6,6',6''-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:3)

Endpoint summary

Additional information

The substance is a salt which is a reaction product of an acid (triazine compound, CAS 80584-91-2) and a base (triethaonoleamine, TEA, CAS 102-71-6) that retain their ionic character. Under aqueous conditions it is expected to be present in its dissociated form. Therefore, the individual components of the salt are assessed separately.

 

 

Assessment of the toxicokinetic behavior of the triazine compound, CAS 80584-91-2

 

The triazine compound is a solid with a molecular weight of 468.55 g/mol and its relative density was determined to be 1280 kg/m³ at 21°C (Ciba-Geigy, 1995). The vapor pressure of CAS 80584-91-2 was calculated at < 0.000001 Pa at 20°C (EpiSuite). The triazine component is furthermore characterized by very low solubility in water (< 0.19 mg/L) with a log P_OW of 0.8 (BASF, 2013). No studies are available investigating the toxicokinetic properties. The toxicokinetic behavior is therefore assessed based on physic-chemical properties and on available toxicity studies.

 

Absorption

 

Absorption via the gastrointestinal tract:

Absorption through the gastrointestinal tract is favored for molecules with a molecular weight below 500 g/mol; molecular weights above 1000 g/mol are not easily absorbed (ECHA GD 7c, 2008). The triazine’s molecular weight is therefore in the absorbable range. However, an additional limiting factor for gastrointestinal absorption is the water solubility. Water-soluble substances will readily dissolve in the fluids of the GI tract (ECHA GD 7c, 2008). The solubility of CAS 80584-91-2 in water is very low, therefore limiting the dissolving in GI fluids and hindering its contact with the mucosal membrane for subsequent absorption. CAS 80584-91-2 could be taken up by passive diffusion, but this mechanism is limited due to possible ionization of the test substance in the small intestine. The dissociation constant was determined experimentally and by calculation to be pKa1= 6.98 for the basic NH groups and pKa2= 4.5 for the acidic COOH groups (Ciba-Geigy, 1995). Accordingly, the substance is expected to be present in ionized form during passage of the GI tract. Thus, the substance is not expected to be absorbed, since ionized substances are generally not expected to readily diffuse through biological membranes (ECHA GD 7c). The compound is furthermore not likely to be taken up by micellular solubilisation, a mechanism which is of particular importance for compounds with a log Pow of > 4 (ECHA GD 7c, 2008). Because the molecular weight of CAS 80584-91-2 is > 200 g/mol, passage through aqueous pores is also not expected (ECHA GD 7c, 2008). In conclusion, absorption via the gastrointestinal tract is expected to be low, since the triazine’s physico-chemical parameters do not support gastrointestinal absorption. This is in line with the results obtained in several oral toxicity studies. In an acute oral toxicity study, male and female rats were treated with CAS 80584-91-2 at a dose level of 5000 mg/kg body weight. No mortality, clinical signs or necropsy findings were observed (Ciba-Geigy, 1980). In two oral repeated dose studies (28 and 90 days), CAS 80584-91-2 was administered to groups of rats at doses levels of up to 1000 mg/kg body weight per day by gavage (Inveresk, 2000 and 2001). Again, no mortality, clinical signs or necropsy findings were observed. No findings in hematology, clinical chemistry and histology were reported that could be attributed to the triazine compound. The lack of systemic toxicity in these studies suggests poor bioavailability upon oral ingestion. As a result an accumulation of CAS 80584-91-2 in the body is not expected.

 

Dermal absorption:

In an acute dermal toxicity study, the LD50 was higher than 2000 mg/kg body weight and no signs of acute dermal toxicity were observed (Ciba-Geigy, 1995). In a guinea pig maximization test, CAS 80584-91-2 did not cause sensitization after dermal challenge application (Inveresk, 2001). These results do not indicate any systemic availability of the triazine compound after dermal exposure. Highly lipophilic substances (log P_OW of 4-6) that come into contact with the skin can readily penetrate the lipid rich stratum corneum but are not well absorbed systemically. Although they may persist in the stratum corneum, they will eventually be cleared as the stratum corneum is sloughed off. For a log P_OW of 1-4 dermal absorption is favored, especially when the substance is soluble in water. The test article has a log P_OW of 0.8 which is close to the above range favorable for absorption, however its water solubility is low. Furthermore, for chemicals with a molecular weight < 100 g/mol, dermal uptake is favored, while for chemicals with a molecular weight > 500 g/mol, dermal uptake is not favored (ECHA GD 7c, 2008). In conclusion, based on the molecular size and the low water solubility together with the results of acute dermal and sensitization studies, dermal absorption of CAS 80584-91-2 is expected to be low.

 

Absorption via inhalation:

No information from acute or repeated dose toxicity studies is available, which could provide information about the systemic distribution of CAS 80584-91-2 after inhalation. CAS 80584-91-2 has a very low vapor pressure of < 0.00001 Pa at 25°C (calculated). Therefore, low absorption of the substance vapor via the inhalative route is considered. Since the material is present in aqueous form, the exposure to dust particles can also be excluded.

 

Metabolism

Based on the physico-chemical parameters and the results obtained in toxicity studies, the substance is most likely not absorbed and excreted unchanged. Nevertheless, potential metabolites were calculated using the OECD toolbox 3.0. Here, the simulator tool for liver metabolism proposed the elimination of acetic acid from the side chains. Acetic acid is part of the endogenous metabolism and may be further metabolized within the citric acid cycle. In general, studies on genotoxicity gave no indications of a reactivity of test substance or its metabolites under the test conditions chosen (i.e. no increased mutagenicity or cytotoxicity in treatments with metabolic activation), except for the chromosomal aberration test performed in vitro with CHO cells. Here, an increase in structural chromosomal aberrations was observed in the presence of a metabolizing system. However, this effect was observed only at high concentrations which resulted in precipitation of the test material and displayed increased cytotoxicity. This result could not be confirmed in vivo when tested in mice.

 

Distribution and Excretion

As already discussed above, absorption and systemic availability of the test substance is not expected. The test substance will most likely be excreted unchanged via the feces. Overall, accumulation of test material within the body is not expected.

 

References

(see also respective IUCLID chapters)

- Report on Density of Solids, CIBA-GEIGY Ltd, AD-95/3T.DES, 1995-05-02

- Vapour pressure of Test Item, BASF SE, 2012.221, 2012-11-23

- Physico-chemical properties of Test Item, BASF SE, 12Y45240, 2013-02-20

- Report on dissociation constant in water, CIBA-GEIGY Ltd, AD-95/3T.DCW, 1995-06-13

- Guidance on information requirements and chemical safety assessment, Chapter R.7c: Endpoint specific guidance, ECHA, 2008

- Acute Oral Median Lethal Dose (LD50) in Rats, Ciba-Geigy, 74/80/S.L., 1980-04-22

- 13 Week Toxicity Study Incorporating Neurotoxicity Screen in Rats with Administration by Gavage Followed by a 4 Week Recovery Period, Inveresk Research, 19904, 2002-06-26

- 4 Week Dose Range Finding Study in Rats with Administration by Gavage, Inveresk Research, 19432, 2001-07-16

- Acute dermal toxicity in the rat, Ciba-Geigy Ltd, 954013, 1995-04-21

- Magnusson-Kligman Maximisation Test in Guinea Pigs for Delayed Skin Sensitisation Potential, Inveresk Research, 19323, 2001-04-02

 

Assessment of the toxicokinetic behavior of the Triethanolamine, CAS 102-71-6

 

1. Physico-chemical properties

TEA (MW 149.2 g/mol) is a liquid with a measured melting point of 20.5°C, a measured boiling pointof 336.1°C at 1013.25 hPa, a measured vapour pressure of 0.00029 hPa at 21°C, and a dissociation constant (pKa) of 7.86 at 25°C. The octanol-water partition coefficient (log Pow) is -2.3at 25°C, and the substance is fully miscible with water.

 

2. Data from acute and repeated dose toxicity studies

Acute toxicity data indicate low toxicity: in rats the oral LD50 was 6400 mg/kg body weight, no mortality was observed at or below 5000 mg/kg body weight. Clinical signs (elevated respiration, anancasm to chew, apathy, reduced grooming) disappeared 2 days after dosing, and gross pathology at necropsy revealed no abnormalities (BASF AG, 1966). In an acute dermal toxicity study in rabbits, no mortality was observed up to the limit concentration and the LD50 was established to be > 2000 mg/kg body weight (TSCATS, 1989). Due to its extremely low vapor pressure, exposure to TEA vapor is very unlikely. One report stated that whole-body exposure of rats to an atmosphere saturated with TEA vapor (concentration not given) at 20°C for 8 hours failed to cause any deaths, therefore no LC50 value was established (BASF AG, 1966).

 

In an oral repeated dose study, rats were administered 0 - 1000 mg/kg body weight/day in the diet for 91 days. Since no adverse effects were observed, the NOAEL was established to be 1000 mg/kg body weight/day (TSCATS, 1989). In a sub-chronic dermal toxicity study, rats were treated with 0 - 2000 mg/kg body weight/day on the skin for 90 days (Battelle Columbus Laboratories, 1987a). At the highest doses, decreases in body weight, irritation and inflammation at the site of application were observed - ranging from minimal acanthosis at the lower doses to chronic active inflammation, erosion and ulceration in higher dose groups - accompanied by hematologic changes. NOAELs for local effects were determined to be 125 and 250 mg/kg body weight/day for males and females, respectively. The NOAEL for systemic effects was established at 125 mg/kg body weight/day, based on renal effects (i.e. increased kidney weight). Similar effects were observed in a sub-chronic dermal toxicity study in mice, receiving 0 - 4000 mg/kg body weight/day TEA on the skin for 90 days (Battelle Columbus Laboratories, 1987b). The kidneys were identified as the target organ at lower doses, accompanied by increased liver weights at the top dose level. Dermal irritation and inflammation was noted at the site of application. In an 28 -day inhalation toxicity study in rats, exposed to 0 - 0.5 mg/L TEA for 6 hours/day and 5 hours/week, the NOAEC for systemic effects was established at 0.5 mg/L since no adverse systemic effects were observed. The NOAEC for local effects (laryngeal inflammation) was determined to be 0.02 mg/L for females; since slight inflammation was still observed in males, this concentration was designated the LOAEC for local effects in males (BASF AG, 1993).

 

3. Absorption, distribution, metabolism, excretion

Studies in experimental animals indicated that TEA is absorbed through the skin. No data on oral and inhalation exposure is available. Besides data regarding the dermal route, data on the i.v. route is also available. Differences in the rate of absorption between rats and mice have been described regarding dermal exposure. In mice, most of the topically applied ¹⁴C-TEA is absorbed, and only 2% to 11% is detected at the site of application after 48 hours (Dow 1988, 1989; Stott, 2000). The dermal absorption of TEA in rats was less extensive and much slower than in mice (Dow, 1988, 1989). An absorption, distribution, metabolism, and excretion study by the NTP (2004) found that after 72 hours of exposure, only 20% to 30% of the applied dermal dose of TEA (68 or 276 mg/kg) was absorbed in rats and 60% to 80% was absorbed in mice (79 or 1120 mg/kg). These differences in absorption have been attributed either to the different doses used in comparative studies or to species-specific factors. No differences in tissue distribution were noted after i.v. or dermal exposure (NTP, 2004).

The elimination of¹⁴C-TEA-derived radioactivity from the blood of mice after a 1 mg/kg intravenous injection displays two-phase elimination kinetics with an initial rapid distribution phase (0.3-0.6 hour half-life) followed by a slower elimination phase (10-hour half-life) (Dow, 1988,1989; Stott, 2000).Radioactivity in blood after dermal application of 2000 mg/kg neat TEA declined in a bi-exponential manner through 3-hour post-dosing with a rapid initial phase (half-life of 1.9 hr) followed by a slower terminal phase (half-life of 31 hr) (Stott, 2000).Both rats and mice rapidly excreted the absorbed dose, primarily in urine (followed by feces) after i.v. and dermal exposure. Regarding dermal exposure, in rats, less than 1% of the dose was present in the tissue samples (except the dose site) 72 hours after treatment; the heart, kidney, liver, lung, and spleen contained elevated concentrations of radiolabel relative to blood (NTP, 2004).

 

In addition to animal studies, human skin penetration of TEA was tested in vitro using diffusion cell techniques (Kraeling, 2003). Oil-in-water emulsions containing 1% or 5% ¹⁴C-TEA were added to the stratum corneum side of 200-300 µm thick human skin sections and penetration of radioactivity into and through the skin (into a receptor fluid, sampled up to 24 hours after application) was determined. At pH 8.0, 1.1 and 1.2% of the dose was absorbed into the receptor fluid with a total penetration of 22.0 and 16.5% for 1 and 5% TEA, respectively. At pH 7.0, 0.43 and 0.28% was absorbed into the receptor fluid with a total penetration of 9.8 and 5.8% after 24 hours for 1 and 5% TEA, respectively. After 48 hours at pH 7.0, 0.68 and 0.60% was absorbed into the receptor fluid with a total penetration of 9.6 and 6.9%, for 1 and 5% TEA respectively. This pH-related difference reflects the higher percentage of unionised test material pH 8.0.