Nanoparticles in the environment can cause serious auto-immune diseases including rheumatoid arthritis, say scientists.
The findings add to increasing concern that carbon nanoparticles in particular can cause major health problems.
Scientists at Trinity College Dublin's School of Medicine examined the development of autoimmune diseases in human cells when exposed to a wide range of nanoparticles with different physical and chemical properties.
They tested the effects of ultrafine carbon black, carbon nanotubes and silicon dioxide particles of different sizes, ranging from 20 to 400 nanometers, on human cells derived from the lining of the airway passages.
They also tested cells of so-called phagocytic origin − those that are most frequently exposed to inhaled foreign particles or are tasked with cleaning up our body from them.
At the same time, collaborating researchers from the US' National Institute for Occupational Safety & Health looked at mice exposed to chronic inhalation of air contaminated with single walled carbon nanotubes.
And, say the teams, the result was clear and convincing. All types of nanoparticles in both studies caused the same response - the transformation of the amino acid arginine into the citrulline molecule, which can lead to the development of autoimmune conditions such as rheumatoid arthritis.
Human proteins which incorporate citrulline as building blocks can no longer function properly and are destroyed and eliminated by the body. Once this process starts, the immune system can start attacking its own tissues and organs, thereby causing the autoimmune processes which may result in rheumatoid arthritis.
"The research establishes a clear link between autoimmune diseases and nanoparticles," says TCD's Professor Volkov.
"Preventing or interfering with the resulting citrullination process looks therefore as a promising target for the development of future preventative and therapeutic approaches in rheumatoid arthritis and possibly other autoimmune conditions."