What are health effects of ultra-fine and nano particles?

What are health effects of ultra-fine and nano particles?

In recent years, scientists have investigated the health effects of airborne particles and of ultra-fine particles in particular. They are finding convincing results indicating that airborne particles damage our health. These results are well described in literature, for example in the WHO Air Quality Guidelines

In short, statistical evidence has been found that acute negative health effects related with increased levels of airborne particles include:

  • Increased use of asthma medication
  • Asthma attacks in patients having asthma
  • COPD (chronic obstructive pulmonary disease) attacks
  • Hospital admissions for cardiovascular diseases
  • Deaths from heart attacks, strokes and respiratory problems

Beside these acute health effects on people with high susceptibility towards particles, scientists also expect a long-term effect on normal people: life expectancy decreases significantly as a result of high particle concentrations. Furthermore, a study describing the relation between the development of the lungs of children and the distance between their homes and a busy road may support this statement.1 

Deposition of ultrafine nanoparticles in the lungs and its relation to the human health

Ultra-fine particles (in the range around one hundred nanometer) seem to play a special role and are potentially more health hazardous than coarse particles. For this reason it is still subject of ongoing scientific research. Some possible explanations have been suggested.

One is that, due to their aerodynamic properties, ultra fine particles penetrate and deposit deeper in the lungs than coarser particles. About 50% of the particles around 20 nm deposits deep in the lungs as is shown in the graph below. Larger particles are caught in the nose and throat.

Deposition of ultrafine nanoparticles as a function of their size

Another explanation is that the concentration of ultra fine particles is generally much higher than the concentration of coarser particles. The lungs cannot deal with the high amounts of particles that deposit in the lung sacs, which lead to inflammation.

Related to this is the relatively high total surface area of ultra fine particles. The surface area of a given number or volume of particles is much higher for ultra-fine particles than for courser particles (see Concentrations). Scientists assume surface area is related to free radical activity and oxidative stress in the lungs. Oxidative stress is known to have inflammatory effects.

A fourth possible explanation is that the size of the particles is much smaller than the human cellular structures. They can enter the human body and end up in the blood stream causing heart and brain diseases.

Yet another aspect in the harmful effect of airborne particles is that (ultra-fine) particles like diesel exhaust are often covered with toxic chemicals like polycyclicaromatic hydrocarbons, which are known carcinogenic.

1 Effect of exposure to traffic on lung development from 10 to 18 years of age: a cohort study, Gauderman, www.thelancet.com. Published online January 26, 2007.


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