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Key value for chemical safety assessment

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Endpoint specific guidance (ECHA, 2008) indicates that absorption of substances following exposure by inhalation, skin contact or ingestion may be predicted based on log Pow and water solubility. Experimentally determined results for substances in this category are as follows:

Substance

Log Pow

Solubility (mg/l)

Resin acids and Rosin acids, hydrogenated, Me esters

6.4 – 7.6

2.1

Resin acids and rosin acids, esters with glycerol

3.97

<0.43

Resin acids and rosin acids, hydrogenated, esters with glycerol

4.7-5.8

0.15

Resin acids and rosin acids, polymerized, esters with glycerol

>6.5

<1.24

Resin acids and rosin acids, esters with ethylene glycol

5.65 - >6.5

<3.7

Resin acids and rosin acids, esters with diethylene glycol

3.1-7.3

<8.2

Resin acids and rosin acids, esters with triethylene glycol

2.44

8.0

Resin acids and rosin acids, hydrogenated, esters with triethylene glycol

>6.5

<32.3

Resin acids and rosin acids, esters with pentaerythritol

3.62

<0.63

Resin acids and rosin acids, hydrogenated, esters with pentaerythritol

4.6-7.3

<0.22

Resin acids and rosin acids, polymerized, esters with pentaerythritol

>6.5

<2.1

 

ECHA (2008) indicates that uptake of substances by the lung and gastrointestinal tract is favoured by moderate log P values (between -1 and 4) with micellular solubilisation favoured where log P is >4 and water solubility is low (< 1 mg/l). Data summarised above suggests that the majority of substances included in this category may be absorbed if inhaled or ingested, although the extent of uptake is not clear. A low vapour pressure means that substances in this category are unlikely to exist as vapour, with inhalation exposure limited to material deposited as particles.

Dermal absorption of highly water soluble substance may occur where the log Pow is between 1-4 with log Pow values between 2 and 3 favouring uptake. When log Pow exceeds 4, penetration may be limited by the rate of transfer between the stratum corneum and epidermis although uptake of a substance by the stratum corneum will be high. Uptake of substances where log Pow exceeds 6 will be low (ECHA, 2008). Based on these criteria, the data summarised above suggests that members of this category are not likely to penetrate the skin.

Experimental data are also available to characterise the toxicokinetic behaviour of the glycerol ester member of this category.

The absorption, disposition and excretion of [C^14]ester gum (Resin acids and rosin acids, esters with glycerol) in the rat was investigated in an oral study conducted by a method similar to that found in OECD Guideline 417 (Southern Research Institute, 1996). Male and female rats were administered a single oral dose of 200 mg/kg bw of [C^14] ester gum following one or ten days of dietary administration of the unlabelled compound. The degree of absorption of ester gum was determined by quantitating the amount of radioactivity eliminated in expired air, urine and feces over the next 120 hours and assessing residual radioactivity in the carcasses at study termination. A separate study investigated the amount of radioactivity excreted in bile and present in blood at 4 or 12-hour intervals after administration of a single bolus dose of [C^14]ester gum. Most of the dose (>95%) was recovered in the feces and cage rinses. Low levels of radioactivity detected in the carcasses at study termination were thought to be from fecal material remaining in the gastrointestinal tract which was not removed prior to analysis of the carcasses. HPLC analysis of fecal and bile extracts indicated that only a very small percentage of the administered [C^14]ester gum was hydrolyzed and there was no significant difference in metabolic profile following one or ten days of dietary administration of the unlabelled compound. Recoveries in the CO2 traps and urine were each 1% or less of the administered dose. Low levels of radioactivity detected in the blood during the first 24 hours after [C^14]ester gum administration accounted for 0.1% or less of the dose and radioactivity in livers from these same rats accounted for 0.1-0.2% of the dose indicating that hepatic retention of radioactivity was essentially negligible. The results indicate that only a small percentage of the administered [C^14]ester gum was absorbed from the gastrointestinal tract, with most of the dose (>95%) recovered in the feces within the first 48 hours.