Kitchen concentrations of fine particulate matter and particle number concentration in households using biomass cookstoves in rural Honduras

Abstract Cooking and heating with solid fuels results in high levels of household air pollutants, including particulate matter (PM); however, limited data exist for size fractions smaller than PM2.5 (diameter less than 2.5 μm). We collected 24-hour time-resolved measurements of PM2.5 (n=27) and particle number concentrations (PNC, average diameter 10-700 nm) (n=44; 24 with paired PM2.5 and PNC) in homes with wood-burning traditional and Justa (i.e., with an engineered combustion chamber and chimney) cookstoves in rural Honduras. The median 24-hour PM2.5 concentration (n=27) was 79 μg/m3 (interquartile range [IQR]: 44 – 174 μg/m3); traditional (n=15): 130 μg/m3 (IQR: 48 – 250 μg/m3); Justa (n=12): 66 μg/m3 (IQR: 44 – 97 μg/m3). The median 24-hour PNC (n=44) was 8.5 x 104 particles (pt)/cm3 (IQR: 3.8 x 104 – 1.8 x 105 pt/cm3); traditional (n=27): 1.3 x 105 pt/cm3 (IQR: 3.3 x 104 – 2.0 x 105 pt/cm3); Justa (n=17): 6.3 x 104 pt/cm3 (IQR: 4.0 x 104 – 1.2 x 105 pt/cm3). The 24-hour average PM2.5 and particle number concentrations were correlated for the full sample of cookstoves (n=24, Spearman ρ: 0.83); correlations between PM2.5 and PNC were higher in traditional stove kitchens (n=12, ρ: 0.93) than in Justa stove kitchens (n=12, ρ: 0.67). The 24-hour average concentrations of PM2.5 and PNC were also correlated with the maximum average concentrations during shorter-term averaging windows of one-, five-, 15-, and 60-minutes, respectively (Spearman ρ: PM2.5 [0.65, 0.85, 0.82, 0.71], PNC [0.74, 0.86, 0.88, 0.86]). Given the moderate correlations observed between 24-hour PM2.5 and PNC and between 24-hour and the shorter-term averaging windows within size fractions, investigators may need to consider cost-effectiveness and information gained by measuring both size fractions for the study objective. Further evaluations of other stove and fuel combinations are needed.