from the WASHplus Project

Neurotoxicology (2011), doi:10.1016/j.neuro.2011.09.004

Neurodevelopmental performance among school age children in rural Guatemala is associated with prenatal and postnatal exposure to carbon monoxide, a marker for exposure to woodsmoke

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Linda Dix-Cooper, Brenda Eskenazi, Carolina Romero, John Balmes, Kirk R. Smith

We investigated whether early life chronic exposure to woodsmoke, using personal passive 48-h carbon monoxide (CO) as an indicator, is associated with children’s neurodevelopmental and behavioral performance. CO measures were collected every 3 months from 2002 to 2005 among mother–child dyads during the Randomized Exposure Study of Pollution Indoors and Respiratory Effects (RESPIRE) stove intervention trial in San Marcos, Guatemala. From March to June, 2010, study children of age 6–7 years, performed a follow-up non-verbal, culturally adapted neurodevelopmental assessment.

We found inverse associations between CO exposure of pregnant mothers during their 3rd trimesters (m = 3.8 ppm 3.0 ppm; range: 0.6–12.5 ppm) and child neuropsychological performance. Scores on 4 out of 11 neuropsychological tests were significantly associated with mothers’ 3rd trimester CO exposures, including visuo-spatial integration (p < 0.05), short-term memory recall (p < 0.05), long-term memory recall (p < 0.05), and fine motor performance (p < 0.01) measured using the Bender Gestalt-II’s Copy, Immediate Recall, and an adapted version of a Delayed Recall Figures drawing, and the Reitan-Indiana’s Finger Tapping Tests, respectively. These 4 significant findings persisted with adjustment for child sex, age, visual acuity, and household assets (socio-economic status). Summary performance scores were also significantly associated with maternal 3rd trimester CO when adjusted for these covariates. Other variables accounting for variance but were excluded in our final multiple regressionmodels included the following: HOME environment stimulation score, child examiner,WHO height-for-age percentile, and age that the infant stopped breastfeeding. This seems to be the first study on woodsmoke exposure and neurodevelopment, and the first longitudinal birth cohort study on chronic early life CO exposures, determined by high quality measures of mothers’ and infants’ personal CO exposures, and using well-established, reliable child neuropsychological tests. Further research is needed to replicate our results and inform future interventions and air quality standards for woodsmoke and CO.

The Lancet, November 2011

Effect of reduction in household air pollution on childhood pneumonia in Guatemala (RESPIRE): a randomised controlled trial

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Prof Kirk R Smith PhD, John P McCracken ScD, Martin W Weber DrMedHabil , Alan Hubbard PhD, Alisa Jenny MPH, Lisa M Thompson PhD, Prof John Balmes MD, Anaité Diaz MPH, Byron Arana PhD, Nigel Bruce PhD

Background – Pneumonia causes more child deaths than does any other disease. Observational studies have indicated that smoke from household solid fuel is a significant risk factor that affects about half the world’s children. We investigated whether an intervention to lower indoor wood smoke emissions would reduce pneumonia in children.

Methods – We undertook a parallel randomised controlled trial in highland Guatemala, in a population using open indoor wood fires for cooking. We randomly assigned 534 households with a pregnant woman or young infant to receive a woodstove with chimney (n=269) or to remain as controls using open woodfires (n=265), by concealed permuted blocks of ten homes. Fieldworkers visited homes every week until children were aged 18 months to record the child’s health status. Sick children with cough and fast breathing, or signs of severe illness were referred to study physicians, masked to intervention status, for clinical examination. The primary outcome was physician-diagnosed pneumonia, without use of a chest radiograph. Analysis was by intention to treat (ITT). Infant 48-h carbon monoxide measurements were used for exposure-response analysis after adjustment for covariates. This trial is registered, number ISRCTN29007941.

Findings – During 29 125 child-weeks of surveillance of 265 intervention and 253 control children, there were 124 physician-diagnosed pneumonia cases in intervention households and 139 in control households (rate ratio [RR] 0·84, 95% CI 0·63—1·13; p=0·257). After multiple imputation, there were 149 cases in intervention households and 180 in controls (0·78, 0·59—1·06, p=0·095; reduction 22%, 95% CI −6% to 41%). ITT analysis was undertaken for secondary outcomes: all and severe fieldworker-assessed pneumonia; severe (hypoxaemic) physician-diagnosed pneumonia; and radiologically confirmed, RSV-negative, and RSV-positive pneumonia, both total and severe. We recorded significant reductions in the intervention group for three severe outcomes—fieldworker-assessed, physician-diagnosed, and RSV-negative pneumonia—but not for others. We identified no adverse effects from the intervention. The chimney stove reduced exposure by 50% on average (from 2·2 to 1·1 ppm carbon monoxide), but exposure distributions for the two groups overlapped substantially. In exposure-response analysis, a 50% exposure reduction was significantly associated with physician-diagnosed pneumonia (RR 0·82, 0·70—0·98), the greater precision resulting from less exposure misclassification compared with use of stove type alone in ITT analysis.

Interpretation – In a population heavily exposed to wood smoke from cooking, a reduction in exposure achieved with chimney stoves did not significantly reduce physician-diagnosed pneumonia for children younger than 18 months. The significant reduction of a third in severe pneumonia, however, if confirmed, could have important implications for reduction of child mortality. The significant exposure-response associations contribute to causal inference and suggest that stove or fuel interventions producing lower average exposures than these chimney stoves might be needed to substantially reduce pneumonia in populations heavily exposed to biomass fuel air pollution.