April 29, 2014
Diesel engine exhaust has long been known to promote cardiovascular
disease and lung cancer. A new understanding of one of the components of
diesel exhaust shows it is also a powerful driver of climate change,
with black carbon particles 3,200 times more damaging to the climate
than carbon dioxide in the near-term. By controlling the dangerous
components in diesel exhaust, as many OECD countries have done, we get
co-benefits: reduced harm to both health and climate.
“Addressing these emissions is a possible win-win. It’s not only
about health but potential climate benefits as well,” said World Bank
Senior Environment Specialist Sameer Akbar, who led a new report
examining the co-benefits of reducing diesel emissions for development
and climate action.
In the near term, reducing the amount of black carbon emitted into
the environment can slow the rate of global temperature increase.
A number of OECD countries have already cut these emissions
dramatically. However, in low- and middle-income countries, where the
majority of all black carbon is emitted, emissions are expected to grow
as economies develop. Transportation accounts for nearly 20 percent of
global black carbon emissions and most of it is estimated to come from
older diesel engines without emission control equipment and using high
sulfur diesel fuel in low- and middle-income countries. These countries
have the opportunity to learn from the experience of OECD countries in
reducing emissions, and achieve significant benefits for both climate
To help decision makers estimate the benefits of diesel emission controls, the World Bank has published a new study, Reducing Black Carbon Emissions from Diesel Vehicles: Impacts, Control Strategies, and Cost-Benefit Analysis.
The study, conducted by the International Council for Clean
Transportation, summarizes a series of technical and policy options
already demonstrated to cut the health and climate risks from diesel
emissions. It also introduces a new analytical framework to monetize the
benefits of black carbon emissions reduction.
In countries without adequate controls, diesel engines spew a toxic
mix of small particles known as particulate matter. These fine
particles, which can be inhaled deeply into the lungs, have long been
known to harm health. The International Agency for Cancer Research, a UN
agency, has labeled them as carcinogenic. The American Heart
Association has warned that these particles can result in premature
deaths and disability from cardiovascular events, including heart
attacks and stroke. The particles are also believed to trigger or
exacerbate chronic bronchitis and childhood asthma.
The health case against particulate matter is so solid that several
industrialized countries have taken steps to nearly eliminate it.
Controlling dangerous diesel exhaust can be accomplished in a number of
ways including changing to cleaner fuels, requiring the use of
specialized exhaust filters, encouraging better engine design and even
buying older vehicles, to send to scrap heaps, or to replace them with
Lately, climate researchers have focused on one of the components in fine particulate matter, the particles of black carbon. A 2013 assessment concluded
that after CO2, black carbon is the second most important pollutant in
the atmosphere in terms of its global warming impacts in the near-term,
and that diesel exhaust is one of the predominant sources that are very
rich in black carbon emissions.
A New Framework
All diesel emission controls produce benefits, but they also have
costs. To aid countries in choosing ways to control diesel emissions,
the World Bank study introduces a new analytical framework.
The framework broadens existing analytical approaches by estimating
values for the social benefits of black carbon mitigation for climate
impacts as well as for health impacts. Determining the social costs of
black carbon is a piece of work in its early days, building on the
on-going work on the social cost of carbon, which is increasingly being
used in OECD countries to monetize the impacts of CO2 emissions.
In the World Bank’s study, the framework was applied to four
different project simulations: diesel engine retrofits in Istanbul,
Turkey; green freight in Sao Paulo, Brazil; fuel and vehicle standards
in Jakarta, Indonesia; and compressed natural gas buses in Cebu,
Philippines. In all four cases, health benefits dominated the
cost-benefit calculus and, in two simulations, the benefits of the
control measures were enhanced by the climate benefits.
The framework is an early effort toward a more comprehensive
assessment of the ways sustainable development can contribute to
multiple benefits, including toward climate mitigation. For example, the
framework could be broadened by adding other components, such as loss
of agriculture production and damage to ecosystems. It is a significant
advance because it allows for assessing the health and climate benefits
of diesel black carbon emissions reduction initiatives.
“We are now beginning to have the tools, the metrics, and the
information to start expanding the economic analysis to factor climate
benefits of black carbon mitigation into the cost-benefit equation,”