Biomedical Engineering Reference
In-Depth Information
Hazard potential
Mild/
reversible
Severe/
irreversible
8 h
kg
Local exhaust
ventilation
Enclosure
mg
15 min
Slurry/
suspension
Highly
disperse
Agglomerate
Physical form
FIGURE 2.2
Major factors influencing exposure risk and hence selection of control measure. (From
NIOSH, 2012.
General Safe Practices for Working with Engineered Nanomaterials in Research Laboratories
.
Cincinnati, OH: U.S. DHHS, CDC, NIOSH. DHHS (NIOSH) Pub. No. 2012-147. With permission.)
2.2.2 d
erMal
Dermal exposure to nanoparticles is considered a potential exposure route for workers associated
with the handling of nano-sized powders. At present, many manufacturing processes in nano-indus-
tries involve direct or indirect skin contact and result in the penetration of nanoparticles through
intact skin (Lademann et al., 1999; Pflücker et al., 2001; Tinkle et al., 2003; Ryman-Rasmussen
et al., 2006). Monteiro-Riviere also indicated that skin could be permeable to quantum dot nanopar-
ticles (Monteiro-Riviere, 2009). However, it is unknown whether skin penetration would result in
adverse health effects.
2.2.3 I
NgestIoN
Very little work has been done to investigate ingestion exposures. Behrens et al. (2001) has indicated
that smaller particles could be transferred across the intestinal wall more easily than larger ones.
The most probable ingestion exposure route for nanoparticles could be due to hand-to-mouth con-
tact, and then the transfer to other organs via ingestion in the intestinal tract.
2.3
EXPOSURE ASSESSMENT
2.3.1 e
xposure
M
etrIcs
The current metric for setting occupational exposure limits (OELs) for micro-sized particles is
based on its mass concentration. However, the appropriateness of the above metric for nanoparticles
has been questioned because nanoparticles feature high particle counts and large surface area per
unit masses. Kreyling et al. (2006) reported that the nanoparticle is less than 10% of PM2.5 con-
centrations in terms of mass but contributes more than 90% of its particle number concentration. To
date, both exposure metrics of the total surface area and total number concentrations of nanopar-
ticles have shown good correlations with their resultant health effects. For example, McCawley
