Stauhkorngrdfien in Staiihlungen 



251 



through the dust fiher. These fine particles do not 

 easily lend themselves to ordinary industrial hygienic 

 control measures. Little is known of their biological 

 effects, and it is difficult to discuss their practical 

 importance, adequate protection against them, etc. 



The electron microscope has made possible closer 

 examinations of these extremely small particles both 

 with regard to general appearance and to si/e. 

 Several methods have been proposed for preparing 

 samples for electron microscopical examination. 

 Special devices have been made and standardized 

 for collecting particle samples from air directly or 

 indirectly via millipore filters onto specimen grids, 

 and in such a way as to make the sample representa- 

 tive of what is contained in the atmosphere. Such 

 investigations of the atmosphere at workplaces 

 where a risk for silicosis exists have shown that the 

 percentage of particles in the submicroscopical range 

 is very high. It has also been shown that dust-com- 

 bating methods, such as wet drilling in mines, chiefly 

 influence the somewhat larger particles. 



In our experimental investigations we have been 

 interested chiefly in determining the particle size 

 distribution of particle samples used for biological 

 investigations. For the preparation of samples we 

 have applied different methods but chiefly we have 

 dispersed the particles in water with the aid of a 

 colloidal mill. The same method has also been used 

 for preparing the particle suspensions used for the 

 biological experiments. 



The particle size distribution was determined by 

 measurements performed on electron micrographs 

 As the irregular particles of ground silica have no 

 definite geometric diameter we have consequently 

 measured in a horizontal direction the distance 

 between two extreme points on the particle. 



It has been known for some time that the bio- 

 logical reaction depends on the particle size, but 

 mostly only gross differences of size have been 

 registered. In the following some examples will be 

 given of the relationship between particle size and 

 biological reaction of particles of silica of different 

 kinds. 



The importance of the particle size is seen in fig. 1 , 

 which shows three fractions from the same ground 



sample, of almost pure (99 "„) a-quartz. There is a 

 close relationship between particle size and toxicity 

 in such a way that the toxicity decreases with in- 

 creasing particle size. The excretion values indicate a 

 similar relationship with an increased excretion with 

 decreasing particle si/e. 



in tig. 2 corresponding investigations on samples 

 of amorphous silica prepared in different ways 

 have been grouped together. The relationship be- 

 tween particle size on the one hand and toxicity and 

 excretion on the other is evident also here. It is, 

 however, obvious that also factors other than particle 

 size must he of importance, which is natural with 

 regard to the differences in mode of preparation and 

 structure of the various samples. 



Regarding the fibrogenetic efTect, it is well estab- 

 lished that this effect is marked in all the different 

 crystalline samples. As for the fine amorphous 

 samples of silica the situation is somewhat more 

 complicated. This is exemplified by the reactions to 

 two different samples prepared in the same way but 

 having different particle sizes (P:5I, average particle 

 size 0.01 microns, toxicity 0.2 r 0.01, and P:55, cf. 

 fig. 2). Sample P:55 one month after intraperitoneal 

 injection in the rat gives a marked cellular reaction 

 with moderate fibrosis, which after 7 months is 

 poorer in cells and slightly more fibrotic than after 

 I month. With sample P:51, the reaction after 

 I month is chiefly a relatively mild cellular reaction 

 with some reticulin reaction. After 7 months the 

 cellular reaction is almost gone and reticulation is 

 minimal. A definite regress has taken place. Macro- 

 scopically it is not possible with this sample to see 

 any changes at all in the peritoneum after 7 months. 



According to these investigations the biological 

 effect of silica particles seems to be highly dependent 

 on the particle size. 



Detailed knowledge about the particle size distri- 

 bution is a necessary basis for a scientific discussion 

 of these problems, and more important than hitherto 

 supposed. 



Reports on results obtained will be published in Aich. 

 Ind. Health, Acta physiol. Scaiul.. and Acta phaniuicol. et 

 toxical. 



Elektronenoptische Untersuchungen von StaubkorngroBen 



in Staiibkingen 



H. W. ScHLiPKOTER und A. Colli 



Imtitut fiir Hygiene unci Milirobiologie der Medizinischen Akademie, Diisseldoif 



Aus dem groBen Problemenkreis der Staublungener- 

 krankungen, vor den sich die medizinische wie auch 

 die physikalische und die chemische Forschung ge- 

 stellt sieht, ist die Frage nach der Staubkorngrof3e 

 von wesentlicher Bedeutung. AusmaB und Starke 



der Gewebsreaktion sind weitgehend von ihr ab- 

 hiingig. Besonders fur Abv\ehrmaf3nahmen, vor 

 allem fiir die Staubbekampfung. ist es wichtig zu 

 wissen, wie groB die Teilchen sind, die die Staub- 

 schiidigungen in den Lungen hervorrufen. 



