The swirling safeguard (1972) Pt. 1 of 2

man's fight against disease is based in antiquity from the propitiation of natural gods to the blossoming of medical science in the last century the path has been long and difficult strewn with misguided and often bizarre ideas a major barrier to his advance throughout the world these afflictions have drained his strength weakened his resources and spread misery through entire populations modern medical science has led to the widespread use of prophylactic vaccines and drugs to prevent the spread of disease in man himself forward-looking governments aided by worldwide educational campaigns have established the necessary health and sanitation facilities so vital to the welfare of urban populations these developments have produced enormous strides in checking debilitating and often fatal disease however major insect-borne diseases still cause serious problems around the world the enormous sums of money spent on eradication schemes the blood-sucking mosquitoes and flies still go on biting and that ancient plague of man the housefly still spreads its filth what else can be done a new technique of insect control has been developed that is rapidly becoming part of the public health scientists armory in the fight against epidemic disease in the opening years of this century the study of disease-carrying insects and their complex relationship with man was already well established henry welcome traveling on the nile in 1901 and appalled by the disease and lack of hygiene he saw there set out to further medical research in the region his floating laboratory working up the white nile from its basin cartoon provided facilities for detailed study in the field this venture taking a lead from the pioneering work of the previous half century was but a single link in the chain of investigations mounted to fight tropical disease the major discoveries made by those early workers are now part of medical history however a hundred years after those first intelligence steps were taken the increasing population of the world combined with the special problems of drug tolerance and insecticide resistance make continuing research absolutely essential working within the extensive facilities of the welcome group the cooper company with a specialist knowledge of industrial and public health insect pest control was the first to develop urban street frogging on a routine basis combining detailed laboratory investigations with widely ranging field experiments modern street fogging formulations have been developed to meet the stringent specifications required by discerning public health authorities ever conscious of the risk to man's environment by the use of insecticides the development of these formulations followed an orderly pattern of control tests into the toxicology of the new materials when shown to be utterly safe and only then the biological performance of the new insecticides was evaluated laboratory testing of many different materials against a variety of insect species naturally led on to field trial work here the behavior of new products was observed under practical conditions in this way street fogging formulations have been developed that provide a rapid knock down and kill of flying insects whilst remaining absolutely safe to use in the presence of man and animals however if the highly effective materials are not applied correctly these benefits will be lost today a wide range of application equipment is available to public health authorities and the choice of the correct machine for the job can appear very difficult spraying equipment falls naturally into two categories of which the first covers the residual sprayers designed to produce a rain of heavy liquid droplets they're used to lay down a deposit of insecticide onto surfaces the second group the air sprayers produce a mist or fog of fine droplets that tends to float in the air and can thus be used to attack insects on the wing of these sprayers experience has shown thermal fog generators to be the most effective in producing the large volumes of fine particles that are required in routine outdoor fogging in these types a petrol engine provides power for a turbine blower and fuel and insecticide pumps a strong air blast produced by the blower is then heated by fuel burnt in a combustion chamber at the fog head insecticide is fed into the hot air stream where it vaporizes on contact with the cooler atmospheric air the vapor condenses into a dense fog of my new droplets calibration of the insecticide supply enables the average droplet size of the fog to be controlled so much for basic principles now for some typical street fogging routines showing the various techniques used in practice effective street fogging in urban areas depends on a thorough knowledge of the area to be treated and precise planning of the action to be taken if time and expense are not to be wasted the operator undertaking the practical work must be correctly briefed to make the best use of an insecticidal fog treatment must be carried out in the early morning or early evening when the air is still and cool windy conditions are useless careful preparation of the insect deciding equipment will pay dividends strict adherence to the instructions on the label when making up the dilute spray from the concentrate will ensure effective and economical use sufficient spray is prepared for the job in hand the fogging machine is checked over and seemed to be working correctly attention is also paid to other spraying equipment used for localized treatment of trouble spots armed with the most modern of insecticides the teams move off to another effective fogging operation there is no fear of the friendly fog among the people in the heart of the town they appreciate its benefits but to the fly death is on the way but it is nowhere in this thriving community where the frog will not reach it and end its disease-carrying days in the markets and the food shops where the fly can do most damage the fog swirls and spreads penetrating into every nook and cranny so you