Risk Assessment of Manufactured Nanomaterials - Environmental and Human Health Impacts of Nanotechnology - page 386

i . Whether current risk assessment methodologies for chemicals are 'fi t for purpose'
given the unique issues presented by nanomaterials.
ii. Whether the current legislation that requires risk assessments (e.g. REACH in
the European Union) covers nanomaterials suffi ciently.

On the international stage, the Organisation for Economic Co-operation and
Development (OECD) is taking a leading role in exchanging information on risk
assessment approaches for nanomaterials through its programme of work under
the Working Party for Manufactured Nanomaterials (http://www.oecd.org/environ-
ment/nanosafety). The primary question is a matter of how risk assessments should
be confi gured for nanomaterials. The EU Commission' s Scientifi c Committee on
Emerging and Newly Identifi ed Health Risks (SCENIHR) has offered ' opinions '
on this (SCENIHR, 2005, 2007; see Section 10.5). The United Kingdom has also
examined the fi tness for purpose of ecotoxicological assessments for nanomaterials
(Crane and Handy, 2007; Crane et al. , 2008). A further evaluation of test methods
using reference nanomaterials is being undertaken by the OECD (Working
Party on Manufactured Nanomaterials, Steering Group 4; http://www.oecd.org/
department/0,3355,en_2649_37015404_1_1_1_1_1,00.html ).

10.2 Risk Assessment Process

Chemical risk assessment has been developed over many years through the pro-
cesses of national and international consensus (Risk Assessment and Toxicology
Steering Committee, 1999). Conventionally, it comprises:

(i) Hazard identifi cation identifi es possible adverse biological effects on organisms
(the ' receptor ') using data published in the peer reviewed literature, the col-
lection of new toxicological data from in vitro and/or in vivo studies, or chemi-
cal modelling (e.g. quantitative structure activity relationships, QSAR). Hazard
identifi cation may include hazards from metabolites or reactive intermediates,
not just the parent compound, and includes a consideration of tolerant and
sensitive organisms. This is important in ecosystems, where the sensitive organ-
ism is a keystone or protected species, and in human health, where it may be
unacceptable to not protect sensitive individuals (e.g. slow metabolisers, or
patients with history of hypersensitivity).
(ii) Hazard assessment establishes the existence of exposure pathways and quan-
titatively evaluates the observed adverse effects including dose-response assess-
ment, species differences or sensitivity distributions as well as mechanisms of
action. Here, quantitative estimates of hazard (e.g. predicted no effects con-
centrations, lethal or sub-lethal effects concentrations) may be estimated.
(iii) Risk estimation addresses the potential risk to the identifi ed receptors via each
of the identifi ed exposure pathways and involves an estimation of intake or
exposure to a chemical (magnitude, duration and frequency) for the general
population, sub-groups or individuals.
(iv) Risk evaluation combines the stages above to draw conclusions on the signifi -
cance of the risk posed.