Phthalic acid

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Principles of method if other than guideline:

Method is in most parts equivalent to the OECD TG 201

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The stability of the test substance was experimentally determined
with HPLC before and after an exposure of 72 hours

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Duration:

72 h

Dose descriptor:

EC0

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

results with pH adjustment

With pH adjustment, the recovery rate was > 98 %, 
therefore the nominal  value was reported. The result is related 
to both endpoints growth rate  and biomass. 
Without pH adjustment at 100 mg/l 100 % inhibition was observed 
after 72  hours; pH was determined to be in the range of 4.9 to 5.1.

Validity criteria fulfilled:

yes

Executive summary:

On Desmodesmus subspicatus two limit tests were conducted each with 100 mg/l with and without pH adjustment. The 72 h-EC0 was >/= 100 mg/l with pH adjustment. The results are related to both endpoints growth rate and biomass (Bayer Industry Services, 2004).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

unsuitable test system

Principles of method if other than guideline:

Method: other: Growth inhibition test

GLP compliance:

not specified

Analytical monitoring:

no

Test organisms (species):

other: other algae: Scenedesmus sp. and Microcystis sp.

Test type:

static

Water media type:

freshwater

The inhibitory effect on the growth of Scenedesmus sp. of rotted  materials 
(on average):
 2-days: 57%
 8-days: 49%
14-days: 41%
21-days: 42%
For Microcystis sp., an antialgal effect of the 2-day rotted materials of  
93% (on average) is reported.
The antialgal effect decreased relative to the rotting time flow for both
  algae.
One of the inhibitory chemicals, released from the rotted plants, was  
identified as 1,2-benzenedicarboxylic acid (o-phthalic acid).

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: It is not clear whether the algae were within the exponential growth throughout the whole exposure period of 7 days

Principles of method if other than guideline:

Method: other: modified to ISO 8692

GLP compliance:

not specified

Analytical monitoring:

no

Test organisms (species):

other: other algae: Scenedesmus subspicatus CHODAT

Test type:

static

Water media type:

freshwater

Limit test:

no

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

258 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Endpoint biomass: 7 d EC50: 506 mg/l
RM-Freetext:
Accepted new scientific name for Scenedesmus subspicatus:
Desmodesmus subspicatus.

Description of key information

On Desmodesmus subspicatus two limit tests were conducted each with 100 mg/l with and without pH adjustment. The 72 h-EC0 was >/= 100 mg/l with pH adjustment. The results are related to both endpoints growth rate and biomass (Bayer Industry Services, 2004).

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

Algal toxicity was determined by a GLP test with Desmodesmus subspicatus in the presence of phthalic acid according to the EU Method C.3 "Algal Inhibition Test" wich is in most parts equivalent to the OECD Guideline 201 “Alga Growth Inhibition Test”. Two limit tests were conducted each with 100 mg/l with and without pH adjustment. The stability of the test substance was experimentally determined via HPLC before and after an exposure of 72 hours. The 72 h-EC0 was >/= 100 mg/l and the recovery rate was > 98 %, therefore the nominal value was reported. The results are related to both endpoints growth rate and biomass. Without pH adjustment at 100 mg/l 100 % inhibition was observed after 72 hours; pH was determined to be in the range of 4.9 to 5.1. This indicates that phthalic acid causes a pH shift in algal medium. It is the resulting pH that determines the impact of phthalic acid on algae as shown with buffered test substance solution. Thus, toxic effects are not due to substance inherent properties but due to a function of the pH (Bayer Industry Services, 2004).