Accepted for/Published in: JMIR Research Protocols
Date Submitted: Dec 9, 2021
Open Peer Review Period: Dec 9, 2021 - Feb 3, 2022
Date Accepted: May 5, 2022
(closed for review but you can still tweet)
The Effect of Particulate Matter Exposure during Pregnancy on Pregnancy and Child Health Outcomes in South Asia: Protocol for an Instrumental Variable Analysis
ABSTRACT
Background:
Determining the longer-term health effects of air pollution has been difficult due to the multitude of potential confounding variables in the relationship between air pollution and health. Air pollution in many areas of South Asia is seasonal, with large spikes in particulate matter (PM) concentration occurring in the winter months. This study exploits this seasonal variation in PM concentration through a natural experiment.
Objective:
This project aims to determine the causal effect of PM exposure during pregnancy on pregnancy and child health outcomes.
Methods:
We use an instrumental variable (IV) design whereby estimated month of conception is our instrument for PM2.5 exposure during pregnancy. We assess the plausibility of our assumption that timing of conception is exogenous with regards to our outcomes of interest and adjust for date of monsoon onset to control for confounding variables related to harvest timing. Primary outcomes are birthweight, pregnancy termination resulting in miscarriage, abortion, or still birth as well as neonatal death, infant death, and child death. Secondary outcomes are low birthweight, very low birthweight, and extremely low birthweight. The data for this project is the Demographic and Health Surveys (DHS) conducted in relevant regions of Bangladesh, India, Nepal, and Pakistan, and monthly gridded data on PM2.5 concentration (0.1° X 0.1° spatial resolution), precipitation data (0.5° X 0.5° resolution), temperature data (0.5° X 0.5°), and agricultural land use data (0.1° X 0.1° resolution).
Results:
Data access to relevant DHS surveys was granted on 6 June 2021 (for India, Nepal, Bangladesh) and August 24 (for Pakistan). Data analysis began in August 2021.
Conclusions:
If the assumptions for a causal interpretation of our instrumental variable analysis are met, this analysis will provide important causal evidence on the maternal and child health effects of PM2.5 exposure during pregnancy. This evidence is important to inform personal behavior and interventions, such as adoption of indoor air filtration during pregnancy, as well as environmental and health policy.
Citation
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