What are the risks of nanos on the environment?

What are the risks of nanos for the environment?

By the AVICENN team – Last modification August 2022

Potential worrying effects on wildlife

Scientists, environmental protection associations and public administrations have called for a better assessment of the environmental risks of nanomaterials. Indeed, studies carried out over the last ten years have shown potential harmful effects on fauna and flora¹Cf Bibliographie générale Nanomatériaux et Environnement.

Carbon nanotubes

At high concentrations, effects of carbon nanoparticles (including C60 fullerenes and carbon nanotubes) have been observed²See the report Toxicity and Ecotoxicity of Carbon Nanotubes, ANSES, February 2011 (updated in November 2012 in the document Note d’actualité, État de l’art 2011-2012). See also in particular Carbon nanotubes: Impacts and behaviour in the terrestrial ecosystem – A review, Liné C et al, Carbon, 123; 767-785, July 2017:

• on microorganisms: effects on the growth and viability of protozoa and other microorganisms,
• on plants: decrease of cell viability or chlorophyll quantity of plants, impact (sometimes positive, sometimes negative) on seed germination and root growth
• on aquatic organisms: reduced fertilization rate in small crustaceans, malformations, delayed hatching and even increased mortality rate of zebrafish embryos
• on terrestrial organisms: reduced mobility or even death of drosophila, reduced reproduction rate of earthworms.
• More recently, researchers have demonstrated a link between the incineration of thermoplastics containing carbon nanotubes and increased emissions and toxicity of polycyclic aromatic hydrocarbons (PAHs)³Cf. Incinerating nano-enabled thermoplastics linked to increased PAH emissions and toxicity, Science for Environment policy, European Commission DG Environment News Alert Service, 508, 24 May 2018.

Titanium dioxide nanoparticles

The dissemination of manufactured nanoparticles of titanium dioxide can be a source of toxicity for terrestrial and aquatic environments⁴See for example: In French:
Doc’ en clip – le risque associé aux nanoparticules contenues dans les creèmes solaires (vidéo), Riccardo Catalano, Aix-Marseille University, 14 October 2019
– Estimation and minimization of the risk associated with TiO2 nanoparticles used in sunscreens, presentation by Labille J, “Nano and cosmetics” technical day organized by LNE, 29 March 2018
– Pollution of coastal waters by UV absorbers from sunscreens, generated by summer activities, Labille J, OHM Littoral project, 2017
– Dynamics, reactivity and ecotoxicity of metal oxide nanoparticles in soils: impact on the functions and diversity of microbial communities, thesis by Marie Simonin (Microbial Ecology / UMR CNRS 5557 Claude Bernard University – Lyon 1), defended in October 2015
– Nano or not: the TiO₂ is toxic for the environment, The Cosmetics Observatory, October (summary in French of the report“Environmental hazard of selected TiO₂ nanomaterials under consideration of relevant exposure scenarios“, Umwelt bundesamt, October 2014).
In English:
– Toxicity of TiO2 nanoparticles to the marine microalga Chaetoceros muelleri Lemmermann, 1898 under long-term exposure, Bameri L et al, Environmental Science and Pollution Research, 29: 30427-30440, 2022
– Proteomics reveals multiple effects of titanium dioxide and silver nanoparticles in the metabolism of turbot, Scophthalmus maximus, Araújo MJ et al, Chemosphere, 2022
– Zinc oxide, titanium dioxide and _C60 fullerene nanoparticles, alone and in mixture, differently affect biomarker responses and proteome in the clam Ruditapes philippinarum, Marisa I et al, Science of the Total Environment, 838 (2), September 2022
– Toxicity of titanium nano-oxide nanoparticles (_TiO2) on the pacific oyster, Crassostrea gigas: immunity and antioxidant defence, Arash Javanshir Khoei and Kiadokht Rezaei, Toxin Reviews, 41, 2022
– Lethal and sub-lethal effects of nanosized titanium dioxide particles on Hydropsyche exocellata Dufour, 1841, Torres-Garcia D et al, Aquatic Insects – International Journal of Freshwater Entomology, 41(1), 2020
– Silver and titanium nanomaterials present in wastewater have toxic effects on crustaceans and fish cells, Norwegian Institute for Water Research (NIVA), November 2019
– TiO₂ nanoparticles in the marine environment: Impact on the toxicity of phenanthrene and Cd2 + to marine zooplankton Artemia salina , Jing Lu, Shengyan Tian, Xiaohui Lv, Zuohong Chen, Baiyang Chen, Xiaoshan Zhu, Zhonghua Cai, Science of The Total Environment, 15 February 2018
University, October 14, 2019
– Mixture toxicity effects and uptake of titanium dioxide (TiO₂) nanoparticles and 3,3′,4,4′-tetrachlorobiphenyl (PCB77) in juvenile brown trout following co-exposure via the diet, Lammel T et al, Aquat Toxicol, 213:105195, August 2019
– Evaluation of the effects of titanium dioxide and aluminum oxide nanoparticles through tarsal contact exposure in the model insect Oncopeltus fasciatus, López-Muñoz D. et al, Science of The Total Environment, 666: 759-765, May 2019
– How do titanium dioxide and zinc oxide nanoparticles affect soil microorganism activity, Kizildag N et al, European Journal of Soil Biology, 91: 18-24, March-April 2019
– Titanium dioxide nanoparticles impaired both photochemical and non-photochemical phases of photosynthesis in wheat, Dias MC, Protoplasma, 256(1): 69-78, January 2019
– The effects and the potential mechanism of environmental transformation of metal nanoparticles on their toxicity in organisms, Zhang J et al, Environ. Sci.: Nano, 5: 2482-2499, 2018
– Transfer and Ecotoxicity of Titanium Dioxide Nanoparticles in the Terrestrial and Aquatic Ecosystems: A Microcosm Study, Vijayaraj V et al, Environmental Science and Technology, 52(21): 12757-12764, October 2018
– TiO₂ nanoparticles enhance bioaccumulation and toxicity of heavy metals in Caenorhabditis elegans via modification of local concentrations during the sedimentation process, Wang J et al, Ecotoxicology and Environmental Safety, 162(30): 160-169, October 2018
– Toxicological impact of TiO₂ nanoparticles on Eudrilus euginiae, Priyanka KP et al, IET Nanobiotechnology, 12 (5):579, August 2018
– Scientists find titanium dioxide from sunscreen is polluting beaches Scientists find titanium dioxide from sunscreen is polluting beaches, presentation by Labille J., Goldschmidt Conference, August 2018.

Nanoparticles contained in sunscreens are released into swimming waters⁵Researchers at CEREGE in France have measured the concentration of titanium in the water of three beaches in Marseille and have estimated the weight of TiO2 released in two months of summer for a small beach at 54 kilos per day, See :
– Doc’ en clip – the risk associated with nanoparticles in sunscreens (video), Riccardo Catalano, Aix-Marseille University, 14 October 2019, and lead to an increase in the concentration of hydrogen peroxide, a molecule with toxic potential, especially for phytoplankton, which is the basic food of marine animals⁶In 2014, Spanish researchers estimated that tourist activity on a Mediterranean beach during a summer day can release about 4 kg of titanium dioxide nanoparticles into the water, resulting in an increase of 270 nM/day in the concentration of hydrogen peroxide (a molecule with toxic potential, especially for phytoplankton, which is the basic food of marine animals, See:
– Nano UV screens: a danger for marine life, The Cosmetics Observatory, September 5, 2014.

These nanoparticles can also come from toothpastes, industrial products such as paints, lacquers, paper, as well as photocatalytic processes such as water treatment⁷See:
– Keller, A. A., McFerran, S., Lazareva, A. & Suh, S. Global life cycle releases of engineered nanomaterials. J. Nanoparticle Res. 15, 1-17 (2013)
– Wang, C., Liu, H., Liu, Y., He, G. & Jiang, C. Comparative activity of TiO2 microspheres and P25 powder for organic degradation: Implicative importance of structural defects and organic adsorption. Appl. Surfing. Sci., 319, 2-7 (2014).
– Mitrano, D. M., Motellier, S., Clavaguera, S. & Nowack, B. Review of nanomaterial aging and transformations through the life cycle of nano-enhanced products. About. Int. 77, 132-147 (2015).
– Wen, J. et al. Photocatalysis fundamentals and surface modification of TiO2 nanomaterials. Chin. J. Catal. 36, 2049-2070 (2015). (among others). A study also shows that TiO2 nanoparticles cause strong disruptions of the nitrogen cycle and a modification of the structure of the bacterial community in agricultural soil, even at a low likely concentration (1 mg kg-1 of dry soil)⁸See: Simonin, M. et al. Titanium dioxide nanoparticles strongly impact soil microbial function by affecting archaeal nitrifiers. Sci. Rep. 6, 33643; doi: 10.1038/srep33643 (2016).

Nano-silver and bactericidal / biocidal nanomaterials

Hundreds of tons of silver nanoparticles are produced every year in the world for their antibacterial or antifungal properties, despite risks for the environment especially for microorganisms, aquatic flora and fauna⁹See- for example :
– Proteomics reveals multiple effects of titanium dioxide and silver nanoparticles in the metabolism of turbot, Scophthalmus maximus, Araújo MJ et al, Chemosphere, 2022
– The Biological Cost of Antimicrobial Nanosilver Exposure, AzoNano, 30 May 2022 > Whole-lake nanosilver additions reduce northern pike (Esox lucius) growth, Slongo BD et al, Science of The Total Environment, 838(2), 56219, September 2022
– Comparative evaluation on the toxic effect of silver (Ag) and zinc oxide (ZnO) nanoparticles on different trophic levels in aquatic ecosystems: A review, Sibiya A et al, Journal of applied toxicology, 2022
– Nanoparticles disrupt algae, University of Geneva, November 25, 2020(Metabolomics for early detection of stress in freshwater alga Poterioochromonas malhamensis exposed to silver nanoparticles, Liu W et al., Scientific Reports, 10, November 2020)
– How Nanosilver Gets Into Our Freshwater, and What We Need To Do About It, Lauren Hayhusrt, Fisheries Research Biologist, IISD Experimental Lakes Area, April 16, 2020
– Silver Uncontrolled: How nanosilver gets into our fresh water, and what we need to do about it, Lauren Hayhusrt, Fisheries Research Biologist, Experimental Lakes Area, November 29, 2019
– Comparative multi-generation study on long-term effects of pristine and wastewater-borne silver and titanium dioxide nanoparticles on key lifecycle parameters in Daphnia magna, Hartmann S et al, NanoImpact, 14, February 2019
– Phytotoxicity of Silver Nanoparticles to Aquatic Plants, Algae, and Microorganisms, Domingo G et al, Nanomaterials in Plants, Algae and Microorganisms – Concepts and Controversies, volume 2: 143-168, 2019
– France Diplomatie, Silver nanoparticles are toxic to aquatic organisms, October 26, 2018 ; Waterborne exposure of adult zebrafish to silver nanoparticles and to ionic silver results in differential silver accumulation and effects at cellular and molecular levels, Lacave JM et al, Science of The Total Environment, 642: 1209-1220, November 2018
– Accumulation of Silver in Yellow Perch (Perca flavescens) and Northern Pike (Esox lucius) From a Lake Dosed with Nanosilver, Jonathan D. Martin, Paul C. Frost, Holger Hintelmann, Karla Newman, Michael J. Paterson, Lauren Hayhurst, Michael D. Rennie, Margerite A. Xenopoulos, Viviane Yargeau, Chris D. Metcalfe, Environmental Science & Technology, 2018and soil microorganisms¹⁰See in particular:
– Nanopore-based metagenomic analysis of the impact of nanoparticles on soil microbial communities, Chavan S et al, Heliyon, 8(6), June 2022
– Destruction of Cell Topography, Morphology, Membrane, Inhibition of Respiration, Biofilm Formation, and Bioactive Molecule Production by Nanoparticles of Ag, ZnO, CuO, TiO2, and Al2O3 toward Beneficial Soil Bacteria, Ahmed B et al, ACS Omega, 5, 14, 7861-7876, 2020
– Effect of silver nanoparticle contaminated biosolids on the soil microbial community, Dias Samarajeewa A et al, NanoImpact, 14, February 2019 as well as health risks (argyrism at high doses ¹¹Colloidal silver in question, RFJ, November 11, 2021 and especially bacterial resistance ).

Moreover, nanosilver harms certain bacteria that play an essential role in wastewater treatment plants: the consequences are not yet well evaluated, but concerns are growing about the problems that could arise in the medium term to ensure water quality.

The numerous scientific uncertainties that remain leave the field open to differences in the assessment of risks by scientists, and even to real controversies. In addition to the problems it could cause in wastewater treatment plants, nanosilver for example, has been identified by some experts as a potential risk factor for the emergence of bacteria that are multi-resistant to antibiotics, risk which others dispute.

Zinc oxide nanoparticles

In 2020, work conducted by French and Spanish researchers showed that zinc oxide nanoparticles are absorbed by reeds, with various toxic effects (reduction of their growth, chlorophyll content, photosynthetic efficiency and transpiration)¹²Cf. Stable Zn isotopes reveal the uptake and toxicity of zinc oxide engineered nanomaterials in Phragmites australis, BioRxiv, Caldelas C et al., 2020,
-For other environmental effects of zinc oxide nanoparticles, see also ZnO and TiO2 nanoparticles alter the ability of Bacillus subtilis to fight against a stress, Eymard- Vernain E et al, PLoS ONE, Public Library of Science, 2020, 15 (10), 2020.

In July 2019, ECHA issued a decision in which it considers ¹³See footnote 3 nano zinc oxide as “very toxic to aquatic life, with persistent effects over time.”
In 2018, the European project SOS-Nano had highlighted that zinc oxide nanoparticles lead to a high level of toxicity in oyster larvae, as seawater does not prevent dissolution¹⁴Cf. The real effects of nanoparticles in their environment, Cordis, March 2018.

In 2020, work conducted by French and Spanish researchers showed that zinc oxide nanoparticles are absorbed by reeds, with various toxic effects (reduction of their growth, chlorophyll content, photosynthetic efficiency and transpiration)¹⁵
– Sunscreens containing zinc oxide nanoparticles can trigger oxidative stress and toxicity to the marine copepod Tigriopus japonicus, Stella W.Y. Wong, Guang-Jie Zhou, Priscilla T.Y. Leung, Jeonghoon Han, Jae-Seong Lee, Kevin W.H. Kwok, Kenneth M.Y. Leung, Marine Pollution Bulletin, Volume 154, May 2020
– Stable Zn isotopes reveal the uptake and toxicity of zinc oxide engineered nanomaterials in Phragmites australis, BioRxiv, Caldelas C et al., 2020.

Silica nanoparticles

Silica nanoparticles can also have adverse effects on the environment, including aquatic life¹⁷See for example:
– Aquatic ecotoxicity of manufactured silica nanoparticles: A systematic review and meta-analysis, Book F and Backhaus T, Science of The Total Environment, 806(4)4, February 2022
– Physiological and Behavioral Effects of _SiO2 Nanoparticle Ingestion on Daphnia magna, Kim Y et al, Micromachines (Basel), 12(9): 1105, September 2021.

Specific risks of nanomaterials in water

It is already known that nanomaterials or nanomaterial residues can enter and accumulate in different aquatic species, be transferred from generation to generation and move up the food chain.

Risks as mobile as nanomaterials

Because of their small size, nanomaterials have a strong propensity to disperse and can reach places inaccessible to larger particles. But to what extent and in what form(s)? Many aspects of the life-cycle of nanomaterials are still largely unknown: the persistence, transformation, mobility and accumulation of nanomaterials in the environment are very difficult to understand.

It is already known that nanomaterials or nanomaterial residues can enter and accumulate in different bacterial, plant, animal, terrestrial and/or aquatic species, be transmitted to the next generation, and move up the food chain. But these data are still very patchy, despite the development of research on this subject.

Risks related to interaction with other pollutants

Nanomaterials can increase the dissemination of other pollutants

We already know that nanomaterials or their residues can pass through the cell wall of plants and bring in external molecules (this is the ” Trojan horse ” effect), and we fear that they will promote the transport of pollutants (heavy metals or pesticides, for example)¹⁸See for example:
– Like a Trojan horse, graphene oxide can act as a carrier of organic pollutants to fish, Campusa (University of the Basque country), May 2021 and Uptake and effects of graphene oxide nanomaterials alone and in combination with polycyclic aromatic hydrocarbons in zebrafish, Martinez-Alvarez I et al, Science of The Total Environment, 775, June 2021
– Fate of single walled carbon nanotubes in wetland ecosystems, Schierz A et al, Environ. Sci.: Nano, 2014 (and associated press release: Nanoparticles accumulate quickly in wetlands: Aquatic food chains might be harmed by molecules ‘piggybacking’ on carbon nanoparticles, Science Daily, October 1, 2014
– Carbon nanotubes as molecular transporters for walled plant cells. Liu Q, Chen B, Wang Q, et al. in Nano Lett, 9(3): 1007-10, 2009
– Toxicity and bioaccumulation of xenobiotic organic compounds in the presence of aqueous suspensions of aggregates of nano-C60, Baun, A., et al, in Aquatic Toxicology, 86: 379-387, 2008
– Enhanced bioaccumulation of cadmium in carp in the presence of titanium dioxide nanoparticles, Zhang et al, Chemosphere 67(1):160-6, 2007.

Increased risks due to interactions of nanomaterials with each other or with other pollutants

How not to fear also a “cocktail effect” with certain molecules? Nanomaterials, combined with other substances, can become (even) more dangerous.

Many uncertainties remain

However, certain difficulties and uncertainties explain why the results are not very generalizable and should be considered with caution. Notably because:

• Risk assessment is complex due to the multitude of parameters to be taken into account
  
• The conditions of experimentation are often very different from those encountered in reality

For the moment, scientists have indeed very limited knowledge of the types of nanomaterials that are incorporated in the products currently on the market and a fortiori residues from the degradation of nanomaterials released into the environment throughout the “life cycle” of these products; they also know little about their mobility and transformation in the environment: here again, many parameters come into play, such as the degree of acidity or salinity of the water for example.

However, the situation is improving (methodologically speaking), with new analytical methods for studying the effects of nanoparticles on ecosystems¹⁹See for example:
– Contribution of mesocosm testing to a single-step and exposure-driven environmental risk assessment of engineered nanomaterials, Auffan M et al, Nanoimpact, 13: 66-69, 2019
– Clarification of methodical questions regarding the investigation of nanomaterials in the environment, UBA, December 2017
– Ecotoxicology of nanomaterials: new analytical approaches, Camille Larue, Bulletin de veille scientifique (BVS), Anses, September 2015
– The Microbial Ecology Laboratory of Lyon 1 University has set up studies on the Dynamics, reactivity and ecotoxicity of metal oxide nanoparticles in soils: impact on the functions and diversity of microbial communities (2015).
– The CEREGE MESONNET project, initiated in 2012, has thus contributed to study the potential consequences of nanoparticles on ecosystems using “mesocosms”..

Furthermore, the adverse effects of nanosilver on plants and microorganisms mentioned above have also been observed under “realistic” experimental conditions.

In this context, how can the precautionary principle be applied?

Given the lack of certainty and guarantees on the harmlessness of nanomaterials for the environment, the precautionary principle, enshrined in the Constitution since 2005, is essential:

“When the realization of a damage, although uncertain in the state of the scientific knowledge, could affect in a serious and irreversible way the environment, the public authorities will take care, by application of the precautionary principle, and in their fields of attribution, to implement procedures of evaluation of the risks and the adoption of provisional and proportionate measures in order to avoid the realization of the damage”.

How can it be applied to the case of nanomaterials, for which there are still many “scientific barriers” that prevent precise knowledge of the risks involved?

Here are some of the possible solutions – sometimes complementary, sometimes exclusive of each other.

Because of all these “delayed-effect” risks and uncertainties, there is an urgent need for not only research efforts (with a financial contribution from companies who produce and use nanomaterials) but also information and training actions (for health professionals and also for public and private decision makers), as well as concrete measures of prevention and precaution.

Action 13 of the National Health and Environment Plan (PNSE 4) published in 2021 is in line with this, but there is much to do, with little time and money.

Everyone has a role to play: consumers, associations, unions, public authorities, companies, media, etc. AVICENN does its part… help us speed things up

Is the environmental issue the gateway to a more global approach?

In 2009, the physicist Richard Jones, pro-Vice Chancellor for Research and Innovation of the University of Sheffield (UK), called on the scientific community to insist that the environmental issues raised by nanos go beyond the simple field of toxicology and technology and confront us with more global questions: who controls these technologies, who benefits from them? according to which governance²²Richard Jones, ‘It’s not just about nanotoxicology’, Nature Nanotechnology, vol 4, October 2009? Because of the uncertainties regarding the effectiveness and potential severity of environmental effects caused throughout the life-cycle of nanomaterials, it is important to consider the issues of their reversibility and our ability to remedy the problems they may cause.

When it comes to reversibility, it is not just technical considerations that need to be taken into account: our experience with other technologies shows that companies, once they have embarked on a specific path, can have great difficulties in going back. This is not only for technical reasons, but also for economic or socio-political reasons.

The question of the usefulness (or futility) of the use of various nanomaterials arises. Similarly, the question of autonomy or dependence on a complex technology: what alternative solutions exist for the expected effect? What resources are devoted to improving them?

Ultimately, it is the functioning of our democracy that is at stake here: who decides what at what point in the life-cycle of innovations? Which actors are involved at each stage of the cycle? Have they been able to express an opinion and is it taken into account when a real choice is still possible, as required by the Aarhus Convention? With what ethics?