2,4-bis(((2-(dimethylammonio)ethyloxy)carbonyl)phen-2-ylazo)benzene-1,3-diolbis(methanesulfonate)

Endpoint summary

Description of key information

Short description of key information on absorption rate: 
The dermal absorption rate of the test substance in rats is considered to be 1.25% at maximum. Furthermore, the results of this study clearly indicate the saturation of penetration with increasing dose (BASF AG, 1999).

Additional information

The data discussed in this section were derived from toxicity studies with the hydrochloride of the same azo dye (read-across to Basisch Gelb 8511, CAS 118208-02-9).

Basisch Gelb 8511 (CAS No. 118208 -02-9) represents the hydrochloride of an azo dye with an intrinsic orange color. Basic yellow 8511 is well soluble in water; the log Pow is -2.58 (25°C; pH 3.8).

According to an OECD TG 417 study the dermal absorption rate of Basisch Gelb 8511 in rats is considered to be 1.25% at maximum. Furthermore, the results clearly indicate the saturation of skin penetration with increasing dose (BASF AG, 1999).

Based on the available physical and chemical information on the test substance and the results from other toxicological studies the following additional assumptions about the toxicokinetic behaviour can be made:

In a study on the acute dermal toxicity in the rat at a dose level of 2000 mg/kg no evidence for a significant dermal absorption of Basisch Gelb 8511 was observed (BASF AG, 1990). This result is supportive of the low dermal absorption rate determined in the above-mentioned dermal absorption study in rats (BASF AG, 1999).

There is evidence for the systemic availability of Basisch Gelb 8511 after oral administration in rats based on the results from the acute oral toxicity study (BASF AG, 1990), and both from the 28-day and the 90-day repeated dose toxicity study by oral gavage (BASF AG, 1991 & 1999). In the acute oral toxicity study a discoloration of the urine was observed on the first two days after administration of the test substance. The discoloration of the urine was also observed in all dose groups of the 28-day repeated dose study (dose levels: 0, 20, 60, 180 mg/kg body weight) and in the mid and high dose groups of the 90-day repeated dose study. These findings prove the systemic availability of Basisch Gelb 8511 as well as its renal elimination. Already on the second day of the post-exposure observation period of the acute and the 28-day studies no more urine discoloration was observed. This leads to the assumption that a fast elimination of Basisch Gelb 8511 occurs.

Due to the chemical structure of Basisch Gelb 8511 the following metabolic reactions are theoretically possible:

1) Reductive splitting of azo bonds (pre-systemic, systemic)

2) Hydrolysis of ester bonds

3) N-dealkylation

4) Conjugation reactions at the phenolic OH-groups

Based on the results of the repeated dose toxicity studies, the low log Pow value as well as the charged structure the bioaccumulation of Basisch Gelb 8511 seems to be rather improbable.

Discussion on absorption rate:

The data discussed in this section were derived from toxicity studies with the hydrochloride of the same azo dye (read-across to Basisch Gelb 8511, CAS 118208-02-9).

A dermal absorption study according to OECD TG 417 was available for assessment (BASF AG, 1999).

¹⁴C-BASISCH GELB 8511 diluted in an acetate buffer (0.080; 0.016; 0.0032 mg/cm²; corresponding to 0.80, 0.16 and 0.032 mg/animal and about 3.8, 0.7 and 0.2 mg/kg body weight) was administered dermally to the back shoulders of rats. Animals were exposed for 8 hours and sacrificed 72 hours after beginning of exposure.

Mean recoveries of radioactivity from all dose groups were in the range of 90.34 - 96.12% of the total radioactivity administered. The largest portion of radioactivity was recovered from the skin wash (>76%). Whereas 1.25% of the applied radioactivity was absorbed at maximum at the low dose level, relative absorption decreased to about 0.85% at the intermediate dose level and to about 0.39% at the high dose level. These results clearly indicated saturation of penetration with increasing dose.