Black Carbon Exposure as a Risk Factor for Child Health in India

 

Black Carbon Exposure as a Risk Factor for Child Health  in India

Rajesh Bag^1,2, Debajit Sarkar², Ram Pravesh Kumar¹, Sagnik Dey^2,3

¹School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.

²Centre for Atmospheric Sciences, Indian Institute of Technology (IIT) Delhi, New Delhi, India.

³Adjunct faculty, Korea University, Seoul, South Korea.

Email: rajeshgeovu@gmail.com

Keywords: Black carbon; stunting; wasting; low birth weight.

Introduction

Black Carbon (BC), a short-lived climate pollutant and a major light-absorbing component of fine particulate matter (PM_2.5) plays a dual role in driving climate change and adversely impacting human health. In India, persistently high levels of ambient PM_2.5 are compounded by household air pollution from biomass combustion, resulting in chronic BC exposure across large sections of the population. Child undernutrition manifested as stunting, wasting, and Low Birth Weight (LBW) continues to be a critical public health challenge in India, contributing to elevated child morbidity, mortality, and long-term developmental deficits. Despite the biological plausibility linking BC exposure to quantifying associated health effects in the Indian context is limited. Addressing this gap, the present study investigates the association between chronic BC exposure and three key indicators of child undernutrition, thereby providing novel insights into the intersection of air pollution and child health.

Methodology

We utilized nationally representative data from the National Family Health Surveys (NFHS-4: 2015-16 and NFHS-5: 2019-21), comprising 437,908 children under five years of age. Among them 10,362 observations had missing mean BC exposure and 35,386 had missing information on fuel type, wealth index, mother Body Mass Index (BMI), mother age, mother education, residence, child sex and mother smoking status. These records were excluded from the analysis. After removing all missing values, the final analytic sample included 402,508 children. Monthly mean BC exposure (2010-2021) at 1 km × 1 km resolution was merged with geocoded DHS cluster coordinates (Dey et al., 2020). For stunting and wasting exposure was averaged from child birth to the month of interview. For in-utero exposure related to LBW, we averaged BC concentrations from 9^th months prior to birth through the month of birth. Generalized Linear Model (GLM) and Generalized Linear Mixed Models (GLMM) were used to estimate associations between long-term BC exposure and odds of stunting, wasting, and LBW, adjusting for household fuel type, mother education, mother wealth index, residence, mother age, mother BMI, child gender and mother smoking status. We estimated the exposure response relationship using a Generalized Additive Model (GAM) incorporating a cubic spline for BC. Effect modification by all covariates was evaluated using multiplicative interaction terms. Stratified ORs with 95% uncertainty intervals were reported only for significant interactions. All models were adjusted for the same covariates.

Results & discussions

 After adjusting for confounders, the odds of stunting and wasting increased to 1.03 (95% UI 1.026-1.032) and 1.04 (95% UI 1.026-1.032) respectively for each 1 μg/m³ increase in long-term ambient BC exposure . Under the GAM framework the exposure response curves for stunting and wasting showed a monotonic increase with rising BC levels.