Rj. Buck et al., Modeled estimates of chlorpyrifos exposure and dose for the Minnesota and Arizona NHEXAS populations, J EXP AN EN, 11(3), 2001, pp. 253-268
Citations number
60
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF EXPOSURE ANALYSIS AND ENVIRONMENTAL EPIDEMIOLOGY
This paper presents a probabilistic, multimedia, multipathway exposure mode
l and assessment for chlorpyrifos developed as part of the National Human E
xposure Assessment Survey (NHEXAS). The model was constructed using availab
le information prior to completion of the NHEXAS study. It simulates the di
stribution of daily aggregate and pathway-specific chlorpyrifos absorbed do
se in the general population of the State of Arizona (AZ) and in children a
ged 3-12 years residing in Minneapolis-St. Paul, Minnesota (MSP). Pathways
included were inhalation of indoor and outdoor air, dietary ingestion, non-
dietary ingestion of dust and soil, and dermal contact with dust and soil.
Probability distributions for model input parameters were derived from the
available literature, and input values were chosen to represent chlorpyrifo
s concentrations and demographics in AZ and MSP to the extent possible. Whe
n the NHEXAS AZ and MSP data become available, they can be compared to the
distributions derived in this and other prototype modeling assessments to t
est the adequacy of this pre-NHEXAS model assessment. Although pathway- spe
cific absorbed dose estimates differed between AZ and MSP due to difference
s in model inputs between simulated adults and children, the aggregate mode
l results and general findings for simulated AZ and MSP populations were si
milar. The major route of chlorpyrifos intake was food ingestion, followed
by indoor air inhalation. Two-stage Monte Carlo simulation was used to deri
ve estimates of both interindividual variability and uncertainty in the est
imated distributions. The variability in the model results reflects the dif
ference in activity patterns, exposure factors, and concentrations contacte
d by individuals during their daily activities. Based on the coefficient of
variation, indoor air inhalation and dust ingestion were most variable rel
ative to the mean, primarily because of variability in concentrations due t
o use or no-use of pesticides. Uncertainty analyses indicated a factor of 1
0-30 for uncertainty of model predictions of 10th, 50th, and 90th percentil
es. The greatest source of uncertainty in the model stems from the definiti
on of no household pesticide use as no use in the past year. Because chlorp
yrifos persists in the residential environment for longer than a year, the
modeled estimates are likely to be low. More information on pesticide usage
and environmental concentrations measured at different post-application ti
mes is needed to refine and evaluate this and other pesticide exposure mode
ls.