Toxic nanotubes
The nanotubes turned out to be extremely toxic
Industrial enterprises need to think about creating systems to prevent them from entering the environment
Researchers from the Far Eastern Federal University (FEFU) together with foreign colleagues have established what potential harm to the environment can be caused by carbon and silicon nanotubes, as well as carbon nanofibers that are part of a number of plastic products and composites. Microscopic seaweed Heterosigma akashivo, widely represented in the waters surrounding the Russian Far East, was used as a model organism. It turned out that even in very small quantities, nanotubes provide an acute and chronic toxic effect. The corresponding article was published in Environmental Research (Pikula et al., Effects of carbon and silicon nanotubes and carbon nanofibers on marine microalgae Heterosigma akashiwo).
Currently, the use of carbon nanofibers and nanotubes is growing rapidly. It is expected that the total market volume for carbon nanotubes alone will exceed five billion dollars by 2020. They, like silicon nanotubes, are often added to composites to increase their hardness. In addition, in modern medicine, nanotubes are proposed to be used as drug delivery systems to human cells.
According to the researchers, from 60 to 80 percent of all plastic and composite materials in the world end up in the oceans, where their decomposition takes hundreds of years. All these wastes often contain several types of nanoparticles added to them to improve consumer characteristics. Therefore, the authors of the work decided to study what effect they have on microalgae – the basis of the food pyramid in the ocean.
For the nanotoxicological study, scientists selected single-celled marine microalgae Heterosigma akashiwo, extracted in Peter the Great Bay in the Sea of Japan. Scientists took a statistically significant decrease in the number of algae cells of an experimental sample of seawater as a criterion for the toxic effect of nanotube impurities in comparison with the control sample, where nanotubes were not added.
It turned out that the toxic effect of impurities of carbon and silicon nanotubes in water occurs already at their concentration of 100 milligrams per liter of water. In other words, already in the proportion of 1 to 10,000 nanotubes caused the death of microalgae cells. Acute toxic effect was detected already on the third day of the experiment, and chronic poisoning of cells occurred on the seventh. At the same time, silicon nanotubes turned out to be much more toxic than carbon nanotubes due to their smaller size and hydrophilic characteristics.
© Environmental Research
Scientists suggest that the main reason for the death of algae cells during the study was their mechanical damage by nanoparticles, as a result of which the integrity of the cells was violated. As one of the co-authors of the article Aristides Tsatsakis from the University of Crete notes: "The volume of nanomaterials present in our lives has increased significantly recently. Previously, laboratories received samples in quantities measured by micrograms. Today we have a multi-ton production of plastics and composites containing nanoparticles, in particular, carbon and silicon nanotubes. The further we go, the more important it is to understand what kind of environmental impact these particles can cause. We know that the diameter of nanotubes is crucial for their toxicity: the smaller the nanoparticles, the more toxic they are. Thus, silicon nanotubes are more toxic than carbon nanotubes. But carbon-based compounds can also cause a series of neurodegenerative disorders, mainly due to the accumulation of oxidative stress and the parallel reduction of antioxidant defense mechanisms."
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