ARE CARBON NANOTUBES A SAFER ALTERNATIVE TO HALOGENATED FLAME RETARDANTS IN CONSUMER PRODUCTS?

Halogenated flame retardants (HFR) are nowadays extensively used in consumer products because of the low loading levels necessary to meet the flame retardancy standards, cost-effective production and their low effect on material properties. However, some of these chemicals are toxic to reproduction, persistent in the environment and in living organisms and are suspected endocrine disrupters. Multi-walled carbon nanotubes (MWCNTs) are able to ameliorate the mechanical and thermal properties of polymers and textiles and could successfully contribute to the replacement of such hazardous chemicals in flame retardant (FR) composites. MWCNTs with different characteristics, such as length, aggregation properties, and surface functionalization have different biological impact. Thus, gaining a clear understanding of MWCNTs toxicological profile is of great importance to perform a comparative risk assessment of the different flame retardant solutions. Short and thin MWCNTs have been regarded as not carcinogenic and immunotoxic in in vitro and in vivo studies in animals while long and thick MWCNTs have been regarded as having asbestos-like toxicity. As a consequence, results coming from toxicity studies performed on one kind of carbon nanotube (CNT) should not be generalized to all carbon nanotubes. This paper will provide an overview of the main toxicity concerns for CNTs together with an analysis of the main exposure scenarios for humans and the environment from commodity articles.