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Commuter exposure to respirable particles inside buses and by bicycle
The Science of the Total Environment 235 Ž1999. 403]405
Commuter exposure to respirable particles inside buses and by bicycle Ivan L. GeeU , David W. Raper Atmospheric Research and Information Centre, Department of En¨ ironmental and Geographical Sciences, The Manchester Metropolitan Uni¨ ersity, Manchester, M1 5GD, UK
Abstract The exposure of bus commuters and a cyclist to respirable particles in the city of Manchester has been evaluated, using personal sampling pumps installed in the cabs of the vehicles and carried by the cyclist. These have provided an estimate of the average exposure of commuters using bus services and cycling in a congested European city. Q 1999 Elsevier Science B.V. All rights reserved. Keywords: Respirable particles; Commuter exposure; Buses; Personal exposure
1. Extended abstract Particles are a serious health concern in our urban areas with high concentrations of particles being associated with increased mortality rates. Recent studies have highlighted the finer particles, PM 2.5 Žparticles passing a sampler entry with 50% efficiency at 2.5 mm. as being particularly associated with increased disease. The UK Department of Health Committee on the Medical Effects of Air pollution ŽCOMEAP. review ŽDepartment of Health, 1995. has described this association as causal. U
Corresponding author. Tel.: q44-161-247-1592; fax: q44161-247-6332. E-mail address: [email protected] ŽI.L. Gee.
Personal activities can have a greater influence on exposure than the ambient concentrations monitored by national networks. It is therefore important to gain a better understanding of where exposure occurs, by the use of personal exposure studies and studies in specific microenvironments. In this study levels of respirable particles were monitored in the microenvironments of the passenger compartments of buses and within a cyclist’s breathing zone. Sampling was undertaken on two typical bus routes in Manchester, UK ŽRoutes 85 and 252.. Sampling pumps operating at 2.2 lrmin ŽSidekick, SKC Ltd. fitted with a cyclone sampling head, designed to sample the respirable particle fraction ŽPM 4.0 . ŽPart No 225-69, SKC Ltd., were placed in the drivers cabs of two vehicles and
0048-9697r99r$ - see front matter Q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 9 9 . 0 0 2 4 7 - 8
404
I.L. Gee, D.W. Raper r The Science of the Total En¨ ironment 235 (1999) 403]405
connected to the main passenger compartment with a TygonW sampling tube Ž; 1.5 m.. Each cyclone contained a pre-weighed Fluoropore W filter ŽPart No FALP02500, Millipore, Ltd.. Preconditioned and exposed filters were weighed using a microbalance capable of weighing 1 mg ŽM3, Mettler Ltd.. In general the mass differences preand post-sampling were at least an order of magnitude greater than the sensitivity of the balance used Ž1 mg.. Analysis of field blanks provided an estimated detection limit of 15 mgrm3 for a 3-h sample. All samples were obtained during a 3-h period between 07.00 h and 10.00 h on weekdays only, and reflected the average concentration over the whole route during this period. The cyclist wore the sampler on their lapel and made repeated journeys along the No. 85 bus route over the same 3-h period. However, sampling was unfortunately erratic and was not always simultaneous on the different routes. This limited the interpretation of the data. Levels monitored within the passenger com-
Table 1 Summary of levels monitored within buses and by cycle in the city of Manchester, UK Žmgrm3 . Transportr route
Mean
S.D.
Min.
Max.
n
Bus No 85 Bus No 192 Cycle Backgrounda
338 252 54 28
300 234 34 14
23.7 12 16.8 9.4
973 953 122 71.8
17 17 8 24
a Background measurements are of PM 10 not the PM 4.0 used in this study.
partments of the two buses were found to be very variable ŽFig. 1.. The lowest levels monitored were in the region of 10]20 mgrm3 and the highest were nearly 1000 mgrm3 ŽTable 1.. This variation did not appear to be dependant on weather conditions and it is suggested that it may reflect one of two possible effects. Firstly the extremely unpredictable traffic conditions that buses may encounter in any period of the day may cause the observed day-to-day variation. Previous studies have indicated that for well-main-
Fig. 1. Concentrations of respirable particles within the compartments of buses and in the breathing zone of a cyclist travelling on the same route Žas Bus No 85 only. in the city of Manchester, UK.
I.L. Gee, D.W. Raper r The Science of the Total En¨ ironment 235 (1999) 403]405
tained vehicles the majority of pollutants present inside a vehicle are derived from the exhausts of surrounding vehicles ŽDuffy and Nelson, 1997., supporting this hypothesis. Secondly pollutants may be concentrated within the vehicles due to limited ventilation. However, further studies including careful monitoring of the bus movements during the day, traffic conditions, etc., would be required to establish the causes of the variability observed in this study. Many of the individual concentrations measured were extremely high, particularly inside the buses. The average levels in the buses were between 250 and 350 mgrm3. This was much higher than background levels measured at the national monitoring station in central Manchester 1. Studies of other pollutants inside vehicles have also shown extremely elevated concentrations. Bevan et al. Ž1991., measured average in-car benzene levels in urban areas of 75 mgrm3. This is approximately 10 times higher than background
1
The measurements in this study were of PM 4.0 and background monitoring is of PM 10 and the two sets of data are therefore not directly comparable. However, by definition PM 10 levels in the buses will be higher than the PM 4.0 measurements and a useful indication can be made by comparison.
405
levels experienced in the UK and indicates the extent to which in-vehicle concentration of pollutants can occur. Levels measured by the cyclist were considerably lower than levels inside buses ŽFig. 1, Table 1.. This could be explained by two factors. Firstly cyclists are most often travelling at the side of the road where concentrations of particles will tend to be lower, whereas buses will often be directly behind other vehicles and concentrations of particles within the intake air are likely to be high. Secondly cyclists can avoid congestion and becoming trapped behind vehicles, hence their exposure is more likely to reflect average roadside concentrations. References Department of Health, Committee on the Medical Effects of Air Pollution, Non-Biological Particles and Health. London: HMSO, 1995. Duffy BL, Nelson AF. Exposure to emissions of 1,3-butadiene and benzene in the cabins of moving vehicles and buses in Sydney, Australia. Atmos Environ 1997;31:3877]3885. Bevan MAJ, Proctor CJ, Baker-Rogers J, Warren ND. Exposure to carbon monoxide, respirable suspended particles and VOC’s while commuting by bicycle. Environ Sci Technol 1991;25:788]790.
Commuter exposure to respirable particles inside buses and by bicycle Ivan L. GeeU , David W. Raper Atmospheric Research and Information Centre, Department of En¨ ironmental and Geographical Sciences, The Manchester Metropolitan Uni¨ ersity, Manchester, M1 5GD, UK
Abstract The exposure of bus commuters and a cyclist to respirable particles in the city of Manchester has been evaluated, using personal sampling pumps installed in the cabs of the vehicles and carried by the cyclist. These have provided an estimate of the average exposure of commuters using bus services and cycling in a congested European city. Q 1999 Elsevier Science B.V. All rights reserved. Keywords: Respirable particles; Commuter exposure; Buses; Personal exposure
1. Extended abstract Particles are a serious health concern in our urban areas with high concentrations of particles being associated with increased mortality rates. Recent studies have highlighted the finer particles, PM 2.5 Žparticles passing a sampler entry with 50% efficiency at 2.5 mm. as being particularly associated with increased disease. The UK Department of Health Committee on the Medical Effects of Air pollution ŽCOMEAP. review ŽDepartment of Health, 1995. has described this association as causal. U
Corresponding author. Tel.: q44-161-247-1592; fax: q44161-247-6332. E-mail address: [email protected] ŽI.L. Gee.
Personal activities can have a greater influence on exposure than the ambient concentrations monitored by national networks. It is therefore important to gain a better understanding of where exposure occurs, by the use of personal exposure studies and studies in specific microenvironments. In this study levels of respirable particles were monitored in the microenvironments of the passenger compartments of buses and within a cyclist’s breathing zone. Sampling was undertaken on two typical bus routes in Manchester, UK ŽRoutes 85 and 252.. Sampling pumps operating at 2.2 lrmin ŽSidekick, SKC Ltd. fitted with a cyclone sampling head, designed to sample the respirable particle fraction ŽPM 4.0 . ŽPart No 225-69, SKC Ltd., were placed in the drivers cabs of two vehicles and
0048-9697r99r$ - see front matter Q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 9 9 . 0 0 2 4 7 - 8
404
I.L. Gee, D.W. Raper r The Science of the Total En¨ ironment 235 (1999) 403]405
connected to the main passenger compartment with a TygonW sampling tube Ž; 1.5 m.. Each cyclone contained a pre-weighed Fluoropore W filter ŽPart No FALP02500, Millipore, Ltd.. Preconditioned and exposed filters were weighed using a microbalance capable of weighing 1 mg ŽM3, Mettler Ltd.. In general the mass differences preand post-sampling were at least an order of magnitude greater than the sensitivity of the balance used Ž1 mg.. Analysis of field blanks provided an estimated detection limit of 15 mgrm3 for a 3-h sample. All samples were obtained during a 3-h period between 07.00 h and 10.00 h on weekdays only, and reflected the average concentration over the whole route during this period. The cyclist wore the sampler on their lapel and made repeated journeys along the No. 85 bus route over the same 3-h period. However, sampling was unfortunately erratic and was not always simultaneous on the different routes. This limited the interpretation of the data. Levels monitored within the passenger com-
Table 1 Summary of levels monitored within buses and by cycle in the city of Manchester, UK Žmgrm3 . Transportr route
Mean
S.D.
Min.
Max.
n
Bus No 85 Bus No 192 Cycle Backgrounda
338 252 54 28
300 234 34 14
23.7 12 16.8 9.4
973 953 122 71.8
17 17 8 24
a Background measurements are of PM 10 not the PM 4.0 used in this study.
partments of the two buses were found to be very variable ŽFig. 1.. The lowest levels monitored were in the region of 10]20 mgrm3 and the highest were nearly 1000 mgrm3 ŽTable 1.. This variation did not appear to be dependant on weather conditions and it is suggested that it may reflect one of two possible effects. Firstly the extremely unpredictable traffic conditions that buses may encounter in any period of the day may cause the observed day-to-day variation. Previous studies have indicated that for well-main-
Fig. 1. Concentrations of respirable particles within the compartments of buses and in the breathing zone of a cyclist travelling on the same route Žas Bus No 85 only. in the city of Manchester, UK.
I.L. Gee, D.W. Raper r The Science of the Total En¨ ironment 235 (1999) 403]405
tained vehicles the majority of pollutants present inside a vehicle are derived from the exhausts of surrounding vehicles ŽDuffy and Nelson, 1997., supporting this hypothesis. Secondly pollutants may be concentrated within the vehicles due to limited ventilation. However, further studies including careful monitoring of the bus movements during the day, traffic conditions, etc., would be required to establish the causes of the variability observed in this study. Many of the individual concentrations measured were extremely high, particularly inside the buses. The average levels in the buses were between 250 and 350 mgrm3. This was much higher than background levels measured at the national monitoring station in central Manchester 1. Studies of other pollutants inside vehicles have also shown extremely elevated concentrations. Bevan et al. Ž1991., measured average in-car benzene levels in urban areas of 75 mgrm3. This is approximately 10 times higher than background
1
The measurements in this study were of PM 4.0 and background monitoring is of PM 10 and the two sets of data are therefore not directly comparable. However, by definition PM 10 levels in the buses will be higher than the PM 4.0 measurements and a useful indication can be made by comparison.
405
levels experienced in the UK and indicates the extent to which in-vehicle concentration of pollutants can occur. Levels measured by the cyclist were considerably lower than levels inside buses ŽFig. 1, Table 1.. This could be explained by two factors. Firstly cyclists are most often travelling at the side of the road where concentrations of particles will tend to be lower, whereas buses will often be directly behind other vehicles and concentrations of particles within the intake air are likely to be high. Secondly cyclists can avoid congestion and becoming trapped behind vehicles, hence their exposure is more likely to reflect average roadside concentrations. References Department of Health, Committee on the Medical Effects of Air Pollution, Non-Biological Particles and Health. London: HMSO, 1995. Duffy BL, Nelson AF. Exposure to emissions of 1,3-butadiene and benzene in the cabins of moving vehicles and buses in Sydney, Australia. Atmos Environ 1997;31:3877]3885. Bevan MAJ, Proctor CJ, Baker-Rogers J, Warren ND. Exposure to carbon monoxide, respirable suspended particles and VOC’s while commuting by bicycle. Environ Sci Technol 1991;25:788]790.