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COMEAP statement: Dust on the London Underground
December 1998 |
1. COMEAP has examined the report of a study of dust concentrations on
the London Underground undertaken by Professor Nick Priest and colleagues
of Middlesex University. The authors found that peak levels of dust, measured
as PM10, were high and argued that people using the Underground
might acquire a large proportion of their daily exposure to particles
whilst travelling by this means. The authors also suggested that, extrapolating
from the findings of epidemiological studies relating daily average concentrations
of PM10 to effects on health, such exposure might have significant
adverse health effects.
2. Members were also provided with a study on the toxicological properties
of dust from the London Underground undertaken by the Institute of Occupational
Medicine (Edinburgh) between 1991 and 1993. This study showed that a large
proportion of the dust was made up of quartz but that this was of comparatively
low toxicity. It was suggested that the high iron content of the dust
reduced the inherent toxicity of the quartz.
3.Members concluded:
- that the study reported by Professor Priest and colleagues had been
done well, though there were concerns about the technical details of
how the dust levels had been monitored and the lack of controls using
other forms of transport in London.
- that the concentrations of dust were indisputably high but it was
recognised that this was not unexpected and had been known for some
time.
- that using published epidemiological studies to predict the effects
of exposure to dust on the Underground on health was unwise in that:
- the epidemiological studies quoted dealt with 24 hour average
and not peak concentrations;
- the epidemiological studies dealt with the effects of the general
ambient aerosol which was different in terms of chemical composition
and, possibly, in terms of particle size distribution from that found
in the Underground;
- those people likely to be most at risk from effects of exposure
to particles, for example the elderly suffering from chronic cardio-respiratory
disease, were not likely to use the Underground to the same extent
as younger and healthier people. This view was supported by an analysis
of the age distribution of Underground passengers provided by London
Underground.
- that the risk posed to health by the quartz content of Underground
dust was likely to be low.
- that there was a case for more work to be done on the composition
and particle-size distribution of Underground dust.
- that there was a case for an epidemiological study of the effects
on health of exposure to Underground dust.
4.It was agreed that these conclusions and recommendations should be
made available to London Underground.
Secretariat
10 December 1998
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