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Demonstrating bias and improved inference for stoves’ health benefits

Valerie Mueller, Alexander Pfaff, John Peabody, Yaping Liu, Kirk R. Smith
International Journal of Epidemiology (2011) 1–9 [doi:10.1093/ije/dyr150]

PDF link iconBACKGROUND: Many studies associate health risks with household air pollution from biomass fuels and stoves. Evaluations of stove improvements can suffer from bias because they rarely address health-relevant differences between the households who get improvements and those who do not. METHODS: We demonstrate both the potential for bias and an option for improved stove inference by applying to household air pollution a technique used elsewhere in epidemiology, propensity-score matching (PSM), based on a stoves-and-health survey for China (15 counties, 3500 households). RESULTS: Health-relevant factors (age, wealth, kitchen ventilation) do in fact differ considerably between the households with stove improvements and those without. We study the resulting bias in estimates of cleaner-stove impacts using a self-reported Physical Component Summary (PCS). Typical stoves-literature regressions with little control for non-stove factors suggest no benefits from a cleaner-fuel stove relative to a traditional biomass stove. Yet increasing controls raises the impact estimates. Our PSM estimates address the differences in health-relevant factors using ‘apples to apples’ comparisons between those with improved stoves and ‘similar’ households. This generates higher estimates of clean-stove benefits, which are on the order of one half the standard deviation of the PCS outcome. CONCLUSIONS: Our data demonstrate the potential importance of bias in household air pollution studies. This results from failure to address the possibility that those receiving improved stoves are themselves prone to better or worse health outcomes. It suggests the value of data collection and of study design for cookstove interventions and, more generally, for policy interventions within many health outcomes.

 

Fuel-choice and indoor air quality: a household-level perspective on economic growth and the environment

Shubham Chaudhuri, Alexander Pfaff
Working paper, Columbia University SIPA

PDF link iconThe fuel-use decisions of households in developing economies, because they directly influence the level of indoor air quality that these households enjoy (with its attendant health effects), provide a natural arena for empirically assessing latent preferences towards the environment and how these evolve with increases in income. Such an assessment is critical for a better understanding of the likely effects of aggregate economic growth on the environment. Using household data from Pakistan we estimate Engel curves for traditional (dirty) and modern (clean) fuels. Our results provide empirical support for a household production framework in which non-monotonic environmental Engel curves can arise quite naturally. Under plausible assumptions about the emissions implied by fuel use, our estimates yield an inverted-U relationship between indoor air pollution and income, mirroring the environmental Kuznets curves that have been documented using aggregate data. We then demonstrate, through a simple voting model, that this household-choice framework can generate aggregate EKCs even in a multi-agent setting with heterogeneous households and purely external environmental effects.