5,5'-(1H-isoindole-1,3(2H)-diylidene)dibarbituric acid

Endpoint summary

Description of key information

The substance is considered to be too poorly soluble for systemic uptake. This is supported by absence of toxicity in all available toxicity studies.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The toxicokinetic assessment is based on experimental data on physico-chemical properties and toxicological properties of Pigment Yellow 139 and its semi-condensate Pigment Yellow 185. Pigment Yellow 139 contains two barbituric acid moieties whereas Pigment Yellow 185 contains only one. The other moiety is the open, not fused “semi-condensate” form. An overview on the properties is given in the tables below.

As can be expected from the chemical structures, both pigments have a similar molecular weight (368 and 337 g/mol), and a similar relative density. They decompose at temperatures > 380°C prior to melting. Both Pigment Yellow 139 and 185 fulfill the criteria of a poorly soluble nanomaterial.

Both are of very low solubility in both water and octanol. From these solubilities, a Low P_OW of 0.31 was calculated for Pigment Yellow 139.

Insoluble pigment particles may form stable dispersions under certain conditions. This is assessed via the OECD testing guideline 318 for environmental media. Pigment Yellow 139, at any of the time points mentioned in the OECD guideline 318, the influence of Ca2+ is critical. Under conditions of high water hardness (10 mM Ca 2 +), agglomeration is observed.

After 6h, the samples showed high dispersion stability in 0 mM Ca, intermediate stability in 1 mM Ca at pH 7. The dispersion stability in at all other conditions was low.

After 24 hours the dispersion stability in 0 mM Ca remained high. For the samples in 1 and 10 mM Ca the dispersion stability was low.

 

Both general poor solubility and unflexible form impair transport across biological membranes. Absence of systemic uptake was indirectly seen by absence of toxicity in any of the available toxicity studies. Also no test-item induced coloration of internal tissues was observed upon necropsy after acute and subacute gavage dosing at the limit dose level.

 

Overall, systemic uptake after ingestion, inhalation and skin contact is not expected, but this information will be updated once all currently ongoing studies will have been completed.

 

Accordingly, metabolism and distribution cannot be considered and elimination is restricted to gastrointestinal passage. Inertness is also indicated from the very low toxicity upon intraperitoneal injection of a high dose (6400 mg/kg bw) of Pigment Yellow 139. During the one-weak observation period, no animal died.

 

Should any substance be taken up, bioaccumulation is not possible since the substance is not soluble in fat.

	PY 139	PY 185
	36888-99-0	76199-85-4
Molecular weight	367.27 g/mol	337.29 g/mol
State of the substance at 20°C and 101.3 kPa	orange powder	yellow powder
Melting point	>460°C at 1013 hPa	Decomposes at 380°C before melting.
Boiling point	Not applicable (decomposes before boiling)	Not applicable (decomposes before boiling)
Relative densitiy	1.73 g/cm³	1.50 g/cm³
Vapour pressure	0.000001 hPa	< 0.000001 hPa
Log Pow (calculated from solubilities)	0.31
Water solubility	2.9 µg/L	< 10 µg/L
n-octanol solubility	5.9 µg/L	< 0.3 mg/L
Surface tension	Not surface active: The water solubility is below 0.1 mg/L.	Not surface active: The water solubility is < 1 mg/L.
Flash point	Not relevant	Not relevant
Auto flammability/self-ignition temperature	400°C at 1013 hPa	359°C at 1013 hPa
Flammability	Non flammable	Non flammable
Explosive properties	Non explosive	Non explosive
Oxidising properties	No oxidizing properties	No oxidizing properties
Dissociation constant	Not applicable	Not applicable

	PY 139	PY 185
	36888-99-0	76199-85-4
Skin and eye irritation	Not irritating K1	Not irritating K2/1
Skin sensitzation	Not sensitizing K1	Not sensitizing K1
acute oral tox (LD50 in mg/kg bw)	> 10000 K2 no mortality	> 5000 K1 no mortality
acute dermal tox (LD50 in mg/kg bw)	> 2500 K2 no mortality
acute inhalation tox		LC50 > 5.42 mg/L K1 no mortality
Repeated dose toxicity (oral)		NOAEL = 1000 K2 (OECD 407)
Bacterial mutagenicity	Non mutagenic K2	Non mutagenic K1
Clastogenicity in vitro		Non clastogenic K1
Mutagenicity in mammalian cells in vitro	Non mutagenic K1
Genetic toxicitiy in vivo - micronucleus test	Non genotoxic K1
Toxicity to reproduction (OECD 421)	NOAEL = 1000 K1
Teratogenicity in rabbits		Ongoing with doses of 100, 300 and 1000 mg/kg bw
Teratogenicity in rats
In-vitro reactivity of cultivated macrophages	release of LDH and H2O2	release of LDH and H2O2
Repeated-dose toxicity (inhalation)