Reduced carbon monoxide exposures from wood fuel use and impact on birth weight and anthropometric growth among a cohort of Guatemalan children less than 36 months of age participating in the RESPIRE randomized stove intervention trial.

摘要

This dissertation assessed the effects of biomass smoke exposure in utero and during early childhood on birth weight and anthropometry among a cohort of 537 infants enrolled in RESPIRE (Randomized Exposure Study of Pollution Indoors and Respiratory Effects), a randomized improved chimney stove intervention trial in rural Guatemala. The present research also characterized the high, transient exposures to carbon monoxide (CO) during use of the temazcal, a traditional steam bath used by this Mam-speaking Mayan population residing in the rural highlands. The two hypotheses were (1) pregnant women differentially exposed to high levels indoor air pollution will have lower birth weight babies and (2) young children exposed to biomass smoke will have decreased anthropometric growth.;The first goal of the study was to determine whether exposures to higher levels of CO among pregnant women who used open fires for cooking (as compared to improved chimney-stove, or "plancha" users) were associated with reductions in birth weight among their offspring. The prevalence of low birth weight among the 190 children who were measured at less than 24 hours was 23.7%. We were able to detect a non-significant 83-gram increase (p 0.15) in birth weight among children born to the 81 women who used an improved chimney stove during their pregnancy, most of whom were in their third trimester before receiving the improved stove.;The second goal of the study was to determine whether exposures to CO (a proxy for particulate matter (PM)) during the first 24-36 months of a child's life were associated with reductions in anthropometric growth, as determined by height-for-age ("stunting"), weight-for-age ("underweight") and height-for-weight ("wasting") median z-scores using the 2006 WHO Multicentre Growth Reference Standards. At the final anthropometry round (average age 26 months), 93% of the children were stunted, 77% were underweight and 8% were wasted. The only anthropometric measure that showed a borderline significant association (p=0.11) with personal child CO was the height-for weight median z-scores. Maternal short stature and/or low body mass index were significantly related to all three anthropometric measures, indicating the intergenerational cycle of maternal poor nutrition and subsequent poor growth of offspring. Diarrheal and acute lower respiratory infections (ALRI) among the children were also significantly associated with all three measures of undernutrition.;The third goal of the study was to conduct an exposure assessment, and to provide a proportional analysis of CO exposures among woman during their reproductive years and very young children who use the temazcal (steam bath) during the postpartum period, and which may represent exposures to CO that rival those due to cooking fires. The Coburn-Forster-Kane equation, which permits specifications for altitude, hemoglobin status, body size, and ventilation rate, was used to model carboxyhemoglobin (COHb) formation. Among 281 temazcal users, the mean exposure to CO was 431 ppm (SD, 235 ppm) with a predicted COHb averaging 17% (SD, 2%). During the postpartum period, women and children residing in plancha homes receive an estimated 78% and 46% of their CO exposures from temazcal use, respectively. The value of this dissertation is that it is one of the first studies, using a longitudinal design with a quantitative, personal exposure assessment, to measure the effects of high CO exposures from biomass smoke on fetal and child growth.