THE AUTOMOBILE AND PUBLIC HEALTH 285 



One of the missions of autotrucks will be the transferring of loading 

 and unloading of freight beyond the city limits. The carrying of freight 

 to warehouses on autotrucks will necessitate complete renovation of roads 

 and construction of relatively dustless road beds. Incidentally this will 

 also do away with much irritating smoke from locomotives. It has been 

 stated that transportation of freight by autotrucks within city limits is 

 economical both in time and expenditure. Improvement in city streets 

 has followed in the wake of the introduction of electric street cars and 

 the decreased use of horses in cities due to automobile traffic will increase 

 possibilities in this direction. 



The injurious influence of dust on the public health is of various 

 nature. The mechanical irritation of the respiratory tract and the 

 accumulation of dust in the lungs and eyes increase susceptibility to in- 

 fections. Inflammations of the conjunctiva, due to infection with such 

 common, usually considered innocent, germs as the ubiquitous hay 

 bacillus, have occurred. Probably such infections follow mechanical irri- 

 tation of the mucous membranes by dust or other causes. The hay 

 bacillus is carried everywhere by dust. It must be remembered that dust 

 is the carrier of germs — harmless as well as injurious ones. Bact- 

 eria, yeasts and molds rarely travel alone. They are generally kept in 

 suspension by floating particles of dust. It is due to this fact that after 

 snow and rain storms there are relatively few microorganisms in the air. 

 Therefore any provision, which materially reduces the amount of dust 

 will reduce the number of microorganisms in the air. Among such pro- 

 visions improvement of road pavements takes a prominent place, since 

 dust in the air can come only from the ground by the action of winds or 

 moving vehicles. 



The diseases which may be communicated by dust are manifold. The 

 germs of pneumonia, various forms of tonsillitis, diphtheria, croup, 

 whooping cough, colds and tuberculosis are undoubtedly carried by dust. 

 In fact, probably all infections of the respiratory tract may be carried in 

 this fashion. Germs of the diseases named have been isolated from the 

 air. The germs of tuberculosis are carried chiefly by the sputum of 

 affected persons and communicated either by inhalation of dust or by 

 food on which germ-laden dust is deposited. It must not be understood 

 that this is necessarily street dust, but no doubt street dust is a contribu- 

 tory factor. 



Diseases of the intestinal tract may also be communicated by dust. 

 Food and water, if contaminated with sewage, are the commonest vehi- 

 cles of infection in typhoid fever and dysentery, but it is quite conceiv- 

 able that some cases of obscure origin may be the result of dust inhala- 

 tion or ingestion of raw food on which dust has fallen. Studies of 

 typhoid fever epidemics have led sanitarians to recognize that food and 

 water do not account for all cases and sometimes disease may be due to 



