Elsevier

Annals of Epidemiology

Volume 20, Issue 11, November 2010, Pages 811-817
Annals of Epidemiology

Biofuel Smoke and Child Anemia in 29 Developing Countries: A Multilevel Analysis

https://doi.org/10.1016/j.annepidem.2010.07.096Get rights and content

Purpose

In this study we examined the effect of biofuel smoke exposure at the national and child levels on child anemia.

Methods

Data are from Demographic and Health Surveys conducted between 2003 and 2007. The respondents were women (15−49 years) and their children (0−59 months) (n = 117,454) in 29 developing countries.

Results

In multinomial logistic regression models, both moderate and high exposure to biofuel smoke at the country level are associated with moderate/severe anemia (odds ratio [OR], 2.36; 95% confidence interval [95% CI], 1.28−4.36 vs OR, 2.80; 95% CI, 1.37−5.72) after adjusting for covariates. Exposure to biofuel smoke at home is associated with mild anemia (OR, 1.07; 95% CI, 1.01−1.13), and there are interactions between biofuel smoke exposure and child age in months on mild anemia (OR, 1.004; 95% CI, 1.002−1.006) and moderate/severe anemia (OR, 1.006; 95% CI, 1.004−1.008). There are also interactions between biofuel smoke exposure at home and diarrhea on mild anemia (OR, 1.22; 95% CI, 1.10−1.34) and on moderate/severe anemia (OR, 1.11; 95% CI, 1.01−1.22); and fever on moderate/severe anemia (OR, 1.33; 95% CI, 1.22−1.45).

Conclusions

Given the increasing number of people relying on biofuels in developing countries, policies and programs are necessary to protect children from being exposed to this harmful smoke at home.

Introduction

Anemia is a major public health problem in developing countries, particularly for pregnant women and young children (1). Approximately 47% of children younger than 5 years of age in developing countries experience anemia, defined as a hemoglobin (Hb) level less than 11 g/dL, with substantial between-country variability in prevalences (2). Childhood anemia has been linked to serious health consequences, including impairments in cognitive function, physical development, psychomotor development, and language development 3, 4. Severe anemia (Hb < 5 g/dL) is associated with an increased risk of mortality (5).

Biofuel smoke exposure has been linked to low birth weight 6, 7, stunted growth 8, 9, and to an increased risk of pneumonia in young children (10) and may also be associated with anemia because it contains a large number of harmful pollutants, including carbon monoxide, benzo(a)pyrene, and cresol (11). Carbon monoxide in biofuel smoke binds with hemoglobin to form carboxyhemoglobin, reducing the quantity of hemoglobin in the blood (12). In addition, exposure to benzo(a)pyrene has been linked to red blood cell damage and anemia (13), and cresol has been linked to kidney problems and anemia (14) in humans. In the only study to examine the association between biofuel smoke exposure and anemia in children, Mishra and Retherford (8) reported a relative risk of 1.58 (95% confidence interval [95% CI], 1.28−1.94) for exposure in the home (8).

Overall, 50% of people in developing countries rely on coal and biomass in the form of wood, straw, dung, and crop residues for domestic energy (15). There are enormous cross-national differences in dependence on biofuels for cooking, from less than 1% in Jordan to 99% in Uganda 16, 17. Women and young children are most likely to be exposed to the smoke produced by burning these fuels (10). The number of people relying on biofuels for cooking and heating is continuing to increase in developing countries (10) and is expected to include 2.6 billion people by 2030 (18).

The high prevalence of childhood anemia in developing countries and its serious health consequences create a need to study the link between biofuel smoke exposure and child anemia, along with factors that may confound or modify this association. For example, poverty and poor child nutritional status may act as confounders. Poverty has been linked to both anemia and the use of biofuels in developing countries 10, 19. Anemia may also occur as a result of underlying acute or chronic infections 20, 21. As part of the immune response to infections, cells of the immune system produce cytokines. These immune cytokines interfere with the iron metabolism as well as the production and normal activity of erythropoietin (a hormone that stimulates bone marrow to produce red blood cells) (21). For children already weakened by fever and diarrhea, the effect of biofuel smoke exposure on anemia may be exacerbated. This may also be true for prolonged exposure to biofuel smoke during the early years.

The objective of this study is to examine the effect of exposure to biofuel smoke at the national and child levels on child anemia in 29 developing countries. The following research questions will be addressed. One, what is the strength of association between biofuel smoke exposure assessed at the country and child levels and child anemia after adjusting for covariates? Two, is the effect of child-level biofuel smoke exposure on child anemia moderated by child age, fever, and diarrhea?

Section snippets

Data

The data are from cross-sectional Demographic and Health Surveys (DHS) conducted between 2003 and 2007 in 29 developing countries. DHS are nationally representative household surveys that have been conducted since 1984 in approximately 70 developing countries worldwide. The sample design for each DHS is based on “simplicity, probability sampling, clustering and stratification” (22). The sampling frame is a list of nonoverlapping area units or enumeration areas that cover the entire country. The

Results

The sample for analyses includes 117,454 children from 29 countries. Sample characteristics are presented in Table 1. There were 117,454 children living in 15,886 clusters or neighborhoods in 29 countries. The average number of children per cluster was 7.39, with a minimum of 1 to a maximum of 74 children. Among all children, about 24% were classified with mild, and 39% were classified with moderate or severe anemia. Approximately 79% of children lived in households that used biofuel for

Discussion

In this study of 29 developing countries, biofuel smoke exposure at the country level exhibits strong associations with moderate/severe anemia in children after controlling for GDP and other covariates. Increasing child age, diarrhea, and fever appear to exacerbate the adverse effects of biofuel smoke exposure at home on child anemia. Prolonged exposure likely accounts for this in older children although we cannot be sure due to the cross-sectional nature of the study.

Our study adds to concerns

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