1,2,3-Propanetriol, homopolymer

Endpoint summary

Additional information

Experimental data for 1,2,3 -Propanetriol, homopolymer (CAS 25618-55-7) are available investigating the short-term toxicity to fish and the toxicity to aquatic microorganisms. However, there are no data available for the remaining aquatic toxicity endpoints. In order to fulfill the standard information requirements set out in Annex VI - IX, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across from structurally related substances was conducted.

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006 whereby physicochemical, toxicological and ecotoxicological properties may be predicted from data for reference substance(s) by interpolation to other substances on the basis of structural similarity, the two substances listed in Table 1 are selected as reference substances and the available endpoint information is used to predict the same endpoints for 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7).

A read across from the source substances in order to assess the environmental fate and aquatic toxicity of 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7) is considered valid, since the reference substances represent the main components of the target substance. The only differences are i) the slightly different proportional composition of these components and ii) the absence of mono-glycerol, a main component of the target substance but not part of reference substance 1. Therefore, data for mono-glycerol (reference substance 2), although listed in Annex V of Regulation (EC) No. 1907/2006 and thus exempted from registration, are considered additionally. Based on the fact that the components of the reference substances and the target substance are identical the functional groups (hydroxyl groups) and the metabolites are expected to be identical as well.

Table 1: Data for the target substance and the two considered reference substances

	Target	Reference 1	Reference 2
CAS No	25618-55-7	-	56-81-5
EC/List No	-	915-741-3 (List No)	200-289-5
Chemical Name	1,2,3-Propanetriol, homopolymer	Reaction mass of 3-[3-(2,3-dihydroxypropoxy)-2-hydroxypropoxy]propane-1,2-diol,3-(2,3-dihydroxypropoxy)propane-1,2-diol,3-[3-[3-(2,3-dihydroxypropoxy)-2-hydroxypropoxy]-2-hydroxypropoxy]propane-1,2-diol	Glycerol
MW	92.09 – 314.34	166.18 – 314.34	92.09
Composition	mono-glycerol: 33.3 % di-glycerol: 28.49 % tri-glycerol: 15.48 % tetra-glycerol: 8.33 %	di-glycerol: 15-35 % tri-glycerol: 35-55 % tetra-glycerol 10-25 %	>80%
Water solubility	Experimental result: > 550 g/L	Experimental result: > 1000 g/L	QSAR calculation:1000 g/L
Log Kow	Experimental result: -2	Experimental result: > -3.9 < -3.3	QSAR calculation: -1.75
Vapour pressure	Experimental result: ≤ 0.047 Pa at 20 °C	Experimental result: 0.00000673 Pa at 20 °C	QSAR calculation: ~ 0.1 Pa at 20 °C
Short-term toxicity to fish	Experimental result: LC50 (96h) > 500 mg/L   RA: Reference 1 RA: Reference 2	Experimental result: LC50 (96h) > 1000 mg/L	Experimental result: LC50 (96h) = 54 g/L
Long-term toxicity to fish	Waiving based on CSA	--	--
Short-term toxicity to aquatic invertebrates	RA: Reference 1 RA: Reference 2	Experimental result: EC50 (48h) > 1000 mg/L	Experimental result: EC50 (24h) > 10 g/L
Long-term toxicity to aquatic invertebrates	Waiving based on CSA	--	--
Toxicity to aquatic algae	RA: Reference 1 RA: Reference 2	Experimental result: EC50 (72h) > 1000 mg/L NOEC (72h) >= 1000 mg/L	Experimental result: EC50 (48h) >100 mg/L
Toxicity to microorganisms	Experimental result: EC10 (16h) > 1000 mg/L   RA: Reference 1 RA: Reference 2	Experimental result: NOEC (3h) >= 100 mg/L	Experimental result: EC10 (16h) >10 g/L

Lack of data for a given endpoint is indicated by “--“.

Ecotoxicological studies with freshwater species from all three trophic levels (fish, aquatic invertebrates and algae) are available from own studies or for the structurally similar reference substances Reaction mass of 3-[3-(2,3-dihydroxypropoxy)-2-hydroxypropoxy]propane-1,2-diol,3-(2,3 dihydroxypropoxy)propane-1,2-diol,3-[3-[3-(2,3-dihydroxypropoxy)-2-hydroxypropoxy]-2-hydroxypropoxy]propane-1,2-diol (List No. 915-741-3) and glycerol (CAS 56-81-5).

 

If ingested and absorbed by fish, the mono-glycerol component is expected to be rapidly metabolised via cleavage of the ether bond as shown by Saunders & Dawson (1962) and Haessler & Isselbacher (1963) in rats and hamster. In contrast the polyglycerols are not expected to be catabolized but excreted rapidly into the urine after absorption as shown, for example, for triglycerol and polyglycerol (C10) by Michael and Coots (1971). Based on this, the polyglycerol components are not considered to be more bioaccumulative and/or toxic but longer bioavailable and thus are considered to be of higher ecotoxicological relevance. Accordingly, studies with reference substance 1, which contains a similar set of polyglycerols as the target substance, was used as key study in the case no own study was available. 

 

The short-term toxicity tests with freshwater species (fish, daphnia, algae) performed for 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7) or reference substance 1 showed no effects up to the highest tested concentrations (500 mg/L: fish; 1000 mg/L: daphnia, algae). This result was also confirmed for the mono-glycerol component in short-term toxicity studies with freshwater organisms. Thus, 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7) can be considered as not acutely harmful to aquatic organisms.

 

Long-term toxicity studies with algae are available for both reference substances. No chronic tocxicity was indicated by these tests up to the highest tested concentration of 1000 mg/L. Long-term toxicity test with fish or aquatic invertebrates are not available. According to Regulation (EC) No. 1907/2006, Annex IX, Column 2, 9.1.6, long-term toxicity testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicate the need to investigate further the effects on aquatic organisms. Since 1,2,3 -Propanetriol, homopolymer (CAS 25618-55-7) is a readily biodegradable and soluble substance (> 550 g/L) extensive biodegradation within conventional STPs can be expected and therefore, only low concentrations are likely to be released into the water phase and directly bioavailable to fish species. Due to the very low log Kow of -2 and the rapid excretion and metabolism after uptake bioaccumulation is not to be expected. Furthermore, the short-term toxicity tests and the available long-term toxicity tests with algae indicate no toxic potential of the substance. Therefore, long-term toxicity testing on fish and aquatic invertebrates are not deemed necessary for the hazard assessment of 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7).

 

Toxicity to microorganisms was assessed in a “weight of evidence” approach using one study for 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7) and two studies for the reference substances Reaction mass of 3-[3-(2,3-dihydroxypropoxy)-2-hydroxypropoxy]propane-1,2-diol,3-(2,3 dihydroxypropoxy)propane-1,2-diol,3-[3-[3-(2,3-dihydroxypropoxy)-2-hydroxypropoxy]-2-hydroxypropoxy]propane-1,2-diol (List No. 915-741-3) and glycerol (CAS 56-81-5). The studies consistently showed that neither the glycerol nor the polyglycerol components of 1,2,3 -Propanetriol, homopolymer exhibit toxic effects to microorganisms. In combination with results from the available biodegradation study it can be concluded that no effects on the STP microorganism community and the subsequent degradation process in sewage treatment plants is anticipated.

 

In conclusion, no effects on aquatic organisms were observed in the available studies for any of the three trophic levels (fish, daphnia, algae) up to 500 mg/L (for fish) and 1000 mg/L (for daphnia and algae), neither in short-term toxicity tests nor in a long-term test with algae. Thus, 1,2,3-Propanetriol, homopolymer (CAS 25618-55-7) can be considered not harmful to aquatic life.

 

Reference

Haessler HA, Isselbacher KJ. 1963.The metabolism of glycerol by intestinal mucosa. Biochem Biophys Acta 73(3): 427 -436

Michael WR, Coots RH. 1971. Metabolism of polyglycerol and polyglycerol esters. Toxicol Appl Pharmacol 20(3): 334 -345

Saunders DR, Dawson AM. 1962. Studies on the metabolism of glycerol by the small intestine in vitro and in vivo.Biochem J 82(3): 477 -483