The Importance of an Accurate Size Determination of Fine Particles 

 when Investigating Their Biological Effects 



G. Bloom, J. Glomme and A. Swensson 



Department of Occupational Medicine, Karolinska sjiikhiiset; 

 King Gitstaf V Research Institute and the Department of Histology, Karolinska Institiitet. Stockholm 



When studying the biological reactions to different 

 particles it has become evident that the size of the 

 latter is of importance. With the aid of the micro- 

 scope it is possible to obtain a particle size distribu- 

 tion of a given sample, but this method is naturally 

 limited by the resolving power of the microscope 

 used. As the biologically most active particles often 

 are of such a size that a closer examination of them 

 is not possible in the ordinary light microscope, 

 indirect methods have been used to determine their 



02 0.4 0.6 0.8 1.0 1.2^ 



I00%| 

 80 

 60 

 40 



20 

 



Q2 0.4 Q6 0,8 1,0 1.2 ^ 



P--3 



TOXICITY 3.4*0.19 

 EXCRETION 2.6 % 



A =0.75^ 



0.2 04 06 0.8 1.0 1.2/J 



sizes. These methods are all suffering from con- 

 siderable errors. 



A great need for new possibilities of examining 

 very fine particles has arisen. In modern dust combat- 

 ing rather effective methods have been worked out 

 for eliminating particles of light microscopical size, 

 but these methods are less effective with regard to 

 submicroscopical particles. Thus recirculation of air 

 in dustladen workrooms may cause a concentration 

 in the air of submicroscopical particles which pass 



100% 

 80 ■ 

 60 • 

 40 ■ 

 20 

 



100% 

 80 



60 



40 



20 







OZ 0.4 Q6 0.8 1,0 1.2 jU 



P:5 5 



TOXICITY 0,5^0,02 

 EXCRETION 23% 



A=0,IOyU 



02 0.4 Q6 0,6 1.0 l,2yU 



P--71 



TOXICITY 2,1 ±0,06 

 EXCRETION 21% 



A = O.I5jU 



02 Q4 0,6 0,8 1,0 12 /J 



Fig. 1 (left). P:l, P;2 and P:3 — diflerent size fractions of the same sample of 99 "o a-quartz. Toxicity: Acute toxicity in mg 

 per 30 g mouse by fractioned intravenous injection ad modum Dale and King (1953). Excretion: Urinary excretion after 

 intraperitoneal injection during first five days in per cent of injected amount. A: Average particle size. 



Histograms: Particle size distribution. 



Electron micrographs: The different particle samples, see text. 



Fig. 2 (right). P:61, Aerosil, Gold- und Silberwerke. P:55, amorphous silica prepared by combustion of SiClj rtf/ /?;o(/«/» 

 Flemmert. P:71, ground, fused silica. 

 Other items as in fig. 1. 



