ABSTRACT
Ultrafine Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 13.2.2 Species Differences in Lung Responses to Inhaled
Fine and Ultrafine TiO
Particles . . . . . . . . . . . . . . . . . 541 13.2.3 Other Factors and Conflicting Results . . . . . . . . . . . . . 543
13.2.3.1 Role of Particle Size-Studies with Different Samples of Nanoscale TiO
Particles . . . 544 13.2.3.2 Studies with Nanoquartz Particles . . . . . . . . . 544
13.3 Pulmonary Bioassay Study with Carbon Nanotubes. . . . . . . . . 544 13.3.1 Pulmonary Inflammation and BAL
Fluid Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548 13.4 Cell Proliferation and Lung Histopathology . . . . . . . . . . . . . . . 549
13.4.1 Safe Handling of Nanomaterials in the Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
13.5 Regulatory Implications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555
The development of new products using nanomaterials, frequently referred to as
nanotechnology
, is an emerging multidisciplinary technology that involves the synthesis of molecules in the nanoscale (i.e., 10
m) size range. The term nanotechnology is derived from the Greek word
nano
, meaning dwarf. Sometimes the nanosize issue is difficult to put into proper perspective, but for relating size comparisons to biological end points, the diameter of an erythrocyte (i.e., red blood cell) is approximately 7
µ
m or 7000 nm; bacteria generally are in the range of 1
µ
m or 1000 nm, and some viruses measure in the 60 to 100 nm size range. From a material science and chemistry standpoint, what makes nanotechnology so exciting is the fact that as one decreases the particle size range, i.e., moves down the nanoscale, for a given material, the laws of physics appear to change, often yielding completely new physical properties. For instance, titanium dioxide, a white particle type, loses its color and becomes transparent at decreasing size ranges less than 50 nm. Other particle types utilized for electrical insulating can suddenly become conductive, and insoluble substances can become more soluble below 100 nm. In the aggregate, these changes in physical properties enhance versatility and, thus, are likely to give rise to new industrial and medical applications as well as more eclectic products. These possibilities have generated great interest in this potentially new technology (Colvin, 2003).
