Respiratory Disease in a Urban Environment

Our plain-English summary of Respiratory Disease in a Urban Environment, by M.H. Lepper, N. Shioura, B. Carnow, et al (1969).

The study

• Authors: M.H. Lepper, N. Shioura, B. Carnow, S. Andelman, L. Lehrer
• Published: Industrial Medicine, Volume 38 No4. April 1969
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article is not about asbestos; it studied air pollution and respiratory disease deaths in Chicago. The authors tried to repeat an earlier Nashville study over single years, using sulfur dioxide measured at 21 city stations in 1964 and 1965 while the deaths occurred. Each death was assigned to a census tract, and tracts were grouped into high, medium and low socioeconomic classes and into low, moderate and high sulfur dioxide levels. There were 2384 total respiratory deaths in 1964 and 2746 in 1965. Rates were adjusted for age, sex and race. Death rates generally rose as socioeconomic level fell within sulfur dioxide levels, while the link with sulfur dioxide was less consistent, especially in 1964. The largest differences were between age groups, then between white and non-white residents. Analyses of adults only or white residents only gave less clear trends. The authors concluded that both factors may play a role in respiratory deaths, but that it was not clear age, sex and race were sufficiently controlled.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Population mortality study grouped by census tract. It attempted to replicate the Nashville study by Zeidberg and colleagues on an annual basis, with pollution measured at the same time as the deaths occurred. 1964 and 1965 were analyzed as two separate experiments.
• Who was studied: Residents of Chicago. Deaths from total respiratory disease (including tuberculosis and lung and bronchial cancer) were coded to census tract of residence: 2384 deaths in 1964 and 2746 in 1965. The total population stratified was printed as 3,530,000.
• Exposure: Two environmental variables were studied. The first was the average annual sulfur dioxide (SO2) concentration in parts per million for each census tract, estimated from 24-hour measurements at 21 stations in 1964 and 1965. The second was a census-tract socioeconomic index based on median income, education and male unemployment. Particulates were also measured, but the analysis was restricted to SO2. No asbestos exposure was studied.
• Main results:
  • In the whole population, within each SO2 level, age-, sex- and race-adjusted respiratory death rates generally rose as socioeconomic level fell, in both years. There was one exception: in the moderate SO2 group, rates did not rise between the high and medium socioeconomic levels. The authors described this socioeconomic trend as seeming definite, though not every step was statistically significant.
  • Within each socioeconomic level, the relationship between SO2 exposure and death rate was less consistent. The general pattern suggested some relationship, with several inconsistencies, particularly in the 1964 data.
  • In 1964, the biggest differences in respiratory death rates were between age groups. The second biggest were between white and non-white populations in each age group for both sexes. Males had significantly higher rates than females except in the 5-24 age group.
  • Among children aged 0-4, neither white nor non-white children showed trends associating respiratory deaths with socioeconomic level or SO2 exposure.
  • In separate analyses of adults only and of the white population only, the trends were less clear than for the entire group.
  • The authors gave a conditional estimate: if the dose-effect curves could be relied upon, the death rate would rise 0.5 to 1 per 10,000 per year per 0.1 ppm of SO2. On the same condition, air free of SO2 would give only 2-3 deaths per 10,000 per year. They said this analysis would require refining the population definition and a multivariate analysis.
• The authors' conclusion: The authors concluded that socioeconomic level and SO2 exposure may each play a role in deaths from respiratory diseases considered together, similar to the Nashville findings. Because these differences were small compared with those for age, sex and race, they said it was not clear those factors were sufficiently controlled. Analysis of adults only and of white residents only weakened rather than strengthened the evidence of association.
• Limitations the authors state:
  • The differences attributed to the environmental factors were small compared with those for age, sex and race, so it was not clear that age, sex and race were sufficiently controlled.
  • The socioeconomic and pollution variables overlap considerably, so neither analysis can show a causative effect of either variable alone.
  • Other pollutants may be involved, and the socioeconomic variables may overlap with the pollution variables.
  • Some cells had small populations and few deaths. In particular, the adjustment ratios for cells with few non-white residents in high socioeconomic areas were based on quite small populations.
  • Census tracts were not uniform, which may have caused misclassification. Examples given were urban renewal in former skid row areas and white residents in isolated high-rise apartments in otherwise low socioeconomic tracts.
  • The differences between white and non-white populations may not reflect race itself. They may reflect socioeconomic classifications meaning different things for different groups, or less adequate medical care for the non-white population.

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