Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 344

It is well recognised, however, that the determining factor which governs the
effectiveness of respiratory protection equipment (RPE) against particulate chal-
lenges is not absolute penetration through the fi lter, but rather face seal leakage
which bypasses the device. Face seal leakage is dependent on many factors, includ-
ing the fi t of the mask to the face, duration of wearing, work activity, and so on.
Since it is expected that nanoparticle aerosols will have high mobility, it is possible
that enhanced leakage will occur although no more than might be expected for a
gas. No relevant research to quantify this has been identifi ed.

8.4.3 Dermal Exposure

Based on our understanding of the various processes by which nanoparticles can
be synthesised there seems to be a strong possibility that dermal exposure may
occur, most likely in the later stages of the process, that is recovery, or resulting
from surface contamination. There is some evidence that dermal exposure to
nanoparticles may lead to direct penetration of nanoparticles into the epidermis
and possibly beyond into the blood stream. Therefore, it may be necessary to intro-
duce control to exclude or limit the level of dermal exposure likely to occur.
As with control of exposure by inhalation, the fi rst approach is enclosure of the
process. This should certainly be achievable as powder handling processes can be
enclosed successfully. However, in practice, particularly with products or processes
that are in development, the main emphasis is on investment and expenditure at
the synthesis end of the process. This is likely to limit the expenditure on sophisti-
cated control and automation processes to deal with what will be perceived as rela-
tively mundane tasks, such as harvesting and packing of nanomaterials.
In any case, even where such processes are in place, the requirements for atten-
tion to breakdowns, maintenance and so on means that the possibility of dermal
exposure cannot be excluded at all times. In these and other instances protection
against dermal exposure typically consists of the use of Skin Protective Equipment
(SPE), that is suits, gloves and other items of protective clothing.
Even for powders in the macroscale, it is recognised that SPE is very limited
in its effectiveness to reduce or control dermal exposure. Based on current under-
standing (Schnieder et al. , 1999) multiple processes contribute to dermal exposure
and the relative ineffectiveness of SPE. In addition to the classical view that the
failure of SPE results from direct penetration or permeation of an agent through
the material from which the equipment is constructed, other failure processes
include transfer of substances by direct contact between surface, skin and outer/
inner layers of clothing or gloves, and redistribution of substances between com-
partments of the same type, e.g. redistribution of contaminants from one part of
the skin contaminant layer to another as a result of touching the face with contami-
nated fi ngers.
Current European testing for certifi cation of PPE against dermal exposure only
takes account of permeation or penetration, although new tests have been pro-
posed which take account of the other human factors based on simulations (Brouwer
et al. , 2005). Since it is likely that nanoparticles which escape into the workplace
will become widely dispersed and will have high specifi c surface area, it is likely