Benzene in Garage
Content
Personal exposure to benzene and the influence of attached and integral garages
H S
Mann, D Crump, V Brown
Hardip Singh Mann, Centre for Safety, Health and Environment, Building Research Establishment, Bucknalls Lane, Garston, Watford WD25 9XX, England Email: [email protected] Derrick Crump, MRSH, Centre for Safety, Health and Environment, Building Research Establishment, Bucknalls Lane, Garston,
Watford WD25 9XX,
England
Email:
[email protected]
Building Research Establishment, Bucknalls Lane, Garston,
Veronica Brown, Centre for Safety, Health and Environment, Watford WD25 9XX, England Email: [email protected]
Corresponding author: Hardip Singh Mann
Received 8 January 2001, revised and accepted 23
January 2001
Key words
Attached garages; benzene; car; health; home;
personal exposure; petrol
Introduction
Abstract
Benzene is an air pollutant that is a recognised human carcinogen. An air quality standard has been established for ambient air in the UK to reduce the population’s exposure. It has been estimated that about 70% of benzene emissions to air in the UK come from petrol vehicles. A number of studies, including the Avon Longitudinal Study of Pregnancy and Childhood in the UK, have found that benzene concentrations in homes with attached or integral garages tend to be higher than in those without such garages. The present paper reviews these studies and reports a detailed investigation of five homes with either an attached or an integral garage. Indoor and outdoor locations were monitored using diffusive sampling to determine the average benzene concentration over approximately 28 days each month for 18 consecutive months (June 1998-November 1999). For one of these homes, ten years of data had shown the indoor benzene concentration to be consistently higher than outdoors. Personal exposure monitoring of one adult in this home showed that the benzene concentration in the main bedroom was a better predictor of personal exposure than the concentration outdoors. In the homes where a car was regularly parked in the garage, 18-month average benzene concentrations of up to 101.3 μgm were measured in the garage, 3 which is more than six times the ambient air quality standard for benzene (16.25 3 μgm running annual average). Mean benzene values in all cars and most of the garages studied exceeded the benzene standard. Mean benzene concentrations in the room abovethe garage ranged from 3.7 3 μgm in one home, where the car was rarely parked in the garage, to 39.9 μgm 3 in another home where a car with high benzene emissions was parked in the garage for six of the 18 months monitored. The mean benzene concentration in the room above the garage in this latter home was nearly 2.5 times the ambient air standard. The study demonstrates that there is a potential for people to have a higher exposure to benzene as a result of living in a home with an attached or integral garage. An understanding of routes of personal exposure is important to develop effective policies to reduce risks to health.
Most people are likely to have the greatest contact with potentially toxic pollutants inside the places
they usually consider to be essentially unpolluted,
and vehicles. Since most 80-90% of their time indoors, espepeople spend cially at home (Mann et al, 1997), personal exposure from pollutants within the home is important. A 12-month study of personal exposure of 30 adults to nitrogen dioxide, carbon monoxide and volatile organic compounds (VOCs) in Hertfordshire, England (Crump et al, 1999) concluded that over 80% of the total exposure to these pollutants occurred during the time spent indoors. A study of 50 volunteers in England undertaken by Leung and Harrison (1998) concluded that although concentrations of VOCs such as benzene within the home were relatively low (compared with activities such as refuelling), because a large proportion of time is spent within the home (particularly at night), annual exposures were
such
as
homes, offices
high.
One harmful pollutant found indoors, benzene, can enter the indoor air because of vehicle emissions and other sources such as tobacco smoke. Benzene and its metabolites have been shown to cause damage or breaks in genetic material, as well as chromosomal abnormalities; the most significant mechanisms of potential adverse health effects of prolonged exposure to low levels of benzene are haematotoxicity, genotoxicity and carcinogenicity (IEH, 1999). The International Agency for Research on Cancer has designated benzene as a Group 1 carcinogen which means that there is ’sufficient evidence of
38
Table
Residential details for Homes 1 to 5
1
carcinogenicity in humans’.
Some 70% of benzene emissions to air in the UK are currently derived from road transport, mainly petrol vehicles (Salway et al, 1997). The most important sources include evaporative losses, refuelling emissions and combustion of petrol (IEH, 1999). The benzene emitted from a car exhaust is likely to be a mixture of unburned benzene and benzene derived from the combustion of other aromatic
for benzene of 5 ~gmand this must be met by 1 January 2010.
Personal exposure to benzene
In the Total Exposure Assessment Method-
study (Sheldon et al, 1991) gave personal, indoor and outdoor mean benzene concentrations of 5.0, 4.0 and 1.2 J.lgffi’
respectively. In another study (Goldstein et al, 1992), day and night 12-hour average
concentrations of benzene were measured for 58 residents of Valdez, Alaska. The mean benzene concentrations in the personal, indoor and outdoor samples for summer were 20, 16 and 5 j~gm~ and 28, 25 and 11 ggtn’ in the winter. In several benzene exposure studies conducted recently in cities across Europe (such as MACBETH and EXPOLIS), personal exposure of study participants to benzene, as well as indoor levels, were higher than outdoor levels in nearly all cities involved. This clearly pointed to contributing sources in the indoor environment where people spend more than 20 hours per day (CON-
1991
petrol components (EBS, 1996).
There are a number of national and international initiatives aimed at reducing population exposure to benzene and the associated risk to health. Throughout Europe, gasoline and diesel fuel qualities with lower environmental impact are being introduced. Most recently the European Union has mandated stricter specifications from the year 2000, including a maximum benzene content for gasoline of 1% by volume (Ross, 1999). In the past, benzene has been present in petrol in a proportion of about 5% and occasionally up to 16% (WHO, 1987). The UK National Air Quality Strategy sets an air quality standard for benzene in the UK of 5 ppb (parts per billion) (16.25 ggm) as a running annual average, and a target guideline of 1 ppb (3.3 Ilgm l The 1997 strategy objective of the 5 ppb standard was originally to have been met by local authorities by 2005 but has now to be achieved by 2003 (DETR, 2000). The Directive Community European 2000/69/EC sets an ambient air limit value
studies of VOCs, Wallace (1987) combined all the existing information about how several hundred people located in five different states in the USA were exposed to benzene. He found that the average concentration of benzene they inhaled was nearly three times higher than typical outdoor levels. Wallace calculated that 45% of the total exposure of the US population to benzene came from smoking (including exposure to environmental tobacco smoke), 36% from inhaling petrol fumes (refuelling) and 16% from other sources such as cars and other items (e.g. petrol, petrol-driven lawnmowers) stored in attached garages. Only 3% of the average person’s exposure was attributed to industrial pollution. A
ology
CAWE, 2000).
In the 12-month
study
of
personal
Table 2
Mean benzene values at different locations and
heights at Home 1
39
Table
Mean benzene concentrations
3
monitoring period
I
(ggm’) for Homes 1
to 5 in all locations over the whole
Table
Details of cars
4
to 5
kept at Homes 1
exposure of 30 adults by Crump et al (1999) personal, indoor (bedroom) and outdoor (at home) benzene concentrations were 7.7, 6.1 and 3.9 ~gm3 respectively In the personal and fixed site exposure study of Leung and Harrison (1998), personal 12hour daytime exposures to benzene ranged from 0.8-295 ~gm’ (mean 6.5 ~gm 3) compared with an annual average concentration of 3.9 ~gm3 at the nearest suburban fixed site monitoring station. The mean benzene concentration within the homes sampled was 16.4 ~gm B Kingham et al (1998) quoted ‘high’ in-car benzene concentrations of over 200 ~gm3 and expressed concern for drivers’ exposure. Leung and Harrison (1998) and Crump etal (1999) reported mean in-car benzene concentrations of 41 and 113
mean
ggm’respectiN,ely.
Other studies have reported indoor and outdoor benzene concentrations. In an
40
investigation of 14 Italian houses, significantly higher benzene concentrations were found in the indoor air (52 Ilgm ~) compared
the outdoor air, with an indoor/outdoor ratio of 3.9 (De Bortoli et al, 1984). A study of urban benzene and population exposure spanning several European towns (Cocheo, 2000) found benzene levels in homes were 1.51 times those measured outside. A nationwide Canadian study (Fellin and Otson, 1993) measured 24-hour indoor air benzene concentrations in 754 randomly selected homes. Winter, spring, summer and autumn seasonal mean indoor benzene concentrations were 6.39, 5.60, 2.72 and 6.98
to
Table 5 Mean benzene concentrations (J.19m-3) due only to indoor sources for June 1998 to November 1999 (outdoor benzene contribution subtracted)
Table 6
Ilgmrespectively. Jones etal (1999) found that benzene levels were higher in urban than rural homes and higher during periods of occupancy. A German study (Levsen et al, 1999) concluded that whilst the sources for certain compounds (such as toluene and xylenes) were found indoors, there were only weak indoor sources for benzene, and most of the benzene found indoors was from outdoor
sources
Benzene concentrations (J19m-3) in the garage, room above the garage and car for Home 3 (after subtracting outdoor benzene value)
(mainly traffic).
These studies therefore show that personal exposure can be higher than indicated by studies of outdoor air. Understanding the sources of this exposure is important for developing policies that can reduce population exposure to benzene. One such source, benzene released by vehicles in garages attached or integral to homes, is discussed in the remainder of this paper and a study of five homes is described.
*
Benzene from vehicles in attached garages Pierson et al (1999) categorised emissions
from motor vehicles as ’fuel vapour emissions’ (i.e. vehicle evaporative emissions) and ’exhaust emissions’ from the tailpipe, which may consist of hydrocarbons such as benzene and other compounds, e.g. carbon monoxide, aldehydes and lead. The evaporative emissions were classified as follows:
~
*
emissions leave the tank Running losses occur when petrol is heated to the point at which it boils in the fuel tank. Once the fuel boils, the evaporative emission control system is overwhelmed and the engine may even be incapable of burning the vaporised fuel Resting losses result from the diffusion of fuel through plastic and rubber fuel system components and the escape of hydrocarbon vapours from the storage canister. Resting losses emission rates are low but occur continuously and in total can be significant
Table 7
Pollutants from vehicle fuel, including are thus released to the atmosphere by evaporative losses and refuelling emissions as well as from the exhaust of the vehicle from petrol combustion (DuarteDavison et al, 1999). Many private motor vehicles are kept, when not in use, in a garage sharing a common wall with the vehicle owner’s home and there is sometimes an interconnecting door to the living area. In some of these homes a room is located directly above the garage. There can be an increase in benzene levels within the home from attached or integral garages; one estimate suggests an 80% increase in ben-
benzene,
~
’Hot-soak’ emissions result from the heating of the fuel system after engine shutdown. Sawyer (1993) suggested that these are more important in carburetted engines than in fuel injected engines Diurnal emissions result from cyclic heating and cooling of the fuel tank during the day and night. As fuel and fuel vapour warm and expand,
Mean concentrations (J.19m-3) of some aromatic hydrocarbons other than benzene in the garage and room above the garage in Home 1
41
zene
concentration from
an
attached garage
to
house, benzene concentrations in the liv-
(Duarte-Davison et al, 1999). The Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) involved the study of indoor air pollution in 174 homes in Avon, England (Berry et al, 1996). Passive air samplers were used to collect 28day samples in the living room and main
bedroom of the home for one year. The mean indoor concentration was 8 ~gm-3 (n=3000 samples) compared with an outdoor mean of 5 ~gm’ (n=125). It was found that higher benzene concentrations in the home were associated with there being a smoker in the household and with the presence of an integral garage (Crump, 1997). Homes with attached or integral garages in which a car was kept (13% of all homes) had 25-30% higher ’within-home’ benzene concentrations than those homes without an attached or integral garage or with an attached or integral garage not used for parking the car. This was further confirmed in a study of 44 homes in Southampton, England (Brown and Crump, 1998a) where concentrations of benzene in both the living rooms and bedrooms were significantly higher for homes where a car was kept in an attached or integral garage (17% of homes). In a study of 42 homes in Hanover, Germany, Levson (1996) found garage benzene concentrations as high as 80.9 ggm’. In homes with connecting doors from garage
ing room were as high as 17.6 f.lgmIn New 1 Jersey, USA, Thomas et al (1993) studied 11 homes selected because of relatively high VOC concentrations measured in a previous study. This study identified attached
garages as a source of benzene and found that benzene was transferred from the garage to the home living areas at relatively high rates. Gammage and White (1984) detected gasoline vapours in 40 homes in Tennessee, USA, most of which had attached garages. Benzene can seep into a house from an attached garage, when benzene in petrol evaporates from the car’s hot engine and tank (Hricko, 1994). A study in the USA of 355 urban apartments reported mean indoor benzene concentrations of 16 gpn’ with an indoor/outdoor ratio of 2.2 (Wallace et al, 1985). Wallace attributed much of the higher indoor levels to benzene entering from vehicles in attached garages and emissions from consumer products that contain benzene such as paint or adhesives. Brown and Crump (1998b) measured benzene concentrations over five years in the upstairs main bedroom of a Hertfordshire, England, home with an integral garage, and outside the home. Diffusive Perkin Elmer type samplers, packed with Tenax TA adsorbent, were employed for measurement of six aromatic hydrocarbons inside and outside the home from Novem-
ber 1990 to February 1996. Although all the annual mean concentrations were below the recommended ambient air quality standard for benzene in the UK (16 Ilgm’ as a running annual average), readings for several months in the bedroom exceeded this value. Monitoring of benzene levels in this home has continued and Figure 1 shows the benzene concentration measured each month with a passive air sampler in the main bedroom (upstairs room not directly over the garage) and outdoors for the period November 1990 to December 1999. Concentrations in the main bedroom are usually higher than outdoors. Figure 2 compares the concentration in the main bedroom with that determined by a passive personal exposure monitor worn by an adult occupant for the period June 1994 to December 1999. This shows a close correlation between the main bedroom concentration and personal exposure and shows that the concentration in the bedroom gave a better estimate of personal exposure than outdoor concentrations.
Materials and methods Sampling involved the use of Perkin Elmer tube-type samplers containing Tenax TA
adsorbent. Benzene was monitored in the home (living room, main bedroom and room above the garage), in the garage, in the car and outdoors in the garden for five homes belonging to Building Research Establishment (BRE) employees. Tubes were exposed for approximately 28 days each month, for 18 months. Analysis of tube samplers was undertaken at BRE using thermal desorption/gas chromatography with flame ionisation detection. Details of the analytical equipment and procedure have been described elsewhere (Berry et al, 1996). A total of five homes (Homes 1-5) were monitored between June 1998 and November 1999. Figures 1 and 2 mentioned above refer to Home 1. A questionnaire giving details about the home was completed by each participant at the outset of the study. Some of the details recorded are shown in Table 1.
Figure
1
Main bedroom (MB) and outside benzene concentrations each month at Home 1, St Albans, November 1990 to December 1999
Every month, participants completed a ’garage questionnaire’ (giving details of garaging over the month) and an ’update
questionnaire’ detailing any activities that may have introduced pollutants into the
indoor air.
42
Results and discussion
Outdoor benzene concentrations measured at different heights and locations for Home 1
Figure 2
-
Main bedroom (MB) and personal benzene concentrations at Home 1, St Albans, June 1994 to December 1999
During the period June 1998 to January 1999, samplers were placed at Home 1 at two different heights at outdoor locations to
both the front and the rear of the home to see if the benzene concentration of outdoor air that may enter the building varied with location. This house is situated on a busy single carriageway road with properties on one side and a large hedgerow and open fields on the other. Results of measurements are shown in Table 2. Benzene concentrations measured at different heights and locations outside this home suggested that there was not a vertical benzene concentration gradient or a difference between the front and rear of the home. Further work should examine a wider range of homes including those in a street ’canyon’, but for Home 1 a single outdoor monitoring location near the property was representative of air at ground and first floor level both to the front and the rear.
the
car
in the garage fewer than five times
Mean benzene levels
over
the whole
monitoring period
Table 3 shows the mean benzene concentrations for all locations in the five homes, over the whole monitoring period (June 1998 to November 1999).’ Details of the cars kept at each home are shown in Table 4. All cars
were
throughout the whole monitoring period, giving negligible benzene emission from the garage into the rooms within the home. Table 5 shows mean indoor benzene values after outdoor concentrations have been deducted. This gives an estimate of
of benzene infiltrating into the living spaces of the home from emissions in the garage assuming no other indoor sources. For Homes 1, 2 and 4, concentrations in rooms due to ingress of benzene from the garage were between 0.3 ~gm3 (living room of Home 1) and 9.1 ~gm(room above the garage of Home 4). The benzene ingress from the garage was itself sufficient at all indoor locations in Home 3 to produce an exceedance of the ambient air quality
amount
the
standard. Homes 2 and 4 had an internal door from the garage to the ground floor living quarters of the house. The mean benzene concentrations in the living rooms were higher than in Home 1, which has no door from garage to living quarters. The relatively high living room benzene concentration for Home 3 (which has no door from garage to living space) was due to benzene
infiltration
was
carburetted; none were fuel-injected.
the living space when Car 2 in the garage. parked
to
The monthly mean benzene values in all cars and garages exceeded the benzene UK ambient air standard with the exception of the garage of Home 5. The standard was exceeded by nearly seven times in the car at Home 4 and in the garage at Home 2. Within Home 3, the standard was exceeded in all
Changes in benzene levels with garaging behaviour
Table 6 shows the mean benzene concentrations in the garage and room above the garage (after subtracting outdoor benzene value) for three different monitoring periods for Home 3. For this home the ques-
indoor locations because of high concentrations between months 5 and 10 when Car 2 (mean benzene concentration 1625.5 ~gm’ during these months) was parked in the garage. Although the standard was not exceeded in the other homes, some relatively high values were found in the room above the garage for Home 1 (11.7 pgm~) and Home 4 (11.5 (igm~). A possible indoor source of benzene was identified in the living room of Home 2 where approximately four ounces of pipe tobacco and ten cigarettes were smoked each week. There were no smokers in the other homes. In Home 5 all values were low; this household parked
Figure
-
3
room
Monthly variation of benzene concentration in the garage and garage (RAG) for Home 4 from July 1998 to August 1999
above the
43
Figure
Chromatogram showing VOCs in air of garage of Home 1
4
room
above the garage for Home 4. The
in June 1998
monthly pattern was similar for Home 2, which was the only other house in which the
same car was garaged over the entire study period. The pattern in other houses was more complicated owing to the fact that different cars were garaged at different times. For Home 4 a significant seasonal varia-
tion was observed in benzene concentrations recorded in the garage. Mean summer
concentrations, during July
1998 (129.8 Ilgm
to
September
(103.7 ~grn ~),
3) and April to August 1999 were higher than during
tionnaires showed that there was no car parked in the garage during months 1-4 and 11-18. During these periods there was relatively little difference between benzene concentrations in the garage and outdoors (< 3.5 ~gm ~ and similarly in the room above the garage (< 0.4 ggm-3). During months 5 to 10, when Car 2 was kept in the garage, the benzene concentration in the garage due to vehicle emissions increased to 189.7 ¡.tgm-1i and in the room above the garage to 60.8 agm 3. The mean in-car benzene concentraj. tion over this period was 1625.5 ¡.tgm-1. These relatively high benzene concentra-
tions may have been in part due to car repairs being undertaken in the garage between months 5 and 10. A similar pattern of elevation in benzene for months 5-10 (compared to the months before and after) was noted in the living room and main bedroom. The results demonstrate that the elevation in benzene levels in the living space between months 5 and 10 was due to infiltration of benzene from the integral garage.
Seasonal variation in benzene levels
Figure 3 shows the monthly variation of benzene concentration in the garage and
October 1998 to March 1999 (74.0 Ilgm~. One reason for the higher levels in the garage in summer than in winter could be the greater emissions from the car and other petrol appliances in the enclosed garage area when the ambient temperature is higher. The room above the garage had reasonably consistent benzene concentrations throughout the monitoring period (10.4, 10.8 and 10.5 ggm’ respectively). The benzene concentration in this room will be affected by infiltration of air from outdoors (including intended ventilation) and from the garage below In summer, although the outdoor air has lower benzene levels than in winter, the air from the garage will have a greater benzene concentration. There may also be an effect arising from differences in air exchange rate, between the garage and house in summer and winter. This might be related to the greater difference in temperature between the garage and house in winter than in summer since garages are not usually heated. Data for ventilation in the main bedroom, collected at the outset of the study (summer 1998), indicated that at that time of the year all participants either ’sometimes’ or ’nearly always’ opened windows at night. No data was available on ventilation patterns within the home during the study or on the use of the fresh air supply within the vehicles.
Other
pollutants Figures 4 and 5 show chromatograms given by analysis of air samplers in Home 1 to illustrate the range of compounds that can be found in an integral garage containing a parked car and the room above the garage. Each peak represents a different VOC and the size of each peak represents the relative concentration of that compound. Many compounds are present in both locations, but as indicated by the differences of scale, peaks for benzene, toluene and m/p-xylene
44
are about ten times larger in the garage than in the room above. Other VOCs are present in the room resulting from other sources,
w
Frequency and duration of garaging
the car Emission characteristics of the car Ventilation of the garage and home Availability of vapour migration pathwaysfrom the garage to the living space Other indoor sources and outdoor levels of benzene Amount and type of car maintenance undertaken in the garage
ference
Air
on
Indoor Air
Quality and
Climate. Indoor
; 1984 4, 21-26
.
including 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (tmpmb), which is a coalescing solvent in emulsion paints.
Mean concentrations of some of the compounds attributable to vehicle fuels in the garage and room above the garage for Home 1 (for the period June to July 1998) are presented in Table 7. This shows that the garage is a potentially significant source of these compounds in the living space.
w
.
OF THE ENVIRONAND THE REGIONS) (2000). The Air Quality Strategy for England, Scotland, Wales and Northern Ireland: Working Together for Clean Air (Cm 4548). Norwich: HMSO
DETR
(DEPARTMENT
MENT, TRANSPORT
.
~
DUARTE-DAVISON R, COURAGE C, RUSHTON L and LEVY L S (1999). General population exposure to environmental levels of benzene in the UK. Indoor Air 1999 5, 333-334 ; EBS BIOMEDICAL SCIENCES) Risk Characterisation. Eastmillstone, New Jersey: Exxon Biomedical Sciences
(EXXON (1996). Benzene
Conclusions
Previous studies have demonstrated that the majority of total exposure of the general population to air pollutants occurs during time spent indoors. Since a large proportion of this time is at home, exposure within the home is important. One source of benzene identified in homes with an attached or integral garage is fuel vapour and exhaust emissions from motor vehicles parked in the garage. These emissions can find their way into the living spaces of the home and therefore increase personal exposure. Ten years of sampling (1990-1999) inside and outside a Hertfordshire home with an integral garage showed benzene levels indoors were significantly higher than outdoors. Personal exposure measurements of one adult occupant from June 1994 to December 1999 gave a close correlation between the main bedroom concentration and personal exposure which suggests that
Further work is recommended to investigate a greater number of homes and to identify the routes of entry of benzene into the living space. Possible remedial measures (e.g. sealing cracks in the ceiling and walls of the garage and increased ventilation of the garage) to reduce benzene concentrations in the living space should also be evaluated. It would also be informative to determine the emission of benzene from a range of vehicle types. This knowledge could then be applied to advise on actions to reduce exposure to benzene for the significant proportion of the population living in homes with attached and integral garages.
FELLIN P and OTSON R (1993). Seasonal Trends of Volatile Organic Compounds (VOCs) in Canadian Homes. In: Indoor Air 1993: Proceedings of the 6th International Conference on Indoor Air Quality and Climate, Vol 1, pp. 339-343. (Edited by JJ K Jaakkola, R Ilmarinen and O Seppänen O). Espoo, Finland: Helsinki University of
Technology
GAMMAGE R B and WHITE D A (1984). Residential measurements of high volatility organics and their sources. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate. IndoorAir 1984; 4, 157-162 GOLDSTEIN B D, TARDIFF R G, BAKER S R, HOFFNAGLE G F, MURRAY D R, CATIZONE P A, et al (1992). Valdez Air Health Study. Anchorage, Alabama: Alyseka Pipeline Service Co
HRICKO A (1994). Rings of controversy around benzene. Environ Health Persp ; 102(3), 276-281
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above the garage. The mean benzene concentration in the room above the garage of one home was 36.9 ~gm’ during six months when a car with high benzene emissions was parked in the garage; this is nearly 2.5 times the air quality standard. Benzene levels in attached or integral garages and the adjacent living space will be influenced by:
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SHELDON L
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46
H S
Mann, D Crump, V Brown
Hardip Singh Mann, Centre for Safety, Health and Environment, Building Research Establishment, Bucknalls Lane, Garston, Watford WD25 9XX, England Email: [email protected] Derrick Crump, MRSH, Centre for Safety, Health and Environment, Building Research Establishment, Bucknalls Lane, Garston,
Watford WD25 9XX,
England
Email:
[email protected]
Building Research Establishment, Bucknalls Lane, Garston,
Veronica Brown, Centre for Safety, Health and Environment, Watford WD25 9XX, England Email: [email protected]
Corresponding author: Hardip Singh Mann
Received 8 January 2001, revised and accepted 23
January 2001
Key words
Attached garages; benzene; car; health; home;
personal exposure; petrol
Introduction
Abstract
Benzene is an air pollutant that is a recognised human carcinogen. An air quality standard has been established for ambient air in the UK to reduce the population’s exposure. It has been estimated that about 70% of benzene emissions to air in the UK come from petrol vehicles. A number of studies, including the Avon Longitudinal Study of Pregnancy and Childhood in the UK, have found that benzene concentrations in homes with attached or integral garages tend to be higher than in those without such garages. The present paper reviews these studies and reports a detailed investigation of five homes with either an attached or an integral garage. Indoor and outdoor locations were monitored using diffusive sampling to determine the average benzene concentration over approximately 28 days each month for 18 consecutive months (June 1998-November 1999). For one of these homes, ten years of data had shown the indoor benzene concentration to be consistently higher than outdoors. Personal exposure monitoring of one adult in this home showed that the benzene concentration in the main bedroom was a better predictor of personal exposure than the concentration outdoors. In the homes where a car was regularly parked in the garage, 18-month average benzene concentrations of up to 101.3 μgm were measured in the garage, 3 which is more than six times the ambient air quality standard for benzene (16.25 3 μgm running annual average). Mean benzene values in all cars and most of the garages studied exceeded the benzene standard. Mean benzene concentrations in the room abovethe garage ranged from 3.7 3 μgm in one home, where the car was rarely parked in the garage, to 39.9 μgm 3 in another home where a car with high benzene emissions was parked in the garage for six of the 18 months monitored. The mean benzene concentration in the room above the garage in this latter home was nearly 2.5 times the ambient air standard. The study demonstrates that there is a potential for people to have a higher exposure to benzene as a result of living in a home with an attached or integral garage. An understanding of routes of personal exposure is important to develop effective policies to reduce risks to health.
Most people are likely to have the greatest contact with potentially toxic pollutants inside the places
they usually consider to be essentially unpolluted,
and vehicles. Since most 80-90% of their time indoors, espepeople spend cially at home (Mann et al, 1997), personal exposure from pollutants within the home is important. A 12-month study of personal exposure of 30 adults to nitrogen dioxide, carbon monoxide and volatile organic compounds (VOCs) in Hertfordshire, England (Crump et al, 1999) concluded that over 80% of the total exposure to these pollutants occurred during the time spent indoors. A study of 50 volunteers in England undertaken by Leung and Harrison (1998) concluded that although concentrations of VOCs such as benzene within the home were relatively low (compared with activities such as refuelling), because a large proportion of time is spent within the home (particularly at night), annual exposures were
such
as
homes, offices
high.
One harmful pollutant found indoors, benzene, can enter the indoor air because of vehicle emissions and other sources such as tobacco smoke. Benzene and its metabolites have been shown to cause damage or breaks in genetic material, as well as chromosomal abnormalities; the most significant mechanisms of potential adverse health effects of prolonged exposure to low levels of benzene are haematotoxicity, genotoxicity and carcinogenicity (IEH, 1999). The International Agency for Research on Cancer has designated benzene as a Group 1 carcinogen which means that there is ’sufficient evidence of
38
Table
Residential details for Homes 1 to 5
1
carcinogenicity in humans’.
Some 70% of benzene emissions to air in the UK are currently derived from road transport, mainly petrol vehicles (Salway et al, 1997). The most important sources include evaporative losses, refuelling emissions and combustion of petrol (IEH, 1999). The benzene emitted from a car exhaust is likely to be a mixture of unburned benzene and benzene derived from the combustion of other aromatic
for benzene of 5 ~gmand this must be met by 1 January 2010.
Personal exposure to benzene
In the Total Exposure Assessment Method-
study (Sheldon et al, 1991) gave personal, indoor and outdoor mean benzene concentrations of 5.0, 4.0 and 1.2 J.lgffi’
respectively. In another study (Goldstein et al, 1992), day and night 12-hour average
concentrations of benzene were measured for 58 residents of Valdez, Alaska. The mean benzene concentrations in the personal, indoor and outdoor samples for summer were 20, 16 and 5 j~gm~ and 28, 25 and 11 ggtn’ in the winter. In several benzene exposure studies conducted recently in cities across Europe (such as MACBETH and EXPOLIS), personal exposure of study participants to benzene, as well as indoor levels, were higher than outdoor levels in nearly all cities involved. This clearly pointed to contributing sources in the indoor environment where people spend more than 20 hours per day (CON-
1991
petrol components (EBS, 1996).
There are a number of national and international initiatives aimed at reducing population exposure to benzene and the associated risk to health. Throughout Europe, gasoline and diesel fuel qualities with lower environmental impact are being introduced. Most recently the European Union has mandated stricter specifications from the year 2000, including a maximum benzene content for gasoline of 1% by volume (Ross, 1999). In the past, benzene has been present in petrol in a proportion of about 5% and occasionally up to 16% (WHO, 1987). The UK National Air Quality Strategy sets an air quality standard for benzene in the UK of 5 ppb (parts per billion) (16.25 ggm) as a running annual average, and a target guideline of 1 ppb (3.3 Ilgm l The 1997 strategy objective of the 5 ppb standard was originally to have been met by local authorities by 2005 but has now to be achieved by 2003 (DETR, 2000). The Directive Community European 2000/69/EC sets an ambient air limit value
studies of VOCs, Wallace (1987) combined all the existing information about how several hundred people located in five different states in the USA were exposed to benzene. He found that the average concentration of benzene they inhaled was nearly three times higher than typical outdoor levels. Wallace calculated that 45% of the total exposure of the US population to benzene came from smoking (including exposure to environmental tobacco smoke), 36% from inhaling petrol fumes (refuelling) and 16% from other sources such as cars and other items (e.g. petrol, petrol-driven lawnmowers) stored in attached garages. Only 3% of the average person’s exposure was attributed to industrial pollution. A
ology
CAWE, 2000).
In the 12-month
study
of
personal
Table 2
Mean benzene values at different locations and
heights at Home 1
39
Table
Mean benzene concentrations
3
monitoring period
I
(ggm’) for Homes 1
to 5 in all locations over the whole
Table
Details of cars
4
to 5
kept at Homes 1
exposure of 30 adults by Crump et al (1999) personal, indoor (bedroom) and outdoor (at home) benzene concentrations were 7.7, 6.1 and 3.9 ~gm3 respectively In the personal and fixed site exposure study of Leung and Harrison (1998), personal 12hour daytime exposures to benzene ranged from 0.8-295 ~gm’ (mean 6.5 ~gm 3) compared with an annual average concentration of 3.9 ~gm3 at the nearest suburban fixed site monitoring station. The mean benzene concentration within the homes sampled was 16.4 ~gm B Kingham et al (1998) quoted ‘high’ in-car benzene concentrations of over 200 ~gm3 and expressed concern for drivers’ exposure. Leung and Harrison (1998) and Crump etal (1999) reported mean in-car benzene concentrations of 41 and 113
mean
ggm’respectiN,ely.
Other studies have reported indoor and outdoor benzene concentrations. In an
40
investigation of 14 Italian houses, significantly higher benzene concentrations were found in the indoor air (52 Ilgm ~) compared
the outdoor air, with an indoor/outdoor ratio of 3.9 (De Bortoli et al, 1984). A study of urban benzene and population exposure spanning several European towns (Cocheo, 2000) found benzene levels in homes were 1.51 times those measured outside. A nationwide Canadian study (Fellin and Otson, 1993) measured 24-hour indoor air benzene concentrations in 754 randomly selected homes. Winter, spring, summer and autumn seasonal mean indoor benzene concentrations were 6.39, 5.60, 2.72 and 6.98
to
Table 5 Mean benzene concentrations (J.19m-3) due only to indoor sources for June 1998 to November 1999 (outdoor benzene contribution subtracted)
Table 6
Ilgmrespectively. Jones etal (1999) found that benzene levels were higher in urban than rural homes and higher during periods of occupancy. A German study (Levsen et al, 1999) concluded that whilst the sources for certain compounds (such as toluene and xylenes) were found indoors, there were only weak indoor sources for benzene, and most of the benzene found indoors was from outdoor
sources
Benzene concentrations (J19m-3) in the garage, room above the garage and car for Home 3 (after subtracting outdoor benzene value)
(mainly traffic).
These studies therefore show that personal exposure can be higher than indicated by studies of outdoor air. Understanding the sources of this exposure is important for developing policies that can reduce population exposure to benzene. One such source, benzene released by vehicles in garages attached or integral to homes, is discussed in the remainder of this paper and a study of five homes is described.
*
Benzene from vehicles in attached garages Pierson et al (1999) categorised emissions
from motor vehicles as ’fuel vapour emissions’ (i.e. vehicle evaporative emissions) and ’exhaust emissions’ from the tailpipe, which may consist of hydrocarbons such as benzene and other compounds, e.g. carbon monoxide, aldehydes and lead. The evaporative emissions were classified as follows:
~
*
emissions leave the tank Running losses occur when petrol is heated to the point at which it boils in the fuel tank. Once the fuel boils, the evaporative emission control system is overwhelmed and the engine may even be incapable of burning the vaporised fuel Resting losses result from the diffusion of fuel through plastic and rubber fuel system components and the escape of hydrocarbon vapours from the storage canister. Resting losses emission rates are low but occur continuously and in total can be significant
Table 7
Pollutants from vehicle fuel, including are thus released to the atmosphere by evaporative losses and refuelling emissions as well as from the exhaust of the vehicle from petrol combustion (DuarteDavison et al, 1999). Many private motor vehicles are kept, when not in use, in a garage sharing a common wall with the vehicle owner’s home and there is sometimes an interconnecting door to the living area. In some of these homes a room is located directly above the garage. There can be an increase in benzene levels within the home from attached or integral garages; one estimate suggests an 80% increase in ben-
benzene,
~
’Hot-soak’ emissions result from the heating of the fuel system after engine shutdown. Sawyer (1993) suggested that these are more important in carburetted engines than in fuel injected engines Diurnal emissions result from cyclic heating and cooling of the fuel tank during the day and night. As fuel and fuel vapour warm and expand,
Mean concentrations (J.19m-3) of some aromatic hydrocarbons other than benzene in the garage and room above the garage in Home 1
41
zene
concentration from
an
attached garage
to
house, benzene concentrations in the liv-
(Duarte-Davison et al, 1999). The Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) involved the study of indoor air pollution in 174 homes in Avon, England (Berry et al, 1996). Passive air samplers were used to collect 28day samples in the living room and main
bedroom of the home for one year. The mean indoor concentration was 8 ~gm-3 (n=3000 samples) compared with an outdoor mean of 5 ~gm’ (n=125). It was found that higher benzene concentrations in the home were associated with there being a smoker in the household and with the presence of an integral garage (Crump, 1997). Homes with attached or integral garages in which a car was kept (13% of all homes) had 25-30% higher ’within-home’ benzene concentrations than those homes without an attached or integral garage or with an attached or integral garage not used for parking the car. This was further confirmed in a study of 44 homes in Southampton, England (Brown and Crump, 1998a) where concentrations of benzene in both the living rooms and bedrooms were significantly higher for homes where a car was kept in an attached or integral garage (17% of homes). In a study of 42 homes in Hanover, Germany, Levson (1996) found garage benzene concentrations as high as 80.9 ggm’. In homes with connecting doors from garage
ing room were as high as 17.6 f.lgmIn New 1 Jersey, USA, Thomas et al (1993) studied 11 homes selected because of relatively high VOC concentrations measured in a previous study. This study identified attached
garages as a source of benzene and found that benzene was transferred from the garage to the home living areas at relatively high rates. Gammage and White (1984) detected gasoline vapours in 40 homes in Tennessee, USA, most of which had attached garages. Benzene can seep into a house from an attached garage, when benzene in petrol evaporates from the car’s hot engine and tank (Hricko, 1994). A study in the USA of 355 urban apartments reported mean indoor benzene concentrations of 16 gpn’ with an indoor/outdoor ratio of 2.2 (Wallace et al, 1985). Wallace attributed much of the higher indoor levels to benzene entering from vehicles in attached garages and emissions from consumer products that contain benzene such as paint or adhesives. Brown and Crump (1998b) measured benzene concentrations over five years in the upstairs main bedroom of a Hertfordshire, England, home with an integral garage, and outside the home. Diffusive Perkin Elmer type samplers, packed with Tenax TA adsorbent, were employed for measurement of six aromatic hydrocarbons inside and outside the home from Novem-
ber 1990 to February 1996. Although all the annual mean concentrations were below the recommended ambient air quality standard for benzene in the UK (16 Ilgm’ as a running annual average), readings for several months in the bedroom exceeded this value. Monitoring of benzene levels in this home has continued and Figure 1 shows the benzene concentration measured each month with a passive air sampler in the main bedroom (upstairs room not directly over the garage) and outdoors for the period November 1990 to December 1999. Concentrations in the main bedroom are usually higher than outdoors. Figure 2 compares the concentration in the main bedroom with that determined by a passive personal exposure monitor worn by an adult occupant for the period June 1994 to December 1999. This shows a close correlation between the main bedroom concentration and personal exposure and shows that the concentration in the bedroom gave a better estimate of personal exposure than outdoor concentrations.
Materials and methods Sampling involved the use of Perkin Elmer tube-type samplers containing Tenax TA
adsorbent. Benzene was monitored in the home (living room, main bedroom and room above the garage), in the garage, in the car and outdoors in the garden for five homes belonging to Building Research Establishment (BRE) employees. Tubes were exposed for approximately 28 days each month, for 18 months. Analysis of tube samplers was undertaken at BRE using thermal desorption/gas chromatography with flame ionisation detection. Details of the analytical equipment and procedure have been described elsewhere (Berry et al, 1996). A total of five homes (Homes 1-5) were monitored between June 1998 and November 1999. Figures 1 and 2 mentioned above refer to Home 1. A questionnaire giving details about the home was completed by each participant at the outset of the study. Some of the details recorded are shown in Table 1.
Figure
1
Main bedroom (MB) and outside benzene concentrations each month at Home 1, St Albans, November 1990 to December 1999
Every month, participants completed a ’garage questionnaire’ (giving details of garaging over the month) and an ’update
questionnaire’ detailing any activities that may have introduced pollutants into the
indoor air.
42
Results and discussion
Outdoor benzene concentrations measured at different heights and locations for Home 1
Figure 2
-
Main bedroom (MB) and personal benzene concentrations at Home 1, St Albans, June 1994 to December 1999
During the period June 1998 to January 1999, samplers were placed at Home 1 at two different heights at outdoor locations to
both the front and the rear of the home to see if the benzene concentration of outdoor air that may enter the building varied with location. This house is situated on a busy single carriageway road with properties on one side and a large hedgerow and open fields on the other. Results of measurements are shown in Table 2. Benzene concentrations measured at different heights and locations outside this home suggested that there was not a vertical benzene concentration gradient or a difference between the front and rear of the home. Further work should examine a wider range of homes including those in a street ’canyon’, but for Home 1 a single outdoor monitoring location near the property was representative of air at ground and first floor level both to the front and the rear.
the
car
in the garage fewer than five times
Mean benzene levels
over
the whole
monitoring period
Table 3 shows the mean benzene concentrations for all locations in the five homes, over the whole monitoring period (June 1998 to November 1999).’ Details of the cars kept at each home are shown in Table 4. All cars
were
throughout the whole monitoring period, giving negligible benzene emission from the garage into the rooms within the home. Table 5 shows mean indoor benzene values after outdoor concentrations have been deducted. This gives an estimate of
of benzene infiltrating into the living spaces of the home from emissions in the garage assuming no other indoor sources. For Homes 1, 2 and 4, concentrations in rooms due to ingress of benzene from the garage were between 0.3 ~gm3 (living room of Home 1) and 9.1 ~gm(room above the garage of Home 4). The benzene ingress from the garage was itself sufficient at all indoor locations in Home 3 to produce an exceedance of the ambient air quality
amount
the
standard. Homes 2 and 4 had an internal door from the garage to the ground floor living quarters of the house. The mean benzene concentrations in the living rooms were higher than in Home 1, which has no door from garage to living quarters. The relatively high living room benzene concentration for Home 3 (which has no door from garage to living space) was due to benzene
infiltration
was
carburetted; none were fuel-injected.
the living space when Car 2 in the garage. parked
to
The monthly mean benzene values in all cars and garages exceeded the benzene UK ambient air standard with the exception of the garage of Home 5. The standard was exceeded by nearly seven times in the car at Home 4 and in the garage at Home 2. Within Home 3, the standard was exceeded in all
Changes in benzene levels with garaging behaviour
Table 6 shows the mean benzene concentrations in the garage and room above the garage (after subtracting outdoor benzene value) for three different monitoring periods for Home 3. For this home the ques-
indoor locations because of high concentrations between months 5 and 10 when Car 2 (mean benzene concentration 1625.5 ~gm’ during these months) was parked in the garage. Although the standard was not exceeded in the other homes, some relatively high values were found in the room above the garage for Home 1 (11.7 pgm~) and Home 4 (11.5 (igm~). A possible indoor source of benzene was identified in the living room of Home 2 where approximately four ounces of pipe tobacco and ten cigarettes were smoked each week. There were no smokers in the other homes. In Home 5 all values were low; this household parked
Figure
-
3
room
Monthly variation of benzene concentration in the garage and garage (RAG) for Home 4 from July 1998 to August 1999
above the
43
Figure
Chromatogram showing VOCs in air of garage of Home 1
4
room
above the garage for Home 4. The
in June 1998
monthly pattern was similar for Home 2, which was the only other house in which the
same car was garaged over the entire study period. The pattern in other houses was more complicated owing to the fact that different cars were garaged at different times. For Home 4 a significant seasonal varia-
tion was observed in benzene concentrations recorded in the garage. Mean summer
concentrations, during July
1998 (129.8 Ilgm
to
September
(103.7 ~grn ~),
3) and April to August 1999 were higher than during
tionnaires showed that there was no car parked in the garage during months 1-4 and 11-18. During these periods there was relatively little difference between benzene concentrations in the garage and outdoors (< 3.5 ~gm ~ and similarly in the room above the garage (< 0.4 ggm-3). During months 5 to 10, when Car 2 was kept in the garage, the benzene concentration in the garage due to vehicle emissions increased to 189.7 ¡.tgm-1i and in the room above the garage to 60.8 agm 3. The mean in-car benzene concentraj. tion over this period was 1625.5 ¡.tgm-1. These relatively high benzene concentra-
tions may have been in part due to car repairs being undertaken in the garage between months 5 and 10. A similar pattern of elevation in benzene for months 5-10 (compared to the months before and after) was noted in the living room and main bedroom. The results demonstrate that the elevation in benzene levels in the living space between months 5 and 10 was due to infiltration of benzene from the integral garage.
Seasonal variation in benzene levels
Figure 3 shows the monthly variation of benzene concentration in the garage and
October 1998 to March 1999 (74.0 Ilgm~. One reason for the higher levels in the garage in summer than in winter could be the greater emissions from the car and other petrol appliances in the enclosed garage area when the ambient temperature is higher. The room above the garage had reasonably consistent benzene concentrations throughout the monitoring period (10.4, 10.8 and 10.5 ggm’ respectively). The benzene concentration in this room will be affected by infiltration of air from outdoors (including intended ventilation) and from the garage below In summer, although the outdoor air has lower benzene levels than in winter, the air from the garage will have a greater benzene concentration. There may also be an effect arising from differences in air exchange rate, between the garage and house in summer and winter. This might be related to the greater difference in temperature between the garage and house in winter than in summer since garages are not usually heated. Data for ventilation in the main bedroom, collected at the outset of the study (summer 1998), indicated that at that time of the year all participants either ’sometimes’ or ’nearly always’ opened windows at night. No data was available on ventilation patterns within the home during the study or on the use of the fresh air supply within the vehicles.
Other
pollutants Figures 4 and 5 show chromatograms given by analysis of air samplers in Home 1 to illustrate the range of compounds that can be found in an integral garage containing a parked car and the room above the garage. Each peak represents a different VOC and the size of each peak represents the relative concentration of that compound. Many compounds are present in both locations, but as indicated by the differences of scale, peaks for benzene, toluene and m/p-xylene
44
are about ten times larger in the garage than in the room above. Other VOCs are present in the room resulting from other sources,
w
Frequency and duration of garaging
the car Emission characteristics of the car Ventilation of the garage and home Availability of vapour migration pathwaysfrom the garage to the living space Other indoor sources and outdoor levels of benzene Amount and type of car maintenance undertaken in the garage
ference
Air
on
Indoor Air
Quality and
Climate. Indoor
; 1984 4, 21-26
.
including 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (tmpmb), which is a coalescing solvent in emulsion paints.
Mean concentrations of some of the compounds attributable to vehicle fuels in the garage and room above the garage for Home 1 (for the period June to July 1998) are presented in Table 7. This shows that the garage is a potentially significant source of these compounds in the living space.
w
.
OF THE ENVIRONAND THE REGIONS) (2000). The Air Quality Strategy for England, Scotland, Wales and Northern Ireland: Working Together for Clean Air (Cm 4548). Norwich: HMSO
DETR
(DEPARTMENT
MENT, TRANSPORT
.
~
DUARTE-DAVISON R, COURAGE C, RUSHTON L and LEVY L S (1999). General population exposure to environmental levels of benzene in the UK. Indoor Air 1999 5, 333-334 ; EBS BIOMEDICAL SCIENCES) Risk Characterisation. Eastmillstone, New Jersey: Exxon Biomedical Sciences
(EXXON (1996). Benzene
Conclusions
Previous studies have demonstrated that the majority of total exposure of the general population to air pollutants occurs during time spent indoors. Since a large proportion of this time is at home, exposure within the home is important. One source of benzene identified in homes with an attached or integral garage is fuel vapour and exhaust emissions from motor vehicles parked in the garage. These emissions can find their way into the living spaces of the home and therefore increase personal exposure. Ten years of sampling (1990-1999) inside and outside a Hertfordshire home with an integral garage showed benzene levels indoors were significantly higher than outdoors. Personal exposure measurements of one adult occupant from June 1994 to December 1999 gave a close correlation between the main bedroom concentration and personal exposure which suggests that
Further work is recommended to investigate a greater number of homes and to identify the routes of entry of benzene into the living space. Possible remedial measures (e.g. sealing cracks in the ceiling and walls of the garage and increased ventilation of the garage) to reduce benzene concentrations in the living space should also be evaluated. It would also be informative to determine the emission of benzene from a range of vehicle types. This knowledge could then be applied to advise on actions to reduce exposure to benzene for the significant proportion of the population living in homes with attached and integral garages.
FELLIN P and OTSON R (1993). Seasonal Trends of Volatile Organic Compounds (VOCs) in Canadian Homes. In: Indoor Air 1993: Proceedings of the 6th International Conference on Indoor Air Quality and Climate, Vol 1, pp. 339-343. (Edited by JJ K Jaakkola, R Ilmarinen and O Seppänen O). Espoo, Finland: Helsinki University of
Technology
GAMMAGE R B and WHITE D A (1984). Residential measurements of high volatility organics and their sources. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate. IndoorAir 1984; 4, 157-162 GOLDSTEIN B D, TARDIFF R G, BAKER S R, HOFFNAGLE G F, MURRAY D R, CATIZONE P A, et al (1992). Valdez Air Health Study. Anchorage, Alabama: Alyseka Pipeline Service Co
HRICKO A (1994). Rings of controversy around benzene. Environ Health Persp ; 102(3), 276-281
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46
