Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
2.3.1 Risk allocation for population subgroups or activities
Exposure studies may also be conducted to provide more realistic
and location-specific information for use in human health risk
assessments. Measurement data on pollutant concentrations and exposure
factors, such as contact rates, can be used instead of relying on
assumed "default" values for an "averaged" or representative
individual. An example of an exposure study designed to collect data
for the purpose of allocating risk to locations, sources and
activities is the Windsor Air Quality Study conducted in Windsor,
Ontario, Canada (Bell et al., 1994).
The Windsor Air Quality Study was designed to investigate the
Windsor airshed characteristics with respect to airborne toxic
compounds and to determine personal inhalation exposures to these
compounds. Data were then used as inputs for a multimedia assessment
of risk due to total pollutant exposure. The air quality study
examined just one aspect, the inhalation route. It was designed to
separately attribute risk to several airborne contaminants by indoor
and outdoor locations. Statistical analysis and inference were used to
impute source contributions to population risk (i.e., the waste
incinerator across the river in Detroit, Michigan, USA) for selected
volatile organic compounds (VOCs), carbonyls and trace metals (see
Table 4) based on microenvironmental and personal measurements and
time activity patterns. In general, air quality was determined to be
relatively poor in recreation halls, new office buildings, cars and
garages when compared to outdoor air quality standards and criteria.
Although high contaminant concentrations were detected in various
microenvironments, population exposures (defined as the product of
concentration and time) were relatively low because the study subjects
did not spend any appreciable time in those microenvironments. This
point is illustrated in Fig. 6. For all of the VOCs, the highest
concentrations were measured during the commuting periods, with
comparable concentrations being measured indoors at the office and
home and the lowest outdoors (Table 3). When time in each
microenvironment is considered, exposure in the home accounted for
over 70% of the total exposure profile for that individual.
Table 4. Target analytes in the Windsor air quality study
Volatile organic compounds
Propane, chloromethane, 2-methylpropane, chloroethene, 1,3-butadiene, butane,
2-methylbutane, pentane, isoprene, 1,1-dichloroethene, dichloromethane, allyl ch
hexane trichloromethane, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene,
tetrachloromethane, xylenes, styrene, o-xylene, 1,1,2,2-tetrachloroethane, nonan
1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,4-dichlorobenzene; decane,
1,2-dichlorobenzene, undecane, 1,2,4-trichlorobenzene, dodecane, tridecane
Carbonyls
Formaldehyde, acetaldehyde, acrolein, acetone, propianaldehyde, crotonaldehyde,
ethyl ketone, benzaldehyde, isovaleraldehyde, 2-pentanone, valeraldehyde, o-tol
m-tolualdehyde, p-tolualdehyde, methyl isobutyl ketone, hexanal, 2,5-dimethylb
Trace metals
Beryllium, chromium, manganese, nickel, arsenic, selenium, cadmium, lead
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6/1/2007