Impact of biogas digesters on cookhouse volatile organic compound exposure for rural Kenyan farmwomen

Women living on rural Kenyan smallholder dairy farms burn wood as biofuel in family cookhouses. Unventilated biofuel combustion produces harmful levels of respirable particles and volatile organic compound (VOC) emissions in indoor environments. Biogas digesters, which can generate high methane-content biogas from livestock manure composting were recently installed on 31 farms. The study objectives were to compare VOC exposure profiles for women cooking on farms with and without biogas digesters, and to compare seasonal variations in VOC exposures for those women cooking with biogas. Participants (n=31 biogas farms, n=31 referent farms) wore passive thermal desorption VOC sampling tubes and recorded cookhouse fuel use on time activity sheets for 7 days. Women using biogas spent significantly less time (mean=509 min/week) exposed to cookhouse wood smoke compared with the referent group (mean=1122 min/week) (P<0.01). Total VOC exposure did not differ between farm groups (P=0.14), though concentrations of trans-1,3-dichloropropene, bromoform, and 1,4-dichlorobenzene in biogas cookhouses were significantly lower than in referent cookhouses, even after Bonferroni correction. The composition of VOC species was also significantly different, reflecting the different fuel sources. Biogas digester technologies have great potential for reducing exposure to wood smoke VOCs in low-income countries.