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VeilleNanos - Nanos in water: Release, fate and effects on fauna and flora

Nanos in water: Release, fate and effects on fauna and flora

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By the AVICENN team – Last updated August 2022

Release, fate and effects on fauna and flora of nanomaterials in water

Release of nanomaterials in water

What quantity of nanomaterials is released in water?

The quantity of nanoparticles released in water is unknown today. One of the major challenges is that nanoparticles are not well detected in water at low concentrations.

Different models1See in particular
Nano silver and nano zinc-oxide in surface waters – Exposure estimation for Europe at high spatial and temporal resolution, Dumont E et al, Environmental Pollution, 196: 341-349, January 2015
– Gottschalk F et al, Probabilistic material flow modeling for assessing the environmental exposure to compounds: methodology and an application to engineered nano-TiO2 particles, Environ Model Software, 25:320-32, 2010
– Blaser SA et al, Estimation of cumulative aquatic exposure and risk due to silver: contribution of nano-functionalized plastics and textiles, Sci Total Environ, 390:396-4092008, February 2008
– Boxall ABA et al, Current and predicted environmental exposure to engineered nanoparticles, York: CSL, 2008
– Mueller NC & Nowack B, Exposure modelling of engineered nanoparticles in the environment, Environ Sci Technol, 42:4447-53, 2008
have been tried in an attempt to quantify the concentrations and fluxes of different types of manufactured nanoparticles in the environment. However, these exercises are based primarily on estimates of the quantities of manufactured nanomaterials produced rather than estimates of the quantities of manufactured nanomaterials contained in consumer products2Cf. How important is drinking water exposure for the risks of engineered nanoparticles to consumers, Tiede K et al, Nanotoxicology, 1-9, 2015.

In 2013, researchers estimated that between 0.4 and 7% of the 300,000 tons of engineered nanomaterials produced worldwide in 2010 were released in water3Cf. Global life cycle releases of engineered nanomaterials, Keller AA et al, Journal of Nanoparticle Research, 15:1692, May 2013. But these figures are far below the reality since we learned the same year thanks to the French mandatory declaration that no less than 500,000 tons of “substances in a nanoparticulate state” had been produced or imported on French territory alone in 2013.

How do nanomaterials get released in water?

Nanomaterials can be released in water:

Which nanomaterials are most likely to be present in water?

Because of the uncertainties about the volumes of nanomaterials marketed and released in water, scientists’ estimates are not consistent and vary according to the methods and assumptions used and the practices of different countries (e.g. land application of sewage sludge versus incineration):

  • According to a recent study, the nanoparticles with the highest potential concentrations in treated water in the UK are titanium dioxide nanoparticles and zinc nanoparticles (from sunscreens and other cosmetics) and silica nanoparticles (toothpaste); carbon, iron or silver nanoparticles come only in 6th, 7th and 8th position respectively, and cerium oxide has the weakest concentration8Cf. How important is drinking water exposure for the risks of engineered nanoparticles to consumers, Tiede K et al, Nanotoxicology, 1-9, 2015.
  • According to another estimate, this time for Denmark, the highest concentrations of nanoparticles in aquatic systems are for carbon black and Photostable TiO2 (contained in sunscreens and not in photocatalytic paints), followed by copper carbonate (CuCO3, assuming its use as a wood preservative will increase). Water treatments would lead to extremely low concentrations of zinc oxide (ZnO) and silver nanoparticles in the environment9Modeling Flows and Concentrations of Nine Engineered Nanomaterials in the Danish Environment, Gottschalk F et al., Int. J. About. Res. Public Health, 12(5), 5581-5602, 2015.

In France, researchers have noted an increase in the presence of silver in the Gironde estuary10Silver (Ag, nanoAg) as an emerging contaminant in the Gironde estuary: scientific assessments and risk governance, Salles D. et al, ERS, 12: 317-323, July/August 2013 whose causes since 2005 are still poorly known, but potentially linked:

  • to agricultural soil erosion
  • to cloud seeding (silver iodide solution) to avoid hail impacts on vine crops and arboriculture
  • to community wastewater discharges.

Fate of nanomaterials in the aquatic environment

In water, nanos can undergo modifications

Knowledge about what happens to nanomaterials in water is beginning to develop but is still very limited. Because of their small size and especially their high reactivity, nanomaterials tend to interact with almost all the elements present in water (mineral, chemical or biological materials), according to very variable configurations depending on their physicochemical characteristics and the composition of the medium.

Phenomena that can alter nanomaterials in the environment – Camille Larue, 201111“Fate of nanomaterials in the water ecosystem” in Impact de nanoparticules de TiO2 et de nanotubes de carbone sur les végétaux, thesis, Camille Larue, 2011

Thus, in water, nanomaterials can undergo the following modifications:

Some nanomaterials tend to sediment by gravity and accumulate in sediments (especially in the case of aggregated and/or hydrophobic nanomaterials such as carbon nanotubes14A research team in the USA has shown the accumulation of single-walled carbon nanotubes in wetland sediments: Fate of single walled carbon nanotubes in wetland ecosystems, Schierz A et al, Environ. Sci: Nano, 2014 (see also associated press release: Nanoparticles accumulate quickly in wetlands, Science Daily, October 1, 2014)) which increases the risk of contact with microorganisms living on aquatic sediments. On the contrary, others would tend to remain in suspension (especially if coated with a hydrophilic surface coating) and disperse easily, increasing the risk of exposure15See in particular Transport of nanoparticulate TiO2 UV-filters through a saturated sand column at environmentally relevant concentrations, Motellier D et al, Science of the Total Environment, 811, 152408, March 2022 and the references cited in the report Toxicity and ecotoxicity of carbon nanotubes, ANSES, February 2011.

Their degradation, or conversely their persistence, are also complex to determine and vary according to the nanomaterials and the quality of the water:

  • According to a 2011 study, carbon nanomaterials (C60 fullerenes, carbon nanotubes) are not biodegradable in liquid media in the environmentBiodegradability16of organic nanoparticles in the aqueous environment, Kummerer K et al, Chemosphere, 82(10):1387-92, 2011.
  • Another study, the results of which were also made public in 201117Cf. Les nanoparticules : quels risques en Seine ?, Yann Sivry et al., communication aux 22èmes Journées Scientifiques de l’Environnement – Reconquête des environnement urbains : les défis du 21ème siècle, février 2011 was conducted on nanoparticles of zinc oxides (ZnO) and titanium dioxide (TiO2) in Seine river water, and showed that:
    • the nanoparticulate form of TiO2 is not more soluble than its microparticulate or macroparticulate counterparts
    • on the other hand, a large proportion of zinc oxide nanoparticles are rapidly dissolved in Seine water
    • the coating, depending on its nature, can decrease or increase the dissolution of nanoparticles.

Nanomaterials in general would tend to be stabilized in media with low ionic strength and high dissolved organic carbon content (COD)18Cf. A review of the properties and processes determining the fate of engineered nanomaterials in the aquatic environment, Peijnenburg W et al, Critical Reviews in Environmental Science and Technology, 45(19): 2084-2134, 2015.

Nanomaterials are already found in wastewater treatment plants and industrial water treatment plants but the treatments in place have not been designed to filter them. A significant part ends up in surface waters, while the others accumulate in the sludge of wastewater treatment plants spread on agricultural land…

In the USA, Marie Simonin has conducted impact studies of NP in mesocosms with CIENT. In 2018 she co-authored two publications in English:

Learn more about these publications

one shows that the biotransformation of nanoparticles should not be ignored, even for nanoparticles generally considered stable in the environment (here gold nanoparticles).
the other is studying the impacts of a citrate-coated gold nanoparticle and a commercial pesticide containing copper (OH) nanoparticles on aquatic primary producers under ambient and enriched nutrient conditions (this mimics fertilizer releases). Wetland mesocosms were repeatedly exposed with low concentrations of nanoparticles and nutrients during a nine-month experiment to replicate realistic field exposure scenarios. In the absence of nutrient enrichment, there were no persistent effects of gold or copper nanoparticles on primary producers or ecosystem productivity. However, combined with nutrient enrichment, both types of nanoparticles intensify their eutrophication. When either nanoparticle was added in combination with nutrients, the algal blooms persisted 50 days longer than in the nutrient-only treatment. These two emerging contaminants and synthetic chemicals may play an underappreciated role in global trends of increasing eutrophication. The study shows that chronic exposure to gold and copper oxide nanoparticles at low concentrations can intensify the eutrophication of wetlands and promote algal blooms.

Transfer through porous environments

Transfer processes through a porous medium (soil or aquifer) are also the subject of research. Experiments are performed in the presence of a solid phase or through a solid phase. They allow a better understanding of the adsorption processes, the impact of hydrodynamics and aggregation on the transport processes of nanoparticles. However, the first experiments were carried out on very simplified models such as silica beads. Trials in more complex environments with multiple minerals and natural organic matter are only beginning to develop19Background note – “Pollution” workshop – “Reducing pollution and impacts on biodiversity” – April 2010 (for the French Biodiversity Conference in May 2010).

What effects do nanomaterials have on aquatic fauna and flora?

The contamination of water by manufactured nanoparticles or their residues also leads to the contamination of aquatic organisms such as algae, shellfish and fish. Studies on the effects of nanomaterials on aquatic fauna and, to a lesser extent, on aquatic flora are developing, but many uncertainties remain (the salinity or acidity of the water can modify their toxicity, for example) and concerns are high.

The transfer of nanomaterials in the food chain

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.
Researchers have demonstrated the transfer of nanomaterials from seawater to the digestive tract of mussels20Uptake and retention of metallic nanoparticles in the Mediterranean mussel (Mytilus galloprovincialis), Aquatic Toxicology, May 2013, from algae to zooplankton and then to the fish that feed on them21See for example Evidence for Biomagnification of Gold Nanoparticles within a Terrestrial Food Chain, Judy. J et al., About. Sci. Technol., 45 (2), 776-781 (2011); Food Chain Transport of Nanoparticles Affects Behaviour and Fat Metabolism in Fish, Cedervall T. et al, PLoS ONE, 7(2): e32254 (2012).
We speak of “biomagnification”: there is an increase in the toxic content from one link in the food chain to the next:

Source: Cedervall et. al, 2012

Even when altered and agglomerated, nanoparticles (including cerium dioxide, used as a protective anti-scratch UV agent in exterior paints) may retain their ecotoxicity to aquatic organisms (microalgae in the experiment conducted)22Prise en compte de l’évolution de l’état d’agglomération dans l’étude de l’écotoxicité des nanoparticules, Nicolas Manier, Rapport scientifique 2013-2014, INERIS, November 2014, p.16.

Some examples of effects observed

Some examples of effects since 201123See for example:
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 Nanomaterials interact with agricultural pesticides, increasing toxicity to fish, The Organic Center, February 2015 (lay summary of scientific article Ecotoxicological effects of carbofuran and oxidised multiwalled carbon nanotubes on the freshwater fish Nile tilapia: Nanotubes enhance pesticide ecotoxicity, Ecotoxicology and Environmental Safety, 111: 131-137, January 2015)
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
Spatial distribution, electron microscopy analysis of titanium and its correlation to heavy metals: Occurrence and sources of titanium nanomaterials in surface sediments from Xiamen Bay, China, Luo Z et al, J. About. Monit., 13, 1046-1052, 2011: this study of sediments from Xiamen Bay in China showed that these sediments contained up to 2.74 g Ti/kg, largely in the form of 300 nm agglomerates composed of nanoparticles of about 50 nanometers. The distribution of titanium in sediments is positively correlated to that of elements such as lead or zinc, which is consistent with the adsorption of pollutants on the surface of nanoparticles.

  • effects on algae: increased mortality, growth retardation, decreased photosynthesis and generation of reactive oxygen species
  • effects on crustaceans: increased mortality, behavioral changes, malformations in Daphnia, accumulation in the body
  • effects on fish: mortality and disruption of development with the appearance of malformations; nano silver in particular can cause very marked malformations in the embryo of zebrafish
  • effects on other aquatic organisms:
    • damage throughout the mussel’s body, including induction of inflammatory processes, increased expression of genes involved in stress regulation, increased activity of antioxidant enzymes and lipid peroxidation
    • toxic effects on freshwater snails, chironomid larvae, cnidarians and polychaetes: decreased nutrition, increased malformations, oxidative stress, DNA damage correlated with increased mortality
    • toxic effects on amphibians
  • At high concentrations, effects of carbon nanotubes have been observed on aquatic organisms: decreased fertilization rate in small crustaceans, malformations, delayed hatching and even increased mortality rate of zebrafish embryos.

In addition to these effects, there are worrying indirect damages

In addition to the toxic effects that they can induce directly, nanomaterials can cause indirect damage that is nonetheless of great concern:

  • Nanomaterials or their residues can pass through the cell wall of plants or animals and bring in external molecules (this is the “Trojan horse” effect), they can act as “vectors” and promote the transport of pollutants (heavy metals, PAHs or pesticides for example).
  • Nanomaterials, combined with other substances, could become (even) more dangerous: This is called the cocktail effect. “Studies agree that the presence of nanoparticles in a liquid medium leads to a greater accumulation of pollutants in organisms. The risks for the food chain up to humans are therefore real, both because of the nanoparticles themselves as well as through their role as a vector of contamination”27What interactions between nanoparticles and other environmental contaminants, Camille Larue, Bulletin de veille scientifique (BVS), Anses, December 2014.

Elsewhere on the Web

Release of nanomaterials in water:

image 20180226_Guide_pratique_des_micropolluants_in_eaux_du_bassin_SeineNormandie.jpg (76.2kB)

– Fate and transformation of nanomaterials in the aquatic environment


Effects on fauna and flora:

In French :

In English:

Any questions or comments? This information sheet compiled by AVICENN is intended to be completed and updated. Please feel free to contribute.

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Sheet originally created in October 2014

Notes and references

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