The Challenge of Air Pollution

Bjørn LarsenVirginia, USA and Vientiane, Lao PDR

Summary

This paper was produced for the Copenhagen Consensus 2008 project.

The fi nal version of this paper can be found in the book, ‘Global Crises, Global Solutions: Second Edition’,

edited by Bjørn Lomborg

(Cambridge University Press, 2009)

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Air Pollution Bjorn Larsen, Guy Hutton and Neha Khanna

INTRODUCTION Air pollution, especially particulate matter (PM) penetrating the human respiratory system, is the cause of nearly 2.5 million deaths globally per year, and countless more cases of respiratory illness. Over 90 percent of these deaths and illness occur in developing countries. In addressing the issues, a broad distinction between indoor and outdoor air pollution needs to be made. Indoor air pollution arises primarily from the burning of solid fuels for cooking and heating, particularly in rural households. Wood, biomass, charcoal and coal are often burnt on open fires or in traditional stoves with low combustion efficiency and no or poor venting of smoke, resulting in high concentrations of air pollution, often 10-30 times higher than WHO guidelines. Outdoor air pollution, on the other hand, arising from motor vehicles, power stations and factories, is primarily a problem of increasing economic development and lack of pollution control. Over 3 billion people are exposed to household pollution from solid fuel use (SFU), almost exclusively in developing countries, particularly affecting poor rural communities. It disproportionately impacts women and young children as they tend to spend more time indoors and near cooking stoves. Outdoor air pollution affects over 2 billion people in more than 3,000 cities around the world with more than 100,000 inhabitants and predominantly impacts adults, particularly in the older age groups. Indoor air pollution from solid fuels can be substantially reduced by the use of improved stoves with good venting of smoke and virtually eliminated by the use of alternative fuels such as liquefied petroleum gas (LPG). Tackling outdoor pollution, however, requires a broad package of measures to achieve significant improvements. HOUSEHOLD AIR POLLUTION FROM SOLID FUELS The Challenge Use of solid fuels in homes in developing countries is estimated to cause 1.5 million deaths annually, or 36 million disability adjusted life years (DALYs) from deaths and illness. The primary health problems are acute lower respiratory infections (ALRI) in young children and chronic obstructive pulmonary disease (COPD) in adults. Evidence also indicates that indoor pollution contributes to a number of other health conditions and is also plausibly linked to heart disease and hence further mortality. Improved domestic fuels such as LPG have replaced nearly 50% of solid fuels in rural areas in the Eastern Mediterranean region and Latin America & Caribbean, but substitution is still less than 15% in rural sub-Saharan Africa and south-Asia and about 1/3rd in rural Western Pacific developing region. Over half of all the deaths from indoor air pollution occur in China and India, and 13 countries – eight in sub-Saharan Africa and five in Asia – account for 80% of them (1.2 million). Average household use of solid fuel is over 80% in these countries. An important question is if countries will grow themselves out of SFU and associated health effects without a need for large scale interventions. A cross-country analysis of

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SFU and per capita income levels suggests that it would take over 50 years to reduce SFU to 50 percent in the majority of sub-Saharan African countries at a per capita income growth rate of 3 percent per year. In China and India it would take 10-20 years at current economic growth rates. However, SFU in China and India has not declined at a rate anywhere close to the rate suggested by the cross-country analysis. Better healthcare and improved child nutrition could also reduce under-5 mortality from ALRI without replacing solid fuels. If child mortality continues to decline at the same rate as in the last two decades then, with no change in SFU and stove technology, ALRI mortality from indoor air pollution would in 50 years still be 40% of levels today. COPD mortality, on the other hand, is largely a problem of aging. COPD mortality from indoor air pollution could therefore increase over time as populations continue to age. Using World Bank demographic projections for China, India, Nigeria and Tanzania, COPD mortality from indoor air pollution could be higher in 50 years than today in all four countries even if solid fuel use declines to 25%. The Solutions A range of solutions is available to reduce exposure to indoor air pollution. This includes reducing pollution at source and altering the living environment and user behavior. Source reduction involves improved cooking devices (with or without flue attached), cleaner fuel, and reduced need for fire. Alterations to the living environment include improved ventilation and improved kitchen design and stove placement. Altered user behavior includes fuel drying, stove and chimney maintenance, use of pot lids to conserve heat, and keeping children away from the smoke. Many of these options have too little evidence associated with them to enable a cost-benefit analysis to be done. The focus of this paper is therefore on two solutions: improved stove technology and fuel substitution. Substantial reductions in particulate matter can be achieved using improved stoves compared to traditional stoves or open fires. Studies in South America showed that improved stoves can reduce PM by 80% of more. Despite this, measured levels of PM are often still substantially higher than those found in most outdoor urban environments. Improvements in indoor air quality also result from use of charcoal rather than wood as a fuel. Charcoal is not normally considered a clean fuel, but is an intermediate step for households unable to afford LPG or other alternatives, and its use is quite common in some urban areas of sub-Saharan Africa. In rural China and Mongolia, the main alternative to biomass is coal, which often reduces indoor pollution by half. This situation can be further improved by use of improved coal stoves with chimneys. Economic Estimates of Costs and Benefits Health benefits are often a major motivation for interventions to reduce indoor air pollution from SFU. Households also value the increased convenience of improved fuels and increased efficiency and fuel savings of improved stoves. Natural resource considerations can also be a motivator for substitution to more efficient stoves and other fuels.

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Two global studies and one each from Colombia and Peru have looked at the costs and benefits of reducing household air pollution. The first global study evaluated an improved stove and substitution to kerosene and LPG. The study assumed an improved stove to reduce adverse health effects of indoor air pollution from SFU by 75%. Kerosene and LPG would, by definition, remove the adverse health effects of SFU. Annual costs per household of cooking systems, including fuel, range across the regions from $40-90 for LPG, $10-20 for kerosene and $3-24 for improved stoves ($3-5 in Africa and Asia). Healthy years gained from this intervention were valued at $1,000. Health benefits were found to exceed costs for improved stoves in Africa and South Asia, and for kerosene in the Western Pacific developing region. The cost of LPG was however found to exceed health benefits in all regions. The second global study looked at both health and other benefits (including time saved from less fuel collection and environmental benefits) across each WHO region of the developing world. Providing an improved, chimneyless stove was assumed to reduce health effects by 35%. For health benefits alone (valuing a DALY at $1,000 and without accounting for time saving, fuel cost savings and environmental benefits), benefit/cost ratios for the improved stove are greater than one in Africa, South Asia and the lower income countries of the Eastern Mediterranean region. Substitution to LPG was found to be cost-effective only in Africa. The studies of Colombia and Peru show a somewhat different distribution of benefits. Colombia's relatively low childhood mortality rate means that the largest monetized benefits are reductions in ARI morbidity, followed by COPD. In Peru, reduction in ARI morbidity in children and women is the largest benefit, with ALRI mortality in children coming second. There are also considerable time savings from reduced firewood collection. Improved wood and LPG stoves are assumed to cost $60. Both studies found the health benefits alone to exceed the cost of improved stoves when DALYs are valued at $1,000. Benefits are however lower than costs of LPG in both studies. All four studies evaluated benefits and costs of reducing indoor air pollution in an “average” household. However, many factors influence children’s death rate from ALRI, nutritional status being one. Death rates from ALRI are reported to be 4-8 times greater for moderately to severely underweight children than for children of normal weight. Studies in for instance Cambodia, Ghana and Senegal show that use of fuel wood, and thus high levels of air pollution, is far more prevalent in households with underweight children. This means that appropriately targeting interventions can make a large difference to their cost-effectiveness. Replacing traditional stoves by improved stoves or LPG in homes with high likelihood of severe child malnutrition could have a benefit/cost ratio about six times higher than if the change was made in the same number of households likely to have well-nourished children. None of the four studies evaluated the option of replacing fuel wood or biomass by charcoal, not usually considered a clean fuel but nonetheless a preferred option for many urban households. Some evidence suggests that charcoal use can result in about 75% reduction in health effects from use of traditional wood and biomass stoves.

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URBAN AIR POLLUTION The Challenge With lead eliminated from gasoline in most countries, the major outdoor urban air pollution problem is particulate matter (PM), with finer particles (PM10 and PM2.5) having the largest health effects. About 2.3 billion people live in cities with populations greater than 100,000, and WHO estimates a total of 865,000 deaths, or 7 million DALYs from deaths and illness in 2002 as a consequence of PM2.5 in these urban areas. About 85% of these deaths occur in low and middle income countries, with more than 55% in Asia. 15 countries account for 77% of these deaths globally, with 45% of them in China and India alone. The current WHO guideline for maximum PM10 concentration is 20µg/m3, but over 55% of the urban population if China is exposed to levels greater than 100µg/m3 . In India, it is estimated that more than half the 70 million people living in the eight largest cities are exposed to similar high levels of pollution. The main health effects of fine particulates are cardio-pulmonary mortality and respiratory illness, with older people being more vulnerable. The health effects of PM pollution can therefore be expected to increase as urbanization continues and the population ages, unless PM levels decline significantly. The Solutions Reducing urban air pollution is largely a technical issue, involving interventions that reduce pollution at source and filter it away from the source. However, application of such interventions is more an economic than a technical issue. Studies in Beijing have found that coal burning contributes 7-20% of PM2.5 concentration levels in the city, with vehicle emissions, biomass burning and secondary particulates (mainly from sulfur dioxide and nitrogen oxides) also being significant sources. Coal-fired power stations fulfill much of China's growing energy needs. Primary and secondary PM2.5 emissions from vehicles are projected to increase seven-fold between 2005 and 2030 in major cities if vehicles and fuels only meet Euro 2 standards, and emissions will double even if tighter Euro 4 standards are met. Similar work in three major cities in India showed that diesel and gasoline contributed 26% of PM2.5, followed by road dust at 23%. The vehicle fleet is projected to increase 10-fold from 2003 to 2030. In other developing countries, road vehicles are generally found to be the major source of particulates, partly because of high levels of diesel use and little or no emission control technology. Studies from Colombia and Senegal indicate that primary PM from road vehicles is responsible for over 1/3rd of ambient PM2.5 concentrations. Reducing vehicle pollution requires an approach combining a range of measures, including improved emissions control, cleaner fuels, newer and smaller vehicles and transport modal shifts (eg to buses, subways and trains). The European Union is progressively tightening limits on emissions, and ultralow-sulfur diesel has been introduced to help meet these. Other developed countries have done the same, and some developing countries are also following suit. Retro-fitting diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) once low-sulfur fuel is available can have a

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very significant effect on emissions. This is especially important in countries with high reliance on diesel vehicle fuel. Economic Estimates of Costs and Benefits Surprisingly few cost-benefit studies have been done for developing countries, which are the countries with the largest health effects of urban air pollution, and the studies relate mostly to single cities, so no global estimates are possible. Available studies do however give indicative results for a number of industrialized and developing world countries or cities, and can be seen as indicative of similar interventions in similar socio-economic situations. In most cases, the health gains of pollution control reported are limited to reductions in premature deaths, lower healthcare costs and increased work days due to lower morbidity. However, other benefits such as avoided damage to agriculture, ecosystems or infrastructure would raise the cost-effectiveness if counted. Five recent studies provide cost-benefit analysis of vehicle emission controls, covering Mexico City, Bogota, Lima, Dakar, and a group of cities in China. The health benefits are here converted to DALYs and valued at $1,000 per DALY for the sake of a meaningful comparison. The Mexico City study looks at retrofitting of older and newer diesel vehicles (buses and delivery trucks) with particulate control devices (DOC or DPF). Benefit-cost ratios (BCR) are in the range of 0.2-0.7. BCRs for DOC and older vehicles are generally higher than for DPF and newer vehicles. Retrofitting of urban buses with DOC or DPF in Bogota, Lima and Dakar have BCRs in the range of 0.5-0.65. Low- and ultralow-sulfur diesel for urban vehicles is evaluated in the studies of Bogota, Lima, and Dakar. The BCRs are in the range of 0.2-0.5. The China study looks at ultralow-sulfur vehicle fuels (diesel and gasoline) and Euro 4,5 vehicle emission standards with benefits and costs evaluated over a 20 year period. For the year 2010, the BCR is 0.1 for vehicle fuels and 0.2 for Euro 4,5 standards with the same valuation of health benefits as above. The Lima study also includes an analysis of a vehicle inspection and maintenance (I&M) program and finds a BCR of 0.5 for diesel vehicles. Other studies provide cost-benefit analysis of pollution control in other areas such as power generation, industry and energy efficiency. Examples include the introduction of national emissions standards for pollutants in the USA (BCR in the range 2.7-13), European emissions reduction initiatives (BCR of 6.0), Shanghai emissions controls (BCR 1.1-2.8), and emissions reductions in the oil extraction industry in Kazakhstan (BCR 5.7). These BCR are however not comparable to the ones presented above for vehicle emission control because they apply generally much higher valuation of mortality than reflected in DALYs at $1,000. IMPLICATIONS AND OUTLOOK Air pollution accounts for 2.5 million deaths annually and countless millions more episodes of illness. For a significant proportion of the world's population, it is a daily fact of life. Poor air quality has both economic and quality of life impacts.

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Although control strategies for indoor and outdoor pollution are largely unrelated, they share three basic approaches – fuel switching, emissions control and fuel use efficiency – each offering different opportunities and drawbacks. There are also a range of barriers to be overcome (political, economic, social, regulatory and access) and government and private sector activities should focus on addressing these according to their priority in each specific context. The most cost-effective interventions analyzed in the CBA studies are presented in the table below for a valuation of a DALY at $1,000 and $5,000. The benefit/cost ratios (BCR) are substantially greater than one for improved cooking stoves in Africa and much of Asia. The BCRs for vehicle particulate control are greater than one only when DALYs are valued at $5,000. The main reason for this is that the older age groups are the main beneficiaries of urban air pollution control, while children benefit substantially from indoor air pollution control. Thus DALYs per death averted from outdoor air pollution control are only a fraction of DALYs per death averted from indoor air pollution control. Table 1 Summary of intervention B/C ratios Interventions B/C ratios

(DALY= US $1,000)B/C ratios

(DALY= US $5,000) Annual Benefits (Reduction in

mortality, ‘000 lives)

Improved cooking stoves 1.7 - 7.5

8 - 37 340-680

Low and ultra-low sulfur diesel for urban road vehicles

0.2 - 0.5 0.9 - 2.5

Diesel vehicle particulate control technology

0.2 - 0.7 0.9 - 3.3

I&M program for diesel vehicles 0.5 2.5

80-160

Valuation of health benefits therefore raises important questions. Value of statistical life (VSL) is generally believed to better reflect individuals' valuation of mortality risk reduction than a relatively arbitrary DALY value, although these are still useful for comparisons by the international community. Thus, even if relatively conservative VSLs are applied for valuation of mortality reductions from urban air pollution control, the BCRs are greater than one in most of the studies reviewed for both low- and ultralow-sulfur diesel and particulate control devices. The cost of programs to achieve impact and change on a large scale in the case of reducing indoor air pollution is often not properly considered, but evidence suggests that this can be substantial, and that relatively low take-up rates of for instance improved stoves promoted by programs imply a rising marginal program cost. For outdoor pollution control, the most important factor is government's willingness and ability to introduce and enforce regulations. Finally, there are important linkages between the topic of this paper and other environmental and health issues. For example, estimation of benefits of reducing indoor air pollution to improve child health would be best done in a multiple risk framework to

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avoid overestimating health benefits if health, nutrition and environmental interventions are implemented simultaneously.