO, while other international partners include the International Water Management Institute, the International Centre for Water Management Services, and the Department of Water and Sanitation in Developing Countries, Swiss Federal Institute of Aquatic Science and Technology. In Uganda, we closely work with the Makerere School of Public Health, the Vector Control Division of the Ministry of Health and the National Water and Sewerage Corporation. In Hanoi, our main partner is the Center for Public Health and Ecosystem Research at Hanoi School of Public Health. Moreover, we closely work with the Department of Parasitology at the National Institute of Malaria, Parasitology and Entomology, the National Institute of Hygiene and Epidemiology, and the National Institute of Veterinary Research. Methods: Two accordant case studies were carried out along the major wastewater recovery and reuse systems in Kampala (along the Nakivubo channel) between September and December 2013 and in Hanoi (along the To Lich River) between April and June 2014. A methodological triangulation was performed, including (i) an environmental assessment; (ii) a cross-sectional survey; and (iii) a quantitative microbial risk assessment (QMRA). In brief, the environmental assessment entailed different standard analyses to observe the variance of microbial contamination (thermotolerant coliforms (TTC), Escherichia coli, Salmonella spp. and helminths (e.g. Ascaris and hookworm eggs) in water at critical control points over a period of two months. In addition, in Kampala, a range of physico-chemical parameters and heavy metal contamination in sediment, soil and plants were measured. Cross-sectional parasitological surveys were conducted to assess intestinal parasitic infections in different population groups (aged ≥18 years) exposed to wastewater and faecal sludge such as sanitation workers, urban farmers and community members living in proximity to wastewater channels. Moreover, comparison groups without exposure to wastewater were included. Stool samples were subjected to the Kato-Katz and formalin-ether concentration methods for the diagnosis of helminth and intestinal protozoa infections. A questionnaire was administered to all participants to identify self-reported signs and symptoms and risk factors for intestinal parasite infections. The QMRA methodology was applied to different scenarios of exposure to wastewater (e.g. farming, flooding of living area, living in informal communities and swimming). Pathogenic strains of norovirus, rotavirus, Campylobacter spp., pathogenic E. coli, pathogenic Salmonella spp., Cryptosporidium spp. and Ascaris lumbricoides were used to estimate annual incidence of gastrointestinal illness and the resulting disease burden. Results: The environmental assessment revealed high concentrations of bacteria along the major wastewater channels in Kampala and Hanoi (e.g. between 105 and 107 colony forming unit (CFU) per 100 mL). In Kampala, along the Nakivubo channel, the concentration of TTC, biological oxygen demand5 (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS) were 2- to 3-fold higher, when compared with data reported in 2008. Moreover, contamination of bacteria measured in water of the Nakivubo wetland, where urban farming takes place, was above national discharge standards and WHO’s tolerable safety limits for unrestricted irrigation. In Hanoi, the To Lich River water used in wastewater-fed agriculture fields in peri-urban areas showed (beside applied treatment in retention ponds) mean contamination with total coliforms (TC), E. coli and Salmonella spp. of 1.3 × 107, 1.1 × 106 CFU/100 mL and 108 most probable number (MPN)/100 mL, respectively. These values are 110-fold above the Vietnam discharge limits for agriculture reuse and even 260-fold above WHO’s tolerable safety limits for unrestricted irrigation. In both cities, the issue of faecal sludge collection is challenged by the provision of formal and adequate collection services, disposal and reuse solutions. Moreover, industrial pollution is a major issue, while registration and the source control of industries and effluents is lacking, leading to elevated concentration of various heavy metals in the environment. The cross-sectional survey in Kampala included 915 individuals and revealed that the highest point-prevalence of intestinal parasite infections was found among urban farmers (75.9%), whereas the lowest point-prevalence was found among workers collecting faecal sludge (35.8%). Hookworm was the predominant helminth species (27.8%). Trichuris trichiura, Schistosoma mansoni, A. lumbricoides, and Entamoeba histolytica/E. dispar showed prevalence rates of 15% and above among urban farmers. For all investigated parasite infections, we found significantly higher odds for urban farmers than for the other groups (adjusted odds ratios ranging between 1.6 and 12.9). In Hanoi, the cross-sectional survey included 681 individuals and showed lower point-prevalence rates of intestinal parasite infections than in Kampala. The highest point-prevalence rate of parasitic infection was found among rural farmers (30.2%), with hookworm and T. trichiura being the predominant helminth species (24.8% and 5.4%, respectively). For intestinal parasite infections, we found significantly higher odds for rural farmers than for other groups (adjusted odds ratios 5.8, 95% confidence interval 2.5 to 13.7). For Kampala, the QMRA estimated an annual disease burden across all 18,204 exposed people of 304,3 disability-adjusted life years (DALYs). Disease burden per person per year (pppy) was highest among urban farmers, sanitation workers and children in slum communities (0.073, 0.040 and 0.017 DALYs, respectively). For Hanoi, QMRA estimated an annual disease burden across 7,125 exposed people of 62.7 DALYs. Disease burden pppy was highest in urban farmers (0.0122 DALYs pppy), followed by sanitation workers (0.006 DALYs pppy) and rural farmers (0.0004 DALYs pppy). Conclusions: The findings from this 3-year PhD thesis make an important contribution for a deeper understanding of the nexus of urban wastewater recovery and reuse systems, wastewater pollution and their implications for public health in the context of a major East African and Southeast Asian city. In both cities, and besides considerable differences in applied infrastructures, wastewater treatment capacities are insufficient for reducing the levels of microbial and chemical contamination to tolerable levels that would allow for safe reuse in agriculture. Major health risks were observed along both wastewater recovery and reuse systems. Children living in informal communities in Kampala are at very high risk of gastrointestinal diseases, especially due to rotavirus, and pathogenic E. coli and Salmonella spp. Epidemiological survey estimates revealed that urban farmers using wastewater were especially vulnerable for schistosomiasis and soil-transmitted helminthiasis in Kampala, whereas the high risk for urban farmers in Hanoi was only evident by means of QMRA. Indeed, for urban farmers, QMRA estimates were as high as 0.073 and 0.011 DALYs pppy in Kampala and Hanoi, respectively. These estimates are several thousand-fold above the revised WHO health-based targets and 7 and 6 times higher than the estimates made by the Global Burden of Disease study 2010 for an average Ugandan and Vietnamese, respectively. It is argued that the current health-based targets should be set according to local reference levels (e.g. to estimates made by the Global Burden of Disease study 2010). Promoting sanitation safety planning while combining evidence generated from environmental surveys, epidemiological surveys and QMRA can contribute to the understanding of existing systems and hazards along critical control points to better evaluate further investments in infrastructure and coordinate actions to protect public health. Considering the increasing attention to wastewater in the framework of the sustainable development goals (SDGs), more integrated studies using sanitation safety planning approaches are needed to generate sufficient understanding of reuse situations in rapidly changing urban contexts to minimise detrimental health effects and maximise gains from the recovered water, nutrients and energy in urban areas of LMICs

Interventions to reduce pesticide exposure from the agricultural sector in Africa: A workshop report

Despite the fact that several cases of unsafe pesticide use among farmers in different parts of Africa have been documented, there is limited evidence regarding which specific interventions are effective in reducing pesticide exposure and associated risks to human health and ecology. The overall goal of the African Pesticide Intervention Project (APsent) study is to better understand ongoing research and public health activities related to interventions in Africa through the implementation of suitable target-specific situations or use contexts. A systematic review of the scientific literature on pesticide intervention studies with a focus on Africa was conducted. This was followed by a qualitative survey among stakeholders involved in pesticide research or management in the African region to learn about barriers to and promoters of successful interventions

Chapitre 11 - Modèles de transmission animaux-humains

Introduction Plus de 60 % des maladies infectieuses humaines sont imputables à des agents pathogènes communs avec les animaux (Karesh et al., 2012). Bien qu’un vaste corpus de connaissances existe sur la transmission intraspécifique des maladies infectieuses, nous en savons étonnamment peu sur la dynamique de transmission d’agents pathogènes zoonotiques entre espèces (Lloyd-Smith et al., 2009). Toutefois, pour comprendre..

Disease burden due to gastrointestinal infections among people living along the major wastewater system in Hanoi, Vietnam

Background : Despite recent improvements of wastewater treatment capacities in urban areas of Hanoi, Vietnam, microbial pollution is still considerable. There is a paucity of burden estimates due to gastrointestinal infection in people living along the wastewater system, and among people who are in direct contact with the wastewater, such as farmers using wastewater in agriculture and aquaculture. Methods : A quantitative microbial risk assessment (QMRA) was pursued focussing on four population groups characterised by different levels of exposure to wastewater: (i) workers maintaining the wastewater conveyance and treatment systems; (ii) urban farmers using wastewater from To Lich River; (iii) community members in urban areas exposed to flooding events in the districts of Hoang Mai and Thanh Tri; and (iv) peri-urban farmers in Thanh Tri district, where Red River water is used for agriculture and aquaculture. The QMRA was developed on the basis of measured concentration of Escherichia coli and Salmonella spp. and Ascaris spp. eggs in water samples. Published ratios between measured organisms and pathogenic strains of norovirus, rotavirus, Campylobacter spp., pathogenic E. coli, pathogenic Salmonella spp., Cryptosporidium spp. and Ascaris lumbricoides were employed to estimate annual risk of gastrointestinal infection and disease burden. Results : The QMRA estimated a disease burden of 0.011 disability-adjusted life years (DALYs) per person per year in urban farmers, 0.006 DALYs for sanitation workers, 0.0005 DALYs for urban communities at risk of flooding events and 0.0004 DALYs for peri-urban farmers. Urban farmers had considerably higher incidence estimates for gastrointestinal disease episodes per year (2.0) compared to the other exposure groups (≤1.0). Conclusions : Urban farmers using wastewater from To Lich River have a high gastrointestinal disease burden, which is about 100 times larger than the health-based targets for wastewater use set by the World Health Organization. These findings are of direct public health relevance and call for upgrading Hanoi's wastewater system to reduce microbial contamination. Finally, this study presents a first example on how to link QMRA to a sanitation safety planning (SSP) approach in an Asian context and its findings are interesting in the frame of Sustainable Development Goal (SDGs) #6

Variability and predictors of weekly pesticide exposure in applicators from organic, sustainable and conventional smallholder farms in Costa Rica

Estimates of pesticide exposure among applicators from low- and middle-income countries (LMICs) are scarce, and exposure assessment methods are sometimes costly or logistically unfeasible. We examined the variability in weeklong pesticide exposure among applicators in Costa Rica and its predictors.; We conducted a cross-sectional survey among 221 pesticide applicators from organic, sustainable and conventional farms in 2016. We administered structured questionnaires to assess pesticide application practices at two time points (4-6 weeks apart). We adapted an existing algorithm to fit the context of smallholders and derive weekly pesticide exposure scores. We used linear mixed-effect models to examine within-worker and between-worker score variability. We then identified sociodemographic and occupational predictors of weekly pesticide exposure scores.; We observed high within-worker and between-worker variability in weekly pesticide exposures (eg, up to 180-fold and 70-fold differences in average weekly exposures within and between workers, respectively; intraclass correlation coefficient=0.4). Applicators working on conventional and sustainable farms had exposure scores twofold and 1.5-fold higher than those working in organic farms, respectively. Farm workers who received training on pesticide use had weekly pesticide exposure scores of 33% (95% CI 1% to 55%) lower than those who did not receive any training.; In this study of applicators from smallholder farms in Costa Rica, we determined the importance of collecting questionnaire data on self-reported pesticide use repeatedly due to its high variability within workers and absence of application records. Our questionnaire-based exposure algorithm could allow the calculation of semiquantitative estimates of average pesticide exposure for applicators from other LMICs

Current use pesticides in soil and air from two agricultural sites in South Africa: Implications for environmental fate and human exposure

Concerns about the possible negative impacts of current use pesticides (CUPs) for both the environment and human health have increased worldwide. However, the knowledge on the occurrence of CUPs in soil and air and the related human exposure in Africa is limited. This study investigated the presence of 30 CUPs in soil and air at two distinct agricultural sites in South Africa and estimated the human exposure and related risks to rural residents via soil ingestion and inhalation (using hazard quotients, hazard index and relative potency factors). We collected 12 soil and 14 air samples over seven days during the main pesticide application season in 2018. All samples were extracted, purified and analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. In soils, nine CUPs were found, with chlorpyrifos, carbaryl and tebuconazole having the highest concentrations (up to 63.6, 1.10 and 0.212 ng g-1, respectively). In air, 16 CUPs were found, with carbaryl, tebuconazole and terbuthylazine having the highest levels (up to 25.0, 22.2 and 1.94 pg m-3, respectively). Spatial differences were observed between the two sites for seven CUPs in air and two in soils. A large dominance towards the particulate phase was found for almost all CUPs, which could be related to mass transport kinetics limitations (non-equilibrium) following pesticide application. The estimated daily intake via soil ingestion and inhalation of individual pesticides ranged from 0.126 fg kg-1 day-1 (isoproturon) to 14.7 ng kg-1 day-1 (chlorpyrifos). Except for chlorpyrifos, soil ingestion generally represented a minor exposure pathway compared to inhalation (i.e. <5%). The pesticide environmental exposure largely differed between the residents of the two distinct agricultural sites in terms of levels and composition. The estimated human health risks due to soil inges-tion and inhalation of pesticides were negligible although future studies should explore other relevant pathways

Quantitative assessment of multiple pesticides in silicone wristbands of children/guardian pairs living in agricultural areas in South Africa

Little is known about personal and time-integrated exposure to past and current used pesticides in agricultural areas and within-family exposure similarities. We aimed to assess exposure to pesticides using silicone wristbands in child/guardian pairs living on farms and in villages within two agricultural areas in South Africa. Using silicone wristbands, we quantified 21 pesticides in child/guardian pairs in 38 households over six days in 2018. Levels (in ng/g wristband) of pesticides and their transformation products (12 current-use pesticides and nine organochlorine pesticides) were measured using GC-MS/MS. We assessed the correlation between pesticide levels and between household members using Spearman correlation coefficients (r(s)). Multivariable generalized least squares (GLS) models, using household id as intercept, were used to determine level of agreement between household members, exposure differences between children and guardians and exposure predictors (study area, household location [farm vs. village] and household pesticide use). We detected 16 pesticides with highest detection frequencies for deltamethrin (89%), chlorpyrifos (78%), boscalid (56%), cypermethrin (55%), and p,p'-DDT (48%). Most wristbands (92%) contained two or more pesticides (median seven (range one to 12)). Children had higher concentrations than guardians for four pesticides. Correlation between the pesticide levels were in most cases moderate (rs 0.30-0.68) and stronger in children than in guardians. Five pesticides showed moderate to strong correlation between household members, with the strongest correlation for boscalid (r(s) 0.84). Exposure differences between the two agricultural areas were observed for chlorpyri fas, diazinon, pmthiofos, cypermethrin, boscalid, p,p'-DDT and p,p'-DDE and within areas for cypermethrin. We showed that for several pesticides children had higher exposure levels than guardians. The positive correlations observed for child/guardian pairs living in the same household suggest non-occupational shared exposure pathways in these communities

Prevalence of diarrhoea and risk factors among children under five years old in Mbour, Senegal: a cross-sectional study

Diarrhoeal diseases remain an important cause of mortality and morbidity among children, particularly in low- and middle-income countries. In Senegal, diarrhoea is responsible for 15% of all deaths in children under the age of five and is the third leading cause of childhood deaths. For targeted planning and implementation of prevention strategies, a context-specific understanding of the determinants of diarrhoeal diseases is needed. The aim of this study was to identify risk factors of diarrhoeal diseases in children under the age of five in Mbour, Senegal.; Between February and March 2014, a cross-sectional survey was conducted in four zones of Mbour to estimate the burden of diarrhoeal diseases (i.e. diarrhoea episodes in the 2 weeks preceding the survey) and associated risk factors. The zones covered urban central, peri-central, north peripheral and south peripheral areas. Overall, 596 households were surveyed by a questionnaire, yielding information on sociodemographic, environmental and hygiene behavioural factors. Univariable and multivariable logistic regression analyses were used to identify risk factors associated with the occurrence of diarrhoea.; The reported prevalence of diarrhoea among children under the age of five during the 2 weeks preceding the survey was 26%. Without adjustment, the highest diarrhoea prevalence rates were observed in the peri-central (44.8%) and urban central zones (36.3%). Multivariable regression revealed significant associations between diarrhoeal diseases and unemployment of mothers (adjusted odds ratio [aOR] = 1.62, 95% confidence interval [CI]: 1.18-2.23), use of open bags for storing household waste (aOR = 1.75, 95% CI: 1.00-3.02), evacuation of household waste in public streets (aOR = 2.07, 95% CI: 1.20-3.55), no treatment of stored drinking water (aOR = 1.69, 95% CI: 1.11-2.56) and use of shared toilets (aOR = 1.69, 95% CI: 1.11-2.56).; We found a high prevalence of diarrhoea in children under the age of five in Mbour, with the highest prevalence occurring in the central and peri-central areas. These findings underscore the need for public health interventions to alleviate the burden of diarrhoea among vulnerable groups. Promotion of solid waste disposal and reduction of wastewater exposure should be implemented without delay

Seasonal variations in air concentrations of 27 organochlorine pesticides (OCPs) and 25 current-use pesticides (CUPs) across three agricultural areas of South Africa

For decades pesticides have been used in agriculture, however, the occurrence of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) is poorly understood in Africa. This study investigates air concentrations of OCPs and CUPs in three South African agricultural areas, their spatial/seasonal variations and mixture profiles. Between 2017 and 2018, 54 polyurethane foam-disks passive air-samplers (PUF-PAS) were positioned in three agricultural areas of the Western Cape, producing mainly apples, table grapes and wheat. Within areas, 25 CUPs were measured at two sites (farm and village), and 27 OCPs at one site (farm). Kruskal-Wallis tests investigated area differences in OCPs concentrations, and linear mixed-effect models studied differences in CUPs concentrations between areas, sites and sampling rounds

Barriers to evidence use for sustainability: Insights from pesticide policy and practice.

Calls for supporting sustainability through more and better research rest on an incomplete understanding of scientific evidence use. We argue that a variety of barriers to a transformative impact of evidence arises from diverse actor motivations within different stages of evidence use. We abductively specify this variety in policy and practice arenas for three actor motivations (truth-seeking, sense-making, and utility-maximizing) and five stages (evidence production, uptake, influence on decisions, effects on sustainability outcomes, and feedback from outcome evaluations). Our interdisciplinary synthesis focuses on the sustainability challenge of reducing environmental and human health risks of agricultural pesticides. It identifies barriers resulting from (1) truth-seekers' desire to reduce uncertainty that is complicated by evidence gaps, (2) sense-makers' evidence needs that differ from the type of evidence available, and (3) utility-maximizers' interests that guide strategic evidence use. We outline context-specific research-policy-practice measures to increase evidence use for sustainable transformation in pesticides and beyond