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EC number: 236-675-5
CAS number: 13463-67-7
Sediment toxicity tests reveal that microsized TiO2 is not
chronically toxic to sediment organisms up to concentrations of at least
100,000 and 14,989 mg/kg dw (nominal) in freshwater and marine sediment,
respectively. Two sediment-spiked toxicity tests and three water-spiked
sediment toxicity tests further point to a low toxic potential of
nanosized TiO2 for freshwater epi- and endobenthic organisms, with NOEC
values of ≥ 851.1 mg/kg dw (measured, initial) as well as EC10, EC50
values > 1000 mg/kg dw (nominal) for sediment-spiked tests and NOEC
values ≥ 100 mg/L (nominal) for water-spiked tests, respectively.
Data are available for freshwater and marine sediments. A 28 d
exposure of upgraded ilmenite (>80% TiO2) up to 100,000 mg/kg dw did not
affect survival and growth of Hyalella azteca in freshwater sediment
(Arcadis et al. 2008).
The 10 day exposure of the marine amphipod Corophium volutator to
a sediment spiked with microsized TiO2 in a non-standardized toxicity
assay under GLP conditions did not affect its survival resulting in a
10-d NOEC of 14,989 mg/kg dw (nominal) (Hudson, 2007).
In a freshwater mesocosm study (Jovanovic et al. 2016), rated as
supporting, autoclaved natural sediment was spiked with 25 mg/kg
titanium dioxide E171 and incubated for 100 days (July to November) in
the original pond. Thereafter, the reinvasion of macroinvertebrates was
analysed by evaluating the macroinvertebrate community structure by
means of non-metric multidimensional scaling (NMDS), multivariate
analysis of variance, and indicator value analysis after identifying all
recovered organisms at the lowest possible taxonomic level.
Czekanowski’s index was 0.61, meaning that 39% of the macroinvertebrate
community structure was negatively or positively affected by TiO2. The
absolute abundance of Chironomus luridus agg, Radix auricularia,
Theodoxus transversalis, Lymnea stagnalis, Psectrotanypus varius,
Trichoptera, Endochironomus tendens, Chaoborus sp., Baetis sp.,
Chironomus plumosus, and Asellus aquaticus was comparable to the
abundance in controls. In contrary, the absolute abundance of the
gastropods P. corneus and R. labiata was significantly lower in the TiO2
treatment compared to control, and the absolute abundance of the
Ceratogonidae (Diptera) per tray was significantly enhanced in the TiO2
treatment compared with the control. Nevertheless, this study is only
considered supporting, since reinvasion or avoidance is generally not
considered as a relevant endpoint for the environmental hazard
assessment. Furthermore, it is not possible to derive valid effect
values, since only one concentration was tested, and sediment and water
were not well characterized.
Regarding the toxicity of TiO2-NP to sediment organisms, a GLP
guideline study following OECD 225 revealed that the total number and
biomass (worm dry weight) of Lumbriculus variegatus were not affected up
to 851.8 mg TiO2/kg sediment dw (28 d NOEC ≥ 851.8 mg/kg dw, measured
(initial)), when TiO2 NP (PC105, anatase, 19 nm) were directly spiked
into artificial sediment (Simon, 2019). Due to the high background level
of the artificial sediment in the test, effect concentrations were based
on the mean measured background-corrected concentration at test start.
Additionally, no effects were observed after 28 d exposure of
adult Lumbriculus variegatus to artificial sediment spiked with TiO2
nanoparticles (NM-104; 26 nm, rutile, Al-coated) in a chronic sediment
toxicity test according to OECD TG 225 by Hund-Rinke et al. (2016). A 28
d EC10 and EC50 of > 1000 mg TiO2 NP/kg sediment dw (nominal) were
derived for both survival/reproduction and growth (dry biomass).
Furthermore, reproduction and growth of Lumbriculus variegatus as
well as emergence and development rate of Chironomus riparius were not
affected up to 100 mg/L TiO2 (rutile/anatase, both tests: 28 d NOEC ≥
100 mg/L) in water-borne exposure tests according to OECD 225 and OECD
219, respectively (Schäfers & Weil, 2013; Hund-Rinke & Klawonn, 2013).
One supporting sediment toxicity study is available and results
indicate that nanosized TiO2 is also not chronically toxic to Hyalella
azteca when applied via the sediment: In a chronic toxicity test
according to EPA 600/R-99/064, Wallis et al. (2014) exposed Hyalella
azteca (7-8 d old) to 20 and 100 mg/L of the nano-sized TiO2 material
P25 (nominal) in a natural sediment under laboratory light and simulated
solar radiation conditions resulting in 21-d NOEC values for survival
and growth rate of ≥ 100 mg/L sediment (nominal). However, the applied
natural lake water was not well characterized by Wallis et al. (2014)
and thus results are considered as supporting data.
In sum, micro- and nanosized TiO2 appears to have a low potential
for acute and chronic freshwater and marine sediment toxicity based on
data available for insect, crustacean and annelid species.
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