Exposure Through Soil and Dust Ingestion - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 262

6.2.1 Tracer Element Methodology .............................

265

6.2.2 Alternative Approaches for Estimating Soil and Dust Ingestion ......... 274

6.2.3 Soil and Dust Ingestion Rates for Children and Adults .............. 276

6.2.4 Soil Ingestion Rates Recommended by International Regulatory Bodies ... 281

6.2.5 Representativeness of Soil and Dust Ingestion Rates ...............

281

6.3 Conclusions ............................................

283

References ................................................ 284

6.1 Introduction

6.1.1 General Aspects

Ingestion of soil and dust is a potentially important pathway of exposure to environ-
mental contaminants, especially for immobile and semi-volatile contaminants such
as metals, PAHs and POPs. Ingestion of soil can be a special concern for young
children who may, per kilogram body weight, ingest up to 10 times more soil than
adults (Egeghy et al. 2007 ). However, in assessing the relative contribution of inges-
tion of soil and dust to overall oral exposure, we need to be aware that, depending
on the agent, the oral bioavailability of contaminants in soil can be lower compared
to e.g. the oral bioavailability in food.
Due to their different behaviour, young children show exposure patterns distinct
from those of adults. Young children play close to the ground and may ingest signif-
icant quantities of outdoor soil, and soil and dust from indoor surfaces and carpets.
Soil and dust ingestion may result from various behaviours including, but not lim-
ited to, mouthing (putting objects or hands in the mouth), eating dropped food, or
consuming soil or dust directly. A special case of soil ingestion is the so-called Soil-
pica, which is the recurrent ingestion of unusually high amounts of soil, i.e., on the
order of 1,000-5,000 mg/d. Geophagy is the intentional ingestion of soil material
and is usually associated with cultural practices (ATSDR 2001 ).
As soil and dust ingestion constitutes one of the major exposure routes for chil-
dren in case of contaminated sites, and to a lesser extent for adults, it is of utmost
importance to derive accurate soil and dust ingestion values for Risk Assessment.

6.1.2 Defining Soil and Dust

Soil consists of particles of unconsolidated mineral and/or organic matter from
the earth's surface that are located outdoors, or are used indoors to support plant
growth. It includes particles that have settled onto outdoor objects and surfaces (US-
EPA 2008 ). House dust is a heterogeneous mixture of tracked-in or re-suspended
soil and non-soil particles, including clothing fluffs, atmospheric deposited particu-
lates, hair, fibres (artificial and natural), moulds, pollen, allergens, bacteria, viruses,
arthropods, ash, soot, animal fur and dander, smoke, skin particles, cooking and
heating residues, and building components.