Impact of reducing indoor air pollution on women's health. RESPIRE Guatemala - Randomised exposure study of pollution indoors and respiratory effects

Abstract

Indoor air pollution (IAP) is a global health problem that affects the most impoverished communities in the world, and especially women and young children among them. Half of the world households, particularly in rural areas, still rely on solid fuels for heating and burning in simple stoves or open fires, often with poor ventilation systems. The high levels of IAP resulting from these practices have been linked to many health hazards. The scientific evidence is strong for a causal association between IAP and acute lower respiratory infections (ALRI) in children under 5 years of age and for chronic obstructive respiratory disease (COPD) and lung cancer (mainly from coal) for adults older than 30 years. The evidence is moderate for lung cancer from biomass smoke, asthma, adverse pregnancy outcomes, cataracts and tuberculosis. The available data on health problems related to IAP comes form observational studies, where the possibility of residual confounding cannot be excluded. Most of these studies have not measured personal exposure to IAP, but rely on exposure proxies, such as time spent near the fire or number of years cooking for the family. In addition, a variety of definitions has been used to study chronic obstructive respiratory disease, and few studies have measured lung function, which is the gold standard for the diagnosis of COPD. Thus, a randomised controlled study that measured personal exposure and lung function of the participants was needed to better understand the effects of IAP on health. Also, to study directly the effects of an intervention, including on a group of younger women in whom COPD would not be well established. RESPIRE (Randomised Exposure Study of Pollution Indoors and Respiratory Effects) is the first randomised controlled study to assess the impact on health of reduced IAP from biomass fuel use. In rural Guatemala, 534 children under 18 months and 504 mothers were included in the RESPIRE study. Wood burned in open fires was the main heating and cooking fuel in all the households. Half part of them (intervention group) received an improved stove with a chimney (plancha). The control households continued to use the open fires, and received a plancha at the end of the study, 18 months later. This thesis presents health outcomes among the mothers taking part in RESPIRE. The participants were young (mean age of 27.8 years), and did not smoke. These women exposed to IAP since birth had a relatively high prevalence of respiratory symptoms at baseline: cough (22.6%), phlegm (15.1%), wheeze (25.1%), and tightness in the chest (31.4%), and reported even higher prevalence of non-respiratory symptoms: sore eyes (53%), headache (70%), and back pain (62%). Lung function at baseline was higher than the most relevant reference population identified (average above predicted FEV1 +4.5% and FVC +4.2%). The randomisation of the households into intervention and control groups appeared to be successful. The plancha significantly reduced exposure to carbon monoxide (CO) by 61.6% as measured by diffusion tubes. For all respiratory symptoms, a consistent reduction in risk was observed in the plancha group for the follow-up period as a whole, the reduction being statistically significant only for wheeze (RR and 95% CI: 0.42 (0.25- 0.70)). The number of respiratory symptoms reported by a woman at each follow-up time was also significantly reduced by the plancha (OR and 95% CI: 0.7 (0.50-0.97)). The odds of having sore eyes and headache were substantially reduced in the plancha group relative to the group using open fires for the follow-up period (RR and 95% CI: 0.37 (0.28-0.49); RR and 95% CI: 0.82 (0.70-0.97), respectively). No significant effects were, however, found on lung function measurements within the 18 months follow-up. Among a subgroup of 89 intervention and 80 control women asked about change in health during the study period, 52.8% of the intervention women reported improvement in health, compared to 23.8% of the control women (p<0.001). When asked how the plancha had changed their lives, 84 intervention women reported a reduction of smoke in the kitchen; 88% of them linked this to improvement in their own health, particularly for non-respiratory symptoms (eye discomfort and headache); 57% linked reduced smoke to improvement in their children’s health, particularly sore eyes. The study had several limitations. The lack of baseline information on symptoms for one of the recruitment groups, the lack of validated questionnaires and of reference values for lung function in this population, the presence of other sources of exposure (temascal) and the relatively short follow-up, were the main challenges in our study. In conclusion, in the frame of a randomised controlled trial, our study supports and strengthens the evidence of a link between long-term exposure to IAP and both respiratory and non-respiratory symptoms among young non-smoking women. The plancha proved to significantly reduce the levels of exposure in the intervention group. Both respiratory and non-respiratory symptoms were significantly reduced in this group, although no effect in lung function could be detected 18 months after the intervention was introduced. The young age of the participants and the relatively short follow-up period are the most probable reasons leading to our inability to detect such an effect.