Mortality among California highway workers

Our plain-English summary of Mortality among California highway workers, by N. Maizlish, J. Beaumont, J. Singleton (American Journal of Industrial Medicine, 1988).

The study

• Authors: N. Maizlish, J. Beaumont, J. Singleton
• Journal: American Journal of Industrial Medicine
• Published: 1988;13(3):363-79
• Cited by: 51 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000249).

Abstract

Standardized proportional mortality ratios (PMR) were computed for a population of highway workers. Hazards of highway maintenance work include exposure to solvents, herbicides, asphalt and welding fumes, diesel and auto exhaust, asbestos, abrasive dusts, hazardous material spills, and moving motor vehicles. Underlying cause of death was obtained for 1,570 workers who separated from the California Department of Transportation between 1970 and 1983, and who died in California between 1970 and 1983 (inclusive). Among 1,260 white males, the major findings were statistically significant excesses of cancers of digestive organs (PMR = 128), skin (PMR = 218), lymphopoietic cancer (PMR = 157), benign neoplasms (PMR = 343), motor vehicle accidents (PMR = 141), and suicide (PMR = 154). Black males (N = 66) experienced nonsignificant excesses of cancer of the digestive organs (PMR = 191) and arteriosclerotic heart disease (PMR = 143). Among 168 white females, deaths from lung cancer (PMR = 189) and suicide (PMR = 215) were elevated. White male retirees, a subgroup with 5 or more years of service, experienced excess mortality due to cancers of the colon (PMR = 245), skin (PMR = 738), brain (PMR = 556), and lymphosarcomas and reticulosarcomas (PMR = 514). Deaths from external causes (PMR = 135) and cirrhosis of the liver (PMR = 229) were elevated among white males with a last job in landscape maintenance. White males whose last job was highway maintenance experienced a deficit in mortality from circulatory diseases (PMR = 83) and excess mortality from emphysema (PMR = 250) and motor vehicle accidents (PMR = 196). Further epidemiologic and industrial hygiene studies are needed to confirm the apparent excess mortality and to quantify occupational and nonoccupational exposures. However, reduction of recognized hazards among highway maintenance workers is a prudent precautionary measure.

In plain English

This study looked at causes of death among 1,570 former California Department of Transportation employees who left the agency between 1970 and 1983 and died in California in those years. The authors used proportional mortality ratios (PMRs). A PMR compares the share of deaths from each cause with the share expected from U.S. death patterns, and a value above 100 means a larger share than expected. The authors noted that a PMR is not a direct measure of absolute risk. Asbestos was listed among the hazards of highway work, but no exposures were measured. Among 1,260 white men, larger-than-expected shares of deaths came from digestive cancers (PMR 128), skin cancer (218), lymphopoietic (blood and lymph system) cancers (157), benign tumors (343), motor vehicle accidents (141) and suicide (154). As a share of cancer deaths, lung cancer in white men was lower than expected. One cancer of the pleura was recorded. Among 168 white women, lung cancer was raised (PMR 189). The authors suggested that office exposures, including cigarette smoke and asbestos, might explain this. The authors concluded that chance alone was unlikely to explain the overall pattern. They added that study limitations and uncontrolled factors might be partly responsible.

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: Standardized proportional mortality ratio (PMR) and proportional cancer mortality ratio (PCMR) study, undertaken as a mortality surveillance exercise, using death certificates
• Who was studied: 1,570 deceased former employees of the California Department of Transportation (CalTRANS), all job types, who left employment between 1970 and 1983 and died in California between 1970 and 1983. They included 1,260 white males, 66 black males and 168 white females.
• Exposure: Employment at CalTRANS, with subgroups by last job classification (highway maintenance, landscape maintenance) and by retirement. Listed hazards included asbestos (linked in a table to brake and clutch repair), asphalt fumes, cement, solvents, pesticides, exhaust and traffic. No fiber type was specified, and no exposure measurements were available.
• Main results:
  • White males (1,260): statistically significant excesses of cancers of the digestive organs (PMR 128), skin (PMR 218), lymphopoietic cancer (PMR 157), benign neoplasms (PMR 343), motor vehicle accidents (PMR 141) and suicide (PMR 154)
  • White males: lung cancer as a share of cancer deaths was significantly lower than expected (PCMR 83)
  • One cancer of the pleura was observed (group as reported in the white male results section)
  • White females: significant excess of lung cancer, 17 observed versus 9.0 expected, PMR 189 (95% CI 110 to 302)
  • 160 white male retirees: significant excess of all malignant neoplasms (PMR 152)
  • White males whose last job was highway maintenance: significant excess of deaths from emphysema (PMR 250), all accidents (PMR 169) and motor vehicle accidents (PMR 196)
• The authors' conclusion: The authors concluded that the pattern of cancer deaths at multiple sites and fatal accidents was unlikely to have arisen entirely by chance. They added that methodologic limitations and uncontrolled confounding factors may be partly responsible, and that further studies are needed.
• Limitations the authors state:
  • The PMR is not a direct measure of absolute risk
  • There were no exposure data or work histories
  • Socioeconomic status, smoking and alcohol were not controlled
  • Many comparisons were made, so some findings may be due to chance
  • Year of hire was not available, so latency and duration effects could not be studied
  • Deaths outside California were not identified
  • Classifying exposure by last job may have misclassified exposure

Topics

Medical terms in this study, explained in our Lexicon: Proportional mortality, Neoplasm, Lung Cancer, Emphysema, Industrial Hygiene.

Related studies

• Guadalupe corridor transportation project asbestos health risk assessment, San Jose, California — W.E. Steiner, J.L. Koehler, et al. (1990)
• Extended follow-up of lung cancer and non-malignant respiratory disease mortality among California diatomaceous earth workers — L.G. Gallagher, R.M. Park, et al. (2015)
• Updated epidemiological study of workers at two California petroleum refineries, 1950-95 — K.P. Satin, W.J. Bailey, et al. (2002)
• Prevalence of radiographic abnormalities among Northern California shipyard workers — P.L. Polakoff, B.R. Horn, et al. (1979)
• Asbestos exposure among Seoul metropolitan subway workers during renovation of subway air-conditioning systems — I.J. Yu, C.Y. Yoo, et al. (2004)
• A cohort mortality study of construction workers — J. Sun, E. Shibata, et al. (1997)

Browse more research in American Journal of Industrial Medicine, or return to medical research.