exploitation of the vast knowledge on biota, ranging from their behavior, physiology, metabolism, reproduction, and genetic peculiarities to community dynamics
and ecosystem functions when interacting with their habitat. Non-standardized tests
may thus be best suited to elucidate toxicity mechanisms or describe pertinent
environmental consequences of spreading potentially toxic nanoparticles. In comparison, standardized tests are limited to easily culturable organisms exposed under
well-defined conditions, using a limited number of rather crude endpoints. The
advantages of using standardized tests are that the results can easily be compared
with those obtained for other chemicals, which in turn permits hazard classification,
and that standardized test results can easily be used for product documentation when
chemicals are used in commercial products requiring approval regarding possible
negative environmental effects.
28.4.1 Standardized Testing Methods
OECD and ISO have published a number of test guidelines (TGs) that describe in all
details how chemicals testing for approval of new chemicals should be conducted.
These tests have been developed for soluble chemicals and have not taken into
account considerations that may be important for toxicity testing of nanoparticles.
Yet, the OECD has concluded that the approaches for testing and assessment of
traditional chemicals are in general appropriate for assessing nanomaterials, but that
the tests may have to be adapted to the specificities of nanomaterials (see ref.
OECD). This concerns, e.g., methods of sample preparation, particularly regarding
homogenization and distribution of the nanoparticles in the test media. Similarly,
adaptations may be needed for certain test guidelines.
The first step is the preparation of a stable suspension of nanomaterials (see
references in Hund-Rinke et al. 2016). This can be obtained through the use of
surface-active agents reducing the attractive forces between particles and causing
them to remain suspended in water or other media for a period of time that would
permit absorption or other interactions causing harm to the test organism. These
surfactants may themselves affect the test organisms, and thereby the test outcome,
and should therefore be included in control treatments.
It is a common requirement of standardized test guidelines that exposure concentrations should remain stable (often stated as no more than 20% deviation
between exposure concentrations and nominal concentrations) over the duration of
the test. This is a challenge with nanomaterials, which easily agglomerate and
sediment out of a water column (to mention the case of aquatic tests), exposing
pelagic organisms to lower concentrations and benthic organisms to higher concentrations than originally intended. Several factors influence the agglomerating and
settling behavior of particles, such as agitation of the test system, ionic strength, pH,
presence of specific ligands/chelating agents, and organic matter content of the
580
C. Coutris et al.
and ecosystem functions when interacting with their habitat. Non-standardized tests
may thus be best suited to elucidate toxicity mechanisms or describe pertinent
environmental consequences of spreading potentially toxic nanoparticles. In comparison, standardized tests are limited to easily culturable organisms exposed under
well-defined conditions, using a limited number of rather crude endpoints. The
advantages of using standardized tests are that the results can easily be compared
with those obtained for other chemicals, which in turn permits hazard classification,
and that standardized test results can easily be used for product documentation when
chemicals are used in commercial products requiring approval regarding possible
negative environmental effects.
28.4.1 Standardized Testing Methods
OECD and ISO have published a number of test guidelines (TGs) that describe in all
details how chemicals testing for approval of new chemicals should be conducted.
These tests have been developed for soluble chemicals and have not taken into
account considerations that may be important for toxicity testing of nanoparticles.
Yet, the OECD has concluded that the approaches for testing and assessment of
traditional chemicals are in general appropriate for assessing nanomaterials, but that
the tests may have to be adapted to the specificities of nanomaterials (see ref.
OECD). This concerns, e.g., methods of sample preparation, particularly regarding
homogenization and distribution of the nanoparticles in the test media. Similarly,
adaptations may be needed for certain test guidelines.
The first step is the preparation of a stable suspension of nanomaterials (see
references in Hund-Rinke et al. 2016). This can be obtained through the use of
surface-active agents reducing the attractive forces between particles and causing
them to remain suspended in water or other media for a period of time that would
permit absorption or other interactions causing harm to the test organism. These
surfactants may themselves affect the test organisms, and thereby the test outcome,
and should therefore be included in control treatments.
It is a common requirement of standardized test guidelines that exposure concentrations should remain stable (often stated as no more than 20% deviation
between exposure concentrations and nominal concentrations) over the duration of
the test. This is a challenge with nanomaterials, which easily agglomerate and
sediment out of a water column (to mention the case of aquatic tests), exposing
pelagic organisms to lower concentrations and benthic organisms to higher concentrations than originally intended. Several factors influence the agglomerating and
settling behavior of particles, such as agitation of the test system, ionic strength, pH,
presence of specific ligands/chelating agents, and organic matter content of the
580
C. Coutris et al.