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Posted: Jan 25, 2012
NanoRiskCat - A conceptual decision support tool for nanomaterials
(Nanowerk Spotlight) In a project funded by the Danish Environemntal Protection Agency (EPA), the Technical University of Denmark (DTU) and National Research Centre for the Working Environment have initiated the development of a screening tool called NanoRiskCat (NRC) for the evaluation of exposure and hazard of nanomaterials contained in products for professional and private use.
The project's aim was to identify, categorize and rank the possible exposure and hazards associated with a nanomaterial in a product. NanoRiskCat is using a stepwise approach based on existing data on the conventional form of the chemical as well as the data that may exist on the nanoform. However, the tool still needs to be further validated and tested on a series of various nano products in order to adjust and optimize the concept and thereby to achieve a screening tool as informative and practical as possible.
It is the view of the Danish EPA that the traffic light ranking of the health effects may be further modified to obtain a better ranking in the various categories. Thus titanium dioxide in sunscreen is ranked as red due to lung effects of titanium dioxide, because the tool in its present form does not sufficiently take account of which type of health effects that are most relevant for the most relevant exposure route of the product. In this case the inhalational exposure of titanium dioxide from a sun screen seems less relevant.
Nanomaterials are being used in a rapidly increasing number of products
available for industries and private consumers. The number of nanomaterials
that can be manufactured using nanotechnologies is immense and the improved
material properties enable use in multiple different products. During
the last decade more and more evidence has emerged in the scientific literature
suggesting that some nanomaterials may have hazardous properties.
With this background, the Danish Environmental Protection Agency has
identified a need for developing a new concept that can provide support to
companies and regulators in regard to assessing, ranking and communicating
what they know about the risks of nanomaterials in specific product uses. In
this case, risk should be defined as a combination of the likelihood of exposure
and adverse effects, i.e. any chance of an adverse outcome to human health,
the quality of life, or the quality of environment.
Through this project, DTU Environment and the National Research Centre
for the Working Environment have initiated the development of a screening
tool, NanoRiskCat (NRC), that is able to identify, categorize and rank exposures
and effects of nanomaterials used in consumer products based on data
available in the peer-reviewed scientific literature and other regulatory relevant
sources of information and data. The primary focus was on nanomaterials
relevant for professional end-users and consumers as, as well as nanomaterials
released into the environment.
The wider goal of NanoRiskCat is to help manufacturers, down-stream endusers,
regulators and other stakeholders to evaluate, rank and communicate
the potential for exposure and effects through a tiered approach in which the
specific applications of a given nanomaterial are evaluated. This is done by
providing detailed guidance on mapping and reporting of the:
1. Exposure potential for professional end-users
2. Exposure potential for consumers
3. Exposure potential for the environment
4. A preliminary hazard evaluation for humans
5. A preliminary hazard evaluation for the environment
A generic template for mapping and reporting these five aspects for a specific
application of a given nanomaterial has been developed and can be found in
Appendix 1 of the report.
In its simplest form, the final outcome of using NanoRiskCat for a nanomaterial
in a given application will be communicated in the form of a short title describing
the use of the nanomaterial (e.g. MeO in ship paint) and a five-color
coded dots, where the first three dots always refer to potential
exposure of professional end-users, consumers and the environment in that
sequence and the last two colors always refer to the hazard potential for humans
and the environment. The colors signify whether the indications of exposures
or effects separately are high (red), medium (yellow), low (green), or
Generic approach used in NanoRiskCat to assign the color-code to products with no, possible and expected exposure depending on the location of the nanomaterial in the product.
The color-coding of the dots representing the exposure potential (dost numbers
one to three) is based on the generic use descriptor system established by
the European Chemicals Agency (ECHA) in the current REACH Guidance
on information requirements and chemical safety assessment Appendix
R.124. For each use category, a color code has been assigned
based on 1) the location of the nanomaterial (bulk, on the surface, liquid or
airborne) and 2) a judgment of the potential for nanomaterial exposure based
on the description and explanation of each process, product category, technical
function, article and environmental release category provided in the
When assigning a color to the dot representing potential human health hazards
(dot number four) related to the specific application of a given nanomaterial
the following indicators/qualifiers should be considered:
1. Does the nanomaterial fulfil the HARN paradigm?
2. Is the bulk form of the nanomaterial known to cause or may cause serious
damaging effects, i.e. is the bulk form classified according to the
CLP with regard to one or more serious health hazards such as germ
cell mutagenicity, carcinogenicity or reproductive toxicity in category
1A, 1B or 2?
3. Is the bulk form of the nanomaterial classified for other less severe adverse
effects according to the CLP such as skin corrosion/irritation category
2 and specific target organ toxicity-single exposure category 3?
4. Is the specific nanomaterial known to be acute toxic?
5. Are there indications that the nanomaterial causes genotoxic, mutagenic,
carcinogenic, respiratory, cardiovascular, neurotoxic or reproductive effects
in humans and/or laboratory animals or has organ-specific accumulation
The human hazards information on the bulk form of the material may be used
as a starting point in order to describe a possible minimum level of concern in
regard to the toxicological profile for the nanomaterial. A guiding principle is
that information about the bulk form of the material can be used under the assumption
that any toxicological and ecotoxicological effects of the nanomaterial
are equal to or larger than those reported on for the bulk material. Thus
hazard data on the bulk material forms the basis of the lowest level of concern
with regard to the nanomaterial.
In NRC, indications of the level of environmental effects (dot number five)
should include considerations of whether the nanomaterial in question is reported
1. Hazardous to environmental species?
4. Leading to potentially irreversible harm to the environment (e.g. ecosystem
5. Readily dispersed?
It is important to note that NanoRiskCat is a stepwise and tiered approach in
the sense that once a color code has been triggered this finalizes the screening
To help communicate the scientific reasoning behind the human health and
environmental hazard categorization and the assigned color code, a number of
standard sentences have been included in the framework. These sentences are
primarily meant to reflect whether the categorization has been reached based
on in vivo or in vitro studies and in regard to which effect or endpoint. Depending
to the final categorization in regard to human health and environment,
the user of NRC has to select one or more of those sentences that best
reflect the scientific basis for assigning the color code.
In order to illustrate the feasibility of NanoRiskCat two nanomaterials (titanium
dioxide and C60) were used as training sets in two different applications
i.e. C60 used in a lubricant and TiO2 used in sunscreen. These examples were
chosen order to be used in the development of the concept but they are also
included in the current report in order to illustrate the applicability of
Example of the evaluation of environmental hazard of C60 in C60 LubExtreme according to NanoRiskCat.
It is important to underline that NanoRiskCat is not a product label and
NanoRiskCat is only to be used for evaluating the nanomaterial as an ingredient
under the physical conditions it occurs in the product. NanoRiskCat does
not evaluate exposure and effects from the other constituents and impurities
in the product nor does it take into account the specific content of nanomaterial
in the product. Thus, NanoRiskCat is directed towards the generic use
descriptors and scenarios, which for instance are apparent in the product
categories used in REACH. Although NanoRiskCat is generic in nature and
can be used on all kinds of nanomaterials and applications, the NanoRiskCat
color code itself is application-specific. Thus, a NanoRiskCat color code does
not in itself allow for an overall evaluation of risks associated with a given
A significant strength of NanoRiskCat is that it can be used even in cases
where lack of data is prominent and hampers the completion of traditional risk
assessment procedures. Another is that the results of NanoRiskCat can be
easily communicated to interested parties. A significant weakness of
NanoRiskCat is that many of the cut-off values used primarily in the environmental
hazard evaluation is based on dose-by-mass which we know is
probably not valid for all nanomaterials as it is an ongoing discussion on
which dose-metrics will be the best to use in nano-ecotoxicology. Furthermore,
the process by which the color code is assigned to human hazards associated
with the nanoform of a given material is based primarily on scientific
expert judgement and a holistic assessment of the evidence of mutagenicity,
carcinogenicity, respiratory toxicity, etc. As expert interpretation of scientific
literature vary, so can the conclusion reached and the human hazard color
code assigned to nanomaterial. It is not possible to provide clear-cut guidance
and rules at this point in time for how to complete holistic evaluation of the
human and environmental hazards associated with the nanoform of a given
material. It is crucial in this context that the users of the NRC explain what
literature they have identified as relevant and explain how they interpret the
reported results and assign the various color codes in the NRC template provided in
The result of NRC does not lead directly to an decision in contrast to other
decision-making tools available for nanomaterials, but NRC does provide a
informed and structured foundation for decision-making by including a number
of indicators that define whether exposure and effects are likely (or
unlikely) to occur and whether the nanomaterial may have harmful properties
Decisions that could come out of using NanoRiskCat are stakeholder-dependent.
Regulators could use NRC as a screening tool to identify possible
uses where risk management measures may be further examined e.g. to develop
guidance on controlled uses, or to evaluate whether specific restrictions
would be required or to indentify data needs. Companies can use NanoRisk-
Cat to communicate what they know about the exposures and effects of the
nanomaterial they use, assess the need to develop guidance for safe uses that
e.g. limit exposures by changing the product formulation or the use of the
nanoproduct or work systematically with designing safer nanomaterials.
Likewise, the company could develop guidelines for professional end-users
and consumers about the safe uses of their nanomaterials and products.
Down-stream users (e.g. consumers) can use NanoRiskCat to make a preliminary
assessment of a range of nanomaterials as a mean to select the seemingly
Finally, independent parties such as academics and nongovernmental
organizations can use the tools to learn more about what companies
know about exposures and effects of their nanomaterials and they can
use NanoRiskCat to do their own independent evaluation and subsequently
engage in an informed dialogue about nanorisks with companies and regulators.
It is finally important to stress that the color coding obtained in
NanoRiskCat should not be seen as an absolute categorization. It rather serves
as a step in an iterative process in which stakeholders in risk-related issues can
reach a common – and guided - understanding of the level of potential exposures
and effects of nanomaterials in specific products.
As decisions that could come out of using NanoRiskCat are stakeholderdependent,
it is important to emphasize that it has not been possible within
the framework of this project to validate the NRC concept further. To promote
a wider use of the tool it is considered necessary to perform additional
case studies and if relevant adjust the processes and decision criteria in order
to obtain a screening tool as informative and practical as possible.