Dipraseodymium tricarbonate

Endpoint summary

Description of key information

For the purposes of human risk assessment, oral absorption of dipraseodymium tricarbonate 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 green powder. No experimental studies with animals or humans on absorption, metabolism, distribution, or elimination are available for the substance. However, information is available from existing toxicology studies to infer potential toxicokinetic properties. Systemic availability of dipraseodymium tricarbonate depends on its ability to be absorbed across body surfaces. A major factor affecting this process is water solubility (4.39 mg/L, “slightly” soluble), The solubility increases as the pH decreases. The material decomposes at 420ºC. The substance has a molecular weight of 461.8 g/mol.  

Absorption

Oral absorption

Non-adverse effects were observed in a GLP-compliant OECD 422 repeat dose toxicology study conducted up to 1000 mg/kg bw/day (read-across from praseodymium oxide) suggesting that there may be some absorption following oral exposures. The NOAEL was considered to be 1000 mg/kg/day (the top dose tested) for parental, reproductive and foetal toxicity. The acute oral LD50 was estimated to be greater than 2000 mg/kg bw in a GLP-compliant OECD 420 oral gavage study, with no clinical signs no effect on body weight gain and, no gross abnormalities upon necropsy. It can be concluded from the study data that significant absorption via the oral route is unlikely, although in the absence of other information, and unknown effect of the acidity of the stomach, 50% bioavailability is assumed.

Dermal absorption

No studies investigating the absorption through the skin were available. A skin sensitisation study was negative, from which nothing can be inferred. Given its low solubility and that it is a solid, dermal absorption is expected to be minimal. For the purposes of DNEL setting however, estimation of mammalian dermal absorption is made in accordance with principles adopted 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, concentrations as high as 5.25 mg/L air did not cause any mortality. Limited clinical signs were observed in few animals during exposure and up to the day following exposure, although these were non-specific and common to inhalation of insoluble powders. 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. However in the absence of any quantitative data, absorption of material that makes it into the alveoli is considered to be 100%.

Distribution and metabolism

No information is available to describe the distribution and metabolism.

Conclusion

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