IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change Co-benefits for human health

Epidemiological studies have identified consistent asso-ciations between human health (mortality and morbidity) and exposure to fine particulate matter and ground-level ozone, both in industrialized and developing countries (WHO, 2003; HEI, 2004). Because the burning of fossil fuels is linked to both climate change and air pollution, lowering the amount of fuel combusted will lead to lower carbon emissions as well as lower health and environmental impacts from reduced emissions of air pollutants and their precursors.

Since the TAR, an increasing number of studies have demonstrated that carbon mitigation strategies result in significant benefits, not only as a result of improved air quality in cities, but also from reduced levels of regional air pollution. These benefits affect a larger share of the population and result from lower levels of secondary air pollutants. Although the literature employs a variety of methodological approaches, a consistent picture emerges from the studies conducted for industrialized regions in Europe and North America, as well as for developing countries in Latin America and Asia (see Table 11.18). Mitigation strategies aiming at moderate reductions of carbon emissions in the next 10 to 20 years (typically involving CO2 reductions between 10 to 20% compared to the business-as-usual baseline) also reduce SO2 emissions by 10 to 20%, and NOx and PM emissions by 5 to 10%. The associated health impacts are substantial. They depend, inter alia, on the level at which air pollution emissions are controlled and how strongly the source sector contributes to population exposure. Studies calculate for Asian and Latin American countries several tens of thousands of premature deaths that could be avoided annually as a side-effect of moderate CO2 mitigation strategies (Wang and Smith, 1999; Aunan et al., 2003; O’Connor et al., 2003; Vennemo et al., 2006 for China; Bussolo and O’Connor, 2001 for India; Cifuentes et al., 2001a; Dessus and O’Connor, 2003; McKinley et al., 2005 for Latin America). Studies for Europe (Bye et al., 2002; van Vuuren et al., 2006), North America (Caton and Constable, 2000; Burtraw et al., 2003) and Korea (Han, 2001; Joh et al., 2003) reveal fewer, but nevertheless substantial, health benefits from moderate CO2 mitigation strategies, typically in the order of several thousand premature deaths that could be avoided annually.

Table 11.18: Implications for air-quality co-benefits from GHG mitigation studies

Authors Country Target year Sector Delta CO2 emissions Carbon price (US$/tCO2) Impact on air pollutant emissions Difference in health impacts Health benefits (US$/tCO2) Difference in air pollution control costs Total benefits 
Burtraw et al., 2003 US 2010 Power sector       1–2 US$/tCO2   
Caton and Constable, 2000 Canada 2010 All sectors -9%   SO2: -9% NOx: -7% PM: -1%   11 (12–77)     
Wang & Smith, 1999 China 2020  Power sector  15% below BAU 11   4,400-5,200 premature deaths per year       
   2020 Domestic sector 15% below BAU 1.4   120,000-180,000 premature deaths per year       
O’Connor, 2003 China 2010 All sources 15% below BAU           No loss in net welfare 
Aunan et al., 2004 Shanxi, China 2000 Cogeneration   -30 (net benefit)     32     
     Modified boiler design   -6     23     
     Boiler replacement   -3     32     
     Improved boiler management       32     
     Coal washing   22     86     
     Briquetting   27      118      
Kan et al., 2004 Shanghai, China 2010 All sources   24   608–5144 premature deaths per year       
   2020         1189–10462 premature deaths per year       
Li, 2006 Thailand                 45% lower welfare losses 
Vennemo et al., 2006 China 2008-2012 Power production, industrial boilers, steel making, cement, chemical industry 80-236 MtCO2 annually 6 for the 80 Mt potential; unknown for the upper estimate SO2: 0.5–3 million tons; TSP: 0.2–1.6 million tons 2700 - 38000 lives saved annually (34–161 lives saved per million tons CO2Avoided deaths: 4.1–20; all health effects: 5–44      
Morgenstern, 2004 Taiyuan, China   Phase-out of small boilers 80%   -95%   38–175 US$/tCO2     
Bussolo & O’Connor, 2001 India   All sources 13-23% below BAU            No welfare loss 
Joh et al., 2003 Korea 2020 All sources 5–15%       2 US$/tCO2     
Han, 2001 Korea 2010 All sources -10%   SO2: -10% NOx: -9.6% PM: -10%   58–76     
Van Vuuren, 2006 Europe 2020 All sources 4–7%    SO2: 5–14%         
Syri et al. 2001 EU-15 2010 All sources -8%   SO2: 13-40% NOx: 10–15%     -10%   
Proost et al., 2003 Belgium 2010-2030 All sources 7–15%           30% of mitigation costs 
Syri et al., 2002 Finland 2010 All sources Kyoto compliance   SO2: -10% NOx : -5% PM: -5%         
Bye et al., 2002 Nordic countries   All sources 20–30%         9-22 US$/tCO2 0.4% to 1.2% of GDP 
Cifuentes et al., 2001a , 2001b Mexico City, Santiago, Sao Paulo, New York 2020         64,000 premature deaths per year       
West et al., 2004 Mexico City 2010 18 GHG measures (mainly transport) 9%   PM10: -1.3% NOx: 1.4% HC: 3.2%         
McKinley et al., 2005 Mexico City 2020 5 mitigation options 0.8 Mt C/yr (1.1%)     100 premature deaths per year       
Dessus et al., 2003  Santiago de Chile 2010   20% below BAU           No welfare loss 

Note: The carbon prices in the table are indicative only. They have been converted to US$/tCO2, but the implicit price bases in the original studies vary and may not be quoted or available.

Several authors conducted an economic valuation of these health effects in order to arrive at a monetary quantification of the benefits, which can then be directly compared with mitigation costs. While the monetization of health benefits remains controversial, especially with respect to the monetary value attributed to mortality risks in an international context, calculated benefits range from 2 US$/tCO2 (Burtraw et al., 2003; Joh et al., 2003) up to a hundred or more US$/tCO2 (Han, 2001; Aunan et al., 2004; Morgenstern et al., 2004). This wide range is partially explained by differences in methodological approaches. The lower estimates emerge from studies that consider health impacts from only one air pollutant (such as SO2 or NOx), while the higher estimates cover multiple pollutants, including fine particulate matter, which has been recently shown to have the greatest impact. Differences in mortality evaluation methods and results also constitute a substantial source of discrepancy in the estimated value of health impact as well.

The benefits also largely depend on the source sector in which the mitigation measure is implemented. Decarbonization strategies that reduce fossil fuel consumption in sectors with a strong impact on population exposure (such as domestic stoves for heating and cooking, especially in developing countries) can typically result in health benefits that are 40 times greater than a reduction in emissions from centralized facilities with high stacks such as power plants (Wang and Smith, 1999). Mestl et al., (2005) show that the local health benefits of reducing emissions from power plants in China are small compared to abating emissions from area sources and small industrial boilers. A third factor is the extent to which air pollution emission controls have already been applied. Health benefits are larger in countries and sectors where pollutants are normally emitted in an uncontrolled way, for instance for small combustion sources in developing countries.

Despite the large range of benefit estimates, all studies agree that monetized health benefits make up a substantial fraction of mitigation costs. Depending on the stringency of the mitigation level, the source sector, the measure and the monetary value attributed to mortality risks, health benefits range from 30 to 50% of estimated mitigation costs (Burtraw et al., 2003; Proost and Regemorter, 2003) up to a factor of three to four (Aunan et al., 2004; McKinley et al., 2005). Particularly in developing countries, several of the studies reviewed indicate that there is scope for measures with benefits that exceed mitigation costs (no-regret measures).

Such potential for no-regret measures in developing countries are consistently confirmed by studies applying a general-equilibrium modelling approach, which takes into account economic feedback within the economy. Bussolo & O’Connor (2001) estimate that the potential for CO2 mitigation in India for 2010, without a net loss in welfare, is between 13 and 23% of the emissions for a business-as-usual scenario. For China, this potential has been estimated by O’Connor (2003) for 2010 at 15 to 20%, and Dessus and O’Connor (2003) arrive at a figure of 20% for Chile compared with the business-as-usual emissions in 2010. Li (2002; 2006) finds for Thailand that inclusion of health impacts reduces the negative impacts on GDP of a carbon tax by 45%, improving welfare for households and resulting in cleaner producers.