Air pollution constitutes
a major global environmental health problem and has been
reported to cause approximately 2 million premature
deaths worldwide every year1. Both indoor and
outdoor pollutants pose serious danger to health. The
WHO Air quality guidelines prescribe limits for the
concentration of selected air pollutants: particulate
matter (PM), ozone (O3), nitrogen dioxide (NO2)
and sulphur dioxide (SO2), applicable across
all WHO regions. It also specifically recommends that a
reduction in particulate matter (PM10)
pollution from 70 to 20 micrograms per cubic metre can
significantly reduce air quality-related deaths by
around 15%.
In developing countries,
the major sources of air pollution include the use of
wood, coal and crop residues for domestic energy, and
the average annual levels of PM10 exceeds 70
micrograms per cubic metre. The global problem of air
pollution is compounded by the observation that although
the proportion of global energy derived from biomass
fuels fell from 50% in 1900 to
around 13% in 2000, there is evidence that their use in
developing countries is ever-increasing2.
The literature contains
an increasing number of reports on the relationship
between air pollution and the incidence of
cardiovascular diseases3,4. A recent
report by Song links air pollution to heart diseases
and stroke; it also reveals that ‘about 6,000 Canadians
die from short-term exposure to air pollution, 69% of
which are from cardio- and cerebrovascular diseases
affecting an artery within the brain or blood supply to
the brain’3. Both short- and long-term
exposure to PM have been shown to contribute to
increased risk of ischaemic heart disease,
atherosclerosis5 and myocardial
infarction6. The
Committee on the Medical
Effects of Air Pollutants (COMEAP) set up by the
Department of Health, UK, to advise on the possible
effects of outdoor air pollutants on cardiovascular
disease in the UK reviewed scientific evidence for the
association between air pollution and cardiovascular
diseases, based on several laboratory animal and
epidemiological studies3. While their
report did not conclusively identify which components of
the ambient pollution mixture are responsible for the
effects of air pollutants, an important role for fine
particles was suggested.
Two main mechanisms
underlying the cardiovascular effects of air pollutants
have been proposed: the clotting hypothesis and the
neural hypothesis3: the
clotting hypothesis suggests that inhaled small
particles may trigger an inflammatory response,
resulting in the production and release of various
chemical mediators which in turn may activate the
clotting process and hence an increased tendency for
clot formation. Also, the various chemical mediators
resulting from inflammation may induce rupture of
atherosclerotic plaques and thus the likelihood of
thrombogenesis in a coronary blood vessel, resulting in
acute myocardial infarction. The neural hypothesis
suggests that air pollutants stimulate neural receptors
in the lungs which may in turn have reflex effect on the
rhythm of the heart. A common link between both
hypotheses is inflammatory stimuli which result in
increased coagulation and reduced fibrinolysis7.
While cardiovascular
diseases are known to be related to outdoor air
pollution as well as active and passive smoking in
developed countries, there is a paucity of information
about similar studies in developing-countries
(particularly in sub-Saharan Africa), where air
pollution from household solid fuel usage constitutes a
major hazard. Thus, very little information is available
to quantify the relationships between air pollutants and
cardiovascular diseases. Extrapolating the results of
air pollution studies in developed countries to
situation in developing countries is fraught with
difficulties8.
Intervention strategies,
particularly, in developing countries, should be geared
towards reducing the level of indoor pollutants and
should be affordable and sustainable, while taking
cognisance of domestic energy requirements, safety,
cultural needs and environmental protection. The use of
cleaner fuels is recommended but this may be beyond the
reach of poor communities. National policies, targeted
at fuel pricing incentives are necessary to increase
access by the poor to cleaner fuels. Finally, there is a
dire need, in developing countries, to alleviate poverty
as well as dependence on polluting fuels in order to
limit the cardiovascular risks associated with air
pollution.
REFERENCES
1. World
Health Organization: Air quality and health. Fact sheet
No. 313, (2008).
http://www.who.int/mediacentre/factsheets/fs313/en/print.html
Accessed 02 Dec 2008.
2. Albalak
R. Cultural practices and exposure to particles
pollution from indoor biomass cooking: effects on
respiratory health and nutrtitional status among the
Aymara Indians of the Bolivian Highlands [Doctoral
dissertation]. University of Michigan, 1997.
3. Ayres,
JG. Cardiovascular diseases and air pollution.
www.advisorybodies.doh.gov.uk/comeap/statementsreports/CardioDisease.pdf (Accessed Accessed 02 Dec 2008.
4.
Song, V. Bad air can boost blood pressure. Study first
to link pollution and hypertension CANOE 2008; Edmonton
Sun.http://www.edmontonsun.com/News/Canada/2008/08/02/pf-6335481.html
5. Brook
RD, Franklin B, Cascio W, Hong Y, Howard G, Lipsett M,
Luepker R, Mittleman M, Samet J, Smith SC Jr, Tager I..
Air pollution and cardiovascular disease: a statement
for healthcare professionals from the Expert Panel on
Population and Prevention Science of the American Heart
Association. Circulation. 2004; 109: 2655–2671.
6.
Zanobetti A, Schwartz J. The effect of particulate air
pollution on emergency admissions for myocardial
infarction: a multicity case-crossover analysis. Environ
Health Perspect. 2005; 113: 978–982.
7. Becker,
R.C. Antithrombotic therapy after myocardial infarction.
Engl. J. Med. 2002; 347: 1019-1022.
8. Bruce N, Perez-Padilla R, Albalak R.
Indoor air
pollution in developing countries: a major environmental
and public health challenge. Bulletin of the World
Health Organization,
2000;
78 (9): 1078-1092.
