Release, fate and transformation of nanos in the environment

Release, fate and transformation of nanos in the environment

By AVICENN Team – Last Added June 2022

What release of manufactured nanomaterials into the environment?

Few data exist on the release of manufactured nanomaterials

The term “release” of nanomaterials refers to the phenomenon by which nanomaterials – or nanomaterial degradation residues – are emitted into the environment. The term "emissivity" is sometimes also used.

We can distinguish the release:

• of natural nanoparticles found for example in dust from erosion or volcanic eruption or even in sea spray;
• of so-called “incidental” nanoparticles because produced "involuntarily" by human activities, emanating from fumes (from combustion of wood, industrial, emanating from diesel engines, incinerators, toasters or ovens) or from the abrasion of non-nanometric raw materials;
• of engineered nanomaterials purposely produced at the nanometric scale by researchers and industrialists to exploit their specific properties.

Today we have a very limited knowledge of the quantities and types of manufactured nanomaterials – or residues of these nanomaterials - which are released into the environment. However, these data are important for better understanding the exposure of ecosystems and populations (particularly workers) to nanomaterials, in order to better protect them from the associated risks.

In 2013, researchers estimated that between 63 and 91% of the approximately 300 tons of manufactured nanomaterials produced in the world in 000 ended up in landfills, the rest being released mainly into the grounds (8 to 28%), in the water (from 0,4 to 7%), or in l'atmosphere (0,1-1,5%)¹-Global life cycle releases of engineered nanomaterials, Journal of Nanoparticle Research, May 2013.
-Also: Note, this clarification by Olivier Boucher, research director at the CNRS dynamic meteorology laboratory, concerning the allegations conveyed on social networks about nanoparticles that would be released by planes (“chemtrails”): “Are planes releasing chemicals without our knowledge? », France Culture, July 28, 2018. In September 2019, however, we learned from Emirates News Agency, that the National Meteorological Center (NMC) of the United Arab Emirates had launched a campaign of cloud seeding tests with titanium dioxide nanoparticles applied to salt crystals. The objective is to better control rainfall. What about the transport and effects of these nanoparticles then in water and soil? The press release does not say.... But these figures are far below reality and the information collected in particular by the r-nano register, still do not allow estimate and locate the volumes of nanomaterials released into the environment.

How are nanomaterials released?

The release of nanomaterials or nanomaterial residues may occur during thedirect use of products which contain it or under theeffect of wear,abrasion or their degradation, for example :

• in soils:
  • in agriculture, when spreading pesticides or fertilizers³Nanopesticides: State of Knowledge, Environmental Fate, and Exposure Modeling, Critical Reviews in Environmental Science and Technology, 43 (16), July 2013 containing nanomaterials,
  • during in-situ soil depollution by injection of nanomaterials.

• in water :
  • when swimming for people who have applied sunscreen⁴Spanish researchers have thus estimated that tourist activity on a Mediterranean beach during a summer day can release around 4 kg of titanium dioxide nanoparticles in the water, and lead to an increase of 270 nM/day in the concentration of hydrogen peroxide (a molecule with toxic potential, in particular for phytoplankton which constitutes the staple food of marine animals). see Nano UV screens: a danger to marine life, The Cosmetics Observatory, September 5, 2014,
  • when washing textiles⁵See in particular:
    - Quantitative characterization of TiO2 nanoparticle release from textiles by conventional and single particle ICP-MS, Mackevica A et al., Journal of Nanoparticle Research, 20:6, January 2018
    - Silver nanoparticles lost in the first wash, Chemistry World, March 30, 2016 and Durability of nano-enhanced textiles through the life cycle: releases from landfilling after washing, DM Mitrano et al, About. Science: Nano, 2016,
  • under the effect of rainwater runoff on exterior cements and paints coated with nanocoatings⁶See in particular
    - Mechanisms limiting the release of TiO2 nanomaterials during photocatalytic cement alteration: the role of surface charge and porous network morphology, Bossa N, Environmental Science: Nano, 2, 2019
    - Sewage spills are a major source of titanium dioxide engineered (nano)-particle release into the environment, Loosli F et al., About. Science: Nano, 6, 763-777, 2019
    - Emission of titanium dioxide nanoparticles from building materials to the environment by wear and weather, Shandilya, N et al., Environmental Science & Technology, 49(4): 2163-2170, 2015; a lay summary is available free of charge here: Nanocoating on buildings releases potentially toxic particles to the air, “Science for Environment Policy”, European Commission, 28 May 2015

According to the current knowledge on the release, it is assumed that the release will be more important, in decreasing order, for sprays, tires, sun creams, textiles, exterior paints and cements (whose share could nevertheless increase considerably in the near future)⁷“in the future, the largest flows and stocks of TiO2 NPs could be related to self-cleaning cement” in Particle Flow Analysis: Exploring Potential Use Phase Emissions of Titanium Dioxide Nanoparticles from Sunscreen, Paint, and Cement, Arvidsson R et al., Journal of Industrial Ecology, 16(3): 343-351, Jun 2012), and to a lesser extent for the plastic or metal coatings of household appliances, or for the windows to which the nanomaterials are more firmly “fixed”.

A complex phenomenon, throughout the “life cycle”

The release of manufactured nanomaterials can occur throughout the " life cycle " Inspiring, without it being known today in what form, in what quantities, and with what effects it takes place precisely. At each stage of this life cycle, many parameters come into play. The release will indeed be different depending on : the way in which nanomaterials are presented (in the form of powder, in solution, deposited on a surface or integrated into a matrix, etc.), the conditions of production / use / waste management, the "medium" which the environment: air, water, soil, etc.

What releases at the "end of life" of the products?

These questions need to be explored, because the work published on the release of nanomaterials into the environment is still fragmented. In addition, many studies have been carried out under conditions often very different from those encountered in reality and on nanomaterials different from those which are actually incorporated in the products currently on the market. Research is underway to find out more¹⁰See for example Nanosafety Analysis of Graphene-Based Polyester Resin Composites on a Life Cycle Perspective, Aznar Molla, F et al., Nanomaterials, 12, 2036, 2022.

To be continued ...¹¹Mid 2022, the review Nanomaterials launched a call for papers for a special issue: See Special Issue “Quantitative Material Releases from Products and Articles Containing Manufactured Nanomaterials”, Nanomaterials, 2022 (deadline for submission of publications: January 31, 2023)

What fate and behavior of manufactured nanomaterials in the environment?

What mobility and accumulation of nanomaterials in the environment?

What happens to nanomaterials or nanomaterial residues once they are released into the environment? We know that because of their small size, nanomaterials have a strong propensity to disperse and can reach inaccessible places to larger particles. But to what extent and in what form(s)?

• In the air: Nanomaterials released into the air can disperse easily and over long distances in the atmosphere before falling¹²Effects of nanoparticles on climate and air pollution, Patrick Rairoux – LASIM and Christian and Georges – IRCELYON, presentation at the seminar “Nanomaterials in the environment and impacts on ecosystems and human health” organized by EnvitéRA, July 2012.
• In the soil¹³See in particular:- Plastic pollution also threatens plants (and by the way, our food), Marcus Dupont-Besnard, June 23, 2020
  -Differentially charged nanoplastics demonstrate distinct accumulation in Arabidopsis thaliana, Xiao-Dong Sun et al., Nature Nanotechnology, June 22 2020
  - Marie Simonin's thesis of 2015: Dynamics, reactivity and ecotoxicity of metal oxide nanoparticles in soils: impact on the functions and diversity of microbial communities. The study concerns titanium dioxide (TiO2) and copper oxide (CuO) NPs in six agricultural soils. The study concludes that TiO2 NPs are not toxic to microbial communities, except in silty-clay soil with a high organic matter content. In this soil, negative effects were observed after 90 days of exposure on microbial activities (respiration, nitrification and denitrification), on the abundance of nitrifying microorganisms and on the diversity of bacteria and archaea. In addition, negative effects are observed on nitrification, even for extremely low concentrations of TiO2 (0.05 mg kg-1), mainly related to a high sensitivity to this pollutant of the ammonium oxidizing archaea (AOA) involved in this process. process.: Do they migrate to groundwater or are they stuck in the ground before reaching groundwater? end up in the soil after spreading on agricultural land of sludge from treatment plants in container (made to complete the purification while serving as fertilizer)?
• In aquatic environments, nanoparticles can:
  • sediment by gravity (especially in the case of aggregated and/or hydrophobic nanomaterials such as carbon nanotubes) which increases the risk of contact with microorganisms that live on aquatic sediments
  • or on the contrary remain in suspension (in particular if they are functionalized on the surface or coated) and disperse easily, increasing the risk of exposure; we would already find nanomaterials in the treatment plants urban and industrial water treatment, but the treatments in place were not designed to filter them¹⁴See on this subject the work of the “Nanotechnology waste” working group Regional observatory of industrial waste in Midi-Pyrénées (ORDIMIP): a non-negligible part of them is therefore found in surface water, as for the others, they accumulate in the sludge of treatment plants spread on agricultural land!

More generally, nanomaterials or residues of nanomaterials can also:

• penetrate and accumulate in different species bacterial, plant, animal, terrestrial and/or aquatic (knowledge should increase in the coming years thanks to advances in metrology allowing the detection of nanomaterials in biological tissues¹⁵See An analytical workflow for dynamic characterization and quantification of metal-bearing nanomaterials in biological matrices, Monikh FA et al., Nature protocols 2022).
• be transferred from generation to generation, and go up the food chain

Many questions still unanswered

Once in the environment, nanomaterials or nanomaterial residues can undergo transformations: which ones and under what conditions? Many parameters can intervene and train, for example, their dispersion or sedimentation in aquatic environments, depending on whether they remain isolated or aggregate. What happens when they come into contact with naturally occurring suspended matter (mineral, chemical or biological materials)?

All these questions cannot have a simple answer, as the factors that come into play are numerous and variable (the light¹⁶On the influence of light on the physico-chemical parameters of nanomaterials, see for example:
- New study shows how engineered nanomaterials degrade and persist in the environment, World News, September 1, 2021 (English release: New Study Shows How Engineered Nanomaterials Degrade, Persist in Environment, George Washington University, September 1, 2021), the degree of acidity¹⁷On the influence of acidity on the physico-chemical parameters of nanomaterials, see for example:
- Fate of iron nanoparticles in the environment. Colloidal stability, chemical reactivity and impacts on plants, thesis of Edwige Demangeat, Geosciences Rennes UMR 6118, 2018
- Natural acids in soil could protect rice from toxic nanoparticles, Science News, April 2015 or salinity¹⁸On the influence of salinity on the physico-chemical parameters of nanomaterials, see for example:On how environmental and experimental conditions affect the results of aquatic nanotoxicology on brine shrimp (Artemia salina): A case of silver nanoparticles toxicity, environmental pollution, 255, 3, 113358, December 2019
- Combined influence of oxygenation and salinity on aggregation kinetics of the silver reference nanomaterial NM-300K, Devoille L et al., Environmental Toxicology and Chemistry, 37(4): 1007-1013, April 2018
- Nanomaterials through a salinity gradient: exposure and ecotoxicological effects during their life cycle , Carole Bertrand, thesis, 2016, with the participation of Laure Giamberini, in connection with the project NanoSALT supported by the ANR to understand the fate of Ag and CeO2 nanoparticles from textiles and paints.
- The influence of salinity on the fate and behavior of silver standardized nanomaterial and toxicity effects in the estuarine bivalve Scrobicularia plana, Bertrand, C et al. , About Toxicol Chem. 2016for example can be decisive). With, as a result, great difficulty in determining, in each case, the effects on ecosystems. Because many studies have long been carried out on synthetic nanoparticles and under conditions different from those encountered in reality; the behavior of nanomaterials observed in experiments does not reflect that (or those) of nanomaterial residues actually present in the environment. The results are therefore still not very generalizable and should be considered with caution.