INDOOR BIOFUEL AIR-POLLUTION AND RESPIRATORY HEALTH - THE ROLE OF CONFOUNDING FACTORS AMONG WOMEN IN HIGHLAND GUATEMALA

Background A number of studies have reported associations between indo or biofuel air pollution in developing countries and chronic obstructi ve lung disease (COLD) in adults and acute lower respiratory infection (ALRI) in children. Most of these studies have used indirect measures of exposure and generally dealt inadequately with confounding. More r eliable, quantified information about this presumed effect is an impor tant pre-requisite for prevention, not least because of the technical, economic and cultural barriers to achieving substantial exposure redu ctions in the world's poorest households, where ambient pollution leve ls are typically between ten and a hundred times higher than recommend ed standards. This study was carried out as parr of a programme of res earch designed to inform the development of intervention studies capab le of providing quantified estimates of health benefits. Methods The a ssociation between respiratory symptoms and the use of open fires and chimney woodstoves ('planchas'), and the distribution of confounding f actors, were examined in a cross-sectional study of 340 women aged 15- 45 years, living in a poor rural area in the western highlands of Guat emala. Results The prevalence of reported cough and phlegm was signifi cantly higher for three of six symptom measures among women using open fires. Although this finding is consistent with a number of other stu dies, none has systematically examined the extent to which strong asso ciations with confounding variables in these settings limit the abilit y of observational studies to define the effect of indoor air pollutio n adequately. Vet-II strong associations (P < 0.0001) were found betwe en the type of fire and a number of household and socioeconomic factor s including the arrangement of rooms, floor type, and possession of a radio and television. The spouse's economic activity type was also sig nificantly associated (P < 0.05). Thus, while 82% of open fire users h ad dirt floors and only 18% cement or tile floors, the situation was r eversed for plancha risers, only 16% of whom had dirt floors. Conclusi ons Confounding presents a substantial problem for observational studi es of indoor air pollution and health, although there is a reasonable case for believing that the observed association is causal. Interventi on studies are required for stronger evidence of this association, and more importantly, to determine the size of health benefit achievable through feasible exposure reductions.