Increased risk of lung cancer in pesticide-exposed male agricultural workers

Our plain-English summary of Increased risk of lung cancer in pesticide-exposed male agricultural workers, by E. Barthel (Journal of Toxicology and Environmental Health, 1981).

The study

• Author: E. Barthel
• Journal: Journal of Toxicology and Environmental Health
• Published: 1981;8(5-6):1027-40
• Cited by: 56 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The cancer morbidity in a large group of male German agricultural workers exposed to pesticides was investigated through a retrospective cohort study. A total of 169 malignant tumors were diagnosed in 1658 men who began to work with pesticides between 1948 and 1972, and who continued this type of activity for at least 5 yr. The SMR (standardized mortality ratio) of 2.0 for lung cancer morbidity (mortality) in these pesticide-exposed subjects was significantly higher than that for the general male population of the German Democratic Republic. A positive correlation between the duration of employment and the mortality due to lung cancer (mainly undifferentiated and small-cell carcinomas) suggested a dose-effect relation. The smoking habits of the exposed men did not differ from those of the general male population of the German Democratic Republic. Because the subjects had been exposed to many different substances, the study does not permit any conclusions to be drawn in respect to the carcinogenicity of individual pesticides. The increased mortality due to lung cancer is presumably the result of an additive effect of different pesticide ingredients or of by-products whose carcinogenic effect has been definitely or tentatively established through experimental or epidemiologic studies (e.g. arsenic, asbestos, chlorinated dibenzodioxins, DDT). The results of the present investigation emphasize the need for effective measures to protect workers during occupational contact with pesticides.

In plain English

This retrospective cohort study followed 1658 men in East Germany (the German Democratic Republic) who had worked at least 5 years between 1948 and 1972 as agricultural plant protection workers or agronomists using pesticides. Up to 1960 pesticides were applied mainly as dusts, and respiratory protection was rarely used. The study did not measure asbestos. The author proposed that the lung cancer excess was presumably due to an additive effect of several pesticide ingredients or by-products, naming asbestos, a possible contaminant of carrier powders in dust pesticides, among them. The men developed 169 cancers, 59 of them lung cancers. From 1970 to 1978, 50 lung cancers were observed against 27.5 expected from general male population rates, a significant 1.8-fold increase. The ratio was 1.2 for under 10 years of exposure, 1.7 for 10 to 19 years and 3.0 for more than 19 years. Other cancer types showed no significant differences. A sample of 163 workers did not differ significantly in smoking from 163 controls. The author concluded that pesticide exposure was connected with increased cancer risk. The author added that exposure to many products allowed no definite conclusions about individual pesticides.

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: retrospective cohort study comparing cancer cases in exposed workers with numbers expected from general male population rates
• Who was studied: 1658 men who had worked at least 5 years as agricultural plant protection workers or plant protection agronomists in the 14 districts of the German Democratic Republic (excluding Berlin) during 1948 to 1972; lung cancer was compared for 1970 to 1978
• Exposure: Mixed pesticides, applied mainly as dusts up to 1960 and increasingly as liquid sprays afterwards. Products included calcium arsenate (banned since 1955), DDT, HCH, toxaphene, 2,4-D, MCPA, zineb, maneb and others. Asbestos was not measured. The author raised it as a possible contaminant of the carrier substances (talcum, kaolin, bentonite) in pesticide dust formulations, and named it among by-products that might have contributed to the lung cancer excess.
• Main results:
  • In the 1658 exposed men, 50 lung (bronchial) carcinomas were observed in 1970 to 1978 against 27.5 expected, a significant 1.8-fold increase (p less than 0.05) compared with the general male population of the German Democratic Republic
  • When calculated for individual years from 1970 to 1978, allowing for deaths in the exposed group, the average increase in lung cancer risk was 2.1-fold
  • The lung cancer ratio rose with years of exposure: 1.2 for under 10 years (7 observed, 5.8 expected), 1.7 for 10 to 19 years (27 observed, 16.2 expected), and 3.0 for more than 19 years (16 observed, 5.5 expected). The 1.7 and 3.0 ratios were marked p less than 0.05. The author said this suggested a dose-effect relation.
  • Lung cancer ratios did not differ significantly by year exposure began: 1.8 for men first exposed 1948 to 1960 (45 observed, 24.5 expected) and 1.7 for men first exposed 1961 to 1972 (5 observed, 3.0 expected)
  • Of the 59 lung carcinomas, 42 were verified histologically: 22 undifferentiated and small-cell carcinomas, 14 squamous carcinomas, 3 adenocarcinomas, 2 solid carcinomas and 1 alveolar cell carcinoma
  • Apart from lung cancer, the ratios for the other tumor types did not differ significantly between the exposed men and the general population
  • In a random sample of 163 exposed workers compared with 163 unexposed persons of the same age and sex, there were no significant differences in smoking habits or tobacco consumption
  • This was the author's interpretation, not a measured result. The author proposed that the increased lung cancer mortality was presumably due to an additive effect of different pesticide ingredients or by-products, with arsenic, asbestos, chlorinated dibenzodioxins and DDT given as examples. Asbestos exposure itself was not measured or analysed separately.
• The authors' conclusion: The author concluded that the study provided additional epidemiologic evidence that occupational exposure to pesticides is connected with an increased risk of cancer
• Limitations the authors state:
  • Because the workers were exposed to many products, no definite conclusions could be drawn about the carcinogenicity of individual pesticides
  • There were no quantitative exposure data, so the extent of exposure could only be deduced from length of employment
  • Individual exposure times for certain pesticides were available but were not used because they appeared too imprecise
  • Results for men first exposed in 1961 to 1972 rested on only 5 lung cancer cases

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Cohort Study, standardized mortality ratio (SMR), Carcinoma, Habit, Carcinogenic.

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