Effects of air pollution on health
BMJ 2007; 335 doi: https://doi.org/10.1136/bmj.39304.389433.AD (Published 16 August 2007) Cite this as: BMJ 2007;335:314
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The effect of air pollution is a major health concern and is well documented (1). The UK government report (draft) written by the Committee on the Medical Effects of Air Pollution is an important and rigorous scientific assessment of the effects of air pollution in the United Kingdom and represents a key tool to influence policy in order to improve health.
Globally however, human exposure to particulate matter (PM) in terms of the number of people, exposure intensity and time spent exposed varies greatly in different parts of the world. Only 1% of global PM exposure occurs in outdoor environments in the developed world with a further 9% occurring indoors in the developed world. 14% occurs outdoors in the developing world while a staggering 77% of human exposure to PM occurs in indoor environments in the developing world (2).
Almost one-half of the world’s population burns organic material such as wood, dung or charcoal for cooking, heating and lighting. This form of energy is associated with very high levels of indoor pollution and an increased incidence of respiratory infections, including tuberculosis, COPD and cataracts to name a few. The World Health Organization lists indoor air pollution from burning solid fuels as one of the top ten global health risks, responsible for 1.6 million premature deaths per year and 2.7% of the global burden of disease (3).
Despite this, research funding, scientific activity and even BMJ editorials continue to be focussed disproportionately on outdoor air pollution in the developed world (4;5). There is a clear and urgent need to expend at least as much effort on indoor air pollution in the developing world as we do on outdoor air pollution in industrialised countries.
(1) Brunekreef B, Holgate ST. Air pollution and health. Lancet 2002; 360(9341):1233-1242.
(2) Smith KR (1996) Indoor air pollution in developing countries: growing evidence of its role in the global disease burden. In: K. Ikeda and T. Iwata, Indoor Air ’96. Published by the Organizing Committee of the 7th International Conference on Indoor Air Quality and climate, SEEC ISHIBASHI Inc., Japan.
(3) WHO. Fuel for life: household energy and health. World Health Organization. 2006. ISBN 92 4 156316 8.
(4) Jaakkola MS, Jaakkola JJ. Biomass fuels and health: the gap between global relevance and research activity. Am J Respir Crit Care Med 2006; 174(8):851-852.
Competing interests:
D G Fullerton is currently funded by the Wellcome Trust investigating the effects of biomass fuels on lung cells
Competing interests: No competing interests
UK continues to undercount Air Pollution's Health-harm
The editorial reviewers, Hales and Howden-Chapman (1), are right to
draw attention to the high cost of urban particulate matter (PM). But the
PM comes not from coal-fired power stations but from city vehicles. The
UK Committee on Medical Effects of Air Pollutants (COMEAP) decided the
American Cancer Society (ACS) cohort study is the best source suitable for
application in the UK. The derived coefficients have been exposed to
searching examination and found robust to reanalysis.
The reviewers fail to ask why COMEAP selected a lower coefficient
(6%, with CI 2%-11% - for increase in all-cause mortality per increment of
PM2.5) than did the leading US epidemiologists Pope and Dockery (6%-17% -
ref.2), on essentially the same set of studies.
They do mention one reason: that faced with wide disagreement, COMEAP
resorted to a Delphi survey of members opinions that resulted in a
distribution centred on 6%. Such a survey includes personal and
institutional biases. Yet COMEAP’s past record shows they have erred badly
toward under-estimates (while some of the individuals participating in
those estimates are still on COMEAP). In 1998 COMEAP decided chronic
effects were too uncertain, accepting only acute effects (health-
compromised people dieing in pollution episodes). In 2001 COMEAP accepted
that PM probably caused chronic mortality, but decided the coefficient
value of 1% was “most likely”.
The main reason argued by Pope & Dockery in 2006 for choosing the
higher coefficient range of 6%-17% is that long term chronic effects are
revealed only by longer term studies. Their comparison of studies reveals
a “duration effect”, ie. that longer term studies reveal stronger effects.
COMEAP do not mention this meta-analysis but their apparent answer is:
“we think that a noteworthy proportion of the total effect is likely
to appear within the first five years”.
Insofar as this belief led COMEAP to give high weight to short-term
studies, their divergence from Pope & Dockery is unconvincing.
Scientific preference goes to the latter. As the reviewers point out,
three studies from 2002, 2004 and 2005 found substantially higher
coefficients.
Thus I question the reviewers’ statement that COMEAP conducted a
rigorous scientific assessment. Rather, COMEAP persisted with the
conservative track record characteristic of UK scientific committees that
are too close to government, as the Southwood committee and SEAC analysed
by the BSE Inquiry (3).
Reference List
(1) Hales S, Howden-Chapman P. Effects of air pollution on health.
BMJ 2007; 335(7615):314-315
(2) Pope, C. A. & Dockery, D. W. J. Air Waste Mgmt Assoc. 56, 709–742,
2006
(3) The inquiry into BSE and variant CJD in the United Kingdom (Phillips
report) October 2000 www.bseinquiry.gov.uk/report/index.htm
Competing interests:
Max Wallis represented Friends of the Earth on Defra’s Air Quality Forum, took part in the European Airnet and Pinche projects reviewing harm from air pollution, and is member of the CIWEM Air Panel.
Competing interests: No competing interests