Environmental Exposure Catalogue
Comprehensive documentation of climate and environmental exposure variables for understanding heat-health impacts across Sub-Saharan Africa. This catalogue serves as both a technical reference for statisticians and a data inventory for the HE2AT Center research projects.
The Heat and Health African Transdisciplinary Center
The world's climate is changing rapidly, with global temperatures having risen more than 1°C since the industrial revolution. Heat waves and rising temperatures have major, though underappreciated, health implications, particularly for vulnerable populations in low-income settings.
The HE2AT Center is developing innovative data science solutions to mitigate the health impacts of climate change in Africa. We are systematically building a data ecosystem containing biomedical data integrated with weather, air quality, and other environmental data to understand the relationships between heat exposure and health outcomes.
Individual Participant Data
Reusing data from cohorts and trials among pregnant women and neonates conducted across Sub-Saharan Africa since 2000, integrated into a harmonized platform.
Climate Integration
Environmental exposures linked to participant records through geolocation and temporal matching, enabling analysis of heat-health relationships.
Health Outcomes
Focus on maternal and child health including preterm birth, birth weight, pre-eclampsia, and heat-related morbidity in vulnerable populations.
Exposure Assignment Methodology
Environmental exposures are assigned to study participants through systematic linkage of climate data to individual records. Each participant receives daily exposure values for their entire observation period, enabling analysis of exposure-outcome relationships at multiple temporal scales.
Patient Exposure Days
Generate individual-level exposure records containing Patient ID, location coordinates, and all exposure dates from pre-conception through post-delivery periods (90 days pre-conception + gestational period + 28 days post-delivery).
Climate Data Extraction
Extract environmental variables from multiple data sources (reanalysis products, satellite imagery, geospatial databases) for each unique location-date combination in the study.
Data Integration
Merge climate-enriched location data with patient records, producing complete exposure profiles for epidemiological analysis across trimester-specific and cumulative windows.
Temperature Exposure
Dataset
Variable: tas (Near-surface air temperature)
Temporal resolution: 3-hourly
Original units: Kelvin (K), converted to Celsius
Methodology
Daily mean temperature is calculated by averaging all 3-hourly observations at the nearest grid point to each participant's location. Values are converted from Kelvin to Celsius and extracted for each day in the participant's exposure window.
Health Relevance
Ambient temperature is a critical determinant of heat-related morbidity. Elevated mean temperatures during pregnancy have been associated with increased risk of preterm birth, low birth weight, and stillbirth.
Dataset
Derived from 3-hourly tas values
Health Relevance
Peak daily temperatures capture acute heat stress events. Maximum temperatures exceeding physiological thresholds trigger thermoregulatory responses that can affect placental blood flow and fetal development.
Health Relevance
Persistently elevated minimum temperatures ("warm nights") indicate conditions where cooling relief is limited, potentially compounding cumulative heat stress over multiple days.
Air Quality & Atmospheric Conditions
Dataset
Variable: pm2p5
Original units: kg/m³, converted to μg/m³ (×10⁹)
Health Relevance
Fine particulate matter can penetrate deep into the lungs and cross the placental barrier, affecting fetal development. Exposure during pregnancy is associated with preterm birth, reduced birth weight, and gestational hypertension.
Dataset
Variable: no2as
Original units: kg/kg, converted to ppb
Health Relevance
NO2 is a marker of traffic-related air pollution. Short-term exposure has been associated with increased risk of spontaneous abortion and adverse birth outcomes.
Dataset
Variable: aod550
Health Relevance
AOD is an integrated measure of atmospheric aerosol loading. Elevated AOD indicates poor air quality and serves as a proxy for particulate matter exposure.
Dataset
Variable: od550bc
Health Relevance
Black carbon results from incomplete combustion. Sources in African settings include vehicle emissions, cooking fires, and agricultural burning. Associated with cardiovascular and respiratory effects.
Dataset
Variable: duaod550_nc (Dust Aerosol Optical Depth at 550nm, non-absorbing)
Health Relevance
Dust aerosols are major contributors to particulate matter in West and East African settings. Elevated dust loading is linked to respiratory and cardiovascular effects, particularly in the Sahel region.
Dataset
Variable: duexttau (Dust Aerosol Optical Depth — total extinction)
Health Relevance
Total dust extinction AOD integrates the full dust aerosol column. Important for quantifying dust burden in Sahelian countries (Burkina Faso, The Gambia) where values are substantially higher than southern African sites.
Dataset
Variable: dusmass25 (Dust PM2.5 surface mass density)
Health Relevance
Surface dust mass in the fine particle fraction directly contributes to respiratory PM2.5 exposure. West African sites experience values comparable to total PM2.5, indicating dust as the dominant aerosol source.
Dataset
Variable: ducmass (Dust Aerosol Column Mass Density)
Health Relevance
Column-integrated dust mass provides an indication of total atmospheric dust loading. Useful for understanding regional dust transport patterns affecting Sahelian and West African populations.
Thermal Comfort Indices
Health Relevance
UTCI accounts for air temperature, humidity, wind speed, and radiation. Values above 32°C indicate strong heat stress. Broadly used in climate-health research for its physiological grounding.
Health Relevance
WBGT is the international standard for occupational heat stress assessment. Used to set work-rest cycles for pregnant women and outdoor workers.
Health Relevance
Heat index represents perceived temperature combining air temperature and relative humidity. Values above 32°C indicate caution; above 41°C is dangerous.
Health Relevance
MRT represents the uniform temperature of surroundings causing the same radiant heat loss as the actual environment. Critical for understanding outdoor thermal comfort and solar radiation effects.
Health Relevance
Values above 32°C are dangerous for prolonged exposure; above 35°C approaches the theoretical human survivability limit. Pregnant women are especially vulnerable due to increased metabolic demands.
Health Relevance
Values 30–39°C cause discomfort; 40–45°C cause great discomfort; above 45°C is dangerous. Humidex is widely used in public health heat communications.
Health Relevance
Combines effects of air temperature, humidity, and wind speed on thermal comfort. Represents the temperature perceived by an average person under given conditions.
Health Relevance
NET accounts for the combined effects of temperature, humidity, and air movement on thermal sensation. Used in bioclimatic assessments.
Health Relevance
Wind chill combines air temperature and wind speed to estimate the cooling effect of wind on exposed skin. In hot climates, it serves as an indicator of how much ventilation mitigates heat exposure — values close to air temperature indicate still, hazardous conditions.
Health Relevance
The simplified WBGT (0.567×Tdb + 0.393×e + 3.94) uses dry-bulb temperature and vapour pressure, making it computable from standard meteorological data without solar radiation inputs. It provides a rapid screen for occupational heat stress and is widely used in epidemiological analyses.
Meteorological Conditions
Health Relevance
Wind speed affects thermal comfort by enhancing evaporative cooling. Important modifier in heat stress calculations across all study sites.
Health Relevance
High dew points (>20°C) impair the body's ability to cool through sweating. Dew point is often a better predictor of heat-related illness than relative humidity alone.
Dataset
Variable: r (Near-surface relative humidity)
Derived from specific humidity and temperature
Health Relevance
High relative humidity impairs the body's ability to cool through sweating. Combined with high temperature, humid conditions create dangerous heat stress situations for pregnant women and outdoor workers. Burkina Faso and The Gambia show wide IQRs reflecting strong seasonal dry–wet cycles.
Precipitation & Vegetation
Health Relevance
Seasonal precipitation affects food availability, vector-borne disease transmission, and healthcare access. Rainfall anomalies have been associated with adverse birth outcomes across Sub-Saharan Africa.
Health Relevance
Residential greenness is associated with improved pregnancy outcomes. NDVI serves as a proxy for green space exposure which can mitigate urban heat island effects and reduce air pollution.
Geographic & Soil
Dataset
Google Earth Engine: MERIT/DEM/v1_0_3
Resolution: ~90m
Health Relevance
Elevation influences atmospheric pressure, temperature patterns, and air quality. High-altitude environments are associated with adverse reproductive outcomes including low birth weight due to reduced oxygen availability.
Dataset
ISDASOIL/Africa/v1/nitrogen_total
Band: mean_0_20 (0–20cm depth)
Health Relevance
Soil nitrogen affects food crop protein content and agricultural productivity. Low nitrogen contributes to maternal malnutrition and adverse pregnancy outcomes.
Dataset
ISDASOIL/Africa/v1/phosphorus_extractable
Health Relevance
Phosphorus is essential for root development and crop yield. Deficient soils reduce agricultural productivity and affect household food security during pregnancy.
Dataset
ISDASOIL/Africa/v1/carbon_organic
Band: mean_0_20 (0–20cm depth)
Health Relevance
Soil organic carbon is a key indicator of soil fertility and water retention capacity. It affects food crop quality and micronutrient availability, which in turn influence maternal nutritional status during pregnancy.
Health Relevance
Potassium regulates water uptake and disease resistance in crops, affecting agricultural productivity and food security.
Health Relevance
Calcium is critical during pregnancy for fetal bone development and blood clotting. Maternal calcium deficiency has been associated with pre-eclampsia and low birth weight.
Socioeconomic Context
Dataset
Chi et al. (2022) Nature Communications
Resolution: ~2.4 km tiles
Methodology
The RWI is derived from satellite imagery and mobile connectivity data using machine learning, calibrated against survey-based wealth indices. Positive values indicate relative wealth; negative values indicate relative poverty compared to the regional mean.
Health Relevance
Socioeconomic status modifies heat vulnerability — lower wealth is associated with reduced access to cooling, poor housing, and outdoor labour. RWI enables adjustment for wealth as a confounder in heat-health analyses and helps identify high-risk populations.
Urbanization & Built Environment
Dataset
JRC/GHSL/P2023A/GHS_SMOD
Available years: 2000, 2005, 2010, 2015, 2020, 2025
SMOD Code Reference
Code Distribution by Site
Health Relevance
Urbanization level influences exposure to air pollution, urban heat islands, and noise — all affecting pregnancy outcomes. GHSL provides consistent classification across African settings.
Climate Classification
Dataset
Based on temperature and precipitation patterns
Code: 1=Tropical, 3=Temperate, 4=Cold, 5=Polar, 6=Boreal/other
IQR of Zone Code by Site
Pending Exposure Variables
Health Relevance
Percentage of exposure days exceeding the local 95th percentile. Studies show trimester-specific effects of extreme heat on preterm birth risk.
Planned Dataset
Landsat thermal bands
Health Relevance
LST captures the actual thermal environment at ground level and is useful for identifying localized heat exposure in urban settings.
Health Relevance
Large day-night temperature swings may stress thermoregulatory systems. Preconceptional and prenatal exposure to high diurnal variation is associated with adverse pregnancy outcomes.
Supporting Literature
Funding Acknowledgement
The research is supported by the Fogarty International Center, the National Institute of Environmental Health Sciences (NIEHS), the Data Science for Health Discovery and Innovation in Africa (DS-I Africa) and the Office of Strategic Coordination (OSC) of the National Institutes of Health under Award Number U54TW012083. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.