The effect of perchlorate, thiocyanate, and nitrate on thyroid function in workers exposed to perchlorate long-term.
Perchlorate (ClO(4)(-)) and thiocyanate (SCN(-)) are potent and nitrate (NO(3)(-)) a weak competitive inhibitor of the thyroid sodium-iodide symporter. To determine the effects of long-term, high ClO(4)(-) exposure on thyroid function, we conducted a study of 29 workers employed for at least 1.7 yr (50% over 5.9 yr) in an ammonium ClO(4)(-) production plant in Utah. Serum ClO(4)(-), SCN(-), and NO(3)(-); serum T(4), free T(4) index, total T(3), thyroglobulin (Tg), and TSH; 14-h thyroid radioactive iodine uptake (RAIU); and urine iodine (I) and ClO(4)(-) were assessed after 3 d off (Pre) and during the last of three 12-h night shifts in the plant (During) and in 12 volunteers (C) not working in the plant. Serum and urine ClO(4)(-) were not detected in C; urine ClO(4)(-) was not detected in 12 of 29 and was 272 microg/liter in 17 Pre workers; serum ClO(4)(-) was not detected in 27 of 29 Pre; and serum and urine ClO(4)(-) were markedly elevated during ClO(4)(-) exposure to 868 microg/liter and 43 mg/g creatinine, respectively. Serum SCN(-) and NO(3)(-) concentrations were similar in all groups. Thyroid RAIUs were markedly decreased in During compared with Pre (13.5 vs. 21.5%; P < 0.01, paired t) and were associated with an increase in urine I excretion (230 vs. 148 microg I/g Cr; P = 0.02, paired t) but were similar to those in the C group (14.4%). Serum TSH and Tg concentrations were normal and similar in the three groups. Serum T(4) (8.3 vs. 7.7 microg/dl), free T(4) index (2.4 vs. 2.2), and total T(3) (147 vs. 134 ng/dl) were slightly but significantly increased in the During vs. Pre workers (P < 0.01, paired t). Thyroid volumes and patterns by ultrasound were similar in the 29 workers and 12 community volunteers. In conclusion, high ClO(4)(-) absorption during three nights work exposure decreased the 14-h thyroid RAIU by 38% in ClO(4)(-) production workers compared with the RAIU after 3 d off. However, serum TSH and Tg concentrations and thyroid volume by ultrasound were not affected by ClO(4)(-), suggesting that long-term, intermittent, high exposure to ClO(4)(-) does not induce hypothyroidism or goiter in adults.
Braverman
Lewis E
LE
Section of Endocrinology, Diabetes and Nutrition, Boston University School of Medicine, Boston, Massachusetts 02118-2347, USA. Lewis.Braverman@bmc.org
He
XueMei
X
Pino
Sam
S
Cross
Mary
M
Magnani
Barbarajean
B
Lamm
Steven H
SH
Kruse
Michael B
MB
Engel
Arnold
A
Crump
Kenny S
KS
Gibbs
John P
JP
D003404:Creatinine / Q000652:urine; D006801:Humans; D007455:Iodine / Q000652:urine; D009566:Nitrates / Q000633:toxicity*; D016273:Occupational Exposure; D010472:Perchlorates / Q000633:toxicity* / Q000652:urine; D012016:Reference Values; D012044:Regression Analysis; D027981:Symporters / Q000037:antagonists & inhibitors; D013861:Thiocyanates / Q000633:toxicity*; D013961:Thyroid Gland / Q000033:anatomy & histology / Q000187:drug effects*; D013972:Thyrotropin / Q000097:blood; D000099209:Sodium-Iodide Symporters
D003404:Creatinine; D007455:Iodine; D009566:Nitrates; D010472:Perchlorates; D027981:Symporters; D013861:Thiocyanates; D013972:Thyrotropin; D000099209:Sodium-Iodide Symporters; C031760:thiocyanate; C494474:perchlorate