Air Pollution and Causes of Death

Although there are now well over a thousand in struments measuring air pollution in one way or another in England and Wales, grave difficulties are involved in using their results to measure the average exposure to pollution experienced by the inhabitants of any given town. Many instruments, for instance, have deliberately been sited near known sources of pollution to measure changes in the level of pollu tion over the years; and few towns have many instruments?Liverpool, for example, had only two in 1954 (Department of Scientific and Industrial Research, 1955)?and there is often considerable variation in the levels indicated.