1. Introduction
In 2000, Shiftan et al. [1] proposed to use activity-based transport models to predict traffic emissions and air
quality. Later activity-based models were identified to be very well suited for air pollution exposure assessment.
There are multiple advantages of using an activity-based model for environmental applications: traffic emissions can
be calculated from predicted traffic streams, space-time information for every individual in a population is
generated, disaggregated exposure analysis is possible. In 2009, Beckx et al. [2] published a study that incorporated
the activity-based model ALBATROSS in a framework that models population exposure to NO2 in the Netherlands.
Several authors around the world developed similar model chains, but still rarely focusing on individuals, exposure
during traveling is poorly accounted for, and a proper validation is often missing [3; 4; 5; 6].
Recently, the AB²C model was introduced: an Activity-Based modeling framework for Black Carbon (BC)
exposure assessment. The development of this model is described elsewhere [7], but in short it combines individual
diaries from an activity-based transportation model with land use regression models, an indoor air model and an intraffic
exposure model to estimate personal exposure to BC. This modeling framework tried to tackle some problems
associated with previous models, and it shifted the focus to personal rather than population exposure. The study area
is Flanders, an urbanized region in Belgium with approximately 7 million inhabitants. Currently, AB²C predicts
exposure to BC: a policy-relevant pollutant because of its health effects and impact on climate change. According to
the WHO, sufficient evidence exists for an association of daily variations in BC concentrations with short-term
changes in health [8]. Long-term average BC exposure is also associated with all-cause and cardiopulmonary
mortality [8]. BC may not be the only/major toxic component of traffic-related particulate matter, but it can be used
as an indicator for exposure to traffic-related air pollution. Traffic particles are heterogeneous in time and space, and
typically have large decay rates when moving away from emission sources [9]. The latter makes the use of highresolution
air pollution surfaces more valuable; as well as taking into account movement of people.
Environmental equality, the principle that no group of people should bear a disproportionate share of harmful
environmental exposure [10], is an important topic, especially in the US [11; 12; 13; 14; 15; 16]. Much less studies
are available for Europe, moreover research in Europe is not always conclusive [2; 10; 17]. As an application of the
AB²C model, this paper investigates BC exposure in different subgroups of the population: we test the hypothesis
that people from a lower socio-economic class (SEC) are exposed to disproportionately high levels of air pollution.