Kicking up nanoparticles – what’s the danger?

Nanoparticles are incredibly small. So small that the material from which they are made – such as silver, copper or zinc – behaves differently to how it would on a larger scale.

The reason for this is the large surface area/volume ratio. Because they are so small, they consist of very little other than surface area and this makes the particles very reactive

It is this that concerned a team of researchers from Rutgers University in New Jersey who have looked at how nanoparticles behave and how they could be contributing to indoor air pollution.

A nanoparticle is generally accepted to measure between 1 and 100 nanometers. When we talk of PM2.5 we do so because were are referring to particles that measure less than 2.5 microns. Consider then that there are 1,000 nanometers in a micron.

Nanoparticles – which may be made from a variety of metal such as silver, copper or zinc – are used in a huge range of applications, many of which are household products: cosmetics, disinfectants, sunscreen, hairsprays, and even food.

It has long been known that particulate matter that has settled on the floor will be resuspended when walked over but much less was known about the possible resuspension of nanoparticles. 

To learn more, the Rutgers team constructed an enclosed, air-controlled chamber with both carpeting and vinyl flooring. Samplers were positioned at various heights in the chamber.

Seven products containing nanoparticles of silver, zinc, and copper were sprayed into the air and, wearing Tyvek suits and respirators, they walked the surface after and measured the results. Additionally, a small robot was used to simulate the actions of a child.

It was found that:

• Particle resuspension rates from the carpet were up to 320 % higher than resuspension rates from vinyl flooring.
• Resuspension rates measured at 0.3 m were up to 195 % higher than those measured at 1.1 m.
• Resuspension rates due to a walking adult were up to 243 % higher than resuspension rates caused to a moving robot that simulated a child.

Gediminas Mainelis, a professor at Rutgers School of Environmental and Biological Sciences, who led the study said: ‘If an adult is walking in a room, and steps on some of these deposited particles, we found that the particles will be re-suspended in the air and rise as high as that person’s breathing zone. A child playing on the floor inhales even more because the concentrations of particles are greater closer to the ground.’

‘There is very limited knowledge of the potential for exposure to nanoparticles from consumer products and resulting health effects.’

‘We can use this knowledge to minimise our exposures, in this case to various nanomaterials. Overall, this work could help us understand the resulting exposures and support future studies on human exposure reduction.’

The full research can be accessed here