Chromium (III) oxide

Toxicity to terrestrial plants

Administrative data

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remarks'

Remarks:

Several methodological shortcomings and insufficient documentation render the study not reliable: No analytical verification of test substance in soil, uncharacterized substrate used pre-growth and uncontrolled 4-month pre-growth phase, test substance applied as highly soluble salt with no information on soil equilibration, insufficient data on growth conditions (pH, temperature, fertilization). In addition, the highly acidic soil (pH 4.4) used in this study and the selected species (hyperaccumulator plant) are of limited relevance for risk assessment.

Data source

Reference

Reference Type:

publication

Title:

Phytotoxicity and phytoaccumulation of trivalent and hexavalent chromium in brake fern

Author:

Su, Y. et al.

Year:

2005

Bibliographic source:

Environmental Toxicology and Chemistry, Vol. 24, No. 8, pp. 2019-2026, 2005

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

In a phytoremediation experiment, four to five months old Chinese brake fern (Pteris vittata) plants were transplanted to metal-treated soil, grown outside and harvested after four weeks. Plant biomass was determined and plant chromium concentrations were measured via ICP-AES. In addition, morphological changes on a cellular level were measured by means of scanning electron microscopy.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 003

Cas Number:

10060-12-5

Molecular formula:

CrCl3.6H20

Sampling and analysis

Analytical monitoring:

yes

Remarks:

extraction methods not reported

Test substrate

Vehicle:

no

Details on preparation and application of test substrate:

Nominal concentrations of the respective Cr salts, i.e. 0, 250, 500, 750 and 1000 mg/kg were ground and gradually mixed with air-dried soil.

Test organisms

Species:

other: Pteris vittata

Plant group:

Cryptogamae, vascular (ferns and allies)

Details on test organisms:

- Common name: Brake fern
- Age at test initiation: adult plants, 4-5 months age

Study design

Test type:

vegetative vigour test

Study type:

semi-field study

Substrate type:

natural soil

Total exposure duration:

1 mo

Test conditions

Nominal and measured concentrations:

Nominal concentrations: 0, 100, 250, 500, 750 and 1000 mg Cr(III)/kg, applied as CrCl3*6 H2O. Final measured concentrations of chromium in treated soils: 47.6 (nominal 0), 295 (nominal 250), 567 (nominal 500), 593 (nominal 750) and 729 (nominal 1000) mg/kg. No information on soil equilibration and extraction method is given.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Species:

other: Pteris vittata

Duration:

23 d

Dose descriptor:

NOEC

Effect conc.:

>= 729 mg/kg soil dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Basis for effect:

other: biomass growth

Remarks on result:

other: total Cr

Effect concentrations 2

Species:

other: Pteris vittata

Duration:

23 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

other: biomass growth

Remarks on result:

other: added concentration

Any other information on results incl. tables

No significant negative effects of the chromium treatment on P. vittata growth (dry biomass) were observed up to a nominal concentration of 1000 mg Cr/kg (highest concentration tested). Effects on plant relative water content could be observed, however without considering osmotic effects potentially caused by the addition of high salt concentrations.

Applicant's summary and conclusion

Conclusions:

In a phytoremediation experiment, 4 to 5 months old Chinese brake fern (Pteris vittata) plants were transplanted to metal-treated soil, grown outside and harvested after 4 weeks. No significant negative effects of the chromium treatment on P. vittata growth (dry biomass) were observed up to a nominal concentration of 1000 mg Cr/kg (highest concentration tested). Effects on plant relative water content could be observed, however without considering osmotic effects potentially caused by the addition of high salt concentrations.

However, results need not be considered carefully since several methodological shortcomings and insufficient documentation render the study not reliable: No analytical verification of test substance in soil was performed. The substrate used pre-growth is not specified and the 4-month pre-growth phase was not under controlled conditions. The test substance was applied as a highly soluble salt with no information on soil equilibration. Further, insufficient data on growth conditions (pH, temperature, fertilization) is provided. In addition, the highly acidic soil (pH 4.4) used in this study and the selected species (hyperaccumulator plant) are of limited relevance for risk assessment.