Guidance on testing the environmental fate and effects of nanomaterials

The assessment of the environmental risks of nanomaterials in Australia will be conducted using the conventional risk assessment paradigm currently applied to all chemical substances, including industrial chemicals.

This risk assessment framework involves parallel evaluations of the environmental fate and effects of chemical substances according to harmonised international test guidelines, followed by a risk characterisation step[1] (Environment Protection and Heritage Council (EPHC), 2009).

The unique properties of nanomaterials may present new challenges, including technical issues to do with the applicability of harmonised test guidelines for chemicals.[2]

However, coordinated global activities by the OECD WPMN have identified critical strengths and weaknesses in the current test guidelines as they may apply to testing of the environmental fate and effects of nanomaterials.

The results of the Working Party's review and supporting scientific data for the behaviour of nanomaterials in aquatic systems provides a basis for general guidance on appropriate approaches to characterising the environmental fate and effects of industrial nanomaterials.

Environmental fate

The OECD test guidelines for environmental fate endpoints have each undergone a preliminary review by the WPMN for applicability to testing nanomaterials.3 According to this preliminary review, several existing test guidelines are applicable for testing the environmental fate of nanomaterials. However, the applicability of individual test methods depends on the behaviour of the nanomaterials in the environment, which in turn depends on the physical and chemical properties of nanomaterials in environmental media.

Based on a detailed evaluation carried out by the WPMN on test guidelines related to abiotic and biotic degradation, available tests seem to be applicable to the same extent for nanomaterials as for the comparable bulk materials. However, fully inorganic nanomaterials will not require testing in any of the biotic degradation tests. The conclusions of the WPMN on the current OECD test guidelines for biodegradability to nanomaterials is summarised in Table 1.

The potential for bioaccumulation of nanomaterials in aquatic organisms to be assessed using OECD TG 305 Bioconcentration: Flow-through Fish test may have some critical limitations in sole testing of bioaccumulation of nanoparticles. For example, it is likely that in most cases the size of nanoparticulate materials (one critical dimension in the range 1 to 100 nm) limits the uptake of these particles through membranes in fish compared to standard molecular chemical substances. Nevertheless, this test provides a valuable starting point for assessing bioaccumulation potential in aquatic organisms.

Table 1: OECD international guidelines for assessing biodegradability— applicability for nanomaterials

OECD test guideline

Limitations

Applicability for nanomaterials

OECD 301A DOC die way

Test substance has to be soluble, non-volatile, not sorbed to vessel or sludge and non-toxic at test concentration

In principle not applicable as the nanomaterial has to be soluble.

OECD 301B CO2 evolution test

Test substance must be non-volatile and non-toxic at test concentration.

Applicable, but higher test material concentration needed—for example, compared to OECD 310 (2–40 mg C/L).

Measures mineralisation.

OECD 301C Modified MITI Test

Test substance has to be non-toxic at test concentration, subject to interference from nitrification.

In principle applicable, but high conc. Needed.

OECD 301D Closed bottle test

Test substance has to be non-toxic at test concentration, subject to interference from nitrification.

In principle applicable.

OECD 301E Modified OECD screening test

Test substance has to be soluble, non-volatile, not sorbed to vessel or sludge and non-toxic at test concentration

In principle not applicable as the nanomaterial has to be soluble.

OECD 301F Manometric respirometry test

Test substance has to be non-toxic at test concentration, subject to interference from nitrification.

In principle applicable, high conc.

OECD 310 (Headspace test)

Test substance must be non-toxic at test concentration (pH 2 for analysis of CO2).

Applicable, test material need not be soluble; carriers can be used.

Measures mineralisation.

Simulation tests for freshwater (marine) and sediment systems

OECD 308 Aerobic and anaerobic transformation in aquatic sediment systems

Simulates suspended sediment only. Test substance has to be non-toxic, non-volatile and soluble. Site specific with respect to sediment. Sorption to sediment may be misleading if 14C not used.

Applicable, but the bioavailability may limit degradation.

Measures mineralisation from labelled particles.

OECD 309 Aerobic mineralisation in surface water

No comment

Applicable.

Measures mineralisation from labelled particles.

Environmental effects

There are 13 OECD guidelines (see: www.oecd-ilibrary.org/environment/oecd-guidelines-for-the-testing-of-chemicals-section-2-effects-on-biotic-systems_20745761) for testing substances for adverse effects on various aquatic life, and these include tests for acute and chronic effects (Table 2). These guidelines have each been reviewed by the WPMN to evaluate their applicability to the testing of nanomaterials.3 In summary, it is likely that the ecotoxicity endpoints described in current test guidelines are applicable. These endpoints generally involve whole-organism responses that integrate many possible modes of toxicity and are thus also likely to be indicators of potential adverse effects of nanomaterials.

However, the WPMN review also highlighted a common challenge associated with applying these test guidelines to nanomaterials: that guidance on preparation, delivery, measurement, and metrology in all test guidelines is insufficient for the testing of nanomaterials. The OECD is coordinating efforts to refine and adapt this aspect of the test guidelines, in particular testing requirements for the environmental effects of nanomaterials. In the interim, it is recommended that the design and conduct of aquatic effects tests of nanomaterials be closely integrated with measurements of the physical and/or chemical properties of these materials. The particularly relevant properties that should be characterised relate to the colloidal stability and solubility of the nanomaterials under typical aquatic exposure conditions.

Table 2: List of OECD guideline tests for aquatic ecotoxicity reviewed for applications to nanomaterials

OECD test guideline

Description of test

201

Alga, Growth Inhibition Test

202

Daphnia sp. Acute Immobilisation Test

203

Fish, Acute Toxicity Test

204

Fish, Prolonged Toxicity Test

209

Activated Sludge, Respiration Inhibition Test

210

Fish, Early-Life Stage Toxicity Test

211

Daphnia magna Reproduction Test

212

Fish, Short-term Toxicity Test on Embryo and Sac-Fry Stages Test

215

Fish, Juvenile Growth Test

218

Sediment-Water Chironomid Toxicity Using Spiked Sediment Test

219

Sediment-Water Chironomid Toxicity Using Spiked Water Test

221

Lemna sp. Growth Inhibition Test

224

Determination of the Inhibition of the Activity of Anaerobic Bacteria Test

Reduction of Gas Production from Anaerobically Digesting (sewage) Sludge Test


[1] EPHC 2009, 'Environmental risk assessment guidance manual for industrial chemicals', Environment Protection and Heritage Council, Australia, p. 109, www.scew.gov.au/system/files/resources/bffdc9e9-7004-4de9-b94f-b758140dbc8c/files/cmgt-nchem-eragm-industrial-chemicals-200902.pdf>, accessed 28 October 2010.

[2] Batley GE & McLaughlin MJ 2010, 'Fate of manufactured nanomaterials', Australian environment. Bangor, Centre for Environmental Contaminants Research, CSIRO Land and Water, p. 76 <www.environment.gov.au/settlements/biotechnology/publications/manufactured-nanomaterials.html>, accessed 11 November 2010.

Last update 30 November 2016