based model does not take seasonal effects into account, a 7-day diary is assumed to be representative for an average
week over the year. The lowest SEC consists of 272,311 adults; the highest SEC of 734,310 agents.
3.1. Time use
A major difference between both SEC, is that people of a higher SEC spend more time at work and less time at
home (Table 2). Also the time spent for utilitarian travel is larger for members of a higher SEC (51 minutes
compared to 33 minutes): these extra minutes are almost exclusively done by car, as a driver, and on traffic peak
hours. Time in public transport or by active modes is only slightly higher. Also the number of trips is remarkably
higher for people of a high SEC: 2.59 trips/day versus 1.55 trips/day.
3.2. Exposure
The average exposure to BC of an agent of the lowest SEC is 1523 ng/m³ (IQR = 652 ng/m³): this number takes
into account exposure at different locations, while traveling, and in indoor microenvironments. This is in contrast
with static exposure assessment that assumes individuals being indoors at home for 24h; in this case the exposure
would be estimated as 1438 ng/m³. Agents from the highest SEC are exposed, on average, to 1409 ng BC/m³ (IQR =
512 ng/m³) using the dynamic exposure estimation. Static exposure is also lower: 1219 ng/m³.
People with a lower socioeconomic status are exposed to higher BC concentrations while being at home (1348
ng/m³ compared to 1160 ng/m³). This is in line with previous research stating that poorer people tend to live in areas
with higher air pollution, e.g. near major roads or in densely populated urban areas [6; 10; 12; 15; 27; 28]. Also on
other locations that these people visit, their exposure tends to be higher than that of people of a high SEC. The AB²C
model does not account for differences in ventilation conditions, which may lead to even higher exposures at home
for people of a lower SEC [6; 13]. Only while traveling, the exposure of people of a high SEC is higher: this can be
explained by the larger number of trips in cars and trips on traffic peak hours; this was also observed by Beckx et al.
[2] in the Netherlands.
3.3. Inhaled dose
With the exposure estimates of the AB²C model and assumptions on inhalation during different activities, dose or
‘internal exposure’ can be calculated. Minute volumes for adults per activity type and in different transport modes
were derived from Allan & Richardson [29] (Table 1).
Inhaled dose is larger for people of lower SECs, but the difference with the other group becomes very small
(22,761 ng/day compared to 22,296 ng/day). The exact numbers depend on the assumptions made on inhalation per
activity, and on the gender distribution within the groups. The analysis nevertheless reveals an important trend:
people from higher SECs inhale more BC particles during shorter time spans, namely while traveling (which
assumes increased physical activity). Lower SECs travel less, but are exposed to higher concentrations at home,
their 24h average breathing rate is assumed to be lower at home, resulting in an almost equal amount of inhaled BC
particles as compared to the higher SEC.
Table 1. Summary of minute volume assumptions (L/min). Numbers based on Allen & Richardson (1998).
Activity Male adults Female adults
Being at home / Car passenger 8.3 7.5
Work / Services / Car driver 10.5 12.5
Bring/get / Shopping / Social visits / Leisure / Other / Public Transport 16.1 13.0
Touring / On foot / Bike 49.2 39.8
based model does not take seasonal effects into account, a 7-day diary is assumed to be representative for an average
week over the year. The lowest SEC consists of 272,311 adults; the highest SEC of 734,310 agents.
3.1. Time use
A major difference between both SEC, is that people of a higher SEC spend more time at work and less time at
home (Table 2). Also the time spent for utilitarian travel is larger for members of a higher SEC (51 minutes
compared to 33 minutes): these extra minutes are almost exclusively done by car, as a driver, and on traffic peak
hours. Time in public transport or by active modes is only slightly higher. Also the number of trips is remarkably
higher for people of a high SEC: 2.59 trips/day versus 1.55 trips/day.
3.2. Exposure
The average exposure to BC of an agent of the lowest SEC is 1523 ng/m³ (IQR = 652 ng/m³): this number takes
into account exposure at different locations, while traveling, and in indoor microenvironments. This is in contrast
with static exposure assessment that assumes individuals being indoors at home for 24h; in this case the exposure
would be estimated as 1438 ng/m³. Agents from the highest SEC are exposed, on average, to 1409 ng BC/m³ (IQR =
512 ng/m³) using the dynamic exposure estimation. Static exposure is also lower: 1219 ng/m³.
People with a lower socioeconomic status are exposed to higher BC concentrations while being at home (1348
ng/m³ compared to 1160 ng/m³). This is in line with previous research stating that poorer people tend to live in areas
with higher air pollution, e.g. near major roads or in densely populated urban areas [6; 10; 12; 15; 27; 28]. Also on
other locations that these people visit, their exposure tends to be higher than that of people of a high SEC. The AB²C
model does not account for differences in ventilation conditions, which may lead to even higher exposures at home
for people of a lower SEC [6; 13]. Only while traveling, the exposure of people of a high SEC is higher: this can be
explained by the larger number of trips in cars and trips on traffic peak hours; this was also observed by Beckx et al.
[2] in the Netherlands.
3.3. Inhaled dose
With the exposure estimates of the AB²C model and assumptions on inhalation during different activities, dose or
‘internal exposure’ can be calculated. Minute volumes for adults per activity type and in different transport modes
were derived from Allan & Richardson [29] (Table 1).
Inhaled dose is larger for people of lower SECs, but the difference with the other group becomes very small
(22,761 ng/day compared to 22,296 ng/day). The exact numbers depend on the assumptions made on inhalation per
activity, and on the gender distribution within the groups. The analysis nevertheless reveals an important trend:
people from higher SECs inhale more BC particles during shorter time spans, namely while traveling (which
assumes increased physical activity). Lower SECs travel less, but are exposed to higher concentrations at home,
their 24h average breathing rate is assumed to be lower at home, resulting in an almost equal amount of inhaled BC
particles as compared to the higher SEC.
Table 1. Summary of minute volume assumptions (L/min). Numbers based on Allen & Richardson (1998).
Activity Male adults Female adults
Being at home / Car passenger 8.3 7.5
Work / Services / Car driver 10.5 12.5
Bring/get / Shopping / Social visits / Leisure / Other / Public Transport 16.1 13.0
Touring / On foot / Bike 49.2 39.8
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