Environmental Management. The London smog of 1952 is one of history's most important air pollution episodes in terms of its impact on science, public perception of air pollution, and government regulation.

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ENVIRONMENTAL MANAGEMENT        

        

Theme: The great smog of 1952

Table of contents

The Great Smog of 1952        

The Early 1900s        

Introduction        

Estimates of Influenza-Related Mortality        

Sensitivity Analysis        

The relationship between the Great Smog and the Sulphur Dioxide        

Air Pollution During The Great London Smog, 1952        

The Clean Air Acts, 1956 & 1968        

Tall Chimneys        

Urban Air Quality After The Clean Air Acts        

The Great Smog of 1952

The Early 1900s

Fog and smog frequencies began to reduce in UK urban areas during the early 1900s, compared with the latter half of the nineteenth century. Air pollution was still a severe problem but the number of major smogs began to decrease. Several changes helped to contribute to this situation, including:

  • changing social conditions;
  • tighter industrial controls;
  • declining importance of coal as a domestic fuel;
  • changes in fuel type - gas and electricity became alternatives to coal.

Introduction

   The London smog of 1952 is one of history's most important air pollution episodes in terms of its impact on science, public perception of air pollution, and government regulation. The association between health and air pollution during the episode was evident as a strong rise in air pollution levels was immediately followed by sharp increases in mortality and morbidity. However, mortality in the months after the smog was also elevated above normal levels. An initial government report proposed the hypothesis that influenza was responsible for high mortality during these months. Estimates of the number of influenza deaths were generated using multiple methods, indicating that only a fraction of the deaths in the months after the smog could be attributable to influenza. Sensitivity analysis reveals that only an extremely severe influenza epidemic could account for the majority of the excess deaths for this time period. Such an epidemic would be on the order of twice the case-fatality rate and quadruple the incidence observed in a general medical practice during the winter of 1953. These results underscore the need for diligence regarding extremely high air pollution that still exists in many parts of the world.

 On December 4th 1952 an anticyclone settled over London. The wind dropped and the air grew damp; a thick fog began to form. The Great London Smog lasted for five days and led to around four thousand more deaths than usual. A thick smog settled over London, resulting in unprecedented morbidity and mortality, bringing the relationship between air pollution and health to the attention of the general public, the government, the media, and the scientific community. The Big Smoke, a 50-year commemoration of the smog, took place in London in December 2002. The conference reviewed the events leading to the episode, the health impacts of the smog, and current air pollution conditions in London and elsewhere. This revisiting of the smog reminded us that much can still be learned from the event, in terms of both how air pollution affected Londoners at the time and how health can be affected by high levels of air pollution in much of the world today.

   Several indicators of morbidity, such as hospital admissions, showed patterns similar to those of pollution levels. Daily mortality during the smog was also associated with daily air pollution levels. Results were not sensitive to the peak day of the pollution and were not confounded by temperature. The relationship between mortality and air pollution levels for longer periods revealed a statistically significant association between weekly ambient levels and mortality. Regression analysis showed that weekly air pollution and mortality were statistically associated, even when the week of the episode was removed from the data set, leaving only air pollution concentrations far below the episode (Bell and Davis 2001). Thus, air pollution was affecting mortality in London, aside from the extreme episode.

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Mortality did not return to normal levels for several months after the episode. The strong immediate health response to the episode is evident in the coinciding sharp increase in mortality; however, the elevated mortality in the months after the smog requires a more detailed analysis. An initial government report (U.K. Ministry of Health 1954) proposed the hypothesis that influenza was responsible for the elevated mortality in the months that followed the episode. The weekly number of excess deaths in Greater London (the number of deaths exceeding those during the same time period the previous year) peaked at about 4,500 for ...

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