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EC number: 236-675-5
CAS number: 13463-67-7
Dispersed microsized TiO2 is not chronically toxic to freshwater
invertebrates, such as Daphnia magna, up to at least 10 mg/L (EC50: > 10
mg/L, nominal). Considering the low solubility of microsized TiO2, it is
further concluded that microsized TiO2 is not toxic up to its solubility
limit. Several guideline studies of dispersed nanosized TiO2 indicate
that the chronic toxicity to aquatic freshwater invertebrates is also
low with NOEC values ranging from > 1 mg/L to ≥ 100 mg/L.
Campos et al. (2013) tested dispersions (1 and 10 mg/L, nominal)
of the TiO2 bulk material (Tiona AT 1, 200 nm, anatase) the age at first
brood, size of first brood, cumulative fecundity, body length of adult
females after 21 d and body length of adults at first maturity, and the
population growth rate of Daphnia magna were not affected in a
semi-static chronic toxicity tests according to OECD 202 (1981, and OECD
211). Derived unbounded 21 d NOEC values for these endpoints amounted ≥
10 mg/L (nominal) and ≥ 2.33 when based on measured concentrations of
Tiona AT 1. Results of additional non-standardised tests by Campos et
al. (2013) are not relevant for the hazard assessment of TiO2 because
the tests were performed under depleting food conditions, which are
expected to enhance daphnia sensitivity, or for a shorter test period
than recommended in OECD 211. One supporting study by Beim et al. (1982)
on the chronic toxicity of microsized TiO2 to Daphnia magna reveals some
toxic effects on the reproduction (30 d NOEC: ≥ 5-<10 mg/L) and survival
(30 d NOEC: 70 mg/L) of daphnids. However, since limited information on
test performance was provided, results from the study by Beim et al.
(1982) are considered supporting data.
Furthermore, transformation/dissolution data of different
microsized TiO2 materials indicate a low solubility in environmental
media as dissolved Ti concentrations after 28 d were below the
respective LOD/LOQ (< 0.11 / < 0.34 µg Ti/L).
Hence, chronic invertebrate tests with dispersed microsized TiO2 were
performed at TiO2 concentrations several magnitudes above the solubility
limit. Thus, it is further concluded that microsized TiO2 is not
chronically toxic to freshwater invertebrates up to its solubility
Data on marine organisms does not exist.
Campos et al. (2013) tested dispersions (1 and 10 mg/L, nominal)
of the nanosized TiO2 materials NM 103 (20 nm, rutile, hydrophobic
coating), NM 104 (20 nm, rutile, glycerin coating), and P25 (21 nm,
rutile-anatase) and the age at first brood, size of first brood,
cumulative fecundity, body length of adult females after 21 d, and the
population growth rate of Daphnia magna were not affected in
semi-static, chronic toxicity tests according to OECD 202 (1981); the
respective 21 d NOEC value amounted to ≥ 10 mg/L (nominal) for all
materials and ≥ 2.80, 3.12, and 2.70 mg/L when based on measured
dispersed concentrations of NM 103, NM 104 and P25.
The body length of adults after 21 d was not affected at 10 mg/L NM 103,
NM 104 or P25 compared to control organisms whereas the body length of
adult organisms at first maturity was reduced at 10 mg P25/L (nominal).
However, the endpoint body length of adults after 21 d is the
standardised endpoint recommended in OECD 211 to assess effects on
growth of D. magna. Furthermore, the observed effects of P25 on body
length of adults at first maturity do not influence age at first brood,
survival of adult organisms, and cumulative fecundity, and fitness
measurements such as population growth rate, i.e. endpoints that are
typically the most sensitive and also the most critical chronical
endpoints according to OECD 211 and ECHA Guidance on IR & CSA, Chapter
R. 7b (Version 3.0; February 2016). Thus, the respective 21 d NOECs of
NM 103, NM 104 and P25 for reproduction and growth of Daphnia magna
amount to ≥ 10 mg/L (nominal dispersed). Results of additional
experiments performed in this study are not considered for the hazard
assessment of nano-TiO2 because the tests were performed under depleting
food conditions, which are expected to enhance daphnia sensitivity, or
for a shorter test period than recommended in OECD 211.
Results of the study of Hund-Rinke et al. (2013) confirm that
dispersed nano-TiO2 is not chronically toxic to daphnids up to 5 mg/L
(nominal). In this study, daphnids were exposed to 1 and 5 mg/L
(nominal) dispersed n-TiO2 (P25, 21 nm) in five independent semi-static
limit tests (OECD 211) and the media were renewed daily or three times
per week. Unbounded 21 d NOEC values of ≥ 5 mg/L (nominal) were
determined for mortality, mobility and body length in all 5 experiments.
Unbounded 21 d NOEC values of ≥ 5 mg/L for reproduction were derived in
three of five experiments. However, reproduction was reduced by 10-16%
at 5 mg/L in two experiments resulting in a LOEC of 5 mg/L (nominal). A
NOEC should nevertheless not be derived from the latter two experiments
since the separation factor should not exceed 3.2 according to OECD 211.
Based on results of all five experiments by Hund-Rinke et al. (2013),
the toxic potential of nano-TiO2 is low for daphnids with the NOEC being
> 1 mg/L up to ≥ 5 mg/L.
In addition, a multigeneration study was performed by Hartmann et
al. (2019) according to OECD Guideline 211 to assess the long-term
toxicity of TiO2-NPs (NM-105) on Daphnia magna over several subsequent
generations. Daphnids were exposed to three concentrations (0.025, 0.05,
0.1 mg Ti/L) of pristine TiO2 NPs dispersed in ASTM reconstituted hard
water as well as three concentrations of wastewater effluent containing
Ti (originating from model STPs operated for 6-10 days in accordance
with OECD 303a). Neither pristine nor wastewater-borne TiO2 NPs caused
any significant effects on the reproduction (mean number of offspring),
adult mortality, body length and time to first brood of Daphnia magna,
and thus a NOEC ≥ 0.1 mg Ti/L (corresponding to ≥ 0.17 mg TiO2/L) was
derived for all six generations. Tested concentrations were however
selected based on environmental relevance, and testing was not performed
at the limit concentration of 10 mg/L (as specified in OECD TG 211).
Evaluating the available data of all five tests by Hund-Rinke et
al. (2013) as well as the results obtained by Hartmann et al. (2019),
and considering that Campos et al. (2013) did not observe effects on
reproduction at concentrations of 10 mg/L n-TiO2 (nominal, dispersed),
one may conclude that the long-term toxic potential of nano-TiO2 is low
Two studies on the chronic toxicity of nano-TiO2 to the epibenthic
and endobenthic freshwater organisms Chironomus riparius and Lumbriculus
variegatus exposed via the water phase, further indicate that the
long-term toxic potential of nano-TiO2 is low for aquatic invertebrates.
Although these tests are sediment tests, the organisms were exposed via
the water phase so that the respective results are relevant for
freshwater assessment. Schaefers et al. (2013) exposed Lumbriculus
variegatus to dispersions of the nanosized TiO2 material P25 (21 nm) by
direct addition to the overlaying water in a chronic sediment toxicity
test according to OECD guideline 225. The derived 28 d NOEC values for
biomass and reproduction of Lumbriculus variegatus were ≥ 100 mg/L
(nominal). Furthermore, Hund-Rinke et al. (2013) tested the chronic
toxicity of dispersions of the nanosized TiO2 materials P25 (anatase,
rutile, 21 nm) and Homibkat UV 100 (anatase, 8 nm) applied to the
overlaying water in a chronic sediment toxicity test according to OECD
219. Emergence and development rate of Chironomus riparius were not
affected resulting in 28 d NOEC values of ≥ 100 mg n-TiO2/L (nominal).
One supporting study on the chronic toxicity of nanosized TiO2 to the
freshwater clam Corbicula fluminea additionally indicates that nanosized
TiO2 is not chronically toxic up to 1 mg/L to freshwater invertebrates.
However, only one concentration was tested and the organisms were not
fed during the test so that results from this study are supporting data.
Data for marine organisms are not available.
In sum, dispersions of microsized TiO2 material are not
chronically toxic to freshwater invertebrates, such as Daphnia magna, up
to 10 mg/L (nominal). Considering the low solubility of microsized TiO2,
it is further concluded that microsized TiO2 is not chronically toxic up
to its solubility limit. The long-term toxic potential of dispersed
nano-TiO2 is also low for freshwater invertebrates with NOEC values
ranging from > 0.2 mg/L to ≥ 100 mg/L.
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