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Environmentally relevant concentrations of titanium dioxide nanoparticles pose negligible risk to marine microbes

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Abstract

Nano-sized titanium dioxide (nTiO2) represents the highest produced nanomaterial by mass worldwide and, due to its prevalent industrial and commercial use, it inevitably reaches the natural environment. Previous work has revealed a negative impact of nTiO2 upon marine phytoplankton growth, however, studies are typically carried out at concentrations far exceeding those measured and predicted to occur in the environment currently. Here, a series of experiments were carried out to assess the effects of both research-grade nTiO2 and nTiO2 extracted from consumer products upon the marine dominant cyanobacterium, Prochlorococcus, and natural marine communities at environmentally relevant and supra-environmental concentrations (i.e., 1 μg L−1 to 100 mg L−1). Cell declines observed in Prochlorococcus cultures were associated with the extensive aggregation behaviour of nTiO2 in saline media and the subsequent entrapment of microbial cells. Hence, higher concentrations of nTiO2 particles exerted a stronger decline of cyanobacterial populations. However, within natural oligotrophic seawater, cultures were able to recover over time as the nanoparticles aggregated out of solution after 72 h. Subsequent shotgun proteomic analysis of Prochlorococcus cultures exposed to environmentally relevant concentrations confirmed minimal molecular features of toxicity, suggesting that direct physical effects are responsible for short-term microbial population decline. In an additional experiment, the diversity and structure of natural marine microbial communities showed negligible variations when exposed to environmentally relevant nTiO2 concentrations (i.e., 25 μg L−1). As such, the environmental risk of nTiO2 towards marine microbial species appears low, however the potential for adverse effects in hotspots of contamination exists. In future, research must be extended to consider any effect of other components of nano-enabled product formulations upon nanomaterial fate and impact within the natural environment.

Graphical abstract: Environmentally relevant concentrations of titanium dioxide nanoparticles pose negligible risk to marine microbes

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Supplementary files

Article information


Submitted
22 Aug 2020
Accepted
06 Apr 2021
First published
09 Apr 2021

This article is Open Access

Environ. Sci.: Nano, 2021, Advance Article
Article type
Paper

Environmentally relevant concentrations of titanium dioxide nanoparticles pose negligible risk to marine microbes

C. J. Dedman, A. M. King, J. A. Christie-Oleza and G. Davies, Environ. Sci.: Nano, 2021, Advance Article , DOI: 10.1039/D0EN00883D

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