operation the chain of infection from rat to called for, i.e., the definition of " receptive rat, from rat to man, and from man to man. areas " as those where R. rattus exists side by There should be no vaccination, which is side with a sufficiently numerous and vulner­ too slow and unreliable for immediate pro­ able field rodent fauna; of "critical areas" as phylaxis, but chemoprophylaxis by means of inveterate wild foci together with the ports, sulfonamides. There should be no cordon even if free from infection, situated in their sanitaire or isolation measures, since these neighbourhood; and, finally, of "immune are rendered pointless by disinsecting, chemo­ areas" as areas free from R. rattus, together prophylaxis of contacts, and treatment of with the neighbouring ports. These defini­ patients with sulfonamides or antibiotics. tions might permit the immediate preparation As regards long-term prophylaxis in in­ of agreements for international assistance in fected territory, once it had been demon­ the event of the invasion of a" receptive area" strated that wild or field rodents alone play a by plague. In this way the threatened country part in the maintenance and propagation of could be provided with everything necessary the infection, it seemed logical to carry out to ensure the rapid eradication of the disease eradi.cation campaigns based on the destruc­ before it had time to take root and spread. tion or at least disinse;tion of field rodents and An international programme for the detec­ their burrows. Because of certain prejudices tion and delimitation of " critical areas " arising from previous failures, public health should be drawn up, making it possible to authorities were at first reluctant to under­ designate " infective p::>rts " and to plan the take such campaigns, but the success of eradication of plague in the areas con:::.::rnd. those carried out in certain inveterate foci In the third report of the WHO Expert Com­ in the USSR showed that they were the only mittee on Plague,5 a programme of this type means pf .obtaining lasting results. headed the Committee's " Recommenda­ Where long-term prophylaxis at the inter­ tions for co-ordinated research ". national level is concerned, certain definitions (as in the case of yellow fever) appear to be ' Wld Hlth Or5. techn. Rep. Szr., !9SJ, 165 AIR POLLUTION In December 1952 many parts of the women, and most of the sick were over 45 British Isles were covered by an anticyclone. years of age. There were appreciably more It was cold, and fog was widespread, parti­ hospital admissions than usual, particularly cularly in and around London, which re­ for cases of acute respiratory infection but mained blanketed in it for five days. Within also for heart disease. The mortality records about 12 hours from the beginning of the fog showed that, during the week of the fog and the morbidity rate in the Greater London the week after, there were 4000 deaths more area became very much higher than usual than the average. Most of the people who for the time of the year. The common form died were recorded as having had chronic of illness experienced was characterized by a bronchitis, bronchopneumonia, other lung relatively unproductive cough, nasal dis­ disease, or disease of the heart. charge, sore throat, and sudden attacks of During the fog the smoke concentration vomiting, and was especially severe in per­ was found to be five times greater than at sons who had had a previous history of other times ; the sulfur dioxide concentration chest trouble. In the very ill, dyspnoea, about six times greater. A Committee on cyanosis, moderate fever, and riiles and Air Pollution set up in 1953 by the Govern­ rhonchi indicative of bronchospasm and the ment of Great Britain " to examine the presence of bronchial secretions were nature, causes and effects of air pollution and present. Men were affected more than the efficacy of present preventive measures " 426 held that, while the evidence did not provide by waste materials, and ground water con­ a clear indictment of any one constituent of taminated-and, as a corollary, they have the fog, the conclusion was inescapalb that been breeding-grounds for vermin and bac­ the excessive mortality and increased inci­ teria and centres of epidemics. The dangers dence of respiratory infection during and of impure water and the indiscriminate dis­ immediately after the fog were the result of posal of sewage and refuse have slowly been irritation of the respiratory tract by contami­ recognized, however, and it is safe to say th~t nants of the fog-the irritants mainly practically all towns of reasonable size in the responsible probably being derived from the world pay at least lip service to the ideals of combustion of coal and its products and their pure water and sanitary disposal of sewage lethal effects being almost wholly exercised and refuse. on persons suffering from chronic respiratory Only relatively recently has so much atten­ or cardiovascular disorders. tion been paid to pollution of the air. The This was not the first time that air pollution biological processes of living matter, certain has been blamed for producing ill effects on natural phenomena and many of man's health in London. The English Parliament activities-especially since the Industrial had passed an act as lor g ago as 1273 for­ Revolution-result in the liberation of gases, bidding the burning of coal in London, and vapours, dust, and aerosols of suspended in 1306 a man was executed for doing so. particles into the air, and some of these The law quickly fell into abeyance as the atmospheric contaminants are harmful to shortage of wood as fuel became more health. The study of the nature, properties, pronounced, and when the Industrial Revolu­ and behaviour of the contaminants is tion came attempts to prevent the pollution difficult, and requires the co-operation of of the atmosphere were unavailing. Towards physicists, chemists, and biologists; the the end of the nineteenth century big in­ polluting gases and vapours may form a creases in mortality occurred in association proportion of only a few parts per million with periods of severe fog in 1873, 1880, 1882, or even one part per thousand million or less, 1891 and 1892. but the toxicity of some compounds in the Air pollution and its evil effects were not, parts per thousand million range may be and are not, confined to England, the home greater than that of others in the parts per of the Industrial Revolution. There was a thousand range. Some of the contaminants notorious occurrence in 1930 in the Meuse have not been identifed, and it will be years valley in Belgium, asscciated with anti­ before full inforrr ation becomes available on cyclonic conditions, cold, fcg, and heavy many aspects of air pollution, so complex is industry. In 1948 the industrial town of the subject, so rr:any and changing the factors Donora, USA, some 30 miles south of involved. Vv hereas the industrial hygienist Pittsburg, was afflicted by a heavy fog from works in a semi-closed atmcsphere where 27 to 31 October; 5910 persons (42.7% of concentrations are higher than in the street, the population) fell ill, 15.5% mildly, 16.8% and conditions are somewhat simpler, so moderately, and 10.4% severely; 17 persons that sarr:pling processes lasting only a few died. There was also the Poza Rica incident minutes are usually suff.cient to give him a of 1950 in Mexico. Mention should be made, picture of what is taking place in the factory, too, of the recurrent " smcg" of Los sampling processes in the open air must usu­ Angeles, occurring during the summer and ally continue for months and often for years early autumn and causing irritation of the before the factors involved in air pollution eyes, nose and throat, damaging vegetation, are understood. Thus the forms of pollution and making the atmosphere hazy. encountered in Los Angeles since 1945 are Wherever men collect they tend to pollute still not well understood, although measure­ their environment. Throughout human ments have been proceeding for over ten years. history towns have been concentrations of Nevertheless, an appreciable amount of refuse and dust, with rivers and wells polluted knowledge exists about air pollution and its 427 effects on human health. This knowledge is so it became necessary for states and muni­ summed up in a WHO monograph that has cipalities to pass laws to make it compulsory just been published.1 In this volume, which for householders and industries to burn is the work of an international group of smokeless fuels or to use more efficient experts, a historical review of atmospheric equipment to burn fuel. In Great Britain pollution is followed by sections on sampling there was no natural gas; oil had to be paid and analysis of the contaminants, the instru­ for in foreign currency; and even if industries ments used, the physical and chemical nature could be compelled to install more efficient of air pollution, the role of meteorology, the machinery for getting rid of smoke the main effects of air pollution on human health, problem would be to prevent the domestic animals, and plants, the economic and social consumer of coal from continuing to burn aspects of air pollution, the control of pollu­ it wastefully in open grates. A considerable tion by site selection and zoning and by proportion of the air pollution of the great process changes or equipment, fuel selection fog of 1952 in London was attributable to and utilization, air pollution legislation, smoke from fires burning in innumerable standards, and enforcement, and finally-and open grates throughout the metropolis.