Answers to some questions raised by the presentation on the graphical analysis of the interrelationships between waterborne asbestos, digestive system cancer and population density

Our plain-English summary of Answers to some questions raised by the presentation on the graphical analysis of the interrelationships between waterborne asbestos, digestive system cancer and population density, by M.E. Tarter (Environmental Health Perspectives, 1983).

The study

• Author: M.E. Tarter
• Journal: Environmental Health Perspectives
• Published: 1983;53:193-4
• Read it: PubMed · Publisher · Free full text

In plain English

This short commentary answered two questions raised after the author presented an earlier paper. That paper graphically analyzed waterborne asbestos, digestive system cancer and population density. The commentary reported no new data on asbestos or cancer. The first question was about the axes in Figure 1. The author explained that the axes passed through the sample means of the displayed data: a mean tract number of 216 and a mean of 5270 individuals per square mile. The author said the data suggested a high degree of skewness for population density and a fairly uniform spread of tract number. The second question was whether two apparent subgroups in the figures were an artifact of sparse data and smoothing. Quoting an earlier paper, the author stated that choosing k within the limits of that paper's equation (2.6) will not affect the variances of any component. The author added that, because the parameter was chosen for smoothing, any spurious effect would tend to hide rather than emphasize components. Tests on benchmark test patterns had uncovered no spurious curve bifurcation.

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: Commentary (author's replies to questions raised after a presentation); no new study
• Who was studied: No population was studied in this commentary. It discusses graphs from the earlier paper that plotted tract number against population density.
• Exposure: Waterborne asbestos, named only as the subject of the earlier paper. No fiber types or doses are given in this commentary.
• Main results:
  • The graph axes pass through the x and y sample means of the displayed data.
  • In Figure 1, the mean tract number was 216 and the mean number of individuals per square mile was 5270.
  • The data in Figure 1 suggested a high degree of skewness for the population density variable.
  • The data in Figure 1 suggested a fairly uniform distribution of the tract number variable.
  • The questioner suggested that the two apparent subgroups were an artifact of sparse data and the smoothing function.
  • Quoting an earlier paper (Tarter and Silvers), the author stated that the choice of k within the limits of that paper's equation (2.6) will not affect the variances of any component.
  • Because the parameter was chosen for smoothing, the author said any spurious effect would tend to hide rather than emphasize components.
  • When the smoothing procedures were applied to benchmark test patterns, no spurious curve bifurcation was found.
• The authors' conclusion: The author maintained that the smoothing method separates or smooths components in one direction with no effect on components in any other direction, and that the subgroups were therefore not a smoothing artifact.

Related studies

• A graphical analysis of the interrelationships among waterborne asbestos, digestive system cancer and population density — M.E. Tarter, R.C. Cooper, et al. (1983)
• Effect of population density on the results of the study of water supplies in five California counties — P.M. Conforti (1983)
• Additional comments on the study of the effect of population density on the results of the California Bay area study — P.M. Conforti (1983)
• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)
• Occupational asbestos exposure and digestive cancers - a cohort study — B. Clin, F. Morlais, et al. (2009)
• Incidence of digestive cancers and occupational exposure to asbestos — S. de La Provôté, N. Desoubeaux, et al. (2002)

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