Diethyl phthalate

Toxicity to microorganisms

Description of key information

Microibial inhibition:  NOEC 20 mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

20 mg/L

Additional information

In accordance with REACH Regulation 1907/2008 Annex VIII Column 2, testing need not be undertaken if microbial toxicity is unlikely (if the substance is insoluble in water or if the substance is readily biodegradable). In a test of ready biodegradability the substance was found to be readily biodegradable. Waiving of the endpoint is thus justified.

A NOEC value has been asssigned based on the concentration used in the ready bidegradability test.

In a review of the aquatic toxicity of eighteen phthalate esters, Staples et.al. (Environmental Toxicology and Chemistry, Vol. 16(5): 875-89l, 1997) summarises published literature on phthalate esters, including diethyl phthalate. No details are available on methodology but the following results are cited:

Test species	Fresh/salt water	Measured/nominal concentration	Test duration	Endpoint/ criteria	EC50/LC50 (95%CL) (mg/L)	NOEC (LOEC) (mg/L)
Protozoa T. pyriformis	F	N	24 hours	Growth inhibition	-	50 (100)
Protozoa T. pyriformis	F	N	48 hours	Growth inhibition	132	50 (100)
Laboratory digester culture	F	M	5-193 hours	Anaerobic metabolic inhibition	-	100
Protozoa Entosiphon sulcatum	F	N	72 hours	5% inhibition of reproduction	-	- (19)
Bacteria P. phosphoreum	S	N	5-30 minutes	Light inhibition	111	-
Bacteria Pseudomonas putida	F	N	16 hours	3% inhibition of reproduction	-	- (400)
Protozoa Uronema parduczi	F	N	20 hours	5% inhibition of reproduction	-	- (48)

This supports the view that the substance is not significantly toxic to microorganisms and that the assigned NOEC is conservative.