Potassium trifluorozincate

Endpoint summary

Description of key information

Based on its water-solubility, low molecular weight and the effects observed in rats upon acute oral exposure and acute/ subacute inhalation exposure, the substance is expected to be absorbed by the gastrointestinal and respiratory tract. In the absence of substance-specific data, a default absorption value of 100% is assumed for both routes. Skin penetration of pure potassium trifluorozincate of 0.98% is considered a worst-case situation for workers.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

0.98

Absorption rate - inhalation (%):

100

Additional information

Oral and respiratory absorption

No data is available on the toxicokinetics of potassium trifluorozincate. The substance is water-soluble and will, therefore, readily dissolve into the gastrointestinal fluids. As it has a molecular weight below 200 g/mole (namely, 162 g/mole), it may pass through aqueous pores or be carried through the epithelial barrier by the bulk passage of water. Further, the results of an acute oral toxicity study in rats, in which all three animals administered 2000 mg/kg body weight died (without visible signs of local toxicity), indicate that the substance is absorbed by the gastrointestinal tract. In the absence of substance-specific absorption data, a default (worst case) oral absorption value of 100% is used for DNEL derivation. Upon acute and subacute exposure by inhalation, rats showed local effects in the lungs, indicating deposition of the substance in the lungs. Absorption of deposited substance is expected based on its water-solubility and molecular weight (similar to oral absorption). Moreover, as the systemic toxicity (mortality) observed in the acute oral toxicity study in rats indicated oral absorption, it is likely that the substance will also be absorbed if it is inhaled. In the absence of substance-specific absorption data, a default (worst case) value of 100% for absorption by the inhalation route is used for DNEL derivation.

 

Dermal absorption

No data is available on the toxicokinetics of potassium trifluorozincate. The results of the acute dermal absorption study, in which Wistar rats were exposed to the test substance indicate that some absorption occurred, but the amount was not determined. Solid substances will only penetrate the skin in (aqueous) solution. Pure potassium trifluorozincate is a salt with a water solubility of 8.2 g/L at neutral pH. Once dissolved, the salt is ionized to its ions Zn2+ , F-, and K+. The ions are hydrophylic and due to lack of lipophilicity, they will not have any affinity to skin(lipids). Therefore, skin absorption can only occur through the water that penetrates the skin and the maximum skin absorption is defined by the maximum water solubility of the salts and the maximum amount of water that can penetrate the skin. The maximum amount of water that can penetrate the skin is determined to be 17 µL per 1 cm2 per 24 hours (Ten Berge, W. A simple dermal absorption model: derivation and application. (Chemosphere 2009; 75(11):1440-5), which equals 6 µL per cm2 per 8 hours. Since 6 µL of water can maximally penetrate 1 cm2 of skin per 8 hours, 6 x 8.2 = 49.2 µg of ionized salt may penetrate 1 cm2 of skin per 8 hours. In an in vitro skin absorption experiment (according to OECD guideline 428), the application should mimic human exposure, normally 1 -5 mg/cm2 (1000 -5000 µg/cm2 ). Thus, in case the skin penetration of pure potassium trifluorozincate would be experimentally determined according to OECD guideline 428 using 5 mg/cm2 as exposure condition, a skin penetration of 0.98% (49.2/5000) would be observed maximally. Therefore a skin penetration of pure potassium trifluorozincate of 0.98% is considered a worse-case situation for workers.