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http://www.nhmrc.gov.au/_files_n ... ttachments/eh42.pdf
Page 70, M5 east outlet
These features are illustrated for the M5 East tunnel (Sydney) in Figure 5.1. On the left are
modelled contours of NOx concentrations and on the right NOx exposure zones are allocated as a
result of the modelling. There are three focal points. Highest concentrations are apparent on the
left and right, relating to the tunnel portals. In the centre a ‘saddle’ point is apparent with a small
area of low concentration surrounded by lobes of higher concentration. This is the exhaust stack.
The shape of the ‘high’ exposure zone describes the interaction of prevailing meteorology with
the emitted NOx plumes from these three sources.
Page 125 conclusion: NOT SURE DUE TO LACK OF DATA to your health
Particle number concentrations or other measurements which more clearly represent ultrafine
particles, will show more clearly the relative contributions of emissions from traffic in a tunnel
and on local surface roads. This is more likely to be the case in peak events. The modelled
high percentile NOx concentrations in the vicinity of the M5 East tunnel (Hibberd 2006) suggest
to us that number concentrations of particles could be enhanced by some thousands per cm3
in high emission or poor dispersion conditions, whereas ambient concentrations tend to be in
the low tens of thousands per cm3, representing a not insignificant enhancement. If such values
are realistic (we have found no data to indicate one way or the other), the expected effects of
such an event on health in the community cannot yet be estimated due to our current lack of
epidemiological data on ultrafine particles, and it may affect too small a population for such
effects to be observable. We must assume that the one hour NO2 standard affords some protection
against the effects of ultrafine particles (and traffic-derived air toxics) on the community, but we
recommend that further research is sorely needed in this area, including modelling and monitoring
of particle number concentrations near road tunnels. |
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