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Health effects of indoor and outdoor air pollution

Health effects of indoor and outdoor air pollution

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Health effects of indoor and outdoor air pollution

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  1. Health effects of indoor and outdoor air pollution Jie-Sheng Tan-Soo Subhrendu K. Pattanayak Duke University Camp Resources 2012

  2. Research questions • What are the joint impacts of indoor and outdoor air pollution on children’s health? • Are impacts different for self-reported and objective health measurements?

  3. Introduction • Respiratory illnesses is top disease burden for developing countries (WHO, 2008) • Environmental causes: indoor and outdoor air pollution • Indoor air pollution from ‘dirty’ household fuel (PM2.5 air particulates, carbon monoxide) • Outdoor air pollution from emissions and forest fires (PM10 air particulates, SO2, NOX, CO, O3) • Climate change to result in worsening outdoor air pollution (IPCC, 2007) • Need better understanding on the concurrent effects of indoor and outdoor air pollution • Need to consider endogenous exposure to indoor air pollution

  4. Why conduct another study? • Epidemiological reason: • Most existing studies are conducted in places where exposure is low compared to developing countries • Econometric reason / omitted variable bias: • 1st: Indoor air pollution highly correlated with outdoor air pollution (see review by Yocom, 1982) • 2nd: Exposure to air pollution may be endogenous (e.g. Mullahy and Portney, 1990)

  5. Study Approach • Panel individual-level dataset from Indonesia • Include measurements for both indoor air pollution (IAP) and outdoor air pollution (OAP) • Use household fixed effects to control time- invariant heterogeneity • Use a wide range of self-reported and objective health measures

  6. Literature Review • Use 1997 Indonesian forest fires as exogenous shock to OAP (Frankenberg et al., 2005 ; Jayachandran, 2008) • Use fuel price as instrument for stove usage (Hanley, 2006) • Include both IAP & OAP in India (Ghosh & Mukherji, 2011)

  7. Model • Health production framework (Rosenzwig & Schultz, 1983) • Maximize household utility subject to health production function and budget constraint • X: consumption good • R: child’s respiratory health • I: indoor air pollution • O: outdoor air pollution • : prices • Y: income • : unobserved family factors such as health preferences or attitudes • Reduced-formed child’s health equation • ‘Hybrid’ health equation are typically estimated because of data constraint

  8. Model • Bias 1: IAP is correlated with OAP where • Marginal effect of IAP is • If IAP is not included, then estimates of will be biased as • Bias 2: Exposure to IAP is endogenous and correlated with other determinants of health • Marginal effect of IAP is

  9. Empirical strategy • Estimating equation • i: child; j: household; k: district • Measures for both IAP and OAP • Dirty stove indicator for IAP • Aerosol index for OAP • Inclusion of household fixed effects to control for time-invariant household heterogeneity • Neglect cross-sectional variation • Identification of the IAP parameter is from households that switched stoves type

  10. Data • Indonesia Family and Life Survey • Main type of stove used & individual health measurements • Four waves (1993, 1997, 2000, 2007) • Panel individual and household survey • High re-contact rate/ Low attrition • ~20,000 children (under age of 12) over three waves • NASA Total Ozone Mapping Spectrometer • Aerosol index • From 1993 onwards • Satellite data at district level

  11. Source: http://www.rand.org/labor/FLS/IFLS.html

  12. Sep 24, 1997 Sep 18, 2000 Sep 21, 2005

  13. Data • Self-reported health measurements • Cough in last 4 weeks? • Breathing difficulties in last 4 weeks? • Number of days ill in last 4 weeks? • Number of days in bed due to poor health in last weeks? • Assessment of overall health (1-4 with 1 being very unhealthy) • Objective health measures: • Lung capacity • Body-mass index • Height-for-age z-score • Weight for age z-score

  14. Results – self-reported health Controls: Age, Gender, Household assets, Year FE Expected signs: +ve for column (1) to (5)

  15. Results – objective health Controls: Age, Gender, Household assets, Year FEs Expected signs: -vefor column (1) to (4)

  16. Robustness checks • Use of fixed effects result in loss of cross-sectional variation • Test of FE vs. RE (Hausman test) • Household fixed effects uncorrelated with regressors

  17. Robustness checks • Hausman-Taylor method (1981) to estimate the impact of time-invariant regressors

  18. Robustness checks • Hausman-Taylor method (1981) to estimate the impact of time-invariant regressors

  19. Summary • Self-reported health likely unreliable • Only OAP has adverse impact on health • Results are driven by HHs that switch stove • Hausman-Taylor estimator however shows that both OAP & IAP are damaging to health • But results are driven by non-switcher HHs • In all, results suggest differences between switchers & non-switchers • Long term exposure vs. short term? • Switchers and non-switchers fundamentally different?

  20. Key points • Effects of air pollution on health is a very important and complex problem • Respiratory illnesses is a major burden • Close relationship between indoor and outdoor pollution • Endogenous exposure to pollution • Indoor and outdoor air pollution harm health • Switchers vs. non-switchers • Self-reported vs. objective health measures • Need structural modeling