Model for
Screening-Level Assessment of Near-Field
Human Exposure to Neutral Organic Chemicals Released Indoors
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Abstract
Screening organic
chemicals for hazard and risk to human health
requires near-field human exposure models that can be readily parametrized
with available data. The integration of a model of human exposure,
uptake, and bioaccumulation into an indoor mass balance model provides
a quantitative framework linking emissions in indoor environments
with human intake rates (<i>iR</i>s), intake fractions (<i>iF</i>s) and steady-state concentrations in humans (<i>C</i>) through consideration of dermal permeation, inhalation,
and nondietary ingestion exposure pathways. Parameterized based on
representative indoor and adult human characteristics, the model is
applied here to 40 chemicals of relevance in the context of human
exposure assessment. Intake fractions and human concentrations (<i>C</i><sub>U</sub>) calculated with the model based on a unit
emission rate to air for these 40 chemicals span 2 and 5 orders of
magnitude, respectively. Differences in priority ranking based on
either <i>iF</i> or <i>C</i><sub>U</sub> can be
attributed to the absorption, biotransformation and elimination processes
within the human body. The model is further applied to a large data
set of hypothetical chemicals representative of many in-use chemicals
to show how the dominant exposure pathways, <i>iF</i> and <i>C</i><sub>U</sub> change as a function of chemical properties
and to illustrate the capacity of the model for high-throughput screening.
These simulations provide hypotheses for the combination of chemical
properties that may result in high exposure and internal dose. The
model is further exploited to highlight the role human contaminant
uptake plays in the overall fate of certain chemicals indoors and
consequently human exposure