Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
Glands at four locations in the mouth produce saliva; the
secretion rate varies at each location. Chemicals enter saliva via
passive diffusion from plasma. Therefore, saliva may become a useful
tool to non-invasively characterize plasma levels of contaminants
(Silbergeld, 1993). Social science research has used saliva sampling
because of its ease of collection and storage (Dabbs, 1991, 1993).
Contaminants found in saliva include cotinine, drugs, metals, organic
solvents, pesticides and steroid hormones (Tomita & Nishimura, 1982;
Nigg & Wade, 1992; Silbergeld, 1993).
Collection of saliva is relatively easy. One approach consists of
having the subject rinse the mouth and chew on a stimulant, typically
a piece of clingfilm or sugar-free gum. The subject then spits into
the sampling container. Another method uses pumps to sample from the
salivary glands. In either case, care should be taken to minimize
contamination from the mouth. Because the concentrations of chemicals
in saliva can fluctuate with circadian rhythm, the collection of
saliva samples should occur at the same time each day (Dabbs, 1991).
Saliva samples are quite stable and can be stored at room temperature
for several days (Dabbs, 1991, 1993). However, in order to reduce
viscosity from proteins, saliva samples are typically frozen prior to
chemical analysis.
10.6.5 Keratinized tissue (hair and nails)
Keratinized tissues, primarily hair and toenails, are practical
sampling media for evaluation of past exposure to metals (Bencko et
al., 1986; Bencko, 1991; Subramanian, 1991; Kemper, 1993; Bencko,
1995). Toenails are usually the medium of choice: see below. These
media integrate exposures over a period of months, contain relatively
larger concentrations of trace elements than blood or urine and are
easy to collect, store and transport (Garland et al., 1993; Kemper,
1993). Therefore, archiving specimens for future analyses is a viable
option. Since hair and toenails are no longer in contact with the
blood supply, they can provide a picture of past exposure. Because of
the ease of collection, hair and toenails have been collected in
numerous environmental studies, especially of children (DiVincenzo et
al., 1985; Bencko et al., 1986; Wilhelm et al., 1989, 1991; Sukumar &
Subramanian, 1992; Bustueva et al., 1994; Santos et al., 1994). Hair
and toenails have been collected for elemental analyses in both
environmental exposure assessment and nutritional evaluation studies
(Garland et al., 1993; MacIntosh et al., 1997).
Hair might be a useful medium to study exposure to environmental
tobacco smoke (ETS). For example, in the framework of the German
Environmental Survey (Krause et al., 1992) it was concluded that in
large population studies nicotine and continine in urine as well as
nicotine in hair are useful indicators of exposure for different
levels of active and passive smoking. Continine and nicotine
concentrations in hair have also been used to study fetal exposure by
maternal smoking (Klein et al., 1993). Hair has also successfully been
used in studies evaluating exposure to organic mercury (Suzuki et al.,
1989) or PCB (Que Hee, 1993).
One of the major concerns in the use of hair as a sampling medium
is the potential for surficial contamination, in part due to the large
surface area and the oily nature of hair. Sources of contamination
include sweat, cosmetics, dirt and clothes (Doi et al., 1988;
Raghupathy et al., 1988). Other potential disadvantages of sampling
http://www.inchem.org/documents/ehc/ehc/ehc214.htm
Page 183 of 284
6/1/2007