Fatty acids, C18-unsatd., phosphates

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: REACH Guidance: Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7c Endpoint specific guidance

Test material

Test material information

Constituent 1

Reference substance name:

Fatty acids, C18-unsatd., phosphates

EC Number:

271-708-7

EC Name:

Fatty acids, C18-unsatd., phosphates

Cas Number:

68604-99-9

IUPAC Name:

Fatty acids, C18-unsatd., phosphates

Test material form:

liquid

Specific details on test material used for the study:

Identification: Fatty acids, C18-unsatd., phosphates
Structure: Not indicated
Molecular formula: Not indicated
Molecular weight: Unknown
CAS Number: 68604-99-9
Description: Yellow liquid
Purity: UVCB

Applicant's summary and conclusion

Conclusions:

A toxicokinetic assessment was performed based on the available data of the test item. Based on the physical/chemical properties of Fatty acids, C18-unsatd., phosphates, absorption factors for this test item are derived to be 100% (oral), 100% (inhalation) and 100% (dermal) for risk assessment purposes. The bioaccumulation potential is expected to be low.

Executive summary:

A toxicant can enter the body via the gastrointestinal tract, the lungs and the skin. In general, a compound needs to be dissolved before it can be taken up from the gastrointestinal tract after oral administration (1).

 

Fatty acids, C18-unsatd., phosphatesis a UVCB and contains a mixture of several mono and bis phosphorylated fatty acids (PFA) and other components.

One mono-PFA (Dimethoxyphosphoryloctadecanoic acid, (m/z391.3)appears to be a main component, according to information submitted by the sponsor. Dimethoxyphosphoryloctadecanoic acid has a low water solubility (0.0235g/L) and is thus expected to dissolve only to a minor extent in the gastrointestinal fluids. The absorption via passive uptake is thus expected to be limited.

The molecular weight(391.3Da) will limit passage through biological membranes. Small amounts of such substances may be transported into epithelial cells by pinocytosis or persorption (passage through gaps in membranes left when the tips of villi are sloughed off). Based on the partition coefficient of >4.6 for dimethoxyphosphoryloctadecanoic acid, uptake via micellar solubilisation can be expected to take place.

Another main component of the mixture is dimethyl-n-propyl-phosphonate which has a high water solubility (211 g/L), a rather low molecular weight (151 Da) and a low partition coefficient (Log Pow >0.68), indicating that it will readily dissolve into the gastrointestinal fluids, make contact with the mucosal surface and be absorbed.

In conclusion, the test item is a UVCB consisting of several components that are not expected to have similar physical chemical properties. Therefore, as a worst case, for risk assessment purposes oral absorption ofFatty acids, C18-unsatd., phosphatesis set at 100% (2). The oral toxicity data do not provide reason to deviate from the proposed oral absorption factor.

 

Both dimethoxyphosphoryloctadecanoic acid and dimethyl-n-propyl-phosphonate have a moderate vapour pressure (< 1.5 × 10-3 Paand< 6.7 × 10-3 Pa, respectively) and the absence of a boiling point (reaction and/or decomposition of the test item starts at > 100°C) indicate that Fatty acids, C18-unsatd., phosphates has low to moderatevolatility. Therefore it cannot be excluded that Fatty acids, C18-unsatd., phosphates will reach the nasopharyncheal region or subsequently the tracheo/bronchial/pulmonary region via inhalation of vapour.

Due to the very low water solubility of one of the main components, some components of Fatty acids, C18-unsatd., phosphatesare expected to be retained within the mucus. Some absorption will occur directly across the respiratory tract epithelium by passive diffusion based on the low log Pow. The constituents with higher Pow will be taken up preferentially via micellar solubilisation as a result of dissolution in the mucus lining the respiratory tract. Based on these considerations, for risk assessment purposes the inhalation absorption ofFatty acids, C18-unsatd., phosphatesis set at 100% (2).

 

Fatty acids, C18-unsatd., phosphatesis a liquid, which can potentially be taken up across the skin. According to the criteria given in the REACH Guidance, a default value of 100% dermal absorption should be used unless MW >500 and log Pow <-1 or >4, in which case a value of 10% skin absorption should be chosen (2). Fatty acids, C18-unsatd., phosphates does not fulfill these criteria. Moreover, the test item is corrosive to the skin and damage to the skin can enhance penetration. Based on these considerations, for risk assessment purposes the dermal absorption of Fatty acids, C18-unsatd., phosphatesis set at 100%.

 

Once absorbed, distribution of the test item throughout the body can be expected based on the molecular weight of at least some of the components. Based on the lipophilicity of the different constituents (a partition coefficient of 4.6 or higher),Fatty acids, C18-unsatd., phosphatesmay accumulate to a limited extent in adipose tissue. However, taking into consideration the moderate to high molecular weight and the low water solubility of the lipophilic components (mono and bis PFA), the bioaccumulation potential ofFatty acids, C18-unsatd., phosphatesis expected to be low.

After absorption in the gastro-intestinal tract,Fatty acids, C18-unsatd., phosphatesmight be metabolized (3). Excretion ofFatty acids, C18-unsatd., phosphatesand its metabolites will occur via the bile (high molecular weight) or the urine (low molecular weight).