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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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3) Synchronic studies
Murai et al. (1987) examined 124 yusho patients 16 years after
the onset and found the serum T3 and T4 levels significantly
higher than in a control group while no difference in the TSH
levels of the two groups was observed. No correlation was
observed between the serum PCB level and T3, T4 or TSH level.
The frequency of goiter was 11/74 (15%) for women. Furthermore,
Tsuji et al. (1997) examined 81 yusho patients 28 years after
the onset and found 8 cases of thyroid diseases (3 Graves'
disease, 2 chronic thyroiditis, 2 thyroid cancer, 1 thyroid
tumor). Most of these patients showed high blood PCB levels.
Apart from the patients, six people showed anomaly in thyroid
check only (4 slight increase and 2 slight decrease in the TSH
level). Three out of the four subjects with high PCB levels were
antithyroid antigen-positive, which suggests latent thyroid
dysfunction due to chronic thyroiditis. The low TSH levels were
not as remarkable as in Graves' disease; the pathological
conditions are unclear. The T4, T3 and TSH levels showed no
difference between the cases and control, or the high and low
exposure groups. The high serum PCB level group showed a higher
positivity frequency for antithyroglobulin (19.5% vs. 2.5%) and
antimicrosome antigen (17%). Guo et al. (1999) reported a high
thyroid tumor frequency (20%) in yusho patients in Taiwan
examined 13 years after the onset.
Langer et al. (1996) studied employees of a PCB manufacturing
plant which caused extensive pollution over 40 years and
residents around the plant. The PCB concentration was about 6
times higher in the fat tissue, and about 2 times in breast
milk, than that in the control group. Comparison of the 245
employees (mostly female) with 572 subjects from the control
area revealed significantly greater thyroid volumes in the
former. The female employees also showed higher frequencies of
enlarged thyroid (20% vs. 9.4% in the control), anti-thyroid
peroxidase antigen positivity (28.4% vs. 19%), anti-thyroglobulin
antibody positivity (41.3% vs. 21%), and TSH receptor antigen
positivity (10.4% vs. 1.3%). The blood levels of T4, T3 and TSH
showed no significant difference. Langer et al. (1998) also
found significantly higher thyroid volumes for 17-year-old
subjects in a polluted city (454 subjects) than for the
counterpart in a control area (965 subjects). Emmet et al.
(1988) compared 55 transformer repair operators exposed to PCBs
(38 ongoing, 17 experienced) with 56 unexposed workers in the
U.S., and found lower blood T4 levels for the former. The free
T4 index calculated from the product of the T4 and RT3U levels
was significantly lower in the exposed group, but sowed no
correlation with the PCB level. Bahn et al. (1980) examined 35
plant operators who were handling PBB (a substance similar to
PCB). Four subjects clearly showed increased TSH levels and were
diagnosed with thyroid dysfunction. One of them had a family
history. Thyroid dysfunction was not found in the control group
consisting of 89 subjects. Many in the PBB-exposed group showed
high TSH levels.
Mahitova et al. (1998) compared the results of thyroid check 12
hospitalized children 7.5-15 years of age from areas around Aral
Sea heavily polluted by PCB with those for children from
Stockholm as the control group. No significant difference was
seen in the levels of thyroid hormones and TSH levels between
the two groups.
Koopman-Esseboom et al. (1994) determined thyroid hormones (TT4,
TT3, FT4, TSH) in 105 neonate-mother pairs as well as PCBs and
dioxins in blood and breast milk, and found that mothers whose
milk shows high PCB levels have low T4 and T3 levels, while
their children showed high TSH levels 2 weeks after birth.
Nagayama et al. (1998) studied the relationship of the thyroid
function of 36 one-year old infants with the TEQs of PCDD, PCDF
and co-PCB levels in breast milk, and found an inverse
correlation between the TEQs of those substances and the T4 and
T3 levels.
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