A Survey Of A Group Of Employees Exposed To Asbestos Dust

Our plain-English summary of A Survey Of A Group Of Employees Exposed To Asbestos Dust, by S.B. Mcpheeters (1936).

The study

• Author: S.B. Mcpheeters
• Published: Journal Of Industrial Hygiene 18(4):229-239, April (1936)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 002967. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1936 article surveyed 210 employees exposed to asbestos dust at one plant. Forty-five were Black ("negroes" in the article). Each employee had a brief examination, a health and work history, and a single chest X-ray. No laboratory tests were done. Dust was greatest in the preparation department, where asbestos was ground, crushed and mixed. Other departments processed asbestos mixed with cotton. Of the 210 films, 33 (15.7 per cent) showed definite asbestosis (25 moderate, 8 more advanced); 20 more were questionable. Of 9 people exposed for more than 15 years to disease-producing dust levels, four (44 per cent) had no asbestosis. Six of the 33 with asbestosis reported shortness of breath, compared with 8.1 per cent of those with normal lungs. Only 2 cases had less than 5 years of exposure. In this group the author observed no worsening effect on tuberculosis, calling that evidence somewhat limited, and no increase in reported respiratory infections. The author concluded that individual response, besides exposure length and dust level, mattered. It was unknown how many employees had died or quit.

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: Cross-sectional survey (one-time medical and chest X-ray examination of current employees)
• Who was studied: 210 employees at one asbestos plant, 45 of whom were Black ("negroes" in the article). The plant is not named; the author was based in Charlotte, North Carolina. Departments included preparation, carding, spinning, twisting, winding, weaving and maintenance.
• Exposure: Asbestos dust; the article does not name a fiber type. The preparation department (grinding, crushing, mixing) had the most dust, almost entirely asbestos. Other departments processed a mixture of asbestos and cotton, with less dust. Dust levels were not reported as measured numbers. Exposures ranged up to 15 to 20 years.
• Main results:
  • Of 210 chest films, 53 (25.2 per cent) showed definite or questionable asbestosis. Of these, 20 were questionable and 33 (15.7 per cent) definite: 25 (11.8 per cent) moderate and 8 (3.8 per cent) more advanced.
  • 123 employees (58.5 per cent in the text; 58.8 in Table 1) had normal lung fields, apart from a small primary tuberculous focus in one.
  • Some long-exposed workers had no asbestosis. Of 9 persons exposed more than 15 years to disease-producing dust concentrations, four (44 per cent) escaped. Of 70 exposed more than 5 years, forty-five (64 per cent) escaped. Of 28 exposed 2 to 5 years, twenty-four (85 per cent) escaped.
  • No length of exposure or dust concentration produced asbestosis in more than 60 per cent of those exposed in any department.
  • Shortness of breath under ordinary circumstances was reported by 6 of the 33 employees with definite asbestosis. It was reported by 8.1 per cent of those with normal lungs.
  • Among employees with definite asbestosis, 69.6 per cent had a chest expansion under 2 inches. Among the normal lung group, the figure was 56 per cent.
  • Average exposure for the whole group with asbestosis was 10.2 years. Only 2 cases occurred with less than 5 years of exposure.
  • Several employees with advanced or moderate asbestosis who had worked in dust more than 10 years were still able to work.
  • The incidence of pulmonary tuberculosis was 2.8 per cent. The author regarded it as comparable to many other industrial groups. No activating or aggravating effect of asbestos dust or asbestosis on tuberculosis was observed, though the author called the evidence on this somewhat limited.
  • Twenty-four films showed abnormalities of the heart or aortic shadow. Five of these employees had definite asbestosis, and none of the five showed cyanosis or shortness of breath.
  • Asked about severe colds, flu or pneumonia, none reported pneumonia, six reported flu, and eight reported colds since exposure. The author wrote that reported respiratory infections did not appear to be excessive and that no increase was reported in this group.
• The authors' conclusion: The author concluded that, in addition to duration of exposure and concentration of effective dust, individual response to inhaled asbestos dust is an important factor in producing asbestosis. Other conclusions in the author's summary: asbestosis is infrequent before 5 years of exposure. Continued work exposed to disease-producing concentrations slowly increases fibrosis and is to be advised against. With dust reduction, significant asbestosis would in time "approach the vanishing point." There was some evidence that asbestosis develops more rapidly in younger persons.
• Limitations the authors state:
  • Survey conditions did not permit the thoroughness the author wanted. Examinations were brief, no laboratory tests were done, and only a single chest film was taken per person.
  • Stereoscopic retakes were not allowed. The author believed the number of questionable films could otherwise have been greatly reduced.
  • Employees were classified by their current department, because tracing each person's transfers between departments was impossible.
  • It was not known how many employees had died or quit during the 15 to 20 years covered, or how many of them had asbestosis. The author said this might add greatly to the gravity of the picture.
  • Blood was not examined, no electrocardiograms were made, and a Wassermann test was not allowed.
  • The evidence on the effect of asbestosis on tuberculosis was described as somewhat limited.

Topics

Medical terms in this study, explained in our Lexicon: Occupational History, Chest X-Ray.

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