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Nanoparticles Toxicity - Inhalation And Pulmonary Toxicology

Updated on March 4, 2012

Nanotoxicity Can Cause Mesothelioma And Other Illnesses

photo by dnnya on Flickr
photo by dnnya on Flickr

Inahaling Toxic Nanoparticles And The Lung's Response

The human lung is an incredibly complex and intricate organ for such a seemingly simple task that it carries out. It has a strong defense mechanism, yet nanoparticle toxicity may present fresh challenges for the future. Besides the respiration function of taking oxygen out of air breathed in and expelling carbon dioxide from the bloodstream, the lungs also carry out an array of secondary tasks. The complexity of these secondary tasks is likely one of the reasons that modern artificial lungs still remain far from ideal solutions to pulmonary complications, being used primarily as a temporary method of sustenance until a donor lung can be found and a lung transplant operation performed. Some of these accessory functions of a real human lung include regulating the pH level of the bloodstream, producing mucus which contains antimicrobial compounds, and ciliary escalator action. There are two types of cilia (motile and non-motile) and it is the motile cilia that line the trachea and beat or stroke in coordinated waves. They look like hairs blowing in the wind. This motion is responsible for the mucociliary escalator action which pushes foreign particles and pathogens out of the system. Smoking is one factor that can sort of paralyze these cilia and by doing so create more susceptibility to airborne infection and respiratory problems. Another portion of the defense mechanism is the respiratory epithelium which is a basic type of tissue that lines the tract and keeps things moist and protected. Healthy epithelium also aids the escalator process. The moist lining of the mouth and nose also serve as a further protection against particles and the body is able to sneeze, spit or blow out those caught in these cavities.

Mucus And Cilia Particle Elimination

Future Health Issues Of Nanotechnology

Due to the mucociliary escalator process, most of the micron level sized entrants that are able to reach the alveoli (site of the actual gas exchange in the lungs) are quickly diverted and expelled from the body. The particles that are not immediately cleared can be ingested by phagocytes such as the pulmonary alveolar microphages. However, the system can be overwhelmed by certain type of particles leading to various illnesses. Silicosis is an illness caused by the inhalation of quartz which over time causes scarring of the air sacs, also known as fibrosis. Coal miners were often subject to pneumoconiosis (Black lung disease) due to the constant inhalation of coal dust. Generally, particles cleared through the escalator will be swallowed and this can lead to stomach and gastric problems such as cancer. It often depends on the type of particle and surface area geometry to tell how much irritation or inflammation can occur when the contaminated air is breathed. This described process has all been pretty well understood by modern medical professionals, but nanoparticles are presenting a new form of air safety issue. It is important that nanoparticle toxicity is studied so that scientists and consumers are not exposed to unjust inhalation hazards as nanotechnology continues to become ever more present in society.

The study of nanoparticle toxicity is called nanotoxicology, and there are all sorts of unique issues at the nanoscale due to the quantum behavior. One such example of a hazardous nanoparticle is the often talked about carbon nanotubes. Their shape, and incredible strength, is a great advancement in science when it can be leveraged for nanotechnology applications, but introduce carbon nanotubes into the human body and they become like asbestos fibers. This can ultimately lead to doctors seeing patients with mesothelioma cancer and other similar symptoms. Due to the nanoparticle toxicity, special handling procedures, manufacturing processes, and disposal methods must all be developed with the health risks in mind. Extensive study is still necessary to truly understand the biodistribution properties of nanoparticles and how exactly they interact within the human body and immune system. Some nanoparticles such as iron oxide and zinc oxide have been experimented with and relieved of most charges with researchers finding them primarily non-toxic. Carbon nanotubes and titanium dioxide have been shown to cause DNA damage, and copper oxide was identified as a "clear health risk." Particles that enter the lungs can be classified by their half-lives of clearing out of the mucociliary escalator system. Often 50-60 percent of the particles will be expelled in 24 hours at the micron level. Nanometer sized particles can be more troublesome. Recent tests relate nanoparticle air pollution with some types of morbidity and mortality as the nano particles pass into the circulatory system and affect cardiovascular processes. With more products haveing ultrafine particles introduced (everything from sunscreen/sunblocks, lotions, and foods!) , a more complete understanding of the health effects will assist process designs and ethical decisions.

New methods of filtering have led to improvement in masks, filters, goggles, and other safety equipment to protect workers from exposure. Interestingly, it has been found that 300nm is about the threshold where filters begin to behave a little differently on particles that small. Were traditional filter membranes rely on impaction, sedimentation and entrapment to capture particles in the sieve-like filter material, below 300nm different forces are at work. Instead of slipping through the porous filter membrane, as might be expected, diffusion and electrostatic forces take up the task and so often a traditional filter will do quite well against toxic nanoparticles. But green nanoparticle purification alternatives are coming about. Brownian motion particle theory is a significant factor. It is wise to fact check against a case study of the particular substances in use as some filters will eliminate a greater portion of smaller particles and will have a lower efficiency rating on particles a few nanometers larger. Respirators, masks, and gloves all have a ways to go in providing better protection. Besides being protected against, nanoparticles can also be used to dope masks and goggles to make them more efficient at eradicating molecules from the air. Around the time of the SARS outbreak, these types of nano-masks became more popular as health concerns increased.

The story of nanoparticles is not all toxic and bad news, however. In fact, pulmonary inhalation of nano-particles looks to be a promising method of administering drugs into the human body. Researchers just recently showed the effectiveness of a silica np that could be inhaled and carry anti-cancer drugs directly to lung tumors and provide protection against common resistance mechanisms as well. Whether intentionally or unknowingly, it is likely that you will inhale a great quantity of nanoparticles in the future.


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