Influence of community-level sanitation coverage and population density on environmental fecal contamination and child health in a longitudinal cohort in rural Bangladesh

To use financial incentives or not? Insights from experiments in encouraging sanitation investments in four countries

We conduct a systematic re-analysis of intervention-based studies that promote hygienic latrines and evaluate via experimental methods. We impose systematic inclusion criteria to identify such studies and compile their microdata to harmonize outcome measures, covariates, and estimands across studies. We then re-analyze their data to report metrics that are consistently defined and measured across studies. We compare the relative effectiveness of different classes of interventions implemented in overlapping ways across four countries: community-level demand encouragement, sanitation subsidies, product information campaigns, and microcredit to finance product purchases. In the sample of studies meeting our inclusion criteria, interventions that offer financial benefits generally outperform information and education campaigns in increasing adoption of improved sanitation. Contrary to a policy concern about sustainability, financial incentives do not undermine usage of adopted latrines. Effects vary by share of women in the household, in both positive and negative directions, and differ little by poverty status.

A comparative life cycle analysis of Sol-Char and anaerobic digestion sanitation systems

In this study, we compared the Sol-Char sanitation system with an Anaerobic Digestion (AD) system using Life Cycle Assessment (LCA) to evaluate their environmental impacts. Since both systems offer opportunities for human waste treatment and resource recovery, understanding their performance is crucial. This comparison aims to determine their environmental impacts while considering diverse factors, such as energy production and nutrient recovery. The Sol-Char system demonstrated a superior life-cycle environmental performance, showing two to five times lower impacts in categories such as Climate Change (e.g., 127 kg CO₂-eq for the Sol-Char system while that 592 kg CO₂-eq for the AD system), Non-Renewable Energy Resources, Ionizing Radiation, Land Use, and Water Use. Both systems exhibited significant potential for resource recovery, with the Sol-Char system producing biochar and disinfected urine, and the AD system generating electricity, heat, and digestate. Updated LCA results, after byproduct application, indicated that both systems potentially have a net positive environmental impact (both with reductions exceeding -500 kg CO₂-eq per day). Nutrient recovery simulations using SAmpSONS2 revealed that the AD system performed better when utilizing multiple biomass sources. The nitrogen content in the solids was 20.25 kg/day after AD and 3.75 kg/day for the Sol-Char system. Our results highlight the Sol-Char system is a viable sanitation solution in rural areas. However, the study also identified key challenges, including the absence of uncertainty analysis and the need for a standardized framework that enables more consistent evaluations and comparisons across diverse sanitation systems and contexts.

Targeted prevention strategy: Exploring the interaction effect of environmental and social factors on infectious diseases

Human disease and health issues are globally significant and closely related to environmental and social factors. However, the interaction effects of such factors on diseases are unclear, which has resulted in a lack of targeted prevention strategies. By taking infectious diseases in China as an example, this study uses an interpretable machine learning method to analyze the impact of environmental and social factors on disease, including industrial SO2 emissions, sanitary toilet coverage rate, and sunshine duration. The modeling results confirm the existence of a nonlinear relationship between infectious diseases incidence and each of the potential factors. That is, increased SO2 emissions can increase infectious diseases incidence, whereas broad sanitary toilet coverage can reduce such risk. This study examines the interaction of the driving factors and reveals that variation in the sunshine duration can affect the impact of SO2 emissions on infectious diseases incidence. This study proposes the use of multilevel risk trigger points (RTPs) to develop early warning and targeted regulation measures and classifies the points as primary, secondary, and tertiary. For example, for Henan Province, the RTPs of SO2 emissions are 291,031, 897,579, and 1,381,342 tons, whereas those for Shandong are 362,802, 1,177,650, and 1,658,118 tons. At the tertiary RTP level, SO2 emissions can significantly increase infectious disease incidence, which has prompted policymakers to implement pollution reduction and disease prevention measures. This study clarifies the role and interaction effects of environmental and social factors on infectious diseases to aid in precise disease prevention and environmental health management.

Spatial-Temporal Patterns in the Enteric Pathogen Contamination of Soil in the Public Environments of Low- and Middle-Income Neighborhoods in Nairobi, Kenya

Public spaces in countries with limited societal development can be contaminated with feces containing pathogenic microbes from animals and people. Data on contamination levels, spatial distribution, and the diversity of enteric pathogens in the public settings of low- and middle-income neighborhoods are crucial for devising strategies that minimize the enteric infection burden. The objective of this study was to compare spatial-temporal differences in the detection rate and diversity of enteric pathogens in the public spaces of low- and middle-income neighborhoods of Nairobi, Kenya. TaqMan array card (TAC) molecular assays were employed to analyze soil samples for 19 enteropathogens, along with a selective bacterial culture for pathogenic Enterobacteriaceae. An observational assessment was conducted during every site visit to document the hygienic infrastructure and sanitation conditions at the sites. We detected at least one pathogen in 79% (127/160) and ≥2 pathogens in 67.5% (108/160) of the soil samples tested. The four most frequently detected pathogens were EAEC (67.5%), ETEC (59%), EPEC (57.5%), and STEC (31%). The detection rate (91% vs. 66%) and mean number of enteric pathogens (5 vs. 4.7) were higher in low-income Kibera than in middle-income Jericho. The more extensive spatial distribution of pathogens in Kibera resulted in increases in the detection of different enteric pathogens from within-site (area < 50 m2) and across-site (across-neighborhood) movements compared to Jericho. The pathogen detection rates fluctuated seasonally in Jericho but remained at sustained high levels in Kibera. While better neighborhood conditions were linked with lower pathogen detection rates, pathogenic E. coli remained prevalent in the public environment across both neighborhoods. Future studies should focus on identifying how the sources of pathogen contamination are modified by improved environmental sanitation and hygiene and the role of these contaminated public environments in enteric infections in children.

Performance of Pit Latrines and Their Herd Protection Against Diarrhea: A Longitudinal Cohort Study in Rural Ethiopia

In sanitation policies, "improved sanitation" is often broadly described as a goal with little rationale for the minimum standard required. We conducted a secondary analysis of data collected as part of a cluster randomized controlled trial in rural Ethiopia. We compared the performance of well-constructed and poorly constructed pit latrines in reducing child diarrhea. In addition, we explored whether having a well-constructed household latrine provides indirect protection to neighbors if cluster-level coverage reaches a certain threshold. We followed up children aged younger than 5 years (U5C) of 906 households in rural areas of the Gurage zone, Ethiopia, for 10 months after community-led total sanitation interventions. A study-improved latrine was defined as having all the following: pit of ≥2 m depth, slab of any material, drop-hole cover, wall, roof, door, and handwashing facilities (water and soap observed). U5C in households with a study-improved latrine had 54% lower odds of contracting diarrhea than those living in households with a latrine missing 1 or more of the characteristics (adjusted odds ratio [aOR]=0.46; 95% confidence interval [CI]=0.27, 0.81; P=.006). Analyses were adjusted for child age and sex, presence of improved water for drinking, and self-reported handwashing at 4 critical times. The odds of having diarrhea among those with an improved latrine based on the World Health Organization/UNICEF Joint Monitoring Program (JMP) definition (i.e., pit latrines with slabs) were not substantially different from those with a JMP-unimproved latrine (aOR=0.99; 95% CI=0.56, 1.79; P=.99). Of U5C living in households without a latrine or with a study-unimproved latrine, those in the high-coverage villages were less likely to contract diarrhea than those in low-coverage villages (aOR=0.55; 95% CI=0.35, 0.86; P=.008). We recommend that academic studies and routine program monitoring and evaluation should measure more latrine characteristics and evaluate multiple latrine categories instead of making binary comparisons only.

Persistent Ascaris Transmission Is Possible in Urban Areas Even Where Sanitation Coverage Is High

In low-income, urban, informal communities lacking sewerage and solid waste services, onsite sanitation (sludges, aqueous effluent) and child feces are potential sources of human fecal contamination in living environments. Working in informal communities of urban Maputo, Mozambique, we developed a quantitative, stochastic, mass-balance approach to evaluate plausible scenarios of localized contamination that could explain why the soil-transmitted helminth Ascaris remains endemic despite nearly universal coverage of latrines that sequester most fecal wastes. We used microscopy to enumerate presumptively viable Ascaris ova in feces, fecal sludges, and soils from compounds (i.e., household clusters) and then constructed a steady-state mass-balance model to evaluate possible contamination scenarios capable of explaining observed ova counts in soils. Observed Ascaris counts (mean = -0.01 log10 ova per wet gram of soil, sd = 0.71 log10) could be explained by deposits of 1.9 grams per day (10th percentile 0.04 grams, 90th percentile 84 grams) of child feces on average, rare fecal sludge contamination events that transport 17 kg every three years (10th percentile 1.0 kg, 90th percentile 260 kg), or a daily discharge of 2.7 kg aqueous effluent from an onsite system (10th percentile 0.09 kg, 90th percentile 82 kg). Results suggest that even limited intermittent flows of fecal wastes in this setting can result in a steady-state density of Ascaris ova in soils capable of sustaining transmission, given the high prevalence of Ascaris shedding by children (prevalence = 25%; mean = 3.7 log10 per wet gram, sd = 1.1 log10), the high Ascaris ova counts in fecal sludges (prevalence = 88%; mean = 1.8 log10 per wet gram, sd = 0.95 log10), and the extended persistence and viability of Ascaris ova in soils. Even near-universal coverage of onsite sanitation may allow for sustained transmission of Ascaris under these conditions.