Tris[(2-hydroxyethyl)ammonium] citrate

Endpoint summary

Description of key information

The NOAEL of 614.6 mg/kg bw/day, based on the read-across with monoethanolamine, will be taken forward as a point of departure for DNEL derivation for tris[(2-hydroxyethyl)ammonium] citrate. 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

614.6 mg/kg bw/day

Species:

rat

Additional information

No substance-specific data on the repeated dose toxicity of tris[(2 -hydroxyethyl)ammonium] citrate are available. However, according to Article 13 of the REACH legislation, in case no appropriate animal studies are available for assessment, information should be generated whenever possible by means other than vertebrate animal tests, i. e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across.

Tris[(2 -hydroxyethyl)ammonium] citrate is a salt of monoethanolamine and citric acid and is expected to dissociated into the respective monoethanolammonium cation and dihydrogen citrate anion (which may subsequently undergo (partial) dissociation to monohydrogen citrate and citrate anions) upon uptake by the body. Therefore it is considered to be acceptable to derive lacking information on toxicological properties of tris[(2 -hydroxyethyl)ammonium] citrate by read-across from its starting materials.Citric acid is an important intermediate of the Krebs cycle (also known as citric acid cycle), and therefore occurs naturally as a metabolite in virtually all living organisms. It is also used as a natural food preservative and a food additive. The average daily intake (ADI) is not limited according to the evaluation of Joint FAO/WHO Expert Committee on Food Additives (1973), which concluded that the substance is non-hazardous to men. Therefore the toxicological behavior of tris[(2 -hydroxyethyl)ammonium] citrate is expected to be governed primarily by the toxicity of monoethanolamine.

Oral route of exposure

No reliable conventional repeated dose toxicity studies with monoethanolamine are available. However, monoethanolamine hydrochloride was tested in an oral two-generation reproduction toxicity study with rats according to OECD Guideline 416 under GLP (BASF AG, 2009). The test substance was administered to groups of 25 male and 25 female rats (F0 parental generation) in diet at dose levels of 0, 100, 300 and 1000 mg/kg bw/day. At least 75 days after the beginning of treatment, F0 animals were mated to produce a litter (F1 generation).After weaning of F1 pups the F0 generation parental animals were terminated. 25 male and 25 female F1 pups from each dose group were chosen to be F1 generation parental animals. They were treated with the test substance at the same dose levels up to about one day before they were terminated. At least 75 days after assignment of the F1 generation parental animals, the males and females were generally mated and the females were allowed to litter and rear their pups (F2 generation pups) until Day 4 (standardization) or 21 post-partum. Shortly after the F2 generation pups had been weaned, the F1 generation parental animals were terminated. All sacrificed F0 and F1 animals were necropsied and assessed by gross pathology and histopathology.

At 1000 mg/kg bw/day, signs of systemic toxicity were observed in parental females, manifested as reduced food consumption and/or body weight gain during gestation and lactation. In the mid and high dose F1 animals statistically significant increases of absolute and relative kidney weights were observed; however, these increases were not accompanied by histopathological changes.In the high-dose F0 and F1 males absolute and relative organ weights of cauda epididymidis and epididymides were statistically significantly decreased. Prostate weight and the number of homogenization resistant caudal epididymal sperm were statistically significantly decreased in the F0 males. These findings were not accompanied by histopathological changes.

Based on the results of the study, the NOAEL for general toxicity was set at 300 mg/kg bw/day.

Inhalation route of exposure

In a 28 days inhalation toxicity study performed according to OECD guideline 412 and under GLP (BASF AG, 2010), groups of five male and five female rats were exposed nose-only to target concentrations of 0, 10, 50 and 150 mg/m³of monoethanolamine for 28 days, 6 h/day, 5 days/week. Animals were observed for clinical signs, body weight changes and food consumption. Ophthalmological examinations were performed prior to exposure and towards the end of the exposure. Hematological and clinical examinations were performed before the end of the study. Gross pathological and histopathological examinations were performed on all animals.

There were no deaths or clinical signs related to treatment. No effects were noted on the body weight and body weight gain, food consumption, organ weights and clinical and hematological parameters at all concentration levels. Concentration-related lesions in larynx, trachea and lung were observed in the mid- and high concentration groups. At 150 mg/m3, submucosal inflammation, degeneration of submucosal glands, focal epithelial necrosis, focal squamous metaplasia and focal epithelial hyperplasia were observed in the larynx of male and female animals. In the trachea, focal squamous metaplasia (carina) accompanied by inflammation in males was observed. At 50 mg/m³, submucosal inflammation and squamous metaplasia of the larynx in males and females was observed. At 10 mg/m³no adverse effects were noted. No histopathological effects were seen in any other organ outside the respiratory tract. The highest concentration of 150 mg/m³was considered a NOAEC for systemic toxicity. The lowest tested concentration of 10 mg/m³was considered a NOAEC for local effects.

No conventional repeated dose toxicity studies with citric acid are available. However, citric acid is considered to be practically non-hazardous and its average daily intake (ADI)is not limited according to the evaluation ofJoint FAO/WHO Expert Committee on Food Additives (1973). Therefore the repeated dose toxicity of tris[(2 -hydroxyethyl)ammonium] citrate is expected to be determined by toxicity of monoethanolamine.

The local effects observed in the inhalation toxicity study with monoethanolamine are expected to be related to the corrosive nature of monoethanolamine and are not relevant for tris[(2 -hydroxyethyl)ammonium] citrate, which is not corrosive. Choosing the NOAEL of 300 mg/kg bw/day as a point of departure, and applying a correction for molecular weight, a NOAEL of 300×(375.37/3)/61.08 = 614.6 mg/kg bw/day can be calculated for tris[(2-hydroxyethyl)ammonium] citrate. This value is far above the cut-off values for the classification according to EU Directive 67/548/EEC and EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008. Therefore classification of tris[(2-hydroxyethyl)ammonium] citrate for repeated dose toxicity is not warranted. The value of 614.6 mg/kg bw/day will be taken forward for risk assessment and will be used for DNEL derivation.

Repeated dose toxicity: via oral route - systemic effects (target organ) urogenital: epididymides; urogenital: kidneys; urogenital: prostate

Justification for classification or non-classification

As the calculated NOAEL for tris[(2 -hydroxyethyl)ammonium] citrate, based on the read-across from monoethanolamine, is far above the classification limits of EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 and EU Directive 67/548/EEC, classification for repeated dose toxicity is not warranted.