In this study, we aimed to establish whether domestic use of wood fuel is associated with reduced birth weight, independent of key maternal, social, and economic confounding factors. We studied 1,717 women and newborn children in rural and urban communities in rural Guatemala. We identified subjects through home births reported by traditional birth attendants in six rural districts (n = 572) and all public hospital births in Quetzaltenango city during the study period (n = 1,145). All were seen within 72 hr of delivery, and data were collected on the type of household fuel used, fire type, and socioeconomic and other confounding factors. Smoking among women in the study community was negligible. Children born to mothers habitually cooking on open fires (n = 861) had the lowest mean birth weight of 2,819 g [95% confidence interval (CI), 2,790-2,848]; those using a chimney stove (n = 490) had an intermediate mean of 2,863 g (95% CI, 2,824-2,902); and those using the cleanest fuels (electricity or gas, n = 365) had the highest mean of 2,948 g (95% CI, 2,898-2,998) (p < 0.0001). The percentage of low birth weights (< 500 g) in these three groups was 19.9% (open fire), 16.8% (chimney stove), and 16.0% (electricity/gas), (trend p = 0.08). Confounding factors were strongly associated with fuel type, but after adjustment wood users still had a birth weight 63 g lower (p = 0.05; 95% CI, 0.4-126). This is the first report of an association between biofuel use and reduced birth weight in a human population. Although there is potential for residual confounding despite adjustment, the better-documented evidence on passive smoking and a feasible mechanism through carbon monoxide exposure suggest this association may be real. Because two-thirds of households in developing countries still rely on biofuels and women of childbearing age perform most cooking tasks, the attributable risk arising from this association, if confirmed, could be substantial. Key words: biofuel, carbon monoxide, indoor air pollution, low birth weight. Environ Health Perspect 110:109-114 (2002). [Online 19 December 2001]
Low birth weight (LBW), defined as birth weight < 2,500 g, is well established as an important risk factor for infant mortality and morbidity. Well over 90% of all LBW babies are born in developing countries, where approximately 18% of newborns weigh less than 2,500 [g.sup.2]. In Guatemala, for the period 1990-1994, 14% of all births fell into this category (1), although there are substantial variations within the country (2). LBW results from a wide range of factors that determine premature birth, intrauterine growth retardation, or combinations of both of these outcomes (3). Any conditions that interfere with transplacental delivery of nutrients, oxygen included, may cause varying degrees and types of intrauterine growth retardation (IUGR). Of the environmental factors linked with reduced birth weight, tobacco smoking--both active and passive--has probably been the most extensively studied (4-8). Active smoking is associated with a mean reduction in birth weight of up to 200 g, whereas passive smoking has a smaller effect variously estimated at 20-120 g (9-12). A recent meta-analysis reported a weighted estimate of 28 g, with a greater decrement of 40 g when pooling was restricted to the more homogeneous studies (8).
Tobacco Smoke, Biofuels, and Low Birth Weight
Although over 4,000 substances have been identified in cigarette smoke, only a few dozen are singled out as important from a health perspective. Carbon monoxide (CO) in particular and possibly nicotine are regarded as the agents most likely to be responsible for detrimental effects on intrauterine growth (10,13,14). CO results from the incomplete combustion of any biomass, which includes tobacco and biofuels (wood, dung, and fiber residues) as well as fossil fuels such as coal and gas, which are used for cooking and heating (15). …