NIOSH: Exposure limits are uncertain for nano particles
Nanotechnology is a broad name given to a wide range of technologies and materials that create, manipulate, or use particles that have one thing in common - their size. Nanotechnology (or nanoscience) involves materials that are extremely small and have dimensions roughly between 1 and 100 nanometres (nm). A nanometre is 1 billionth of a meter. To give you an idea of the scale of nanoparticles:
- A piece of paper is about 100,000 nm thick.
- A human hair is about 70,000 to 80,000 nm.
- A red blood cell is about 7,000 nm.
- A virus is about 10 to 100 nm.
While the exact definition of nanotechnology may vary, most research and studies have concentrated on particles with a dimension of less than 100 nm.
There are many types of nanoparticles - they can be particles, tubes, shells, quantum dots, etc. Other terms are nanomaterials or ultra fine particles.
Nanoparticles appear to enter the body the same way other particles - through inhalation, ingestion or absorption through the skin. While there is no cut off in size that makes particles toxic or non-toxic, some studies have shown that as particles become smaller, there is an increased likelihood of injury to occur.
In all cases, more studies are needed to determine the health concerns for humans. How a nanoparticle enters the body and the effect it may have depends on many factors including:
- Surface area.
- Composition / chemistry.
Current respiratory research indicates the following:
Nanoparticles can be deposited in all areas of the respiratory tract depending on the size and composition of that particular nanoparticle. They can also enter the blood and lymph circulation systems and be distributed throughout the entire body. When in the blood system, they can be taken up by the liver, spleen, bone marrow, heart and other organs.
NIOSH states the following health concerns:
- Animal and human studies have shown that airborne nanoparticles can be deposited in the respiratory tract. Animal studies have also shown nanoparticles with the ability to enter the blood and move to other organs.
- Animal studies have shown that nanoparticles show more effects than large particles of similar composition (showing pulmonary inflammation and lung tumors when inhaled).
- Studies in animals and cells have shown changes in the nanoparticle’s chemical composition, structure, and size make a difference in their properties and toxicity.
- Workers exposed to fine or ultrafine particles have shown lung effects.
NIOSH also cautions that current occupational exposure limits for "normal" chemicals or materials may not equally apply to related nanoparticles.