Potassium iodide

Endpoint summary

Description of key information

The 24 hours LD50 to rat by oral is 3118 mg/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

3 118 mg/kg bw

Additional information

Since the granular size of the crystals of potassium iodide is evidently bigger than 100 μm, the VP of potassium iodide is low as well; the inhalation is unlikely exposure route for human.

From research (Louk A. R. M. Pechtold et al., 2001), in order to study at the ultrastructural level which part of the skin is associated with percutaneous iodide transport by passive diffusion, the iodide (KI solution) was applied to the frozen skin of human. Then by the transmission electron microscopy (TEM) and X-ray microanalysis (XRMA), the distribution of iodide in each layer of skin after passive diffusion can be well investigated. It concluded that the iodide can penetrate into stratum corneum (SC), but little can enter viable epidermis. Based on this the absorption of iodide by dermal route is also negligible. Therefore the key value of acute toxicity is only available by oral route.

The most relevant study on vertebrates by oral route is a company study (A. Hausner, G. Weise, and A. Hofmann, 1980). In the test the effects of iodide were studied in male and female Wistar rats. 10 male and 10 female in each dose and control groups were administrated with potassium iodide for 14 days at dose of 0 (control), 2000, 2500, 2800 3200, 3600, and 4000 mg/kg body weight mg/kg bw respectively. The key value of LD50 was calculated by Probit-analysis (Fink und Hund 1965).

It shows the 24 hour and 7-14 days of LD50 to rats (male/female) was respectively 3118 and 2779 mg/kg bw under test conditions.

The human data is from an accident, in which a suicide was attempted; an adult male survived the ingestion of 15 g of iodine as a potassium iodide solution (Tresch et al., 1974). From the human data, the default body weight (70 kg) was used, and the 100% absorption was assumed, by which the LD50 for human in this accident is over 214 mg/kg bw, which is well supported the LD50 data from the company study report.

Therefore the key value which is used in the hazard classification and chemical safety assessment is 3118 mg/kg bw.

Justification for classification or non-classification

The LD50 oral is 3118 mg/kg bw, which is definitely above 2000 (mg/kg bodyweight) so the iodide should not be classified under any categories of acute toxicity in the Regulation (EC) No. 1272/2008, and the Directive 67/548/EEC.