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Advisory Committee on Health Effects of Endocrine Disruptors
The Supplement II to the Intermediary Report
1.4.2.2_7 |
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Bloom et al. (2001) studied 66 subjects from participants in the
New York State Angler Cohort Study for thyroid functions as
related to organochlorine compounds in the environment. Analysis
was based on a cross-sectional design. In addition to
determination of the total T4, triglycerides, cholesterol, HDL
and LDL in blood, gas chromatography with an electron capture
detector was made for compounds known to disrupt the thyroid
functions (HCB, PCB-19, PCB-28, PCB-47, PCB-99, PCB-118,
PCB-153, PCB-169, PCB-180, PCB-183 and PCB-187). The average
concentration of T4 was 7.78 Ęg/dl. The average age of the
subjects was 31.81 years. The relationship of organochlorine
compounds and total serum thyroxine was analyzed using
multivariate regression models. For each subject the time of
sampling, serum triglyceride, cholesterol, HDL, LDL, age, and
smoking habit were taken into account in adjustment for possibly
confounding factors. A "full" model involved all the variables
(R2 = 0.380, p = 0.136); the variables were then selected
stepwise, applying the criterion of maximum partial correlation
at each step, resulting in "reduced" models (ż = 0.15). Some
adjustments were made in the reduced models to handle
contaminants under the detection limit without changing the
selected prediction factors.
Hexachlorobenzene (Ŕ = -0.113) and age (Ŕ = 0.007) were selected
as the prediction factors of serum T4 in the reduced models (R2
= 0.083, P = 0.065). Power analysis suggested that by doubling
the sample size the existing results would be statistically
significant with a type I error of 0.05 and a power of 0.80.
Sala et al. (2001) studied residents of a rural area exposed to
high concentrations of HCB in Flix, Catalonia for the
relationship of blood PCB and HCB with thyroid hormones and
liver enzymes. Serum and 24-hour urine were collected from a
total of 608 subjects 14 or higher years of age (249 men and 359
women of an averaged age of 48.8 years). Blood samples were
taken during the fasting state. Thyroid stimulating hormone (TSH)
was determined for 608 cases, and the total and free thyroxine
(T4), aspartate aminotransferase (AST), alanine aminotransferase
(ALT), and Á-glutamyltransferase (GGT) for 192 cases. Blood HCB
was determined with a gas chromatograph with an electron capture
detector. While 166 men (66.7%) and 21 women (5.8%) were former
employees in a manufacturing plant of electronic chemicals,
subjects without employment history showed a higher average HCB
level (16.8 ng/ml) than general populations in other studies.
After correcting data for confounding factors such as sex, age,
BMI and drinking habit, the HCB and PCB levels were not
significantly correlated with serum TSH, free T4, AST and ALT.
On the other hand, the serum HCB level showed a significant
inverse correlation with the total T4 and a significant positive
correlation with GGT: an increase in HCB by 1 unit of natural
logarithm of ng/ml corresponded to a decrease of the total T4 by
0.32 Ęg/dl (p < 0.05) and a relative increase of GGT by 10% (p <
0.05). Correction for total lipid or other organochlorines did
not affect these correlations. The correlation of PCB with T4
and GGT was also significant, though small, although both of
them were in the normal ranges in most subjects (92%). No
correlation was found with other biological markers.
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