Anesthesia Progress Blog - Part 8

For epidemiologic purposes, design of a questionnaire to distinguish among asthma, chronic bronchitis, emphysema and other respiratory diseases has proved difficult. Realistically, questionnaires should not expect to define the many chronic airway diseases separately, but should aim to accurately measure a number of well-recognized symptoms. The relation of such defined symptoms to excess mortality and to abnormalities in lung function can then be assessed. Read the rest of this entry »

Epidemiology of Chronic Airways DiseaseThis document summarizes the papers presented at the WHO/I UATLD meeting on chronic airways disease (CAD), sets out future research needs relating to the epidemiology of CAD, and outlines several important initiatives to be undertaken by WHO/IUAXLD.
1.2 Aims
The aims of obtaining epidemiologic data relating to CAD are to obtain estimates of the magnitude of the problem and to identify its etiologic factors. Based on this information, stragegies to prevent and control CAD can be introduced. The articles presented leave little doubt that, although the mortality rate from CAD is falling in the United Kingdom and appears to be falling in other European countries, the mortality and morbidity from his disease continues to rise in many countries. Thus, the disease presents a mounting public health problem in many countries, particularly developing countries, and may continue to do so, at least in the short term, because it attracts relatively little attention from governments and health organizations when compared with other diseases of the lung. add comment
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The role of early childhood illnesses also was featured in a study of 18-year-olds brought up in two contrasting areas, London and a relatively pollution-free new town. Results of a logistic regression analysis of findings on the prevalence of respiratory symptoms (Table 4) showed that after smoking, a history of early respiratory illnesses (bronchitis, asthma, pneumonia, pleurisy) appeared to be the most important factor in relation to symptoms in adolescence. Beyond that, area of residence, with the implied differences in exposure to urban air pollution did not have much effect, but individual exposures, whether to outdoor or indoor pollutants could have contributed to the contrasts in respiratory illnesses. Read the rest of this entry »

Atmospheric Pollution: Chronic Airways DiseaseInterrelationships Between Air Pollution and Other Factors in the Development of Chronic Airways Disease
One pointer in the past to the possible role of air pollution in the development of CAD was the marked urban excess of bronchitis mortality seen in the UK, but this excess has been diminishing for some considerable time (Table 2). Such a trend is consistent with the general decline in air pollution which, especially in London, had been evident to some extent for two or three decades prior to the introduction of the Clean Air Act in 1956. Whether the improvement in terms of mortality might be attributable to reduced exposure in the latter years of life, to the overall reduction in lifetime exposures or perhaps to changes in exposure at a more specific period, such as in childhood, cannot be judged effectively from a simple inspection of mortality data, and urban/rural comparisons are in any case compounded by other factors such as different smoking prevalences or selective migration in and out of cities. Read the rest of this entry »

Indoor/Outdoor Relationships
Although the topic of indoor pollution is considered in a separate article, the extent to which people are actually exposed to pollutants of outdoor origin deserves some comment. Most people in developed countries spend a large proportion of their time indoors, which can be protective. The modern tendency in the interests of fuel economy is toward “tight” buildings that limit the exchange of air between indoors and outdoors. In these circumstances particulates and sulfur dioxide infiltrate only slowly, and the latter is quite rapidly absorbed on furnishings, clothes, and other surfaces so that concentrations fall to a small fraction of those outdoors. Air-conditioning systems may reduce concentrations still further. Read the rest of this entry »

Atmospheric Pollution: Control MeasuresControl Measures
In view of points made above, attention is directed here mainly to the avoidance of exposure to combustion products from domestic or industrial sources. The indications are that in many countries the control measures already instituted have reduced urban concentrations of sulfur dioxide and particulates to levels considered not to produce detectable effects in terms of chronic respiratory disease, but the range of approaches used provides guidance where further action needs to be taken. Avoidance of emissions at the source is the best remedy, and this was the course taken in respect to coal smoke under the Clean Air Act of 1956 in the United Kingdom. This required the elimination of black smoke from all industrial sources through improved combustion where coal was still used or, more commonly, through a change to oil or other fuels. In designated urban areas, smoke from domestic sources was also to be eliminated, and this happened mainly through the outlawing of coal in favor of other fuels, and notably natural gas when that became available. The dramatic reductions in smoke concentrations achieved, together with the unexpected but welcome reductions in sulfur dioxide as a result of switches to low-sulfur fuels, have been illustrated in an accompanying paper.
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Outdoor Pollutants
The traditional kind of pollution associated with the London “smogs” that became notorious in the latter part of the 19th century through the early 1960s was that from the incomplete combustion of coal, leading to the emission of black smoke and sulfur dioxide. Its special feature was that the major contribution to urban concentrations came not from industry, but from domestic open coal fires, and the particularly inefficient combustion yielded not only black carbonaceous particles but also a large amount of tar. A further feature was the high relative humidity that often prevailed in winter, when emissions were at a maximum, and in the resultant smoke/fog/S02 mixture, further reactions occurred, leading to the formation of irritant species of particulates, including sulfuric acid. There is clear reason to believe that this particular set of circumstances led to substantial short-term effects, and there is still considerable interest in the role of acid aerosols in that connection. To what extent the specific chemical and physical characteristics of London smog have been special in respect to the development of CAD is less clear, but it seems likely that pollution of this particular type played an important part in the marked urban excess of morbidity and mortality from CAD. Read the rest of this entry »

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