The effect of nano-and microscale alumina was investigated in a variety of organisms, with only very high, often not environmentally relevant concentrations having a toxic effect. For boehmite, another alumina, no ecotoxicological studies are available.

 

Thus, the soil-dwelling model organisms mud tube worm (see picture), shrimp, earth worm and basket shells were investigated [1]. In this study, only the shrimp showed an impairment of growth and survival at very high, not environmentally relevant concentrations of nanoscale Al2O3. Regarding the uptake of alumina particles, large differences both between organisms and between nano-and microscale Al2O3 were observed.

 

The tube worm. © Wikipedia.deThe tube worm. © Wikipedia.de

For a nematode Al2O3 was toxic, as demonstrated by growth inhibition and reduction of reproduction [2]. Here nanoparticles acted stronger than coarser particles. Interestingly, for aluminum salt an even higher toxicity than for the nanoparticles had been detected. An earthworm exposed to Al2O3 in the ground for 4 weeks shows no increased mortality, even in very high, not environmentally relevant concentrations. The worms, however, were impaired in their propagation [3]. Nanoscale alumina has no strong antimicrobial properties. The metabolic activity of bacteria was not influenced by Al2O3 particles [4,5]. Very high particle concentrations, which are not expected to occur in the environment, caused a slight reduction in bacterial growth by an interaction with the bacterial surface [6]. In contrast, there are results that show a growth inhibition of different bacterial species also at lower particle concentrations [7,8]. Moreover, a stronger effect of the nanoparticles compared with larger particles was observed here. Nanoscale Al2O3 induces no mutagenic effects [9]. Daphnia responded to exposure to very high concentrations of Al2O3 nanoparticles with reduced mobility and increased mortality [10,11]. As shown in the figure, the water fleas internalise nanoparticles from the water in the intestine. An increased sensitivity towards nanoscale compared to microscale particles was observed [10].

 

A water flea with aluminia nanoparticles in the body. © Zhu et al., 2009.A water flea with aluminia nanoparticles in the body. © Zhu et al., 2009.

For embryos and larvae of zebrafish, however, neither nano- nor microscale particles were toxic [12,13]. Several plants, such as the California Kidney bean and ryegrass showed a normal growth in the presence of nanoparticulate Al2O3. Kidney beans internalise no particles from the soil into the leaves, while the aluminum concentration in the leaves of the ryegrass approximately doubled [14]. Also, no toxic effects of aluminum oxide on germination, root growth and leaf number of the thale cress (Arabidopsis) were observed [13]. Corn, carrots, soy, cabbage and cucumber showed a reduced root growth in the presence of Al2O3[15]. Interestingly, this effect disappeared when the particles were previously loaded with phenanthrene. It is speculated, that the phenanthrene changed certain surface properties of the particles so that they are no longer toxic. In another study, however, radish, rapeseed, rye, lettuce, corn and cucumber were not affected in germination and root growth [16]. No toxicity was observed in algae [5]. The risk posed by Al2O3 nanoparticles for environmental organisms is considered to be low. Because of little or no toxicity, often no differences between nano-and microscale particles are observed. If, however, a stronger toxic effect occurs, this is more pronounced for nanoscale than for micro-scale particles.

 

Literatur arrow down

  1. Stanley, JK et al. (2010), Environ Toxicol Chem, 29(2): 422-429.
  2. Wang, H et al. (2009), Environ Pollut, 157(4): 1171-1177.
  3. Coleman, JG et al. (2010), Environ Toxicol Chem, 29(7): 1575-1580.
  4. Doshi, R et al. (2008), Environ Res, 106(3): 296-303.
  5. Velzeboer, I et al. (2008), Environ Toxicol Chem, 27(9): 1942-1947.
  6. Sadiq, IM et al. (2009), Nanomedicine, 5(3): 282-286.
  7. Jiang, W et al. (2009), Environ Pollut, 157(5): 1619-1625.
  8. Hu, X et al. (2009), Sci Total Environ, 407(8): 3070-3072.
  9. Pan, X et al. (2010), Chemosphere, 79(1): 113-116.
  10. Zhu, X et al. (2008), J Nanopart Res, 11(1): 67-75.
  11. Griffitt, RJ et al. (2008), Environ Toxicol Chem, 27(9): 1972-1978.
  12. Zhu, X et al. (2008), J Environ Sci Health A Tox Hazard Subst Environ Eng, 43(3): 278-284.
  13. Harper, S et al. (2008), J Exp Nanosci, 3(3): 195-206.
  14. Lee, CW et al. (2010), Environ Toxicol Chem, 29(3): 669-675.
  15. Yang, L et al. (2005), Toxicol Lett, 158(2): 122-132.
  16. Lin, D et al. (2007), Environ Pollut, 150(2): 243-250.

 

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