The Air We Breathe


About the author: James Dale is a PhD candidate in Geosciences at Virginia Tech. Check out his profile on the VTSuN student page.

Environmental research is often oriented around environmental stewardship: the protection of natural resources is important for as long as we are stuck on this rock we call Earth.  It is important that we keep natural systems like streams, lakes, forests, etc. healthy, not just for its own sake (though that is a good cause as well) but because these systems both directly and indirectly affect human health in numerous ways.  Recently, Jake Metch wrote about waterways and why it’s important that we study them.  Waterways are one of the most studied environmental systems and for good reason!  We need to carefully protect our supply of fresh water from both current and future hazards in order to retain access to clean drinking water.  But water isn’t the only resource that needs to be protected in order to maintain ready supply in the future; another important resource is our atmosphere.

Air pollution can drastically reduce life expectancy and sharply increase cancer rates and respiratory issues, therefore it is vitally important that we protect the air we breathe going into the future.  Preserving our atmosphere is a tricky subject though: it’s vast and is capable of spreading pollutants far and wide.  Atmospheric research is therefore often aimed at preventing large-scale contamination, rather than containment or cleanup.  Virginia Tech’s Sustainable Nanotechnology Center fits into the research picture by investigating how nanoparticles form, transform, are transported, and where they ultimately deposit when they travel through the atmosphere.  By being able to make accurate predictions about nanoparticles that enter the atmosphere, we can make judgments about the potential safety of products that use those nanoparticles.

We know air pollution is unhealthy, particularly when we see dramatic images like these, but polluted air isn’t always visible to the naked eye. (Image source: Wikipedia)
We know air pollution is unhealthy, particularly when we see dramatic images like these, but polluted air isn’t always visible to the naked eye. (Image source: Wikipedia)

The uniqueness of nanoparticles is often why scientists are so interested in them, but it can also make these nanoparticles a greater health hazard if they are emitted into the atmosphere.  As mentioned previously, the atmosphere can transport pollutants large distances and deposit them in completely new places.  This transport is largely controlled by a few factors: the wind speed and direction, and particle size and density.  Due to their incredibly small size, this means contaminant nanoparticles in the atmosphere can travel extended distances before being deposited widely across the globe, even when the source is confined to a small geographical area.  This is important because the decisions of individual countries to permit the use of certain products affects more than just themselves or even their immediate neighbors, it can affect the entire world!

Our atmosphere is a complex system with multiple layers and processes all interacting and reacting simultaneously.  It’s no wonder we can’t perfectly model it yet! Source: Wikipedia
Our atmosphere is a complex system with multiple layers and processes all interacting and reacting simultaneously. It’s no wonder we can’t perfectly model it yet! Source: Wikipedia

During their residence in the atmosphere, suspended particles may be inhaled and potentially cause a new set of problems. This direct pathway to the lungs is of concern because the lungs have fewer protections than the digestive tract or skin, the more commonly studied exposure routes.  The lungs provide a fast and relatively direct route to the bloodstream, where contaminants can disrupt normal cell functions throughout the body.  As with atmospheric transport, the size of particles also controls their depth of penetration in the airways during inhalation.  It has been shown that inhaled particles are predominately trapped either in the nose, throat, or lungs based on their size.  The particles that most readily deposit deep in the lungs are in the nanoparticle size range. It is important that we minimize the release of and exposure to particles in this size range for the protection of human health.

The particles we inhale can deposit in a number of different locations within our bodies.  This figure shows the particle size ranges that deposit at different locations within our airways and the physical mechanisms that control that deposition. (Image adapted from Quadros 2010 and Oberdorster 2007)
The particles we inhale can deposit in a number of different locations within our bodies. This figure shows the particle size ranges that deposit at different locations within our airways and the physical mechanisms that control that deposition. (Image adapted from Quadros 2010 and Oberdorster 2007)

Many researchers around the world, including here at Virginia Tech’s Sustainable Nanotechnology center, study nanoparticle contamination of the atmosphere and the threat it poses to human and environmental health.  Our goal is to understand the processes that control nanoparticles’ transport and deposition (both in the environment and the human body) so that we might predict which consumer products containing nanoparticles are safe for use and which are likely to cause problems.  Ultimately, a deep understanding of these processes could allow us to predict the threat posed by new products before their introduction into the mass market, preventing large scale contamination.

 References:

Oberdorster, Stone, and Donaldson, Toxicology of nanoparticles: a historical perspective. Nanotoxicology (2007)

Quadros and Marr, Environmental and human health risks of aerosolized silver nanoparticles. Journal of the Air & Waste Management Association (2010)

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