Environmental Engineering Reference
In-Depth Information
Intake Fraction for Benzene Traffic Emissions
in Helsinki
Joana Soares, Miranda Loh, Ari Karppinen, Leena Kangas, Kari Riikonen,
Matti Jantunen, and Jaakko Kukkonen
Introduction
Intake fraction (iF) is defined as the integrated incremental intake of Bz released
from a source (or source category) and summed over all exposed individuals during
a given exposure time, per unit of emitted pollutant
[1]
.
∑
,
mass intake of pollutant by an individual (
mass
)
(1)
people time
iF
=
mass released into the environment (mass)
The intake fraction concept has been developed as a metric which can be useful
in both screening-level order-of-magnitude estimates and more detailed policy
modeling
[2]
. For instance, an intake fraction of 1 in a million (10
-6
) means that for
every ton of a pollutant emitted, 1 g is taken in by the exposed population. Intake
fraction takes into account the dispersion of pollutants, locations and activity of
population and human breathing rates. The calculated intake fraction for benzene
is directly applicable to any other inert substance emitted by the traffic, for example
CO, NO
X
, so the calculations also provide a ready-to-use tool for health effect studies
concerning other pollutants and emission scenarios. However, for chemically active
urban pollutants like NO
2
and O
3
, the presented intake fraction results are not appli-
cable, thus a model run accounting correctly for the most important chemical
mechanism must be performed for these substances.
Intake fractions have been most frequently calculated for whole populations,
rather than for individuals. Population intake fraction is the sum of individual
