Global health benefits of mitigating ozone pollution with methane emission controls

doi:10.1073/pnas.0600201103

Global health benefits of mitigating ozone pollution with methane emission controls

*Department of Geosciences and Atmospheric and Oceanic Sciences Program, Princeton University, Sayre Hall, Princeton, NJ 08544;
^†Woodrow Wilson School of Public and International Affairs, Princeton University, Robertson Hall, Princeton, NJ 08544; and
^§Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration, 201 Forrestal Road, Princeton, NJ 08542

Communicated by James E. Hansen, Goddard Institute for Space Studies, New York, NY, January 11, 2006 (received for review September 6, 2005)

Abstract

Methane (CH₄) contributes to the growing global background concentration of tropospheric ozone (O₃), an air pollutant associated with premature mortality. Methane and ozone are also important greenhouse gases. Reducing methane emissions therefore decreases surface ozone everywhere while slowing climate warming, but although methane mitigation has been considered to address climate change, it has not for air quality. Here we show that global decreases in surface ozone concentrations, due to methane mitigation, result in substantial and widespread decreases in premature human mortality. Reducing global anthropogenic methane emissions by 20% beginning in 2010 would decrease the average daily maximum 8-h surface ozone by ≈1 part per billion by volume globally. By using epidemiologic ozone-mortality relationships, this ozone reduction is estimated to prevent ≈30,000 premature all-cause mortalities globally in 2030, and ≈370,000 between 2010 and 2030. If only cardiovascular and respiratory mortalities are considered, ≈17,000 global mortalities can be avoided in 2030. The marginal cost-effectiveness of this 20% methane reduction is estimated to be ≈$420,000 per avoided mortality. If avoided mortalities are valued at $1 million each, the benefit is ≈$240 per tonne of CH₄ (≈$12 per tonne of CO₂ equivalent), which exceeds the marginal cost of the methane reduction. These estimated air pollution ancillary benefits of climate-motivated methane emission reductions are comparable with those estimated previously for CO₂. Methane mitigation offers a unique opportunity to improve air quality globally and can be a cost-effective component of international ozone management, bringing multiple benefits for air quality, public health, agriculture, climate, and energy.

Footnotes

^‡To whom correspondence may be addressed at:
Atmospheric and Oceanic Sciences Program and Woodrow Wilson School of Public and International Affairs, Princeton University, 409 Robertson Hall, Princeton, NJ 08544.
E-mail: jwest{at}princeton.edu
^¶To whom correspondence may be addressed at:
Woodrow Wilson School of Public and International Affairs, Princeton University, 406 Robertson Hall, Princeton, NJ 08544.
E-mail: mauzeral{at}princeton.edu
Author contributions: J.J.W., A.M.F., L.W.H., and D.L.M. designed research; J.J.W., A.M.F., and L.W.H. performed atmospheric modeling; J.J.W. and A.M.F. performed mortality calculations; J.J.W. performed economic calculations; J.J.W. wrote the paper; and J.J.W., A.M.F., L.W.H., and D.L.M. edited the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations:

CR,

cardiovascular and respiratory;

PM,

particulate matter;

ppbv,

part(s) per billion by volume;

VOC,

volatile organic compound;

VSL,

value of a statistical life.