Health Hazard: Ultrafine Particulate Matter & Nanoparticles

How does particulate matter, or ultrafine particulate matter, actually form?

Particulate matter, especially ultrafine particulate matter, doesn't occur in nature. Particulate matter forms through friction, combustion processes, and chemical reactions, when nitrogen dioxide reacts to form secondary particulate matter. So it's possible for a particulate matter reading from an exhaust measurement to look unremarkable, while secondary particulate matter forms with a time delay.

As combustion processes keep improving, there's a tendency for smaller particulate matter, or ultrafine particulate matter, to be produced in favor of reducing coarse particulate matter.

"High-pressure direct-injection engines produce significantly more particulate matter (ultrafine particulate matter) than conventional engines did, since fuel is broken down into extremely fine particles before combustion. This lays the groundwork for ultrafine particulate matter emissions," says Frank Hoferecht, particulate matter expert at ETE EmTechEngineering GmbH — the first spin-off from the DBFZ German Biomass Research Centre non-profit GmbH.

Not to be neglected is particulate matter arising from tire and brake wear during vehicle use. "This is also the case with modern electric vehicles," adds Frank Hoferecht.

Particulate matter, ultrafine particulate matter, nanoparticles: what are the differences?

Not all particulate matter is the same — it pays to look closely here. The amount of particulate matter is usually measured in µg/m³ (micrograms per cubic meter). This obscures the fact that particles sized 10 µm (PM10) — also called coarse particulate matter — and PM1 have a volume ratio of about 1:1,000. A PM10 particle, at the same density, accordingly weighs about 1,000 times more than a PM1 particle. For PM0.1 (ultrafine particulate matter), the factor is even 1:1,000,000 compared to PM10. So for every PM10 particle, there are a million PM0.1 particles (ultrafine particulate matter) at the same mass per µg/m³.

This creates potential for misinterpretation: usually, the PM10 particulate matter reading also includes all smaller particles (i.e. PM2.5, PM1, and even ultrafine particulate matter). In practice, though, there are several problems here:

1. Differentiated statements about the various particles can't be made. If, for example, the number of PM10 particles has decreased, there can still be significantly more particulate matter particles in the air. That's why PM1 should also be measured separately from PM2.5. It's also advisable to record particle count, not just a pure mass figure. This makes no difference to scientists, but it makes the effect clearer to laypeople.

1. Current sensors measure on the principle that all smaller particulate matter is also counted, but for technical reasons can't fully capture the smallest particles. This is especially true for inexpensive measuring devices. According to manufacturer datasheets, often at most 10 percent of the smaller particles are captured.

1. Claims that filters reduce the share of particulate matter particles therefore can't be made across the board, without also conducting separate studies in the coarse particulate matter, particulate matter (PM2.5), and ultrafine particulate matter range (PM1; PM0.1 and below).

How dangerous are nanoparticles?

Over 95 percent of the lung's surface consists of thin alveolar tissue. The delicate tissue of the alveoli enables efficient exchange of oxygen and carbon dioxide with the blood. It also forms a tissue barrier just 1 micrometer thin, which blocks larger particles from entering. Smaller particles, such as nanoparticles under 20 nanometers in size, get through anyway and can distribute much more readily throughout the body than larger microparticles. The smaller the particles, the more reactive they are. This is due to the surface-to-volume ratio. Via the bloodstream, the particles reach every organ, such as the lymph nodes, spleen, bone marrow, placenta, liver, kidneys, heart, or even the brain. When we inhale ultrafine particulate matter and nanoparticles, they penetrate deep into the body and can cause health effects here.

While biodegradable materials dilute through mixing with bodily fluids and dissolve over time, biopersistent materials become lodged in tissues and cells. This becomes dangerous when such biopersistent nanoparticles contain transition metals and/or their oxides, for example zinc, cadmium, copper, or silver. These metal ions are released in the body and can, under certain circumstances, exert a toxic effect. Besides size and composition, the shape of nanoparticles is also decisive for their effect. Fiber-like particles, for example, have aerodynamic properties that let them penetrate even deeper into the lungs and deposit more effectively there than spherical particles of the same mass. Fiber-like nanoparticles occur, for example, in asbestos or carbon nanotubes.

Through so-called endocytosis, a cellular transport process, metal-containing nanoparticles cross the cell membrane and thus gain access to every body cell. At a pH of 4 to 5, even poorly soluble metal oxides are readily soluble. If the substances dissolve inside the cell, metal concentrations arise that the cell can barely defend against. The cell responds with stress and inflammatory reactions, and cell death can also be a possible result.

Possible effects & impending health risks from nanoparticles

Nanoparticles are often not recognized by the immune system's natural cleanup cells, the macrophages. This lets the ultrafine particles penetrate membranes and mucous membranes. They can thus accumulate on lung tissue or reach the blood via the lungs. The deposited nanodust can trigger both acute effects like cardiac arrhythmia and long-term effects on the lungs.

Possible health effects from nanoparticles:

• chronic lung disease & increased likelihood of lung tumors
• increase in inflammatory markers in the blood
• increased tendency toward blood clotting
• increased risk of cardiac arrhythmia and heart attack
• allergies & eczema (e.g. hay fever, elevated IgE antibodies against common allergens)
• local inflammatory reactions (fibrosing/scarring changes in the lungs)

Large population studies show that the effects of ultrafine particulate matter and nanoparticles are especially evident in children, who experience an increased incidence of respiratory infections.

How does particulate matter settle out?

Particulate matter tends to agglomerate, meaning to accumulate. The cause is Van der Waals forces, which cause particles to attract each other at the molecular level. That's why particulate matter particles tend to bond together. Ultrafine and regular particulate matter readily attaches to materially similar dust. The clusters (agglomerates) that form over time this way eventually become heavy enough to fall to the ground. High humidity or rain can accelerate this effect further.

If large particles (dust and coarse dust) are now removed from the air, particulate matter and ultrafine particulate matter particles remain. Due to their size and the weaker Van der Waals forces of these particles, they collide with each other much less often and thus also stick together less often. Over the years, dust and coarse dust have been increasingly filtered out of the air thanks to ever-improving filter technology in vehicle exhaust systems. What remains are the fine and ultrafine dust particles, whose occurrence can't be reduced by filter technology.

"According to the latest studies, smaller particulate matter particles and ultrafine particulate matter stay airborne for a very long time, in some cases indefinitely, since they don't fall to the ground," argues Hoferecht of ETE EmTechEngineering GmbH. There is thus a danger from very small particulate matter particles that has so far been underestimated.

The latest studies show that especially small particulate matter particles are much more harmful than large particulate matter particles, since these penetrate via the alveoli into the bloodstream and even into human cells. There, they can trigger inflammatory reactions that can lead to cancer. Disease incidence and mortality, especially in large cities and metropolitan areas, is rising dramatically¹.

Nanoparticles & pollutants from laser printers and copiers

Nanoparticles such as ultrafine particulate matter aren't only released into the air by vehicle exhaust. Another source of air pollutants are technical devices such as laser printers and copiers. An estimated over one billion laser printers and copiers worldwide release, unfiltered, a mix of particulate matter, nanoparticles, and pollutants, thus polluting the air breathed by humans and animals. The emissions contain metallic and carbon nanoparticles from the toners, which enter the body with every breath. In the lungs, blood, and all organs and cells they reach, nanoparticles can deposit and trigger cell-damaging oxidative stress, inflammation, or even genotoxic effects.

Typical symptoms of nanoparticle exposure from laser printers

Do you frequently deal with laser printers, fax/copy machines, or toner dust — for example at the office or your home workplace? Then you should watch for possible effects. Monitor your health and well-being near the devices. Do the following symptoms occur frequently?

• Cold-like symptoms such as sneezing, runny nose, coughing, sore throat, asthma, or chronic bronchitis (COPD)
• red, itchy, burning eyes
  skin redness, itching, pustules, especially in exposed areas like the face, décolletage, or hands
• headaches or pain in the musculoskeletal system, especially in the muscles
• inflammation of the bladder or prostate
• concentration, memory, and word-finding problems
• exhaustion, burnout, or depression

Do you notice these symptoms regularly in connection with the devices, and do they ease when, for example, you're on vacation and thus not near the devices? Do the symptoms also worsen when the devices run more, or when there's less ventilation? Then the toner or the devices' emissions could be the cause of your complaints.

How do you reduce the effects of laser printers & copiers?

• Prefer printing with an inkjet printer (ink instead of toner)
• Always use a filter for laser printers (toner-based print systems).
• Place laser printers and copiers in separate rooms where possible. Ideally, this room should have its own supply and exhaust air, not coupled to the central air conditioning system for supply and exhaust air.
• Check air quality with an air monitor like the air-Q.

Tip: nano-Control, the international foundation for healthy indoor air, advises businesses, schools, daycare centers, authorities, and organizations. The foundation shows concrete measures and developments for safe printing.

Reliably detecting particulate matter with the air-Q air monitor

The air-Q air analyzer can detect particulate matter of different particle sizes. With this sensitive air monitor, you detect all three different sizes, PM₁, PM₂.₅, and PM₁₀, in real time via sensors. If the particulate matter reading or the thresholds of other air pollutants are exceeded, the air-Q sounds an alarm. Using the intuitively readable traffic-light system, you can see via the LED lights whether and how air quality is changing. Detailed reading development is charted in tables and charts in the web browser or in our air-Q web app.