Risk Assessment of Manufactured Nanomaterials - Environmental and Human Health Impacts of Nanotechnology - page 404

algae, plants, bacteria and the higher vertebrates. Most of the existing toxicological
studies have used mg L 1 concentrations for exposures. Data at low

g L 1 concentra-

µ

tions and over long timescales (weeks, months) are lacking.
Information on exposure concentration is currently hampered by technical bar-
riers in our ability to measure engineered nanomaterials in the natural environment
(Handy et al. , 2008a), and it is most likely that a combination of separation and
quantifi cation methods will be needed to measure nanomaterials in natural waters,
sediments, and soils. These are tractable problems but, with current technology,
measurements are laborious and require high levels of expertise, with perhaps only
a few samples being analysed each day at best. The development of rapid tech-
niques that might be employed in routine environmental monitoring programmes
to protect the environment or public health is a long way off.
An alternative approach is to model predicted worse case concentrations on the
basis of product usage and information on likely occurence in effl uents (Boxall et
al. , 2007). This is a useful interim approach while measurement technology is being
developed. Data for modelling are currently based on product information volun-
teered by users/manufacturers. The responses to voluntary reporting schemes in
the United Kingdom have been limited, and one way to strengthen the data set
would be to implement a mandatory reporting scheme (as reported by Royal
Commission as Environmental Pollution, http://www.rcep.org.uk/reports/27-
novel%20materials/27 - novelmaterials.htm ).
There are also levels of complexity in the chemistry that leave knowledge gaps.
Hazard data on the abiotic factors that infl uence aggregation chemistry and, there-
fore, toxicity are lacking (discussed above). The aim in the short term should be to
identify whether toxicity increases or decreases with changes in pH, ionic strength,
Ca 2+ concentration, presence/absence of humic substances and other conditions,
with a selected set of organisms that are used in regulatory tests. This will provide
a basis for some risk calculations and, similar to the situations with metals, many
decades of research will be needed to add the fi ne detail and mechanistic explana-
tions of abiotic effects. There is also a signifi cant lack of knowledge on mixtures
and concerns exist that some hydrophobic nanomaterials may act as delivery vehi-
cles for other organic chemicals (Baun et al. , 2008 ).
There are a number of knowledge gaps that relate to the product life cycle of
nanomaterials. The manufacture of nanomaterials will presumably generate waste
material and wastewater effl uents. Of course, some nanomaterials are expensive to
produce and manufacturers will be seeking to minimise losses during production.
However, without chemical monitoring methods, we cannot quantify these losses
to the environment directly. Data might be collected from the manufacturers on
aspects of production effi ciency so that losses may be estimated, but many of the
companies that produce nanomaterials are small manufacturers that do not have
the automated plant engineering that could provide such data.
Exposure in the work place must be controlled and, while individual users will
have made risk assessments (e.g. general risk assessments of work procedures,
COSHH assessments) and local arrangements for occupational health will be in
place, there are not enough data to determine if these measures are being effective.
In the short term, at least to our knowledge, no clinical conditions have arisen from