Citric acid

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was well documented and meets generally accepted scientific principles, but it was not conducted in compliance with GLP and no analytical monitoring was carried out.

Qualifier:

according to guideline

Guideline:

other: Bringmann and Kuhn (1977)

Deviations:

not specified

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: dispersion, neutralised.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Common name: water flea

- Strain: Daphnia magna IRCHA

- Source: Laboratory culture

- Age at study initiation: <24h

- Feeding during test: not reported


ACCLIMATION

- Acclimation period: not reported

- Type and amount of food: dry algae

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

24 h

Test temperature:

ca. 20 °C

pH:

7.6-7.7

Dissolved oxygen:

Saturated oxygen levels in test water

Nominal and measured concentrations:

A range of concentrations to achieve three or more responses between 0 and 100% immobilisation. Details on concentrations tested not reported.

Details on test conditions:

TEST SYSTEM

- Test vessel: flask

- Size: 50 ml

- Aeration: none

- No. of organisms per vessel: 10

- No. of vessels per concentration: 2

- No. of vessels per control: 2



TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: standardised synthetic fresh water

- Intervals of water quality measurement: daily


OTHER TEST CONDITIONS

- Adjustment of pH: the test solution was neutralised.

- Photoperiod: 9h artificial light



EFFECT PARAMETERS MEASURED: immobility.

Reference substance (positive control):

not specified

Key result

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

1 535 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: P95%

Remarks:

1436-1641 mg/L

Duration:

24 h

Dose descriptor:

LC0

Effect conc.:

1 206 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

24 h

Dose descriptor:

LC100

Effect conc.:

2 083 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Reported statistics and error estimates:

Reported as standard statistical methods available at the time the study was conducted and analysis of EC50 on probit scale.

A test was also carried out without neutralisation of the test solution resulting in a higher toxicity of the test substance due to lower pH. The 24 h LC values with Daphnia magna in a non-neutralised solution were as follows:

LC0	73
LC50	85
LC100	98

Validity criteria fulfilled:

not specified

Conclusions:

A 24h EC50 of 1535 mg/L has been determined for the effects of the test substance in a neutralised test solution on immobility of the freshwater flea Daphnia magna.

Description of key information

Short-term toxicity to invertebrates: A number of publications are available indicating low short-term toxicity to inverebrates using a Weight of Evidence approach

Freshwater: EC₅₀ ca. 120 -1535 mg/L with Daphnia magna (Ellis 1937, as reported in OECD SIDS 2001, and Bringmann and Kuhn 1982, rel. 4 and 2 respectively).

Marine: EC₅₀ >50 to 160 mg/L with Dreissena polymorpha and Carcinus maenas (Cope et al. 1997 and Portman and Wilson 1971, both rel. 4).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1 535 mg/L

Additional information

Freshwater

A reliable 24h LC₅₀ value of 1535 mg/L has been determined for the effects of the test substance on immobility of Daphnia magna in a neutralised solution (Bringmann and Kuhn 1982). Although reported as an LC₅₀ value it can be considered analogous to an EC₅₀ value based on immobility; it is difficult to differentiate dead and immobile daphnids by visual inspection. The study reflects the lowest value that is available for this endpoint and is part of the weight of evidence for low toxicity of citric acid to the freshwater compartment.
A further freshwater invertebrate reliability 4 study indicates that citric acid is of low short-term toxicity and has been used in a weight of evidence approach:

Ellis (1937, as reported in European Chemical Bureau, IUCLID Dataset Citric Acid, 2000) determined a 72h EC₅₀ of ca. 120 mg/L for the effects of citric acid on immobility of the freshwater flea D. magna. It was not possible to access the original source and the study has been assigned reliability 4.

Khomenco et al. (1969, as reported in OECD SIDS 2001 on Citric Acid CAS 77-92-9) determined an EC₅₀ of 98 mg/L for the effects of citric acid on immobility of the freshwater flea D. magna, based on a geometric mean. The duration of the test is unkown and the original source could not be accessed (refernced in OECD SIDS 2001). In addition the conclusions are said to indicate that acidity is likely to be the cause of the effects seen. Therefore the study has not been taken into account in the assessment.

Marine

A reliable 48h EC₅₀ value of >50 mg/L has been determined for the effects of citric acid on substrate reattachment abilities of the zebra mussel Dreissena polymorpha (Cope et al. 1997). The study does not present a conclusive EC₅₀ (> value), however it has been selected as weight of evidence for low short-term toxicity to marine aquatic invertebrates.

A reliability 4 study (due to lack of information on the test methodology) indicates that citric acid is of low short-term toxicity to invertebrates in neutralised solutions:

Portmann & Wilson (1971) reported an LC₅₀ of 160 mg/L for the effects of citric acid on mortality of the crab Carcinus maenas.

Additionally, Nelson and Kursar (1999) report a 24 h LD₅₀ of 190-279 mg/L (three experiments) for the effects of citric acid on mortality of the marine invertebrate Artemia franciscana. Citric acid is a strong acid and there is no evidence that the pH of the test medium was neutralised. At a concentration of 200 mg/L it is estimated that the solution would have a pH <4. The test organisms are not expected to be significantly more sensitive than the freshwater species Daphnia magna, where an EC₅₀ of 1535 mg/L has been determined in a neutralised solution with citric acid. Therefore it is likely that effects reported are due to low pH. This study has not been selected as part of the weight of evidence approach.

In addition, a SafePharm 2006 study is reported in the CLH consultation on citric acid, indicating a 48 h EC50 value 34 mg/L. The study has been assigned reliability 1, however the pH is 8 in the controls and decreases with increasing citric acid concentrations, down to pH 4.1-4.2 at 100 mg/L. OECD 202 guidance indicates that "If the pH does not remain in the range 6-9, then a second test could be carried out, adjusting the pH of the stock solution to that of the dilution water before addition of the test substance.", therefore the study deviates from the guidance. The outcome of the study is likely to have been negatively affected by the pH of the medium and the results are disregarded by the current reviewer.

Access to the report has not been purchased, for details please refer to the CLH consultation here https://echa.europa.eu/documents/10162/c721decb-298f-92a3-b425-55cbf9c6cc9b [accessed January 2019]