Did you know that in addition to the smoke from combustion, also cosmetics, sunscreens, fabrics, textiles and medicines could contain nanoparticles? But what exactly are they and why the U.S. Agency for the Environmental Protection (EPA) is studying their effects on human health and ecosystems? And what the butterfly effect has to do with them?
The market of nanomaterials is growing strongly and they are currently used in more than 500 products. We could find them in cosmetics, sunscreens, fabrics, textiles, medicines, paints, food packaging, vehicles, electronics, sports equipment, fuel, biomedical supplies. Their impacts on human health and the ecosystems are still largely unknown. For this reason, and to make potentially dangerous nanomaterials harmless, EPA (U.S. Environment Protection Agency) is undertaking assessments on nanotechnology.
Nanoparticles are so small that cannot be visible with any type of microscope. They have unique and different optical, mechanical, magnetic, conductive and adsorption properties, if compared to the same substances in a larger scale. Current investigations are aimed primarily at ensuring that there are no negative consequences with the exposure of human beings and ecosystems to nanoparticles. The assessments also deepen the knowledge for the sustainable use of nanotechnology, which prevents any form of pollution, resulting in possible limit values of exposure and concentration for the different substances. Values that the legislature should then regulate.
The EPA assessments cover the following most commonly used materials:
- Carbon nanotubes (vehicles, sports equipment, electronics, flat screen TVs, car dashboards), for which it has already been observed toxicity, especially in aquatic environments, and their already verified and unwanted interactions with natural organic matter;
- Nanoparticles of cerium oxide (electronics, energy, fuel additives, bio-medical supplies), which are easily dispersed in the environment with still unknown effects on public health and ecosystems;
- Nanoparticles of titanium dioxide (cosmetics, sunscreens, paints, coatings, removal of contaminants in drinking water);
- Silver nanoparticles (embedded in fabrics and materials to eliminate bacteria and unpleasant odors, and in food packaging for their antimicrobial properties, used in spray disinfectants);
- Iron nanoparticles (optics, source of easily absorbable iron, removal of contaminants in wastewater);
- Micronized copper (treated wood).
Currently, March 2014, the research is still in progress. It concerns the risk assessment and includes the entire life cycle of products, from the raw material extraction to the production cycle, to their use, recycling and final disposal. It aims also to determine the impacts of nanoparticles coming from the combustion and the consequent potential air pollution. It concerns detection, quantification and characterization of nanomaterials, and studies their properties.
Nanoparticles are small pieces of any substance, whose dimensions are measured in nanometers. A nanometer is a billionth of a meter, or one millionth of a millimeter. Take a ruler, look at the space occupied by a millimeter and imagine the millionth part of this small space. It is an infinitesimal size, an atomic size.
A nanometer (nm), also called millimicron (mμ), measures 10-9 meters, or 10-6 mm.
In the cake shaped model of the atom, in which electrons are assumed as distributed here and there just like raisins in a cake, of the British physicist Joseph John Thomson (1856 – 1940), the atom is compared to a sphere with a radius of about 10-10 meters (one angstrom Ǻ, that is 0.1 nm).
In the model of the atom with orbiting electrons of the Danish physicist Niels Bohr (1885 – 1962), the radius of the hydrogen atom at the minimum energy state is about 5.3 • 10-11 meters. The hydrogen atom is the smallest atom with atomic number equal to 1.
Such small particles, with infinitesimal mass, are not affected by the force of gravity, which acts only on massive bodies, and they follow laws different from those ones of classical physics. The force of gravity does not have significant influence at the atomic and subatomic level. A complex physical system, such as that one of the nanoparticles, for example, could have a chaotic dynamic behavior and could need to be studied with the science of chaos, or deterministic chaos, developed by the U.S. mathematician and meteorologist Edward Norton Lorenz (1917-2008) . It is to him that we owe the definition of the butterfly effect: ” … modest phenomena, which are generated on a small scale, such as the beating of a butterfly’s wings, can cause changes of immense level and high intensity on a large scale, such as the development of a tornado … ” . Such small particles, their interactions and their physical characteristics can also be studied through quantum physics.
The minimum dimensional levels in biology include ultramicroscopic size from 1 to 200 nanometers, which allow the investigation of cellular ultrastructures, viruses and macromolecules with the electron microscope, while for the study of molecules and atoms below the nanometer size the survey with X-ray diffraction is used in the study of the molecular structure. In the animal cell, with the electron microscope, we can observe, for example, ribosomes which contain ribonucleic acid (RNA) and have a diameter of about 20 nm, the mitochondria, with a diameter of about 500 nm, the lysosomes, place of enzymatic processes and of biochemical functions, with a diameter ranging between 300 and 800 nm, the cytoplasmic membrane, with a thickness between 6 and 10 nm, which controls the passage of molecules and ions from the cell to the environment and vice versa.
Nanoparticles are smaller, so small that they could either enter in the food chain, or pass directly through cell membranes. It is precisely for this reason that they are used to convey medicines and trace elements, such as iron, as described above. Some of these substances can be useful, some harmless, others are dangerous.
In addition to those ones recently used in the industry of nanotechnology, particles, and thus nanoparticles, are already produced by the natural and man-made combustion, for instance by lightning, volcanic eruptions, fires, traffic, heating plants, power plants, industrial waste incinerators, and can contribute to air pollution.
Nanoparticles, nanomaterials and nanotechnologies represent a future not yet completely known, that comes to us and of which we must be aware . Absence of detection with the microscope, unpredictability of behavior, non-compliance with the laws of classical physics, and atomic dimensions suggest to manage them with the utmost caution and with full transparency.
(Translation of the article: Paola Morgese, “Effetti delle nanoparticelle sulla salute e sull’ambiente: le ultime ricerche US EPA” published in the blog of Sostenibile.com))
Paola Morgese, PMP
Civil Hydraulic Engineer
M.S. Sanitary and Environmental Engineering
Halliday, R. Resnick, Fisica 2, Casa Editrice Ambrosiana
Montalenti, V. Giacomini, Biologia, Sansoni
Ricci, Fisica, Giunti
www.epa.gov (Nanoparticles, March 2014)