Nano- and ultrafine particulate matter in air

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STAMI will organise a conference on nano and ultrafine particulate matter next year in Norway (3-6 June 2019). The conference is also in our event calendar on the PEROSH website.

Below you can find a contribution on this topic from Balazs Berlinger. He is a research associate professor at the National Institute of Occupational Health in Oslo (2008-present), previously working at the Hungarian Institute of Occupational Health in Budapest, Hungary (2003-2008). Until now, he authored 26 publications including one chapter of a book. His main research interests are occupational exposures to workplace aerosols, biological monitoring of inorganic substances and workplace aerosol characterization.

Nano- and ultrafine particulate matter in air
Balazs Berlinger

Humans are exposed to nanoparticles from ambient, indoor and workroom air. There are several sources and types of nanoparticles, such as combustion derived particles, e.g. diesel exhaust and wood smoke, unintentionally formed particles e.g. metal and welding fumes, which are often called ultrafine particles, and manufactured or engineered nanoparticles e.g., titanium dioxide, carbon nanotubes, silver nanoparticles, cellulose nanocrystals.

Nanoparticles are particles with lengths from 1 to 100 nm in two or three dimensions. The number of consumer products containing nanomaterials (often in form of nanoparticles) is increasing rapidly. In 2005, there were reported only 54 such products, while in 2015 that number was over 1800 different products.

Health effects of nanoparticles

Toxicological studies in the 1990s and 2000s showed that nanoparticles cause more adverse respiratory health effects and inflammation than larger particles made from the same material. It was also assumed, that in general, smaller particles exhibit higher toxicity than larger particles of the same chemical composition and crystalline structure.

Several epidemiological studies have demonstrated that exposure to particulate matter in urban air is associated with adverse health effects in humans, including an increase in morbidity and mortality related to pulmonary and cardiovascular diseases in susceptible populations. Exposure to welding fumes and other particulate matter derived from combustion sources in the industry may also have significant effect on human health. Numerous studies have addressed the effects of such particulate matter on pulmonary function of workers. At the same time, limited evidence of the relationship between particulate matter exposure at workplaces and adverse cardiovascular effects has emerged from studies in occupational settings.

Higher risk when exposed?

Exposure to nanoparticles pose a potentially higher health risk for humans than exposure to larger particles (>100 nm). The possible explanations include that nanoparticles are less efficiently removed, and pass the cell membranes more easily than larger particles. Nanoparticles have much larger surface area relative to particle size compared to larger particles, which can influence the biological effects together with other properties, such as solubility, shape and surface reactivity.

Ultrafine particles derived from combustion sources are heterogeneous in size as well as in physical and chemical properties, and most often exist in agglomerated form. Whereas, engineered nanoparticles have a relatively homogeneous composition and size compared to ultrafine particles.

There are many published studies that have investigated the toxicity of engineered nanoparticles in vivo and in vitro. At the same time, such studies with ultrafine particles are almost completely missing. There is also a lack of research data on the association between exposure to ultrafine particles and health outcomes. Exposure to engineered nanoparticles has been investigated in a limited number of studies that have found relatively low concentrations of nanoparticles in the workplace air. No clear evidence that these concentrations can cause any detectable health effects in workers has been found.

A challenging task – investigating ultrafine particles in air

It is quite obvious that investigating ultrafine particles in air with respect to toxicity and health effects is very challenging as the fraction of ultrafine particles is only a sub-fraction of ambient and workplace particulate matter. Ultrafine particles are always co-existing with larger particles, which can also have an influence on toxicity and health effects.

Before performing further research on nanoparticles in the field of environmental and occupational health there are several issues that should be raised and/or clarified.

There is, of course, the obvious need for experts who are dealing with nano and ultrafine particulate matter to come together and exchange ideas and knowledge in order to set the best way to obtain relevant research results and practical use. Be them biologists, toxicologist, chemist, physicians and/or occupational hygienists.

In addressing this, there are several questions to address. For example, to what extent can knowledge on the toxicity of engineered nanoparticles be used in the evaluation of the toxicity of ultrafine particles? Or, for example, is it possible to discuss engineered nanoparticles and ultrafine particles together, or should one define a clear difference between them?

Main source for the scientific facts:

  1. Crisponi, V. M. Nurchi, J. I. Lachowitz, et al. Chapter 18 – Toxicity of Nanoparticles: Etiology and Mechanisms in Antimicrobial Nanoarchitectonics, ed. A. H. Grumezescu, Elsevier, 2017, ISBN 978-0-323-52733-0, p. 511-546

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