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Specific investigations: other studies

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specific investigations: other studies
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
no data
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Review on serum levels of thiocynate and effects related to the mechanism of action, competitive inhibition of thyroidal iodide uptake at the sodium-iodide symporter. No guideline followed, not GLP.

Data source

Reference Type:

Materials and methods

Test material

Results and discussion

Applicant's summary and conclusion

Executive summary:

Thiocyanate and perchlorate are known to competitively inhibit thyroidal iodide uptake at the sodium-iodide symporter. Estimates of their relative potencies have recently been refined; thiocyanate is 15 times less potent than perchlorate on a serum concentration basis. Numerous studies have been published relating serum thiocyanate concentrations (or surrogate measures) with thyroid function in various populations including pregnant women and neonates in regions with varying degrees of iodine deficiency. Fifteen published studies were located that relate serum thiocyanate concentrations with thyroid function. In the absence of severe iodine deficiency or iodine excess, adverse thyroidal effects occur with chronic serum thiocyanate concentrations ≥200 µmol/L whereas non-adverse effects are observed with concentrations in the range of 65–85 µmol/L. No adverse or non-adverse effects are observed at serum concentrations below 50 µmol/L, even among sensitive subpopulations. Recently, studies relating serum perchlorate concentrations with perchlorate dose have become available, thus making it possible to predict the perchlorate dose associated with a serum perchlorate concentration. Serum thiocyanate concentrations found to induce non-adverse or adverse thyroid effects can thereby be used to predict the perchlorate concentration and thus the perchlorate dose that would be expected to induce similar effects. To place a perspective on environmental perchlorate exposure, a serum thiocyanate concentration of 50 µmol/L is equivalent to a serum perchlorate concentration of 3.3 µmol/L in terms of iodine uptake inhibition. This serum perchlorate concentration would require a perchlorate dose

of 0.27 mg/kg-day, or a drinking water equivalent level of 9 mg/L using standard default assumptions of a 70 kg adult drinking 2 liters of water daily.