Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
guide, one order of magnitude below and above the concentrat
Reproducibility (precision) as measured by percentage relati
is usually inversely proportional to integration time or amo
Selectivity Response to a specific compound or analyte without interfere
instruments may be appropriate if exposure situation (e.g.,
Specific or selective response may require more expensive eq
analytical procedures
Response rate There are two aspects of response rate: (i) time required fo
step change in concentration; (ii) time required between sam
appropriate instrument response rate depends, in part, on th
and the health effect of interest. Acute effects may require
exposures over intervals of minutes. If health effects from
or the metabolic half-life is long, then rapid response is n
Portability Instruments and sampling procedures should not modify behavi
size, weight, noise, power, and safety considerations. Porta
usually involves a tradeoff with sensitivity and response ra
continuous)
Durability Instruments used for air sampling are subjected to a broad r
and humidity are potentially interferents and are not easily
instruments/methods must be fully evaluated
Cost Instrument cost and analytical expenses will influence study
off sample cost for accuracy, precision, and response rate.
subject and/or the number of subjects, or relaxing resolutio
use of less expensive methods
microenvironmental sampling in combination with questionnaires and
time-activity logs. Ambient air monitors can also be used to estimate
exposures when combined with information such as building
characteristics, indoor/outdoor contaminant ratios and time-activity
patterns.
The direct approach depends largely on the availability of
sensitive, small, quiet, lightweight and portable personal monitors.
Personal air monitors can be used for microenvironmental monitoring as
well. In addition, microenvironmental monitors with larger sampling
flows are used for indoor/outdoor sampling. Ambient monitors are
generally high-volume samplers and are not suitable for indoor use.
Suitable air monitors must also fulfil several requirements, such as
detection limits, interferences, time resolution, easy operation and
of course, cost. There are several good references on air monitoring
and analysis. The reader is referred to Air Sampling Instruments
for Evaluation of Atmospheric Contamination (ACGIH, 1995).
Additional general publications include US EPA (1994, 1996b), and
Lodge (1988). It is important, however, to refer to the published
scientific literature for the most appropriate and recent air
monitoring methods.
The following sections describe methods available for air
sampling of gases and vapours, airborne particulate matter, SVOCs and
reactive gases. The methods are classified into active and passive or
continuous monitors. A detailed list of sampling methods, air
pollutants for which they are used, sources and other pertinent
information is presented in Table 21-24. An indicator of their
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