Human Exposure Pathways - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 511

with average body weight values used in child and adult exposure estimates. The
estimates for skin surface area are based on population mean values for males and
females combined.
For typical residential exposures, US EPA ( 2004a , b ) recommended using skin
surface areas of 2,800 and 5,700 square centimetres (cm 2 ) for child and adult resi-
dents, respectively, assuming the exposed skin surface is limited to the head, hands,
lower legs, and forearms (short-sleeved shirts, shorts, and shoes are assumed to
be worn). Exposure scenarios for worker contact with soil assume that skin con-
tact is limited to the head, hands, and forearms, which have a skin surface area of
3,300 cm 2 (US EPA 2004b ). Estimates are provided of skin surface area for individ-
ual body parts so that area estimates for additional scenarios may be calculated.
11.7.5 Reliability and Limitations
It is generally recognized that exposure estimates for dermal uptake are highly
uncertain. Few studies have been conducted that accurately characterize the poten-
tial for dermal absorption under the conditions present at contaminated sites.
Volatile contaminants can be excluded from dermal uptake assessments with a high
degree of confidence, and most metals can also likely be excluded without any
substantial concern for underestimating total exposures. That leaves semi-volatile
contaminants as the critical group to evaluate. Available empirical data in the
group of semi-volatile contaminants suggest that dermal uptake could be substan-
tial enough to require quantification in most Risk Assessments. However, dermal
uptake from weathered soils may be much less than suggested by studies in which
the contaminants are added to soils shortly before testing.
Reliability could be increased when oral Toxicological Reference Values are
converted to an absorbed dose or uptake before using those values to assess der-
mal exposures. Moreover, applying realistic values for skin surface, for example
depending on normal clothing characteristics in regard to climatic conditions, could
also improve the quality of site-specific dermal exposure calculations.
References
Alexander M (2000) Aging, bioavailability, and overestimation of risk from environmental
pollutants. Environ Sci Technol 34:4259-4265
Andelman JB (1990) Total exposure to volatile organic compounds in potable water. In:
Significance and treatment of volatile organic compounds in water supplies, pp 485-504
ASTM (2004) Standard guide for risk-based corrective action, Standard E 2081-00 (Reapproved
2004), ASTM International, American society for testing and materials, USA
Beamer P, Castano A, Leckie JO (2002) Vertical profile particulate matter measurements in a
California daycare. Proceedings: Indoor Air 2002, pp 103-108
Brand E, Otte PF, Lijzen JPA (2007) CSOIL 2007: an exposure model for human risk assessment
of soil contamination. RIVM report 711701054 RIVM, Bilthoven, the Netherlands
Bright DA, Richardson GM, Dodd M (2006) Do current standards of practice in Canada measure
what is relevant to human exposure at contaminated sites? I: a discussion of soil particle size
and contaminant portioning in soil. Human Ecol Risk Assess 12(3):591-605