Calcium oxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

September 6, 2007 - September 10, 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP study according to OECD 203. No. of replicates per concentration used = 1. Rationale for read-across: in the environment, lime substances rapidly dissociate or react with water. These reactions, together with the equivalent amount of hydroxyl ions set free when considering 100mg of the lime compound (hypothetic example), are illustrated below: Ca(OH)2 <-> Ca2+ + 2OH- 100 mg Ca(OH)2 or 1.35 mmol sets free 2.70 mmol OH- CaO + H2O <-> Ca2+ + 2OH- 100 mg CaO or 1.78 mmol sets free 3.56 mmol OH- From these reactions it is clear that the effect of calcium oxide will be caused either by calcium or hydroxyl ions. Since calcium is abundantly present in the environment and since the effect concentrations are within the same order of magnitude of its natural concentration, it can be assumed that the adverse effects are mainly caused by the pH increase caused by the hydroxyl ions. Furthermore, the above mentioned calculations show that the base equivalents are within a factor 2 for calcium oxide and calcium hydroxide. As such, it can be reasonably expected that the effect on pH of calcium oxide is comparable to calcium hydroxide for a same application on a weight basis. Consequently, read-across from calcium hydroxide to calcium oxide is justified.

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

yes

Remarks:

No pH adjustment in test medium

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

TEST MEDIUM
- samples were taken in duplicate of all test solutions and the control
- stored with minimum headspace above solution at ambient temperature in plastic bottles
- sampling time points: at beginning of test and at the end of test immediately after determination of biological and physico-chemical parameters

Vehicle:

no

Details on test solutions:

- see 'Test medium' in table 1
- Evidence of undissolved material (e.g. precipitate, surface film, etc): With increasing test item concentrations, precipitates formed over time. The formation of precipitates is likely the result of the reaction between Calcium hydroxide and Carbon dioxide dissolved in the medium yielding poorly soluble Calcium carbonate. At the end of the test, precipitates were found to be difficult to release from the bottom of the test vessels.
- test item was weighed for each test vessel into a weighboat, added to 10L of temperature adapted test medium directly in the test tank and stirred vigorously for 1 minute. under stirring the pH was measured.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

- common name: rainbow trout
- source: Forellenzucht Trostadt GbR, 98646 Trostadt, Thüringen, Germany
- date of purchase: August 13, 2007
- additional information see 'Holding conditions' in table 1

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

not applicable

Hardness:

232 mg/L CaCO3

Test temperature:

15.0-15.5°C

pH:

7.6-11.1

Dissolved oxygen:

8.4-10.1 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

- see 'Nominal concentrations' in table 1
Nominal and measured concentrations were approximately similar.

Details on test conditions:

- see 'Test medium' and 'Holding conditions' in table 1

EXPOSURE CONDITIONS
− Amount of test solution per test vessel: 10 L
− Depth of test solution in the test vessels: 11.5 cm
− Number of fish per test vessel: 7
− Average length of fish: 4.8 ± 0.6 cm (n = 11)
− Average weight of fish: 1.2 ± 0.5 g (n = 11)
− Fish loading: 0.84 g per L
− Renewal of the test solution during the test period: none
− Feeding: none
− Photoperiod: light/dark - 12 h/12 h
− Light intensity: 100 - 1000 lx; measured: 255 ± 34 (SD) lx
− Temperature (min / max): 15.0 / 15.5 °C
− Aeration: permanent

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

50.6 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

mortality (fish)

Details on results:

- Behavioural abnormalities: no data
- Other biological observations: at 33.3 mg/L and higher an increased mucus production was observed. At 50 and 75 mg/L (initial pH 11.1) all fish showed whitish discoloration of the fins, probably due to severe corrosion.
- Mortality of control: no
- Other adverse effects control: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: the measured Ca concentrations were much below the nominal concentrations, due to the high concentration of Ca from CaCl2 already present in the test medium, and due to the reaction of the test item with CO2 to poorly soluble CaCO3, thus forming precipitates. However, measurement of Ca after acidification at the end of the test resulted in a recovery of 98% (58-122%).
- Initial pH values: 7.8 (control), 9.6 (14.8 mg/L), 9.9 (22.2 mg/L), 10.4 (33.3 mg/L), 10.8 (50 mg/L) and 11.1 (75 mg/L).

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

- probit analysis using linear maximum likelihood regression used to calculate LC50 values (statistical software package: ToxRat Professional 2.09 )
- polynomial regression analysis used to correlate biological effects with initial pH values (Microsoft Excel, 2003)

Validity criteria fulfilled:

yes

Remarks:

Mortality in the control: 0%. Dissolved oxygen concentration in control and test vessels: ≥84,8%.

Conclusions:

A clear concentration-response relationship was observed.
The biological findings were closely related to the initial pH of the test solutions. Therefore the initial pH is considered to be the main reason for the effects of the test item on the test organisms.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Acceptable, well-documented publication, which meets basic scientific principles. Rationale for read-across: in the environment, lime substances rapidly dissociate or react with water. These reactions, together with the equivalent amount of hydroxyl ions set free when considering 100mg of the lime compound (hypothetic example), are illustrated below: Ca(OH)2 <-> Ca2+ + 2OH- 100 mg Ca(OH)2 or 1.35 mmol sets free 2.70 mmol OH- CaO + H2O <-> Ca2+ + 2OH- 100 mg CaO or 1.78 mmol sets free 3.56 mmol OH- From these reactions it is clear that the effect of calcium oxide will be caused either by calcium or hydroxyl ions. Since calcium is abundantly present in the environment and since the effect concentrations are within the same order of magnitude of its natural concentration, it can be assumed that the adverse effects are mainly caused by the pH increase caused by the hydroxyl ions. Furthermore, the above mentioned calculations show that the base equivalents are within a factor 2 for calcium oxide and calcium hydroxide. As such, it can be reasonably expected that the effect on pH of calcium oxide is comparable to calcium hydroxide for a same application on a weight basis. Consequently, read-across from calcium hydroxide to calcium oxide is justified.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: Biological test method: Acute lethality test using Threespine stickleback (Gasterosteus aculeatus). Environment Canada, Ottowa, Ontario. Report EPS 1/RM/10. July, 1990 (Including March 2000 amendments).

Deviations:

not specified

Principles of method if other than guideline:

96h bioassay in natural seawater.

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

Water quality was measured daily (temperature, dissolved oxygen, salinity, pH).

Vehicle:

no

Details on test solutions:

Test solutions were prepared for the samples in natural seawater, aerated for 30 min, and initial water quality was measured.

Test organisms (species):

Gasterosteus aculeatus

Details on test organisms:

TEST ORGANISM
- Common name: Threespine stickleback
- Source: Lawrencetown, NS
- Mean wet biomass: 0.33 g +/- 0.12, N=20
- Fish were randomly introduced into test vessels.

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

not applicable

Hardness:

no data

Test temperature:

no data

pH:

7.93 (at control) - 10.51 (at highest test dose)

Dissolved oxygen:

no data

Salinity:

2.8-3.0%

Nominal and measured concentrations:

Nominal concentrations: 0, 32, 100, 320, 1000, 3200 mg/L

Details on test conditions:

Ten fish were randomly introduced into 20 L of each test concentration. The test was checked for mortalities frequently the first day, then once a day thereafter. Any dead fish were removed.

Reference substance (positive control):

yes

Remarks:

phenol

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

457 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Lime

Basis for effect:

mortality (fish)

Remarks on result:

other: 95% Cl: 262 - 785 mg/l

Details on results:

The pH was 7.91-7.94 in the control, but reached 10.40-10.61 in the 3200 mg/L dose group. There was no mortality in the control or in treatments up to 100 mg/L.
At 320 mg/L: 50% mortality, at 1000 mg/L: 70% mortality and at 3200 mg/L all fish died.

Results with reference substance (positive control):

A monthly reference toxicant test conducted with phenol ensured that normal operating conditions were maintained and that the population of fish used was of normal sensitivity.

Reported statistics and error estimates:

The NOEC was approximated from the concentrations resulting in <=10% mortality in fish.

Validity criteria fulfilled:

not specified

Conclusions:

In the current test with threespine stickleback, the 96h-LC50 for hydrated lime was 457 mg/L. Based on pH values measured at t=0 this is equivalent to 10.47 (10.26-10.52) pH units.

Description of key information

Klimisch 1 study: 96h-LC50 = 50.6 mg/L for calcium dihydroxide and this for the freshwater fish rainbow trout (Egeler et al., 2007)
Klimisch 2 study: 96h-LC50 = 457 mg/L for calcium dihydroxide and this for the marine species Gasterosteus aculeatus (threespine stickleback) (Locke et al., 2009)
Rationale for read-across: in the environment, lime substances rapidly dissociate or react with water. These reactions, together with the equivalent amount of hydroxyl ions set free when considering 100mg of the lime compound (hypothetic example), are illustrated below:
Ca(OH)2 <-> Ca2+ + 2OH-
100 mg Ca(OH)2 or 1.35 mmol sets free 2.70 mmol OH-
CaO + H2O <-> Ca2+ + 2OH-
100 mg CaO or 1.78 mmol sets free 3.56 mmol OH-
From these reactions it is clear that the effect of calcium oxide will be caused either by calcium or hydroxyl ions. Since calcium is abundantly present in the environment and since the effect concentrations are within the same order of magnitude of its natural concentration, it can be assumed that the adverse effects are mainly caused by the pH increase caused by the hydroxyl ions. Furthermore, the above mentioned calculations show that the base equivalents are within a factor 2 for calcium oxide and calcium hydroxide. As such, it can be reasonably expected that the effect on pH of calcium oxide is comparable to calcium hydroxide for a same application on a weight basis. Consequently, read-across from calcium hydroxide to calcium oxide is justified.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

50.6 mg/L

Marine water fish

Marine water fish

Effect concentration:

457 mg/L

Additional information

The short-term toxicity study with the freshwater fish rainbow trout (Egeler et al., 2007) was executed according to OECD 203, resulting in a Klimisch 1 score. The biological findings (LC50 = 50.6 mg/L) were closely related to the initial pH of the test solutions. Therefore the initial high pH is considered to be the main reason for the effects of the test item on the fish.

The short-term toxicity study with the marine species Gasterosteus aculeatus Linnaeus (threespine stickleback) (Locke et al., 2009) was well described and a dose-response relationship was established (LC50 = 457 mg/L). However, the study was not carried out according to GLP, resulting in a Klimisch 2 score.

The acute toxicity to fish of calcium carbonate (nano) was assessed in a study performed according to OECD TG 203 under GLP (Priestly, 2010). In this study Oncorhynchus mykiss (rainbow trout) were exposed to a 100 %v/v saturated solution of calcium carbonate. No mortalities or adverse effects were noted at the concentration tested. Hence the 96-h LC50 for calcium carbonate (nano) was found to be >100% v/v saturated solution and the NOEC was 100% v/v saturated solution.

The concentration of calcium carbonate (nano) that might cause acute toxicity is therefore greater than the maximum solubility of calcium carbonate in water.

Based on the results of the studies performed on the read-across substance calcium dihydroxide and on calcium carbonate, it may be concluded that the acute toxicity to fish of grades of calcium oxide containing up to 35% calcium carbonate will be driven by the calcium oxide content and hence the results available for the read-across substance calcium dihydroxide represent the worse-case for all grades of calcium oxide.