Carbon nanotubes and graphene can cause lung inflammation in rats in an experimental setting, but carbon black and graphite nanoplatelets do not, finds research in BioMed Central's open access journal Particle and Fibre Toxicology.

Carbon nanotubes, graphene, and graphite nanoplatelets are strong, and conduct electricity, meaning that they have been incorporated in to everyday industrial applications, such as microelectronics and lightweight materials.

Another carbon-based nanomaterial, carbon black, has been used for decades in car tyres to improve grip and stability. It has already been established in mice that carbon black can causes inflammation within the lung and results in an increased risk of lung adenoma and adenocarcinoma.

Researchers from BASF SE, Germany, developed a test for inflammation due to inhaled particles in rats. No adverse effects were seen with short term inhalation of carbon black or graphite nanoplatelets, while carbon nanotubes and graphene both caused lung inflammation even at low concentrations. The effect of the nanotubes was markedly higher than that of graphene.

The cause of the toxicity of carbon nanotubes and graphene in rats has yet to be identified. Dr Robert Landsiedel explained, "We do not yet know exactly what material properties make a carbon nanomaterial toxic and others not. Until the properties which determine toxicity are identified we will need to assess them carefully to prevent harm to humans and the environment."

Dr Flemming Cassee, Editor in Chief of Particle and Fibre Toxicology commented, "The exponential use of nanomaterials requires a dedicated risk assessment. This study was really targeted towards the needs for appropriate inhalation toxicity data."