Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
use of gasoline, lead-based paint on housing and steel structures, and
airborne emissions from industrial point sources that settle in
residential environments. In the USA, house dust is considered a major
source of lead to most children (CDC, 1991; Lanphear & Roghmann,
1997). Older homes are especially susceptible to lead dust exposure if
paint is peeling or renovations are being done (Roberts et al., 1992).
Soil and settled dust can be a significant source of exposure to
numerous other toxicants in addition to lead, including pesticides and
PAHs. Pesticides, although designed to degrade to different extents
through natural environmental processes such as sun, rain and soil
microbial activity, may accumulate in soil and dust and persist for
long periods of time. Because of the lack of these external
degradation processes, pesticides may be particularly persistent in
indoor settled dust (Simcox et al., 1995). Studies have shown that in
the general population in the USA the highest concentrations and
largest number of pesticides are found in house dust as compared to
soil, air and food (Whitmore et al., 1993; Lewis et al., 1994).
Although many pesticides in house dust come from outdoor sources, many
households use pesticides indoors. Because little or no training is
provided for users of household pesticides, unnecessary exposures
often occur. Pesticides often found in house dust include those used
for control of insects; e.g., chlordane and heptachlor in homes
treated for termites, pentachlorophenol and lindane in homes where
wood preservatives had been used, and other harmful pesticides
contained in flea and garden treatment (Roberts et al., 1992).
Hazardous substances that originate at the worksite may also find
their way (e.g., via clothes) into the homes of workers. The US
National Institute for Occupational Safety and Health compiled a
bibliography of more than 350 published and unpublished accounts of
take-home, or "para-occupational" contamination worldwide (NIOSH,
1994). The reports identified by NIOSH document the spread from
workplace to home of toxic metals (lead, beryllium, cadmium and
mercury), asbestos, and various other potentially hazardous
substances. Settled dust was a major source of familial exposure in
most of these studies.
8.2 Selected sampling methods
8.2.1 Soil
Soil constitutes a potential exposure pathway through direct
contact and ingestion or inhalation of resuspended soil particles.
Children's activities make them more likely to be affected by such
exposures. In addition, contaminated soil can be tracked inside homes,
or may infiltrate indoors when resuspended. In either case, soil may
become a component of settled indoor dust. There are no standard
collection methods for soil sampling, as discussed later for settled
dust (section 8.2.2). This limitation affects the ability to make
comparisons of results from soil sampling across studies. However,
information on soil contamination can provide insights into the
relative importance of multimedia contaminants as they may affect
exposure.
8.2.1.1 Surface soil collection
The most commonly used approaches make use of an auger or similar
sampler such that a sample is defined by cross-sectional area and
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