Letter | Published:

Robust relationship between air quality and infant mortality in Africa

Naturevolume 559pages254258 (2018) | Download Citation

Abstract

Poor air quality is thought to be an important mortality risk factor globally1,2,3, but there is little direct evidence from the developing world on how mortality risk varies with changing exposure to ambient particulate matter. Current global estimates apply exposure–response relationships that have been derived mostly from wealthy, mid-latitude countries to spatial population data4, and these estimates remain unvalidated across large portions of the globe. Here we combine household survey-based information on the location and timing of nearly 1 million births across sub-Saharan Africa with satellite-based estimates5 of exposure to ambient respirable particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) to estimate the impact of air quality on mortality rates among infants in Africa. We find that a 10 μg m−3 increase in PM2.5 concentration is associated with a 9% (95% confidence interval, 4–14%) rise in infant mortality across the dataset. This effect has not declined over the last 15 years and does not diminish with higher levels of household wealth. Our estimates suggest that PM2.5 concentrations above minimum exposure levels were responsible for 22% (95% confidence interval, 9–35%) of infant deaths in our 30 study countries and led to 449,000 (95% confidence interval, 194,000–709,000) additional deaths of infants in 2015, an estimate that is more than three times higher than existing estimates that attribute death of infants to poor air quality for these countries2,6. Upward revision of disease-burden estimates in the studied countries in Africa alone would result in a doubling of current estimates of global deaths of infants that are associated with air pollution, and modest reductions in African PM2.5 exposures are predicted to have health benefits to infants that are larger than most known health interventions.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from $8.99

All prices are NET prices.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  1. 1.

    Lelieveld, J., Evans, J. S., Fnais, M., Giannadaki, D. & Pozzer, A. The contribution of outdoor air pollution sources to premature mortality on a global scale. Nature 525, 367–371 (2015).

  2. 2.

    Cohen, A. J. et al. Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015. Lancet 389, 1907–1918 (2017).

  3. 3.

    Anenberg, S. C. et al. Impacts and mitigation of excess diesel-related NOx emissions in 11 major vehicle markets. Nature 545, 467–471 (2017).

  4. 4.

    Burnett, R. T. et al. An integrated risk function for estimating the global burden of disease attributable to ambient fine particulate matter exposure. Environ. Health Perspect. 122, 397–403 (2014).

  5. 5.

    van Donkelaar, A. et al. Global estimates of fine particulate matter using a combined geophysical-statistical method with information from satellites, models, and monitors. Environ. Sci. Technol. 50, 3762–3772 (2016).

  6. 6.

    Institute for Health Metrics and Evaluation. Global Burden of Disease study 2015 (GBD, 2015) results. http://ghdx.healthdata.org/gbd-results-tool (2016). URL.

  7. 7.

    Shindell, D. et al. Simultaneously mitigating near-term climate change and improving human health and food security. Science 335, 183–189 (2012).

  8. 8.

    Zhang, Q. et al. Transboundary health impacts of transported global air pollution and international trade. Nature 543, 705–709 (2017).

  9. 9.

    Ebisu, K., Belanger, K. & Bell, M. L. Association between airborne PM2.5 chemical constituents and birth weight—implication of buffer exposure assignment. Environ. Res. Lett. 9, 084007 (2014).

  10. 10.

    West, J. J. et al. What we breathe impacts our health: improving understanding of the link between air pollution and health. Environ. Sci. Technol. 50, 4895–4904 (2016).

  11. 11.

    Burke, M., Heft-Neal, S. & Bendavid, E. Sources of variation in under-5 mortality across sub-Saharan Africa: a spatial analysis. Lancet Glob. Health 4, e936–e945 (2016).

  12. 12.

    Brauer, M. et al. Ambient air pollution exposure estimation for the Global Burden of Disease 2013. Environ. Sci. Technol. 50, 79–88 (2016).

  13. 13.

    Zhang, F. et al. Sensitivity of mesoscale modeling of smoke direct radiative effect to the emission inventory: a case study in northern sub-Saharan African region. Environ. Res. Lett. 9, 075002 (2014).

  14. 14.

    Butt, E. W. et al. The impact of residential combustion emissions on atmospheric aerosol, human health, and climate. Atmos. Chem. Phys. 16, 873–905 (2016).

  15. 15.

    Di, Q. et al. Air pollution and mortality in the medicare population. N. Engl. J. Med. 376, 2513–2522 (2017).

  16. 16.

    Occupational and Environmental Health Team. WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide : global update 2005 : summary of risk assessment. World Health Organization http://www.who.int/iris/handle/10665/69477 (WHO, 2006).

  17. 17.

    Patt, A. G. et al. Estimating least-developed countries’ vulnerability to climate-related extreme events over the next 50 years. Proc. Natl Acad. Sci. USA 107, 1333–1337 (2010).

  18. 18.

    Smith, K. R. et al. in Climate Change 2014: Impacts, Adaptation, and Vulnerability (eds Field, C. B. et al.) 709–794 (IPCC, Cambridge Univ. Press, 2014).

  19. 19.

    Walker, N., Tam, Y. & Friberg, I. K. Overview of the lives saved tool (list). BMC Public Health 13, S1 (2013).

  20. 20.

    Institute for Health Metrics and Evaluation. GBD Compare data visualization. http://vizhub.healthdata.org/gbd-compare (2017).

  21. 21.

    Bell, M. L., Ebisu, K. & Belanger, K. Ambient air pollution and low birth weight in Connecticut and Massachusetts. Environ. Health Perspect. 115, 1118–1124 (2007).

  22. 22.

    Pope, D. P. et al. Risk of low birth weight and stillbirth associated with indoor air pollution from solid fuel use in developing countries. Epidemiol. Rev. 32, 70–81 (2010).

  23. 23.

    Pereira, G., Belanger, K., Ebisu, K. & Bell, M. L. Fine particulate matter and risk of preterm birth in Connecticut in 2000–2006: a longitudinal study. Am. J. Epidemiol. 179, 67–74 (2014).

  24. 24.

    Chay, K. Y. & Greenstone, M. The impact of air pollution on infant mortality: evidence from geographic variation in pollution shocks induced by a recession. Q. J. Econ. 118, 1121–1167 (2003).

  25. 25.

    Chay, K. Y. & Greenstone, M. Air Quality, Infant Mortality, and the Clean Air Act of 1970. Report No. 10053 (National Bureau of Economic Research, 2003).

  26. 26.

    Arceo, E., Hanna, R. & Oliva, P. Does the effect of pollution on infant mortality differ between developing and developed countries? Evidence from Mexico City. Econ. J. 126, 257–280 (2016).

  27. 27.

    He, G., Fan, M. & Zhou, M. The effect of air pollution on mortality in China: Evidence from the 2008 Beijing Olympic games. J. Environ. Econ. Manage. 79, 18–39 (2016).

  28. 28.

    Knittel, C. R., Miller, D. L. & Sanders, N. J. Caution, drivers! Children present: traffic, pollution, and infant health. Rev. Econ. Stat. 98, 350–366 (2016).

  29. 29.

    Cesur, R., Tekin, E. & Ulker, A. Air pollution and infant mortality: evidence from the expansion of natural gas infrastructure. Econ. J. 127, 330–362 (2017).

  30. 30.

    Global Administrative Areas. GADM database of Global Administrative Areas, version 2.0. https://gadm.org/ (2012).

  31. 31.

    ICF. The DHS program, Data. http://dhsprogram.com/data (1998).

  32. 32.

    Bendavid, E. Is health aid reaching the poor? Analysis of household data from aid recipient countries. PLoS ONE 9, e84025 (2014).

  33. 33.

    Lee, H. J., Coull, B. A., Bell, M. L. & Koutrakis, P. Use of satellite-based aerosol optical depth and spatial clustering to predict ambient PM2.5 concentrations. Environ. Res. 118, 8–15 (2012).

  34. 34.

    Hyder, A. et al. PM2.5 exposure and birth outcomes: use of satellite- and monitor-based data. Epidemiology 25, 58–67 (2014).

  35. 35.

    Crouse, D. L. et al. A new method to jointly estimate the mortality risk of long-term exposure to fine particulate matter and its components. Sci. Rep. 6, 18916 (2016).

  36. 36.

    Burke, M., Gong, E. & Jones, K. Income shocks and HIV in Africa. Econ. J. 125, 1157–1189 (2015).

  37. 37.

    Funk, C. et al. The climate hazards infrared precipitation with stations—a new environmental record for monitoring extremes. Sci. Data 2, 150066 (2015).

  38. 38.

    LP DAAC. MODIS/aqua land surface temperature and emissivity (LST/E). version 6. USGS Earth Resources Observation And Science Center. https://lpdaac.usgs.gov (NASA, 2016).

  39. 39.

    Baird, S., Friedman, J. & Schady, N. Aggregate income shocks and infant mortality in the developing world. Rev. Econ. Stat. 93, 847–856 (2011).

  40. 40.

    Tatem, A. J. et al. Millennium development health metrics: where do Africa’s children and women of childbearing age live? Popul. Health Metr. 11, 11 (2013).

  41. 41.

    Rehman, I., Ahmed, T., Praveen, P., Kar, A. & Ramanathan, V. Black carbon emissions from biomass and fossil fuels in rural India. Atmos. Chem. Phys. 11, 7289–7299 (2011).

  42. 42.

    Anenberg, S. C., Horowitz, L. W., Tong, D. Q. & West, J. J. An estimate of the global burden of anthropogenic ozone and fine particulate matter on premature human mortality using atmospheric modeling. Environ. Health Perspect. 118, 1189–1195 (2010).

  43. 43.

    Isen, A., Rossin-Slater, M. & Walker, W. R. Every breath you take, every dollar you’ll make: the long-term consequences of the clean air act of 1970. J. Polit. Econ. 125, 848–902 (2017).

  44. 44.

    Wilson, W. E. & Suh, H. H. Fine particles and coarse particles: concentration relationships relevant to epidemiologic studies. J. Air Waste Manag. Assoc. 47, 1238–1249 (1997).

  45. 45.

    Brook, J. R., Dann, T. F. & Burnett, R. T. The relationship among TSP, PM10, PM2.5, and inorganic constituents of atmospheric participate matter at multiple Canadian locations. J. Air Waste Manage. Assoc. 47, 2–19 (1997).

  46. 46.

    Dionisio, K. L. et al. Measuring the exposure of infants and children to indoor air pollution from biomass fuels in the Gambia. Indoor Air 18, 317–327 (2008).

  47. 47.

    Ezzati, M., Saleh, H. & Kammen, D. M. The contributions of emissions and spatial microenvironments to exposure to indoor air pollution from biomass combustion in Kenya. Environ. Health Perspect. 108, 833–839 (2000).

  48. 48.

    Kilabuko, J. H., Matsuki, H. & Nakai, S. Air quality and acute respiratory illness in biomass fuel using homes in Bagamoyo, Tanzania. Int. J. Environ. Res. Public Health 4, 39–44 (2007).

  49. 49.

    Yamamoto, S. S., Louis, V. R., Sié, A. & Sauerborn, R. Biomass smoke in Burkina Faso: what is the relationship between particulate matter, carbon monoxide, and kitchen characteristics? Environ. Sci. Pollut. Res. 21, 2581–2591 (2014).

  50. 50.

    Fischer, S. L. & Koshland, C. P. Daily and peak 1 h indoor air pollution and driving factors in a rural Chinese village. Environ. Sci. Technol. 41, 3121–3126 (2007).

  51. 51.

    Ni, K. et al. Seasonal variation in outdoor, indoor, and personal air pollution exposures of women using wood stoves in the Tibetan Plateau: baseline assessment for an energy intervention study. Environ. Int. 94, 449–457 (2016).

  52. 52.

    Parikh, J., Balakrishnan, K., Laxmi, V. & Biswas, H. Exposure from cooking with biofuels: pollution monitoring and analysis for rural Tamil Nadu, India. Energy 26, 949–962 (2001).

  53. 53.

    Cyrys, J., Pitz, M., Bischof, W., Wichmann, H.-E. & Heinrich, J. Relationship between indoor and outdoor levels of fine particle mass, particle number concentrations and black smoke under different ventilation conditions. J. Expo. Anal. Environ. Epidemiol. 14, 275–283 (2004).

  54. 54.

    Pedersen, M. et al. Ambient air pollution and low birthweight: a European cohort study (ESCAPE). Lancet Respir. Med. 1, 695–704 (2013).

  55. 55.

    Chang, H. H., Warren, J. L., Darrow, L. A., Reich, B. J. & Waller, L. A. Assessment of critical exposure and outcome windows in time-to-event analysis with application to air pollution and preterm birth study. Biostatistics 16, 509–521 (2015).

  56. 56.

    Li, X. et al. Association between ambient fine particulate matter and preterm birth or term low birth weight: an updated systematic review and meta-analysis. Environ. Pollut. 227, 596–605 (2017).

  57. 57.

    Blum, J. L., Chen, L.-C. & Zelikoff, J. T. Exposure to ambient particulate matter during specific gestational periods produces adverse obstetric consequences in mice. Environ. Health Perspect. 125, 077020 (2017).

  58. 58.

    Kampa, M. & Castanas, E. Human health effects of air pollution. Environ. Pollut. 151, 362–367 (2008).

  59. 59.

    Slama, R. et al. Meeting report: atmospheric pollution and human reproduction. Environ. Health Perspect. 116, 791–798 (2008).

  60. 60.

    Jerrett, M. et al. Traffic-related air pollution and obesity formation in children: a longitudinal, multilevel analysis. Environ. Health 13, 49 (2014).

  61. 61.

    Suades-González, E., Gascon, M., Guxens, M. & Sunyer, J. Air pollution and neuropsychological development: a review of the latest evidence. Endocrinology 156, 3473–3482 (2015).

  62. 62.

    Jayachandran, S. Air quality and early-life mortality: evidence from Indonesia’s wildfires. J. Hum. Resour. 44, 916–954 (2009).

  63. 63.

    Tielsch, J. M. et al. Exposure to indoor biomass fuel and tobacco smoke and risk of adverse reproductive outcomes, mortality, respiratory morbidity and growth among newborn infants in south India. Int. J. Epidemiol. 38, 1351–1363 (2009).

  64. 64.

    Black, R. E. et al. Maternal and child undernutrition: global and regional exposures and health consequences. Lancet 371, 243–260 (2008).

  65. 65.

    Malilay, J., Mariana, G. R., Ramirez Vanegas, A., Non, E. & Sinks, T. Public health surveillance after a volcanic eruption: lessons from Cerro Negro, Nicaragua, 1992. Bull. Pan. Am. Health. Organ. 30, 218–226 (1996).

  66. 66.

    Menetrez, M. Y. et al. An evaluation of indoor and outdoor biological particulate matter. Atmos. Environ. 43, 5476–5483 (2009).

  67. 67.

    Luby, S. P. et al. Effect of handwashing on child health: a randomised controlled trial. Lancet 366, 225–233 (2005).

Download references

Acknowledgements

We thank D. Lobell, G. McCord, M. P. Burke and W. Schlenker for useful comments and V. Tanutama for research assistance. We thank the Stanford Environmental Ventures Fund and the National Science Foundation (CNH Award #1715557) for funding.

Reviewer information

Nature thanks R. Black, J. Lelieveld, L. Waller and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

Affiliations

  1. Center on Food Security and the Environment, Stanford University, Stanford, CA, USA

    • Sam Heft-Neal
    •  & Marshall Burke
  2. School of Global Policy and Strategy, University of California, San Diego, San Diego, CA, USA

    • Jennifer Burney
  3. School of Medicine, Stanford University, Stanford, CA, USA

    • Eran Bendavid
  4. Department of Earth System Science, Stanford University, Stanford, CA, USA

    • Marshall Burke
  5. National Bureau of Economic Research, Cambridge, MA, USA

    • Marshall Burke

Authors

  1. Search for Sam Heft-Neal in:

  2. Search for Jennifer Burney in:

  3. Search for Eran Bendavid in:

  4. Search for Marshall Burke in:

Contributions

S.H.N., J.B., E.B. and M.B. designed the research; S.H.N. analysed the data; S.H.N., J.B., E.B. and M.B. interpreted results and wrote the paper.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Marshall Burke.

Extended data figures and tables

  1. Extended Data Fig. 1 Integrated exposure risk curve estimated by the GBD project.

    Data were obtained from a previous study4. a, Relative risk curve representing the risk from acute lower respiratory infections in infants (obtained from figure 2 of Burnett et al.4). The curve combines point estimates from ambient air pollution (AAP) studies, indoor air pollution (HAP) studies and second-hand smoking (SHS) studies to derive risk responses across the PM2.5 exposure distribution. The histograms show the share of population exposed to different long-run (15-year average) ambient PM2.5 concentrations in North American and Europe where most GBD studies took place, in SSA countries in our sample, and globally. In total, 49% of the overall population in Africa, and 51% globally, live in areas with ambient pollution concentrations exceeding the maximum ambient PM2.5 concentration from the GBD study (25 μg m−3). b, Most studies used to estimate the GBD integrated exposure response4 were carried out in North America or Europe, with the exception of a household air pollution study in Guatemala and second-hand smoking studies in Vietnam, India and South Africa. Median sample size (depicted by marker size in the plot) across these studies is n = 1,250. Country outlines were obtained from Global Administrative Areas, version 2.030.

  2. Extended Data Fig. 2 Overview of birth data from DHS surveys and study regions in Africa.

    a, Location of DHS clusters included in our sample. b, The number of births observed in each year in our sample. More births are observed in earlier years because births are recalled in the surveys so each new survey round potentially adds births from all previous years. c, Regional categorization of countries, for regional analysis in Fig. 2c. Sample countries assigned to West Africa region are Benin, Burkina Faso, Ivory Coast, Ghana, Guinea, Liberia, Mali, Nigeria, Senegal, Sierra Leone and Togo. Sample countries assigned to ‘rest of Africa’ are Angola, Burundi, Cameroon, Comoros, DRC, Ethiopia, Gabon, Kenya, Lesotho, Madagascar, Malawi, Mozambique, Namibia, Rwanda, Swaziland, Uganda, Zambia and Zimbabwe. Country outlines were obtained from Global Administrative Areas, version 2.030.

  3. Extended Data Fig. 3 Effect of post-birth PM2.5 exposure is robust under different regression models.

    Estimated responses under higher-order polynomials (a), different specifications of the fixed effects (b), restricted cubic spline functions of PM2.5 (c) and additional time controls (d). In each panel, the blue line and shaded region indicate the estimated baseline response shown in Fig. 2a and the bootstrapped 95% confidence interval. Splines in c have knots at 10 μg m−3 (single knot spline) or evenly spaced knots (three- and four-knot splines).

  4. Extended Data Fig. 4 Piecewise linear and cross-sectional relationships between post-birth PM2.5 exposure and infant mortality.

    a, Piecewise linear estimates of the effect of PM2.5 exposure below and above the WHO PM2.5 guideline of 10 μg m−3. Shaded regions represent bootstrapped 95% confidence intervals. Slopes above and below the 10 μg m−3 threshold are very similar, although confidence intervals are wider below the threshold due to smaller sample sizes. b, Cross-sectional and panel models give similar estimated effects of post-birth PM2.5 exposure on infant mortality. Blue line shows baseline panel model, orange line shows a cross-sectional model that relates cluster-average mortality to cluster-average PM2.5 exposure. Each response function is centred at sample median exposure (25 μg m−3). Histograms at the bottom show counts of exposure at different PM2.5 levels, for the panel sample (blue) and cross-sectional sample (orange); cross-sectional exposures are slightly narrower given that year-to-year variation has been averaged out.

  5. Extended Data Fig. 5 Heterogeneous effects of post-birth PM2.5 exposure.

    Effects are estimated by interacting a dummy for each modifying variable with linear PM2.5, and are measured as the percentage change in infant mortality per 10 μg m−3 increase in PM2.5 exposure, relative to baseline mortality rates in each subgroup. Circles indicate point estimates, and whiskers the 95% confidence interval on the point estimate. The last column shows the baseline estimate from the full (uninteracted) linear model.

  6. Extended Data Fig. 6 Linear effect of post-birth PM2.5 exposure by year for different time periods.

    Panels are the same as Fig. 2e but replicated for different time periods, showing effects in each year independently. Circles indicate point estimates, and whiskers the 95% confidence interval on the point estimate. For each time period 2001 − year t, the sample was restricted to births between 2001 and year t and to surveys that were conducted after year t. These steps help to approximate a consistent geographical sample across the time periods.

  7. Extended Data Fig. 7 Effect of different assumed counterfactual PM2.5 levels on the estimated share of infant deaths attributable to PM2.5.

    Each point represents the same calculation described in the Methods, under different counterfactual minimum PM2.5 exposure levels. Data are from Cohen et al.2, Burnett et al.4 and the WHO guidelines16.

  8. Extended Data Fig. 8 Effect of PM2.5 on non-respiratory mortality and mortality risk factors.

    ac, Effect of in utero PM2.5 exposure on low birth weight, low birth size as reported by mothers on a scale from 1 to 5, and neonatal mortality (NMR). d, e, Effect of post-birth PM2.5 exposure on height-for-age and diarrhoeal incidence for living children. In each case, higher PM2.5 concentrations worsen health outcomes. fh, Placebo tests that relate PM2.5 exposures to child outcomes that should be unaffected: child sex, whether child was born in a multiple birth, and child’s use of a bed net. i, PM2.5 exposure in the 13–24 months after birth has no effect on mortality in the first 12 months after birth. Shaded regions represent bootstrapped 95% confidence intervals in each panel. j, Estimates of the effect of PM2.5 on all-cause infant mortality from published quasi-experimental studies24,25,26,27,28,29, expressed as the percentage change in the infant mortality rate per 10 μg m−3 increase in PM2.5.

  9. Extended Data Table 1 Regression results for main specification and for subsample of households with asset data
  10. Extended Data Table 2 Understanding potential bias from unobserved indoor air pollution exposure

Supplementary information

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/s41586-018-0263-3

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.