Worker Health Study Summaries
Research on long-term exposure
Shoe Manufacturers (Toluene)
Why the Study Was Done
The study was done to find out the long-term health risks from exposure to toluene and other solvents.
Solvent exposures could occur in the Fitting, Sole Leather, Last, Bottoming, and Packing Departments of a shoe manufacturing plant. Exposure could be from breathing or through the skin.
We especially wanted to know if working in shoe manufacturing plants increased workers’ chances of getting leukemia, a type of cancer.
Studies of other shoe workers have found increased leukemia. In the other studies, workers were exposed to high levels of benzene. Benzene is a solvent that can cause leukemia. However, the plants in our study never used benzene-based solvents or glues.
How the Study Was Done
We studied about 7800 men and women shoe workers who worked at least one month between 1940 and 1982.
In this study, we did not contact workers directly. We used company and government records to find out which workers had died. We learned the cause of death from death certificates.
We looked to see if deaths from specific diseases occurred in shoe workers more than they would in the general public. The expected number of deaths is based on deaths in the general public.
The study did not find evidence that working in these shoe manufacturing plants leads to leukemia.
Among men, there were about as many leukemia deaths as expected. Among women, there were 9 leukemia deaths compared to about 7 expected. However, an increase of two deaths is too small to show that shoe workers are at risk for leukemia.
The increase in leukemia deaths in women may not have been due to workplace exposures.
As evidence for this, the risk of leukemia did not occur more in people who worked more years in a plant. No leukemia deaths have occurred in people hired after 1955.
We found an excess of lung cancer, but we don’t know if the excess was related to shoe making. There were 99 lung cancer deaths compared to 67 expected. Smoking could not have accounted for all the excess lung cancer.
The lung cancer may not have been due to exposures in the shoe factory.
As evidence for this, the risk of lung cancer did not depend on how long people worked in a plant.
Other Lung Diseases
Men had a higher than expected risk for long-term lung diseases besides cancer (for example, bronchitis and emphysema). Among men, there were 40 deaths due to these diseases, with 25 expected. Women’s risk was lower than expected.
We don’t know if the findings in men for these lung diseases were due to workplace exposures or not.
The study shows that the workers in the study might be at risk for lung cancer or other lung diseases.
We do not know if the excesses are due to the workplace, smoking, or other causes.
However, the finding of an increased risk of developing lung cancer and other lung diseases applies to the shoe workers as a group and not to individuals.
What Can You Do to Protect Your Health?
It is important that employers maintain safe and healthy workplaces, and that employees follow safe work practices and established safety rules. This includes avoiding breathing solvents (in cleaners and glues) and getting them on your skin.
If you smoke, you should stop.
If you have any questions or would like further information, please call the NIOSH toll-free number at 800-356-4674
Say you are calling about the shoe worker study.
Walker J, Bloom T, Stern F, et al. (1993). Mortality of workers employed in shoe manufacturing. Scandinavian Journal of Work, Environment, and Health 19:89-95. (Study Report).