Thomas Clasen

• JD, MSc, PhD
• Professor at Rollins School of Public Health, Emory University

Lead (Pb) and cadmium (Cd) are metals that occur naturally in the environment and are present in biomass fuels, such as wood. When these fuels are burned, they can release Pb and Cd into the air, leading to exposure through inhalation. Studies of exposure to metals and health outcomes suggest harmful impacts, including cardiovascular diseases. We a...

Exposure to household air pollution has been linked to adverse health outcomes among women aged 40–79. Little is known about how shifting from biomass cooking to a cleaner fuel like liquefied petroleum gas (LPG) could impact exposures for this population. We report 24-h exposures to particulate matter (PM2.5), black carbon (BC), and carbon monoxide...

Background Anaemia during pregnancy is a major public health concern in India. Biomass fuel use is common in a few rural areas of Tamil Nadu state and there is growing evidence that its use is associated with anaemia. The aim of this study was to estimate the prevalence of anaemia and to identify the coexisting determinants of anaemia among exclusi...

Climate change and weather-related hazards, such as droughts and floods, pose substantial threats to the human health and well-being, especially for those in low-income households and informal settlements. Resilience, defined as the ability to cope, adapt, and recover, is critical for communities to manage these evolving threats. While there has be...

Inadequate solid waste management (SWM) can cause environmental contamination and health risks. Minimizing the health risks from SWM practices requires the identification of linkages between potential sources of exposure, environmental transport pathways, and adverse health outcomes. A safety planning approach can represent an innovative tool for r...

Household water treatment and safe storage interventions can improve microbiological water quality and reduce diarrheal disease in areas lacking access to safe water. However, with few studies evaluating effectiveness of interventions delivered programmatically for more than a year post-implementation, little is known about their sustainability. We...

Combined water, sanitation, and handwashing (WSH) interventions could reduce fecal contamination along more transmission pathways than single interventions alone. We measured Escherichia coli levels in 3909 drinking water samples, 2691 child hand rinses, and 2422 toy ball rinses collected from households enrolled in a 2-year cluster-randomized cont...

Background: An estimated 3 billion people, largely in low- and middle-income countries, rely on unclean fuels for cooking, heating, and lighting to meet household energy needs. The resulting exposure to household air pollution (HAP) is a leading cause of pneumonia, chronic lung disease, and other adverse health effects. In the last decade, randomiz...

Background Quantifying contributions of environmental faecal contamination to child diarrhoea and growth faltering can illuminate causal mechanisms behind modest health benefits in recent water, sanitation, and hygiene (WASH) trials. We aimed to assess associations between environmental detection of enteropathogens and human or animal microbial sou...

Exposure to household air pollution is a leading cause of ill-health globally. The Household Air Pollution Intervention Network (HAPIN) randomized controlled trial evaluated the impact of a free liquefied petroleum gas stove and fuel intervention on birth outcomes and maternal and child health. As part of HAPIN, extensive exposure assessment was co...

Background: Assessments of disease burden are important to inform national, regional, and global strategies and to guide investment. We aimed to estimate the drinking water, sanitation, and hygiene (WASH)-attributable burden of disease for diarrhoea, acute respiratory infections, undernutrition, and soil-transmitted helminthiasis, using the WASH s...

Background: Household air pollution (HAP) from solid fuel use is associated with adverse birth outcomes, but data for exposure-response relationships are scarce. We examined associations between HAP exposures and birthweight in rural Guatemala, India, Peru, and Rwanda during the Household Air Pollution Intervention Network (HAPIN) trial. Methods:...

Background: Water, sanitation, and hygiene (WASH) improvements are promoted to reduce diarrhoea in low-income countries. However, trials from the past 5 years have found mixed effects of household-level and community-level WASH interventions on child health. Measuring pathogens and host-specific faecal markers in the environment can help investiga...

Background: Women living in urban informal settlements may be particularly vulnerable to the detrimental effects of the COVID-19 pandemic because of increased economic and psychosocial stressors in resource-limited environments. Objectives: The objective of this study was to assess the associations between food and water insecurity during the pa...

Water is a crucial resource for many household functions, including drinking, cooking, bathing, and washing clothes. Globally, women bear the burden of water collection in households without piped water, as well as responsibility for household chores that require water. Carrying water has a number of health and safety risks, and women often rely on...

Background: Diarrhoea is a major contributor to the global disease burden, particularly amongst children under five years in low- and middle-income countries (LMICs). As many of the infectious agents associated with diarrhoea are transmitted through faeces, sanitation interventions to safely contain and manage human faeces have the potential to re...

Here, we present a visual representation of standard procedures to collect population level data on personal exposures to household air pollution (HAP) from two different study sites in a resource-constrained setting of Tamil Nadu, India. Particulate matter PM2.5 (particles smaller than 2.5 microns in aerodynamic diameter), carbon monoxide (CO), an...

Exposure to heat is associated with a substantial burden of disease and is an emerging issue in the context of climate change. Heat exposure is of particular concern in India, one of the world's hotter countries and soon to be its most populous, where a large fraction of the population works outdoors, lives in dwellings that are thermally inefficie...

Introduction Despite clear linkages between provision of clean water and improvements in child health, limited information exists about the health impacts of large water infrastructure improvements in low-income settings. Billions of dollars are spent annually to improve urban water supply, and rigorous evaluation of these improvements, especially...

Inadequate solid waste management (SWM) can lead to environmental contamination and human health risks. The health risks from poor SWM can vary based on specific practices and exposure pathways. Thus, it is necessary to adequately understand the local context. This information, however, is rarely available in low-resource settings, particularly in...

Unsafe drinking water remains a major cause of mortality and morbidity. While Rwanda’s Community-Based Environmental Health Promotion Programme (CBEHPP) promotes boiling and safe storage, previous research found these efforts to be ineffective in reducing fecal contamination of drinking water. We conducted a cluster randomized control led trial to...

Background: Exposure to PM2.5 arising from solid fuel combustion is estimated to result in ∼2.3 million premature deaths and 91 million lost disability-adjusted life years annually. Interventions attempting to mitigate this burden have had limited success in reducing exposures to levels thought to provide substantive health benefits. Objectives:...

Background Household air pollution (HAP) from solid fuel use is associated with adverse birth outcomes, but data on exposure-response relationships are limited. We examined associations between HAP exposures and birthweight in rural Guatemala, India, Peru, and Rwanda during the Household Air Pollution Intervention Network (HAPIN) trial. Methods We...

Background: Estimates of the effectiveness of water, sanitation, and hygiene (WASH) interventions that provide high levels of service on childhood diarrhoea are scarce. We aimed to provide up-to-date estimates on the burden of disease attributable to WASH and on the effects of different types of WASH interventions on childhood diarrhoea in low-inc...

There is a significant challenge in global health and development research that pivots on the difficulties of delivering (cost-)effective treatments or interventions that are scalable and are transferable across settings. That is, how does one deliver “true effects”, proven treatments, into new settings? This is often addressed in pragmatic trials...

Background Sanitation workers are essential to global public health and societal wellbeing. However, the health risks and outcomes associated with exposure to occupational risk factors among sanitation workers are neither well understood nor well quantified. We undertook a systematic review to (1) identify occupational risk factors among sanitation...

Globally, cleaner cooking fuels are increasingly promoted to reduce household air pollution. However, there is concern that reductions in smoke from biomass fuels could lead to more favorable conditions for mosquitoes and potentially increase vectorborne disease risk. We investigated household entry, host-seeking, household exit, and mortality amon...

Background Uptake of Government-promoted sanitation remains a challenge in India. We aimed to investigate a low-cost, theory-driven, behavioural intervention designed to increase latrine use and safe disposal of child faeces in India. Methods We did a cluster-randomised controlled trial between Jan 30, 2018, and Feb 18, 2019, in 66 rural villages...

Background The Household Air Pollution Intervention Network (HAPIN) trial is an ongoing multi-center randomized controlled trial assessing the impact of a liquified petroleum gas (LPG) cookstove and fuel intervention on health. Given the potential impacts of household air pollution (HAP) exposure from burning solid fuels on cardiovascular health du...

Adequate menstrual hygiene management (MHM) requires access to water and sanitation and can be challenging for many women and girls living in resource-poor settings. Inadequate MHM has been associated with urogenital infections. The aim of this study is to assess the impact of a combined household-level piped water and sanitation intervention on MH...

Background: Ambient fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] is a major health risk for children, particularly in South Asia, which currently experiences the highest PM2.5 levels globally. Nevertheless, there is comparatively little epidemiological evidence from this region to quantify the effects of PM2.5 on child survi...

Background Exposure to PM 2.5 arising from solid fuel combustion is estimated to result in approximately 2.3 million premature deaths and 90 million lost disability-adjusted life years annually. ‘Clean’ cooking interventions attempting to mitigate this burden have had limited success in reducing exposures to levels that may yield improved health ou...

The Household Air Pollution Intervention Network trial is a multi-country study on the effects of a liquefied petroleum gas (LPG) stove and fuel distribution intervention on women's and children's health. There is limited data on exposure reductions achieved by switching from solid to clean cooking fuels in rural settings across multiple countries....

Background: The intense interactions between people, animals and environmental systems in urban informal settlements compromise human and environmental health. Inadequate water and sanitation services, compounded by exposure to flooding and climate change risks, expose inhabitants to environmental contamination causing poor health and wellbeing and...

Water, sanitation, and hygiene (WASH) practices emerged as a critical component to controlling and preventing the spread of the COVID-19 pandemic. We conducted 131 semistructured phone interviews with households in rural Odisha, India, to understand behavior changes made in WASH practices as a result of the pandemic and challenges that would preven...

Municipal solid waste (MSW) can pose a threat to public health if it is not safely managed. Despite prior research, uncertainties remain and refurbished evidence is needed along with new approaches. We conducted a systematic review of recently published literature to update and expand the epidemiological evidence on the association between MSW mana...

Rationale The spread of severe acute respiratory syndrome coronavirus-2 has suspended many non-COVID-19 related research activities. Where restarting research activities is permitted, investigators need to evaluate the risks and benefits of resuming data collection and adapt procedures to minimize risk. Objectives In the context of the multicountr...

Background Household air pollution adversely affects human health and the environment, yet more than 40% of the world still depends on solid cooking fuels. The House Air Pollution Intervention Network (HAPIN) randomized controlled trial is assessing the health effects of a liquefied petroleum gas (LPG) stove and 18-month supply of free fuel in 3,20...

We conducted 131 semi-structured phone interviews with householders in rural Odisha, India to explore participants’ COVID-19 related knowledge, perceptions, and preventative actions, as well as how the pandemic affected their daily life, economic and food security, and the village-level response. Interviews were conducted with 73 heads of household...

Poor water, sanitation and hygiene (WaSH) conditions are hypothesized to contribute to environmental enteric dysfunction (EED), a subclinical condition that may be associated with chronic undernutrition and impaired linear growth. We evaluated the effect of a combined water and sanitation intervention on biomarkers of EED, and then assessed associa...

Abstract Background Global temperatures are projected to rise by ≥2 °C by the end of the century, with expected impacts on infectious disease incidence. Establishing the historic relationship between temperature and childhood diarrhea is important to inform future vulnerability under projected climate change scenarios. Methods We compiled a nationa...

Water, sanitation, and hygiene (WASH) practices emerged as a critical component to controlling and preventing the spread of the COVID-19 pandemic. We conducted 131 semi-structured phone interviews with households in rural Odisha, India to understand behavior changes made in WASH practices as a result of the pandemic and challenges that would preven...

Background The causal attribution of bacterial pathogens to severe acute respiratory infections (SARI) is challenging because many bacteria are frequently detected in the upper respiratory tract of asymptomatic persons. Quantification of pathogen load may help differentiate asymptomatic pathogen carriage from clinically significant infection. We ai...

BACKGROUND: Two of the most important causes of global disease fall in the realm of environmental health: household air pollution (HAP) and poor water, sanitation, and hygiene (WASH) conditions. Interventions, such as clean cookstoves, household water treatment, and improved sanitation facilities, have great potential to yield reductions in disease...

Background The Household Air Pollution Intervention Network (HAPIN) trial aims to assess health benefits of a liquefied petroleum gas (LPG) cookfuel and stove intervention among women and children across four low- and middle-income countries (LMICs). We measured exposure contrasts for women, achievable under alternative conditions of biomass or LPG...

We conducted 131 semi-structured phone interviews with householders in rural Odisha, India to explore participants’ COVID-19 related knowledge, perceptions, and preventative actions, as well as how the pandemic was impacting their daily life, economic and food security, and the village-level response. Interviews were conducted with 73 heads of hous...

Rationale: The spread of severe acute respiratory syndrome coronavirus-2 has suspended many non-COVID-19 related research activities. Where restarting research activities is permitted, investigators need to evaluate the risks and benefits of resuming data collection and adapt procedures to minimize risk. Objectives: In the context of the multicount...

Background We compared the relationship of past and contemporary sodium (Na) intake with cardiometabolic biomarkers. Methods and Results A total of 1191 participants' data from a randomized controlled trial in coastal Bangladesh were analyzed. Participants provided 24‐hour urine Na (24UNa) data for 5 monthly visits. Their fasting blood glucose, to...

Background: Exposure to faecal contamination is believed to be associated with child diarrhoea and possibly stunting; however, few studies have explicitly measured the association between faecal contamination and health. We aimed to assess individual participant data (IPD) across multiple trials and observational studies to quantify the relationsh...

Background: Drinking-water salinity has been associated with high blood pressure (BP) among communities in south-west coastal Bangladesh. We evaluated whether access to water from managed aquifer recharge (MAR)-a hydrogeological intervention to lower groundwater salinity by infiltrating rainwater into the aquifers-can reduce community BP. Methods...

The Household Air Pollution Intervention Network (HAPIN) trial is evaluating health benefits of a liquefied petroleum gas (LPG) stove intervention in biomass cook-fuel using homes (n = 3200) in four low-and middle-income countries (LMICs) that include Peru, Guatemala, Rwanda and India. Longitudinal urine samples (n = 6000) collected from enrolled p...

Qualitative research has documented menstruator’s challenges, particularly in water and sanitation poor environments, but quantitative assessment is limited. We created and validated a culturally-grounded measure of Menstrual Insecurity to assess women’s menstruation-related concerns and negative experiences. With cross-sectional data from 878 mens...

Characterizing child immunological responses to enteric infections with antibody detection in serum can be challenging in resource-constrained field settings, because sample collection requires trained individuals and its invasive procedure may lead to low response rates, especially among children. Saliva may present a promising non-invasive altern...

This study explores the associations of drinking rainwater with mineral intake and cardiometabolic health in the Bangladeshi population. We pooled 10030 person-visit data on drinking water sources, blood pressure (BP) and 24-h urine minerals. Fasting blood glucose (FBG) was measured in 3724 person-visits, and lipids in 1118 person-visits. We measur...

Background: Biomarkers of exposure, susceptibility, and effect are fundamental for understanding environmental exposures, mechanistic pathways of effect, and monitoring early adverse outcomes. To date, no study has comprehensively evaluated a large suite and variety of biomarkers in household air pollution (HAP) studies in concert with exposure an...

Background: High quality personal exposure data is fundamental to understanding the health implications of household energy interventions, interpreting analyses across assigned study arms, and characterizing exposure-response relationships for household air pollution. This paper describes the exposure data collection for the Household Air Pollutio...

Background: Globally, nearly 3 billion people rely on solid fuels for cooking and heating, the vast majority residing in low- and middle-income countries (LMICs). The resulting household air pollution (HAP) is a leading environmental risk factor, accounting for an estimated 1.6 million premature deaths annually. Previous interventions of cleaner s...

Managed aquifer recharge (MAR), a hydro-geological intervention designed to dilute groundwater salinity, pumps pond water treated through a slow sand filter into the underground aquifers. We evaluated the microbiological safety of the resulting MAR water at sites from three districts in southwest coastal Bangladesh. We collected monthly paired pond...

Background: In resource-limited settings, pneumonia diagnosis and management are based on thresholds for respiratory rate (RR) and oxyhaemoglobin saturation (SpO2) recommended by WHO. However, as RR increases and SpO2 decreases with elevation, these thresholds might not be applicable at all altitudes. We sought to determine upper thresholds for RR...

Community-level action may be required to achieve the levels of sanitation uptake necessary for health gains. Evidence suggests that collective action is influenced by collective efficacy (CE)-a group's belief in its abilities to organize and execute action to achieve common goals. The extent to which it is necessary to fully contextualize existing...

Background: Three large new trials of unprecedented scale and cost, which included novel factorial designs, have found no effect of basic water, sanitation and hygiene (WASH) interventions on childhood stunting, and only mixed effects on childhood diarrhea. Arriving at the inception of the United Nations' Sustainable Development Goals, and the bol...

Safe child feces management (CFM) is likely critical for reducing exposure to fecal pathogens in and around the home, but the effectiveness of different CFM practices in reducing fecal contamination is not well understood. We conducted a cross-sectional study of households with children <6 years in rural Odisha, India, using household surveys (188...

Background We compared the relationship between sodium (Na) intake and blood pressure when Na intake was estimated from first‐ and second‐morning spot urine samples using the INTERSALT (International Study on Salt and Blood Pressure) formula, versus directly measured 24‐hour samples. Methods and Results We collected 24‐hour urine and first‐ and se...

Background: Despite a strong theoretical rationale for combining water, sanitation and hygiene (WaSH) interventions to improve child health, study findings are heterogeneous with little understanding of the mechanisms for these effects. Our study objective was to demonstrate the utility of structural equation modeling (SEM) to assess intervention...

This study examined drivers and barriers of water, sanitation, and hygiene (WASH) policies in urban informal settlements in low and middle-income countries. We conducted a search of peer-reviewed and grey literature published between January 2000 and April 2018. We organized evidence into six domains of drivers and barriers: economic, spatial, soci...

Pneumonia is a leading killer of children younger than 5 years despite high vaccination coverage, improved nutrition, and widespread implementation of the Integrated Management of Childhood Illnesses algorithm. Assessing the effect of interventions on childhood pneumonia is challenging because the choice of case definition and surveillance approach...

Background: Diarrhoea and soil-transmitted helminth (STH) infections represent a large disease burden worldwide, particularly in low-income countries. As the aetiological agents associated with diarrhoea and STHs are transmitted through faeces, the safe containment and management of human excreta has the potential to reduce exposure and disease. C...

Combined water, sanitation, and handwashing (WSH) interventions have the potential to reduce fecal pathogens along more transmission pathways than single interventions alone. We measured Escherichia coli levels in 3909 drinking water samples, 2691 child hand rinses, and 2422 toy ball rinses collected from households enrolled in a two-year cluster-r...

Background: Open defecation is widespread in rural India, and few households have piped water connections. While government and other efforts have increased toilet coverage in India, and evaluations found limited immediate impacts on health, longer-term effects have not been rigorously assessed. Methods: We conducted a matched cohort study to asses...

There has been growing recognition of menstrual hygiene management (MHM) as a significant public health issue. However, research has predominately focused on the experiences of adolescent girls in school settings. The purpose of this research is to examine detailed accounts of menstruation for women in rural Odisha, India at various life stages wit...