2-amino-2-(hydroxymethyl)propane-1,3-diol hydrochloride

Endpoint summary

Description of key information

A short-term study with TRIS HCl is available for daphnia magna (6.1.3-1). Since data for toxicity to algae and fish were not available for assessment, a read-across approach from TRIS AMINO (6.1.5-1) and AEPD (6.1.1-1) were used.  TRIS AMINO and AEPD are both soluble in water, non-volatile and have low potential for adsorption, thus their main target environmental compartment is water. All tests demonstrate low aquatic toxicity, with LC/EC50 values >100 mg/L for fish, daphnia and alga, respectively.

AEPD, TRIS AMINO and TRIS HCl are well soluble in water (> 600 g/L) and have a very low vapour pressure (< 0.01 Pa). The low partition coefficient (log Kow) of -2.31 (TRIS AMINO), -1.02 (AEPD) and -3.6 (TRIS HCl) indicate low potential to accumulate in biological systems. Additionally, AEPD and TRIS AMINO are rapidly biodegradable. In the ready biodegradation test (301F), TRIS AMINO reached 100% degradation within 28 days and AEPD was rapidly degraded in the inherent test (> 90% with 7 days).

The read-across from AEPD and TRIS AMINO to TRIS HCl for the endpoints short-term toxicity to fish and toxicity to algae is justified by the data comparison discussed above as well as by structural and physico-chemical similarity of the two substances.

Furthermore, both OASIS and ECOSAR classification models indicate narcosis as mode of action for TRIS HCl, TRIS AMINO and AEPD. However, it is known that for amines the toxicity can be enhanced with respect to baseline, and the mode of action can be classified as “amine narcosis”. Nevertheless, as in the general case of narcosis (i.e. with absence of specific and reactive effects – what is confirmed by the presence of only amine and alcohol functional groups), log Kow is the main toxicity trigger. This descriptor takes very low values for both substances as discussed before and this fact is reflected in high experimental acute toxicity values for fish, Daphnia and algae.

OECD QSAR Toolbox (v. 3.3.0) profiling in regard to aquatic toxicity is presented in the table below.

Table: OECD QSAR Toolbox characteristics of environmental toxicity profiles of target and source substances

Profiling	Target chemical, TRIS HCl CAS 1185-53-1	Source chemical, Trometamol CAS 77-86-1	Source chemical, AEPD CAS 115-70-8
Acute aquatic toxicity classification by Verhaar (modified)	Class 5 (not possible to classify according to these rules)	Class 5 (not possible to classify according to these rules)	Class 5 (not possible to classify according to these rules)
Acute aquatic toxicity MOA by OASIS	Narcotic amine	Narcotic amine	Narcotic amine
Aquatic toxicity classification by ECOSAR	Aliphatic amine	Aliphatic amine	Aliphatic amine
Organic functional groups (nested)	Alcohol, aliphatic amine (primary)	Alcohol, aliphatic amine (primary)	Alcohol, aliphatic amine (primary)

Table: Environmental fate and toxicity

Endpoint	Target chemical, TRIS HCl CAS 1185-53-1	Source chemical, Trometamol CAS 77-86-1	Source chemical, AEPD CAS 115-70-8
Biodegradation	RA CAS 77-86-1 readily biodegradable	readily biodegradable	rapidly biodegradable
Adsorption, log Koc	no data available	1.87 (QSAR)	2.96 (QSAR)
Short-term toxicity to fish, 96h-LC50, mg/L	RA CAS 115-70-8 460	RA CAS 115-70-8 460	460
Short-term toxicity to daphnia, 48h-EC50, mg/L	> 117	> 980	668
Toxicity to algae, 72h-EC50, mg/L	RA CAS 77-86-1 397	397	548
Toxicity to algae, 72h-NOEC, mg/L	RA CAS 77-86-1 100	100	31.3
Toxicity to microorganisms, EC50, mg/L	> 1000 (3 h)	> 1000 (3 h)	640
Toxicity to microorganisms, EC10, mg/L	> 1000 (3 h-NOEC)	> 1000 (3 h-NOEC)	300

Terrestrial studies are not available for TRIS HCl or for potential analogue substances. However, the substances are expected to partition mainly into the aquatic compartment and to be removed quickly due to rapid biodegradation. Additionally, significant bioaccumulation is not likely due to the low Kow, and the data available for aquatic organisms indicates low toxicity concern.