Appendix D - Dossier (PDF) - Tera

date: 20–JUL–2005
5. Toxicity Substance ID: 71–43–2
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5.11 Additional Remarks
Type: other: A new dose model for assessment of health risk due to
contaminants in air.
Remark: The problem of making quant. assessments of the risks
assocd. with human exposure to toxic contaminants in the
environment is a pressing one. This study demonstrates the
capability of a new computational technique involving the
use of fuzzy logic and neural networks to produce realistic
risk assessments. The approach to this challenge tested
here is to use a new model incorporating sophisticated
artificial intelligence algorithms. Exposure assessment
often requires that a no. of factors be evaluated, including
exposure concns., intake rates, exposure times, and
frequencies. These factors are incorporated into a system
that can "learn" the relevant relationships based on a known
data set. The results can then be applied to new data sets
and thus be applied widely without the need for extensive
measurements. In this anal., an example is developed for
human health risk through inhalation exposure to benzene
from vehicular emissions in the cities of Auckland and
Christchurch, New Zealand. Risk factors considered were
inhaled contaminant concn., age, body wt., and activity
patterns of humans. Three major variables affecting the
inhaled contaminant concn. were emissions (mainly from motor
vehicles), meteorol. conditions (wind speed, temp., and atm.
stability), and site factors (hilly, flat, etc.). The
results are preliminary and used principally to demonstrate
the technique, but they are very encouraging.
Source: ExxonMobil Biomedical Sciences Inc. Annadale, New Jersey
13–FEB–2002 (918)
Type: other: New PBPK model applied to old occupational exposure to
benzene.
Remark: An intensive program of benzene monitoring using new
techniques was undertaken in Western Europe in the late
1960s and early 1970s. Significant exposure was found in the
transport of benzene and gasoline, particularly during the
loading of barges, and during the loading and operation of
sea–going vessels. The ceiling threshold limit value of 25
ppm recommended at that time generated problems in assessing
exposure, so alternative criteria were proposed. During that
period some shore–based exposures were reported, and their
significance was discussed in several articles. The
information gained at that time is reexamined by
physiologically based pharmacokinetic (PBPK) modeling and is
used to help validate an improved PBPK model, which is
described and tested on results from experimental exposure
in a companion article. The old field data, comprising five
specific studies, confirm the relevance of modeling to
assessment of occupational exposure, and demonstrate its
value for interpretation of field data, which is seldom as
complete, systematic, or accurate as that obtained in
experimental work. The model suggests that metabolism of
Appendix D: Benzene SIDS Dossier
– 770/957 –