Cerium trifluoride

Endpoint summary

Description of key information

For the purposes of human risk assessment, oral absorption of the substance is estimated at 50%, inhalation absorption is estimated at 100% and dermal absorption is estimated at 25%.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

25

Absorption rate - inhalation (%):

100

Additional information

Introduction

The substance is a pale pink powder.

No experimental studies of cerium fluoride with animals or humans on absorption, metabolism, distribution, or elimination in mammals are available. However, information is available from existing toxicology studies from which limited inferal of potential toxicokinetic properties might be made.

Systemic availability of cerium fluoride depends on its ability to be absorbed across body surfaces. Factors that affect this process include water solubility, lipophilicity (measured by the partition coefficient, Kow), degree of ionization (the dissociation constant, pKa), and molecular size. The substance has a molecular weight of 197.1 g/mol and is sparingly soluble in water (0.16 mg/L in purified water, rising to 1.1 mg/L at pH 4). No dissociation constant or log Kow is available for this substance. Kow are not required for inorganic substances.

Absorption

Oral absorption

The acute oral LD50 was estimated to be greater than 2000 mg/kg bw in an OECD 420 oral gavage study, with no clinical signs and no effect on body weight observed. In addition, no gross abnormalities were observed at necropsy. Nothing can be inferred about the nature of oral absorption from this study.

In an OECD 422 repeat-dose/reproductive study treatment with cerium trifluoride at levels up to 1000 mg/kg/day was not associated with any observable effect on any parameter. Nothing can be inferred about the nature of oral absorption from this study.

Because of the insolubility of the material in water absorption via the oral route is unlikely, although in the absence of other information, the unquantified effect on solubility of stomach acid, and for the purposes of human DNEL setting, 50% bioavailability is assumed.

Dermal absorption

No acute dermal toxicity study is available.

Skin irritation and sensitisation studies gave no signs that the test material reacted chemically with living layers of the skin.

Nothing can be inferred about the dermal penetration properties of the test material from these studies.

For the purposes of DNEL setting however, estimation of mammalian dermal absorption is made in accordance with principles adopted in the EFSA guidance on estimating dermal absorption of pesticide active substances (EFSA, 2012). On this basis, dermal absorption is estimated at 25% for undiluted material.

Inhalation absorption

In an acute inhalation study, nose-only exposure for 4 hours at a concentration as high as 5.53 mg/L air did not cause any mortality. Limited non specific clinical signs were observed in few animals during exposure and up to the day following exposure. Macroscopic examination at termination, 14 days after the 4-hrs exposure revealed no macroscopic abnormalities. It can be concluded from the study data that significant absorption via the inhalation route is unlikely. Nothing can be inferred with respect to inhalation absorption from this study. In the absence of any quantitative data, absorption of material that makes it into the alveoli is considered to be 100%.

Distribution, metabolism, excretion

No information is available to describe the distribution, metabolism of the material. Given there is unlikely to be any oral absorption, ingested material is likely to pass through the GIT and merger in the faeces.

Conclusion

For the purposes of human risk assessment, oral absorption of the substance is estimated at 50%, inhalation absorption is estimated at 100% and dermal absorption is estimated at 25%.