A clean fuel cookstove is associated with improved lung function: Effect modification by age and secondhand tobacco smoke exposure

Abstract

Household air pollution (HAP) secondary to the burning of solid fuels is a major risk factor for the development of COPD. Our study seeks to examine the impact of a clean cookstove, liquid petroleum gas (LPG), on respiratory outcomes. Women (n = 200) from neighboring Indian communities, one cooking with LPG and one with biomass, were enrolled. Spirometry was performed. Relationships between primary cooking fuel and spirometry measures, as raw values, Global Lung Initiative (GLI) percent predicted (pp), and GLI z-scores, were examined using linear regression. Effect modification by age was explored. Women were young (average age 33.3 years), with low education (median 5.0 years), and the majority had multiple sources of air pollution exposures. Overall, the lung function in both groups was poor [FEV1 z-score median -2.05, IQR (-2.64, -1.41). Biomass was associated with lower FEV1/FVC (raw values -7.0, p = 0.04; GLI pp -7.62, p = 0.05, and z-score -0.86, p = 0.05) and FEF25-75 (GLI pp -25.78, p = 0.05, z-score -1.24, p = 0.05), after adjusting for confounders. Increasing impairment in lung function with age was found among biomass users (p-interaction = 0.01). In conclusion, use of a clean fuel cookstove may improve lung function. These findings have broad implications for research and public policy.

Figure 1

Distribution of spirometry variable Global Lung Function Initiative (GLI) z-scores. The X-axis displays the spirometry variables and the Y-axis demonstrates the z-score values. The box portion of the boxplot represents the 25^th and 75^th percentile with the solid mid-line representing the median and the whisker portion representing the 2.5^th to the 97.5^th percentile. Each dot represents a participant measurement. Median z-score values were well below zero [FEV1 = −2.05 (IQR −2.64, −1.41); FVC = −1.61 (IQR −2.30, −0.99); FEV1/FVC = −0.78 (IQR −1.40, −0.23); FEF25–75 = −1.53 (IQR −2.41, −0.86)]. Notably the median value for FEV1 z-score was less than −1.64, the GLI-defined lower limit of normal, and FVC and FEF25–75 approached this value.

Figure 2

FEV1/FVC and Age Stratified by Biomass Exposure. Linear regression models and 95% CI of Age and FEV1/FVC stratified by Biomass Exposure after adjustment for height, education level, and other environmental exposures. Biomass x Age p for interaction 0.01. Similar results were seen for FEV1 and FEF25–75.

Figure 3

(A) Household and (B) Ambient levels of average PM_2.5 concentration of black carbon and UV-POC by fuel use. Mean levels determined from 10 households in each village ± SE.