Release, fate and transformation of nanos in the environment

Release, fate and transformation of nanos in the environment

By the AVICENN team – Last updated June 2022

Release of manufactured nanomaterials into the environment

Little data exists on the release of manufactured nanomaterials

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

A distinction can be made between:

• natural nanoparticles found, for example, in erosion or volcanic eruption dust or in sea spray
• nanoparticles known as “incidental” because they are produced “involuntarily” by human activities, emanating from smoke (from wood combustion, industrial smoke, smoke from diesel engines, incinerators, toasters or ovens) or from the abrasion of non-nanometric raw materials
• manufactured nanomaterials purposely produced at the nanoscale by researchers and industry to exploit their specific properties.

There is currently very limited knowledge of the quantities and types of manufactured nanomaterials – or residues of these nanomaterials – that are released into the environment. These data are important to better understand the exposure to nanomaterials of ecosystems and populations (especially workers), in order to better protect them from the associated risks.

In 2013, researchers estimated that between 63 and 91% of the approximately 300,000 tons of manufactured nanomaterials produced worldwide in 2010 ended up in landfills, with the remainder being released primarily into soils (8 to 28%), in water (from 0.4 to 7%), or in the 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, director of research at the CNRS laboratory of dynamic meteorology, concerning the allegations made on social networks about nanoparticles released by airplanes (“chemtrails”): “Do planes release chemicals without our knowledge?”, France Culture, July 28, 2018. In September 2019, however, it was learned by 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 in water and soil? The press release does not say so….. However, these figures are far below reality and the information collected by the r-nano register, in particular, still does not allow us to estimate and locate the volumes of nanomaterials released into the environment.

How are nanomaterials released?

The release of nanomaterials or nanomaterial residues can occur during the direct use of products containing them or under the effect of wear, abrasion or their degradation, for example:

• in soils :
  • in agriculture, when applying 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 remediation by injection of nanomaterials.

• in water :
  • when swimming after having applied sunscreen⁴Spanish researchers have estimated that tourist activity on a Mediterranean beach during a summer day can release about 4 kg of nanoparticles of titanium dioxide in 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). Cf. Nanos 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, 30 March 2016 and Durability of nano-enhanced textiles through the life cycle: releases from landfilling after washing, DM Mitrano et al, Environ. Sci.: Nano, 2016,
  • from rainwater runoff on nano-coated cement and exterior paint⁶Cf.
    – 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., Environ. Sci.: 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 summary available for free: Nanocoating on buildings releases potentially toxic particles to the air, « Science for Environment Policy », European Commission, 28 may 2015

Based on current knowledge of nano release, it is assumed that it will be at its highest, in descending order, for sprays, tires, sunscreens, textiles, exterior paints and cements (whose share could nevertheless increase considerably in the near future⁷“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, June 2012), and to a lesser extent for plastic or metallic coatings of household appliances, or for glass, to which nanomaterials are more firmly “attached”.

A complex phenomenon occurring throughout the “life cycle

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

What are the releases at the “end of life” of products?

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

To be continued…¹¹In mid-2022, the journal Nanomaterials issued a call for papers for a special issue: Cf. Special Issue “Quantitative Material Releases from Products and Articles Containing Manufactured Nanomaterials Nanomaterials, 2022 (deadline for submission of publications: January 31, 2023)

What is the 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? It is known that due to their small size, nanomaterials have a strong propensity to disperse and can reach places inaccessible to larger particles. 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 falling back down¹²Effects 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, 23 June 2020
  –Differentially charged nanoplastics demonstrate distinct accumulation in Arabidopsis thaliana, Xiao-Dong Sun et al, Nature Nanotechnology, 22 June 2020
  -Marie Simonin’s 2015 thesis: 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) nanoparticles in six agricultural soils. The study concludes that there is no toxicity of TiO2 nanoparticles on the microbial communities, except in a 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 the diversity of bacteria and archaea. Moreover, negative effects are observed on nitrification, even for extremely low concentrations of TiO2 (0.05 mg kg-1), mainly related to a strong sensitivity to this pollutant of the ammonium oxidizing archaea (AOA) involved in this process.: do they migrate into groundwater or are they trapped in the soil before reaching the water table? Do they end up in the soil after the application of sludge from wastewater treatment plants containing them (which is done to complete the treatment process while serving as a fertilizer) to agricultural land?
• 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 living on aquatic sediments
  • or on the contrary remain in suspension (especially if they are functionalized on the surface or coated) and disperse easily, increasing the risk of exposure; nanomaterials are already found in water treatment plants and industrial water treatment, but the treatments in place were not designed to filter them¹⁴See the work of the “Nanotechnology waste” working group of the Midi-Pyrenees Regional Industrial Waste Observatory (ORDIMIP). A significant part ends up in surface waters, while the others accumulate in the sludge of wastewater treatment plants spread on agricultural land…

More generally, nanomaterials or nanomaterial residues can also :

• penetrate and accumulate in different species bacterial, plant, animal, terrestrial or aquatic (knowledge should increase in the coming years thanks to advances in metrology allowing the detection of nanomaterials in biological tissue¹⁵Cf. 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 move up the food chain

Many questions are still unanswered

Once in the environment, nanomaterials or nanomaterial residues can undergo transformations: which ones and under what conditions? Many parameters come into play and lead, for example, to 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 involved are so numerous and variable (the light¹⁶On the influence of light on the physicochemical parameters of nanomaterials, see for example:
– New Study Shows How Engineered Nanomaterials Degrade, Persist in Environment, News of the World, Sept. 1, 2021 (news release in English: New Study Shows How Engineered Nanomaterials Degrade, Persist in Environment, George Washington University, Sept. 1, 2021), the degree of acidity¹⁷On the influence of acidity on the physicochemical parameters of nanomaterials, see for example:
– Fate of iron nanoparticles in the environment. Colloidal stability, chemical reactivity and impacts on plants Edwige Demangeat’s thesis, 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 physicochemical 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 across 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. , Environ Toxicol Chem, 2016 for example, can be decisive). As a result, it is very difficult to determine the effects on ecosystems in each case. Because many studies have long been conducted on synthetic nanoparticles 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 not yet generalizable and should be considered with caution.