Environmental Engineering Reference
In-Depth Information
mentioned or defined in the existing legislation. There is an urgent need to agree and
harmonize the nomenclature of NMs for risk assessment.
There are also concerns that many manufacturers of NMs will not be considered
under the REACH legislation, since it only applies to producers with material production
capability of greater than 1 ton. In addition, NMs may not be classified as 'new
substances' because the current definition of a new substance is based on the idea that a
new substance has a unique, or new, chemical formula. The Chemicals Abstracting
Service provides a series of unique identifying numbers for existing chemicals (CAS
numbers), and a new material without a CAS number would require testing. However,
there is a problem with NMs because their chemical formula may be very similar or
identical to an existing compound. For example, SWCN and ordinary graphite are both
made of carbon, and therefore may have the same CAS number (CAS No. 7440-44-0).
Metal oxide, such as ZnO powder and ZnO NPs, may have the same number (CAS No.
1314-13-2). For the end user and the public, safety data on chemicals are often
organized by the CAS number, and thus, the chemical safety information available to the
public on the bulk materials and NMs (e.g., graphite and SWCN) may be the same
without a full safety evaluation.
In the case of NPs, the simplifying assumptions commonly applied in theoretical
considerations of particle attachment may not be valid anymore. Despite the existence of
numerous publications with reported nanoparticle sizes, shapes, and compositions, little
theoretical work has been considered the special properties of NPs that might affect their
aggregation and stability in the environment, and little evaluation has been done on the
transport properties of these new materials in aqueous systems. Most manufacturers of
NMs recognize the fact that the materials have small sizes with unique physical and
chemical properties. These unique properties make them as a novel substance, and many
companies are testing the materials for safety evaluation, even though their product may
already have a CAS number. This information is being collated on data bases, and data
libraries with some product information are available for the public
(
http://nanotech.csl.gov.uk/
).
Nonetheless, from the view point of legislation, it might be
prudent to include a phrase relating to the unique property of NPs so that we ensure
NMs are captured by the regulatory definition as a new substance.
Previous studies, mainly focusing on mammalian cells, have revealed three
principal mechanisms of cytotoxicity: oxidative stress, metal toxicity, and physical
piercing. However, the specific properties related to NM's toxic effects to living
organisms are as yet poorly understood. Mechanisms allowing NMs to pass through cell
walls and membranes, and the mechanism underlying NMs' trophic transfers are not
Search WWH ::
Custom Search