PART X — ENVIRONMENTAL CONTAMINANTS 



Figure X-21 — EJECTION OF SMALL DROPLETS INTO THE 

 ATMOSPHERE BY BURSTING BUBBLES 



THIS SEQUENCE OF PHOTO- 

 GRAPHS SHOWS THE COL- 

 LAPSE OF A 1.7 mm DIAME- 

 TER BUBBLE AND THE FOR- 

 MATION OF A JET. 



THE TIM.E INTERVAL BE- _ 

 TWEEN FRAMES 1 AND 4 £ 

 IS ABOUT 2.3 MILLISECONDS. 



OBLIQUE VIEW OF THE JET 

 FROM A t mm DIAMETER 

 BUBBLE 



C =^T 



r # BACTERIA/, 





r ^ 



.: ' . i - . - yj - . . . j i . — •**.v.*.V 



• w.v ■/••• • : *.* :* * • •.-. v.v * : • .' 



■.-;©■■ '• 



CONCENTRATION OF BACTERIA IN JE" 

 DROPS FROM BURSTING BUBBLES 



The diagram shows how disease-laden water vapor can enter the atmosphere. 

 When a droplet of water such as rain falls out of the atmosphere through a surface 

 of water, its shape changes and shortly triggers a jetlet, which is then ejected up- 

 ward from the water surface. A droplet of water from the jetlet remains in the 

 atmosphere, while the rest of it collapses. A similar situation occurs when bubbles 

 formed beneath the water surface, as by decomposition, rise to the surface and 

 burst. If, in either of these cases, the water surface is contaminated, then con- 

 taminated droplets enter the atmosphere and may be transported great distances. 

 It is thought that hoof-and-mouth disease spreads in this manner. 



Needed Activity — Priorities for re- 

 search include: 



1. Improved and more economical 

 diagnosis; a simpler serological 

 test. 



2. Expanded exploration of possi- 

 bilities for a vaccine. 



3. A breakthrough on measures 

 for vector control, particularly 



since the insecticides now relied 

 on may have to be discouraged 

 because of their cumulative tox- 

 icity in the environment. (One 

 household may require several 

 kilograms of 5-percent benzene 

 hexachloride for each spraying, 

 and some houses have been 

 sprayed several times. The rate 

 of application is 0.5 gram of the 

 active insecticide per square 

 meter of surface inside and out. 



Latin America has enough well- 

 qualified people in the subject. Those 

 in research need financial help. If they 

 are in national control programs, they 

 need advice and support. Most coun- 

 tries need to be pushed into more ag- 

 gressive control efforts. The immuno- 

 logical studies can be supported both 

 in and out of the endemic zones. In- 

 ternationally supported control cam- 

 paigns to improve, not replace, houses 

 and to spray houses could have a 

 dramatic impact on the disease. 



370 



