Fumes, silica

Toxicity to microorganisms

Administrative data

Endpoint:

toxicity to microorganisms

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-standard test methods used

Data source

Reference

Reference Type:

publication

Title:

Comparative eco-toxicity of nanoscale TiO2, SiO2, and ZnO water suspen-sions,

Author:

Adams, L.K. Lyon D.Y. and Alvarez, P.J.J,

Year:

2006

Bibliographic source:

Water Research, 40: 3527–3532.

Materials and methods

Principles of method if other than guideline:

Toxicity of silicon dioxide particles was studied in water suspensions on Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Colonies were counted and compared to control plates to calculate percentage growth inhibition. All treatments were prepared in duplicate and repeated on three separate occasions.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Automatically generated during migration to IUCLID 6, no data available

IUPAC Name:

Automatically generated during migration to IUCLID 6, no data available

Details on test material:

Silicon dioxide particles, 14 nm, 930 nm, and 60 µm initial particle size (Sigma-Aldrich) Actual particle size range in water was: initially 14 nm led to observed range 135–510 nm (average 205 nm), 930nm to 380–605 nm (aver. 480 nm) and 60 µm to range 10–75 µm, (aver. 47µm)).

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

not specified

Details on test solutions:

E. coli DH5a and B. subtilis CB310 (courtesy of Dr. Charles Stewart, Rice University, Houston, TX) were maintained on Luria–Bertani (LB) plates. For all experiments, the bacteria were cultivated in a minimal Davis medium (MD). MD is a variation of Davis medium in which the potassiumphosphate concentration was reduced by 90%. This medium consisted of 0.7 g K2HPO4, 0.2 g KH2PO4, 1 g (NH4)2SO4, 0.5 g Nacitrate, 0.1 g MgSO4 7H2O, and 1 g glucose in 1 l of Milli-Qs at pH 7.0. MD medium was chosen as the antibacterial test medium as previous research has shown that other nanosized aggregates precipitate out of suspension in media containing high phosphate concentrations

Test organisms

Test organisms (species):

Bacillus subtilis

Details on inoculum:

toxicity of silicon dioxide particles, in water suspensions on Gram-positive Bacillus subtilis and Gram-negative Escherichia coli in light and dark conditions

Study design

Test type:

static

Water media type:

not specified

Limit test:

no

Test conditions

Test temperature:

37 Celsius

pH:

7

Details on test conditions:

Cultures were diluted to achieve cell concentrations of approximately 103 CFU/ml, spread onto LB plates, and left to grow at 36 1C
for 14–20 h.

Reference substance (positive control):

not specified

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

20 h

Dose descriptor:

EC100

Effect conc.:

5 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(averege size: 205 nm)

Basis for effect:

other: growth inhibition Addition of SiO2 at 5000ppm resulted in 99% growth reduction of B. subtilis

Effect concentrations 2

Duration:

20 h

Dose descriptor:

EC50

Effect conc.:

5 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(averege size: 205 nm)

Basis for effect:

other: growth inhibition At 5000 mg/l a 48% reductionof E. coli.

Details on results:

The particles were harmful to varying degrees, with antibacterial activity increasing with particle concentration. Advertised particle size did not correspond to true particle size in the test system. Apparently, aggregation produced similarly sized particles that had similar antibacterial activity at a given concentration. Actual particle size range in water was: initially 14 nm led to observed range 135–510 nm (average 205 nm), 930nm to 380–605 nm (aver. 480 nm) and 60 µm to range 10–75 µm, (aver. 47µm)). Relatively high concentrations were required to achieve a reduction in cell growth. Addition of SiO2 (aver size 205 nm) at 5000ppm resulted in 99% growth reduction of B. subtilis and 1000 ppm to 7 ± 4.7%. At 5000 mg/l a 48% reduction and at 500 mg/l reduction of 15±6.4 % of E. coli was observed.