Household Air Pollution Concentrations after Liquefied Petroleum Gas Interventions in Rural Peru: Findings from a One-Year Randomized Controlled Trial Followed by a One-Year Pragmatic Crossover Trial

Abstract

Background: Household air pollution (HAP) from biomass fuel combustion remains a leading environmental risk factor for morbidity worldwide.

Objective: Measure the effect of liquefied petroleum gas (LPG) interventions on HAP exposures in Puno, Peru.

Methods: We conducted a 1-y randomized controlled trial followed by a 1-y pragmatic crossover trial in 180 women age 25-64 y. During the first year, intervention participants received a free LPG stove, continuous fuel delivery, and regular behavioral messaging, whereas controls continued their biomass cooking practices. During the second year, control participants received a free LPG stove, regular behavioral messaging, and vouchers to obtain LPG tanks from a nearby distributor, whereas fuel distribution stopped for intervention participants. We collected 48-h kitchen area concentrations and personal exposures to fine particulate matter (PM) with aerodynamic diameter ≤2.5μm (PM2.5), black carbon (BC), and carbon monoxide (CO) at baseline and 3-, 6-, 12-, 18-, and 24-months post randomization.

Results: Baseline mean [±standard deviation (SD)] PM2.5 (kitchen area concentrations 1,220±1,010 vs. 1,190±880 μg/m3; personal exposure 126±214 vs. 104±100 μg/m3), CO (kitchen 53±49 vs. 50±41 ppm; personal 7±8 vs. 7±8 ppm), and BC (kitchen 180±120 vs. 210±150 μg/m3; personal 19±16 vs. 21±22 μg/m3) were similar between control and intervention participants. Intervention participants had consistently lower mean (±SD) concentrations at the 12-month visit for kitchen (41±59 μg/m3, 3±6 μg/m3, and 8±13 ppm) and personal exposures (26±34 μg/m3, 2±3 μg/m3, and 3±4 ppm) to PM2.5, BC, and CO when compared to controls during the first year. In the second year, we observed comparable HAP reductions among controls after the voucher-based intervention for LPG fuel was implemented (24-month visit PM2.5, BC, and CO kitchen mean concentrations of 34±74 μg/m3, 3±5 μg/m3, and 6±6 ppm and personal exposures of 17±15 μg/m3, 2±2 μg/m3, and 3±4 ppm, respectively), and average reductions were present among intervention participants even after free fuel distribution stopped (24-month visit PM2.5, BC, and CO kitchen mean concentrations of 561±1,251 μg/m3, 82±124 μg/m3, and 23±28 ppm and personal exposures of 35±38 μg/m3, 6±6 μg/m3, and 4±5 ppm, respectively).

Discussion: Both home delivery and voucher-based provision of free LPG over a 1-y period, in combination with provision of a free LPG stove and longitudinal behavioral messaging, reduced HAP to levels below 24-h World Health Organization air quality guidelines. Moreover, the effects of the intervention on HAP persisted for a year after fuel delivery stopped. Such strategies could be applied in LPG programs to reduce HAP and potentially improve health. https://doi.org/10.1289/EHP10054.

Trial registration: ClinicalTrials.gov NCT02994680.

Figures

Figure 1.

Kitchens of participants with an intervention LPG stove (A) and a traditional biomass cookstove in rural Peru. Note: LPG, liquefied petroleum gas. [Photo credit: (A) and (B): Kendra N. Williams; figures being reused with her permission as the copyright holder.]

Figure 2.

PM2.5 and CO box plots of daily mean kitchen area exposure concentrations at each follow-up visit (baseline, 3-, 6-, 12-, 18-, and 24-months) for LPG stove intervention participants (LPG) and control participants (Control). Daily mean metric used is defined as the mean of the two consecutive 24-h average concentrations, where available. During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Interquartile ranges of the box plots represent the 25th and the 75th percentiles of the daily means for each group; the middle line of the box represents the 50th percentile. Numeric data is provided in Table 2. Note: CO, carbon monoxide; LPG, liquefied petroleum gas; PM2.5, fine particulate matter with aerodynamic diameter of ≤2.5μm; WHO 24-h guideline, World Health Organization daily guideline (PM2.5: 25 μg/m3, CO: 9.4 ppm).

Figure 3.

PM2.5 and CO box plots of daily mean personal exposure concentrations at each follow-up visit (baseline, 3-, 6-, 12-, 18-, and 24-months) for LPG stove intervention participants (LPG) and control participants (Control). Daily mean metric used is defined as the mean of the two consecutive 24-h average concentrations, where available. During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Interquartile ranges of the box plots represent the 25th and the 75th percentiles of the daily means for each group; the middle line of the box represents the 50th percentile. Numeric data is provided in Table 2. Note: CO, carbon monoxide; LPG, liquefied petroleum gas; PM, particulate matter; WHO 24-h guideline, World Health Organization daily guideline (PM2.5: 25 μg/m3, CO: 9.4 ppm).

Figure 4.

Percent of kitchen area samples within different PM2.5 concentration ranges by minute of a day for the intervention group (B,D,F) and control group (A,C,E) at baseline (A,B), at follow-up samples taken at the 3-, 6-, 12-month time points (C,D), and 18-, and 24-month time points (E,F) in rural Peru. Samples <LOD were replaced by LOD/2: 7μg for PM2.5 gravimetric integrated samples, respectively. The sample size for baseline, 3-, 6-, 12, 18-, and 24-month visits for control and intervention households are: n0=89 and 89, n3=89 and 90, n6=88 and 90, n12=89 and 87, n18=88 and 87, n24=84 and 84. During the second year (follow-up visits:18- and 24 months), the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Note: LOD, limit of detection; LPG, liquefied petroleum gas; PM, particulate matter.

Figure 5.

Percent of kitchen area samples within different CO concentration ranges by minute of a day for the intervention group (B,D,F) and control group (A,C,E) at baseline (A,B), at follow-up samples taken at the 3-, 6-, 12-month time points (C,D) and at 18-, and 24-month time points (E,F) in rural Peru. Samples <LOD were replaced by LOD/2: 0.7 ppm for direct reading CO measurements. The sample size for baseline, 3-, 6-, 12, 18-, and 24-month visits for control and intervention households are: n0=84 and 85, n3=84 and 80, n6=86 and 82, n12=86 and 77, n18=83 and 79, n24=80 and 79. During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Note: CO, carbon monoxide; LOD, limit of detection; LPG, liquefied petroleum gas.

Figure 6.

Percent of personal exposure samples within different PM2.5 concentration ranges by minute of a day for the intervention group (B,D,F) and control group (A,C,E) at baseline (A,B), at follow-up samples taken at the 3-, 6-, 12-month time points (C,D) and at 18-, and 24-month time points (E,F) in rural Peru. Samples <LOD were replaced by LOD/27μg for PM2.5 gravimetric integrated samples, respectively. The sample size for baseline, 3-, 6-, 12, 18-, and 24-month visits for control and intervention households are: n0=90 and 90, n3=87 and 90, n6=90 and 89, n12=90 and 87, n18=90 and 88, n24=85 and 84. During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Note: LOD, limit of detection; LPG, liquefied petroleum gas.

Figure 7.

Percent of personal exposure samples within different CO concentration ranges by minute of a day for the intervention group (B,D,F) and control group (A,C,E) at baseline (A,B), at follow-up samples taken at the 3-, 6-, 12-month time points (C,D) and at 18-, and 24-month time points (E,F) in rural Peru. Samples <LOD were replaced by LOD/2): 0.7 ppm for direct reading CO measurements. The sample size for baseline, 3-, 6-, 12, 18-, and 24-month visits for control and intervention households are: n0=81 and 79, n3=79 and 76, n6=81 and 79, n12=81 and 79, n18=75 and 80, n24=73 and 76. During the second year (follow-up visits:18- and 24 months) the control participants received the LPG stove intervention and vouchers for 1-y supply of free fuel and intervention participants stopped receiving free fuel but kept the LPG stove. Note: CO, carbon monoxide; LPG, liquefied petroleum gas; LOD, limit of detection.