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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
Absorption rate - dermal (%):
Absorption rate - inhalation (%):

Additional information

In accordance with point 8.8.1 of column 1 (Standard Information Required), Annex VIII of REACH (Regulation EC No. 1907/2006), assessment of the toxicokinetic behaviour of the substance is performed to the extent that can be derived from the relevant available information. A toxicokinetic assessment was performed based on the available physical-chemical data and toxicological information available. Further testing for the assessment of toxicokinetic behaviour is omitted on this basis.


Naphthenic acids, potassium salts (CAS 68002-54-0) is an organic UVCB substance and is a dark brown viscous liquid.

No experimental studies of the absorption, metabolism, distribution, or elimination of Naphthenic acids, potassium salts (“the substance”) in mammals are available. However, information is utilized from existing toxicology studies on the substance, or for other very similar materials, and this data is used to infer, as far as possible, the potential toxicokinetics of the substance.

Physicochemical properties

Systemic availability of the substance 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. Given the large number of components within the substance, it has a molecular weight in the approximate range of 290-270 g/mol. It is forms a stable dispersion in water, but the actual water solubility could not be measured. Likewise measuring the dissociation constant or log Kow was not technically feasible. Based on the structures however, the estimated log Kow ranged from -0.05 to 8.64. From the detailed estimate, the higher the MW of each component of the substance, the higher the log Kow.


Oral absorption

The acute oral LD50was greater than 2000 mg/kg bw in an OECD 423 oral gavage study, with only non-specific clinical signs in 2/3 animals, and no effect on body weight observed. In addition, no gross abnormalities were observed at necropsy. The clinical signs suggest that absorption may take place. 

In an OECD 422 repeat-dose/reproductive toxicity study, treatment with the substance at dose levels up to 750 mg/kg/day was associated with liver toxicity and secondary thyroid toxicity (LOAEL 250 mg/kg/day) suggesting that some absorption took place.

Lower MW components of the substance would be more readily absorbed than the higher MW components.

The physical chemical properties do not preclude absorption. In the absence of quantitative information, 50% bioavailability following oral administration is assumed for the purposes of human risk assessment.

Dermal absorption                                                                                               

The acute dermal LD50for the unsalted naphthenic acids (likely to be worse case for the potassium salt, as they cause metal corrosion, whereas the salts thereof can be used as corrosion inhibitors) was greater than 20000 mg/kg bw in acute dermal toxicity studies, with no clinical signs, effects on body weight or gross abnormalities at necropsy. An in vitro skin irritation study with the substance also showed no toxicity to the test system, and the substance was not a sensitiser in the LLNA. Nothing can be inferred about the nature of dermal absorption from these studies. 

Lower MW components of the substance would be more readily absorbed than the higher MW components.

For the purposes of risk assessment however, estimation of mammalian dermal absorption is made in accordance with principles adopted by the EFSA guidance on estimating dermal absorption of pesticide active substances (EFSA, 2012). On this basis, dermal absorption is estimated at 50% for undiluted substance, which is considered conservative.

Inhalation absorption

In the absence of any quantitative data, absorption of inhaled substance is considered to be 100%.

Distribution, Metabolism and Elimination

No information is available to describe the distribution, metabolism or elimination of the substance.


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 50%.