Reference dose for perchlorate based on thyroid hormone change in pregnant women as the critical effect

ELF MFs: Straif et al. Respond

“…Using the second approach, a NOAEL of 0.005 mg/kgday (Gibbs et al 2004) can be identified from thyroid hormone and goiter data in a sensitive population. The RfD based on this approach would lie near the value of 0.002 mg/kg-day proposed by Strawson et al (2004).…”

Environmental Thyroid Disruptors and Human Endocrine Health

“…Serum perchlorate levels of approximately 15 μg/l result in minimal inhibition of iodine uptake (about 2%) compared to serum 871 μg/l level, which results in about 70% inhibition of iodine uptake (Strawson et al, 2004). By contrast, several adult studies of differing exposure duration, reported serum T4 levels do not decrease after perchlorate exposure resulting in serum perchlorate levels up to 20,000 μg/l (Gibbs et al, 1998;Greer et al, 2002;Lamm et al, 1999;Lawrence et al, 2000).…”

“…If sufficient inhibition of iodide uptake occurs, pharmacological effect results in subnormal levels of T4 and T3, and an associated compensatory increase in TSH secretion (Loh, 2000). Therefore, perchlorate exposure both results in hypothyroidism leading to the potential for altered neurodevelopment if observed in either dams or fetus/neonates, and increases in serum TSH leading to the potential for thyroid hyperplasia (Strawson et al, 2004).…”

“…Beside its pharmacological applications, perchlorate has been widely used as solid rocket propellants and ignitable sources in munitions, fireworks and matches (Strawson et al, 2004). Furthermore, perchlorates are laboratory waste by-products of perchloric acid.…”

Perchlorate Toxicity and Risk Assessment

“…However, these data also demonstrate that rats may respond to perchlorate exposures in a very different manner than humans. 55 The reason that such comparisons are not definitive is that the human data do not include information on pregnant individuals.…”