~ Pergamon Atmospheric Environment Vol. 31, No. 17, pp. 2893-2895, 1997 Elsevier Science Ltd

PII: ~ 5 1 3 5 2 - 2 3 1 0 ( 9 0 1 1 U I 1 ~ 2 , - - 7 Printed in Great Britain 1352-2310/97 $17.00 + 0.00

N E W D I R E C T I O N S

LIGHT BLUE TOUCH PAPER A N D RETIRE...

Particles are one of the current major concerns in the continuing debate over the impact of atmospheric pollutants on our health. The details and mechanisms of their effects are still under study, but the recent report by the Expert Panel on Air Quality Standards ("Particles", EPAQS, 1995) came to a consensus that they do indeed increase the risk incurred by sensitive groups of the population to heart disease and the symptoms of asthma.

One of the major sources of particles is from the combustion of fuels containing carbon--especially under uncontrolled conditions--which is quite a good scientific definition of a bonfire. It should not be much of a surprise then, that over the period of 5th November, when bonfires and fireworks are lit across England and Wales, the particle levels measured in U.K. cities increase dramatically. In fact, those out celebrating the discovery of the gunpowder plot are probably i~ahaling more particles than if they were standing in their local town centre during the rush hour.

As with all air pollution episodes, the effect of Bonfire Night is highly weather dependent. Guy Fawkes Night of 1995 was a particularly good example of this. Since 5th November was a Sunday, most of the celebrations--and hence the increase in PM10 (particles of 10 #m diameter of less)--took place on Saturday 4th. At the time, PM10 particles were monitored at 16 urban locations across the U.K. Five of these showed very minor changes in levels--either because these areas do not celebrate bonfire night, or because weather conditions allowed the efficient dispersal of the pollutants. The remaining eleven all showed significant increases--the table below gives the maximum hourly average recorded PM10 levels at the monitoring stations that were in operation over the period from midnight 3rd November to midnight 6th November.

Figure 1 graphs hourly PM10 levels during the period 4-6 November, for the 6 sites recording the highest values (NB. the concentrations from the Leeds site are plotted separately on the right hand axis). All the sites except Leeds recorded high concentrations on both the Saturday and Sunday evenings, although only at the London Bexley site were the two peaks roughly equal. All the sites except Leeds (which is d:Lscussed further in the following paragraph) showed the highest concentrations be-

tween 8 and 10 pm--which is probably around the time when the bonfire celebrations would have taken place. The recorded concentrations of particles then fell off as bonfires finished.

There was no obvious pattern in the geographical distribution of the maxima in PM10--high and low values seemed to be found in most regions of the country. It is likely, therefore, that the PM10 levels on Bonfire Night were most strongly influenced by local conditions, i.e. how close the sites were to large bonfires, and local meteorology, rather than country- wide variations in atmospheric conditions.

By far the highest PM10 levels of the three day period were recorded in Leeds, where low tempera- tures with light winds combined to trap the particles close to their sources and thus caused the observed build up. The combined effect of sources and meteorology can be seen quite clearly from the time series in Fig. 1. This shows that levels started to rise around 5 pm, then increased steeply from 91 to 421 #g m -3 between 6 pm and 8 pm. However, they continued to rise after this period, with the 782/~g m -3 maximum occurring at 11 pm, when most of the bonfires would have subsided to smouldering heaps. This effect was due to the falling temperature,

Table 1. Maximum hourly average PM10 levels recorded between midnight 3rd November to midnight 6th November

1995

Monitoring Site

Maximum recorded No. exceedences

hourly average of EPAQS (/lg m -3) standard

London Bloomsbury Maximum No. exceedences Leeds Centre 782 37 Birmingham East 477 43 London Bexley 351 47 Southampton Centre 307 47 Bristol Centre 250 38 London Bloomsbury 222 31 Cardiff Centre 219 23 Newcastle Centre 203 45 Birmingham Centre 196 22 Middlesborough 182 27 Swansea 116 16 Liverpool Centre 103 27 Hull Centre 80 2 Belfast Centre 77 0 Edinburgh Centre 76 0 Leicester Centre 69 0

2893

2894 New Directions

500

400

~ 300

~ 200

100

0 0

• Southampton Centre = . --=- London Bexley

• , London Bloomsbury .:l,I - °- Bristol Centre .*1:1_.7 ~ I ~ - ,,- Birmingham East !1 ', [ IN ~ Leeds Centre

x ~

00 04 08 12 16 20 00 04 08 12 16 20 00 04 08 12 16 20

4 / 1 1 / 9 5 5 / 1 1 / 9 5 6 / 1 1 / 9 5

800

600 ~"

400

200 -J

Fig.. 1. Time series of PM10 from 4th to 6th November 1995 at selected urban sites in the U.K.

pulling the boundary layer closer to ground level, and increasing the levels of particles by decreasing the volume of air that was available for their dispersion. Levels remained high throughout the rest of the night, only dropping off during the following morning.

5th November in 1994 (not shown) was rather different; although PM10 values were elevated (the Leeds site recorded a maximum value of 310 pg m3; still well above normal levels), the maximum level was recorded at 8 pm, after which time levels dropped off steadily. Since this would have been around the same time as the celebrations, this indicates that the 1994 episode was not exacerbated by meteorology to nearly the same degree as that in 1995.

Table 1 also shows the exceedences of the recommended U.K. EPAQS air quality stan- dard, which is a running 24 h mean of 50 pg m 3, for the 1995 Bonfire Night weekend. Exceedences were calculated for the 72 h period from 4th to 6th November inclusive, giving 49 possible running 24 h periods. At Bexley and Southampton the EPAQS standard was exceeded for 47 of these periods, i.e. nearly all of the weekend. Significant numbers of exceedences were also observed at all except four of the remaining sites. Clearly this festival will tend to give rise to particle concentrations that are higher than the recommended air quality standard across much of England and Wales.

The U.K. Department of the Environment has recently proposed a specific objective for PM 10 levels in the consultation draft of the "United Kingdom Air Quality Strategy" document (DOE, 1996). The objective for 2005 is that the fifth highest daily concentration of particles shall not exceed the recommended EPAQS standard. The fact that a small

number of exceedences is to be allowed is partly a concession to the inevitable occurrence of bonfire and fireworks parties as observed here. It would clearly be socially unacceptable to attempt to regulate or ban such festive activities. If, however, there is an awareness that elevated levels of particles are highly likely around bonfires, especially when weather conditions are cold and still, then sensitive groups of the population will know that they should, if possible, avoid them.

Since fireworks and sometimes bonfires are used to celebrate many events world-wide--for instance Independence Day in the USA, Bastille Day in France, Las Fallas in Spain, New Years Days in Holland, the Chinese New Year (world wide!), and the Occidental New Year in Hawai i - - the issue of exposure to elevated particle concen- trations during such festivals has implications in many countries of the world. Obviously the impact of the event will vary considerably--the time of year and the climate in which the events are held will give an enormous range of local meteorological conditions. The presence or otherwise of bonfires will also strongly influence ground level particle impacts. It is, however, an issue worth bringing to the

attention of the local population, so that those likely to be at most risk from the effects of pollution are able to take appropriate action to minimise exposure.

Helen Clark National Environmental Technology Centre

AEA Technology plc Culham

Abindgon OX14 3DB

U.K.

New Directions 2895

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