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Documentos de trabajo
> Health Impact of Outdoor Air Pollution in
Bogotá
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A Risk
Assessment of the Health Impact of Outdoor Air
Pollution in Bogotá*
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full text paper
Blanca Amalia Llorente Carreño
Executive summary
 Taking
advantage of the features of environmental risk
assessment as a tool to support policy
recommendations and to identify areas where re-
search is needed, we apply this methodology to
estimate the disease burden attributable to
outdoor air pollution in Bogotá, a South
American city of 7 million inhabitants. A first
task was the gathering of literature on three
areas: methodologies and guidelines to perform
risk assessment, international literature on the
association between outdoor air pollution and
health outcomes and national/local studies to
collect as much direct evidence as possible and
to avoid unnecessary extrapolation of the inputs
in burden estimation.
Next, the evidence was critically reviewed to
choose the most reliable and relevant
information from local and international sources.
As a result, we decided to apply recent
methodological recommendations by WHO (Ostro
2004) to estimate burden at local levels, that
included the use of the results of a systematic
search (WHO 2000). The selected pollutant was
particulate matter, differentiating relative
risks according to several health outcomes
associated with PM10 and PM2.5. Local sources
provided information for exposure, baseline
mortality data and some possible policy
scenarios to estimate avoidable burden. The
period of reference is 2005.
Our conservative estimate of the burden of
disease, measured in an- nual cases, indicates
that the city faces 2,307 cardiopulmonary and
lung cancer premature deaths attributable to
PM2.5 exposure. Range estimates for this outcome
are 936-3,393 using the limits of 95% CI for the
relative ratio. On the other hand, estimated
effects of short term exposure to PM10 are 2
premature deaths from respiratory disease among
children under 5 years of age (range estimate
1-4) and 1,372 premature deaths considering all
causes (range estimate 1,036-1,704). This last
estimate may include some of the cases
considered in the other categories, and
therefore should not be added to the previous
results. A sensitivity analysis considered
values for PM2.5/PM10 ratio between 0.5 and 0.6
and showed that even at the highest ratio
assumed in this analysis, the death estimates
for lung cancer and cardiopulmonary mortality
remain within the boundaries of the basic
scenario.
One application of this type of models is the
discussion of policy scenarios. We performed two
calculations of avoidable burden. The target
values were taken from one study that produced
estimates of the impact on emission levels of
several interventions in Bogotá (Sepúlveda
2006). Our first scenario assumes an expansion
of Transmilenio, Bogotá’s mass transportation
system, resulting in a 30% reduction in exposure
to PM10. This intervention could avoid 406
cardiopulmonary and lung cancer premature deaths
annually. A second scenario considers a 50%
reduction in exposure obtained by lowering
diesel sulphur content from 1,000ppm to 500ppm.
In this case 764 annual deaths would be avoided.
In the future, we suggest to dedicate efforts to
increase precision of the model presented here.
Also, look for feedback within the academic
community, contributing to the current
discussion and the development of new projects
that may benefit from the inputs offered by this
assessment. Finally, the main purpose of any
risk assessment is to be able to com- municate
the evidence about risks to different groups in
society, so they can make informed decisions.
Finding appropriate channels to present and
discuss model results should be a priority. For
instance, among pol- icy makers one interesting
opportunity is CONAIRE, an inter-sectoral
national committee created in 2006 responsible
for coordinating policies with incidence on air
quality. Supplying this information to committee
members may help to improve communication
between its members and contribute to discuss
policy decisions and define their priority
recommendations based on evidence.
______________________
* Research Project for the MSc
in Public Health, Paul Wilkinson (Tutor), LSHTM-University
of London, November 2, 2007
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