Worker Health Study Summaries
Research on long-term exposure
Munitions Workers (Dinitrotoluene Exposure)
Two studies of the Army Arsenal
NIOSH conducted two studies of workers at the Army Arsenal:
- One studied the effects of DNT and nitroglycerin (NG) on the heart.
- One studied the risk of liver and bile duct cancer in workers exposed to dinitrotoluene (DNT).
We were concerned that two chemicals used at the Arsenal, dinitrotoluene (DNT) and nitroglycerin (NG), caused heart disease. We knew that NG swells blood vessels. When the workers’ NG levels dropped while away from work, their blood vessels may have tightened. This may have caused some workers to have chest pains or heart attacks.
Thus, the heart disease part of the study looked at heart attack deaths in employees who “actively” worked with NG. We define “actively” exposed to NG as having worked with NG within the last 30 days.
Other studies have reported that workers who used NG or DNT for many years also had an increased risk of heart attacks. Hence, we also looked at heart attack risk in employees who have worked with DNT or NG for many years.
How NIOSH Did the Heart Disease Study
We examined the records of all workers who had worked more than 5 months at the Arsenal. We classified people who worked either in the double-or triple-base lines that used NG as having worked with NG.
Employees who worked on the single-base line, which used DNT, were classified as having worked with DNT.
We studied three groups of workers:
- 5,529 men who worked with NG,
- 4,989 men who worked with DNT, and
- 5,136 men who worked with neither NG nor DNT.
2,512 men who worked with both NG and DNT were included in both groups 1 and 2. If we did not know whether you used DNT or NG, we excluded you from the heart study.
Records Used in the Heart Disease Study
This study was done without contacting the individual worker because it was based on records. It included living and deceased workers.
Government records were used to find out which workers had died. Death certificates reported the cause of death.
NIOSH used public records to find out the death rate for certain diseases in the general public. We calculated the number of deaths from each disease that we would expect to find in the workers, based on the death rates for these diseases in the entire U.S. population.
If the number of deaths from a disease in exposed workers is higher than the expected number, then NG or DNT exposures may be the reason.
We also compared death rates among different groups of workers.
Results of the Heart Disease Study
We compared employees exposed to NG to workers without any exposure to NG or DNT.
- Before 1970, workers who were actively exposed to NG had about twice the normal risk of a sudden heart attack.
- After 1970, this risk was reduced to normal.
- The risk of heart attacks was 3 1/3 times higher in workers under 45 years of age who actively worked with NG.
There were 8 deaths among workers younger than 45 from heart attacks. Only one of these deaths occurred after 1970.
Three factors may have combined to lower these risks after 1970.
- Workers with signs of heart disease or high blood pressure on medical tests were not allowed to work with NG.
- Exposures to NG have been lowered.
- Medical treatment for heart attacks has improved in recent years. Thus, more patients with heart attacks may have survived.
We compared workers exposed to NG or DNT to all unexposed workers.
Other studies suggested that we might see an increase in heart attacks in employees exposed to NG and DNT for more than 5 years.
- However, we did not see an increased risk of heart attacks in these workers.
- The workers who had worked less than a year with NG and DNT had the highest risk of heart disease.
The likely reason for these findings is that the Arsenal tested workers exposed to NG and DNT frequently for heart disease. If you worked with NG, they examined you every six months. If you worked with DNT, you were examined once a year.
They transferred workers who had signs of heart disease or high blood pressure to jobs without NG or DNT exposure. Those who worked for more than 5 years with DNT or NG had to pass many heart disease tests.
Hence, those who had worked for more than 5 years were likely to be healthier than those with less exposure.
Thus, it is not surprising that we did not see an increased risk of heart disease in workers with long-term exposure to DNT and NG.
If the DNT- or NG-exposed workers had not been tested so often, we may have seen an increase in heart disease in these long-term workers.
Other Findings of the Heart Disease Study
NIOSH also found an increased risk of accidents, violence, and mental illness mostly due to alcoholism.
These increased risks occurred in all three groups studied and, thus, were not related to exposure to NG or DNT.
In unexposed workers, we also found an increased risk of chronic lung diseases usually related to smoking or to coal mining. We found 34 deaths but expected only 21. We do not know the cause of this increase.
We do not believe that workers who still work with NG have an increased risk of fatal heart attacks.
However, if you work with NG and have chest pains, call your doctor, 911 or Emergency Medical Services immediately.
The fact sheet Steps to Protect Your Health has further information on the symptoms of a heart attack.
If you have any questions or want copies of the technical reports, please call the NIOSH toll free number at 800-356-4674.
NIOSH completed a study of workers employed at the Army Arsenal who worked with dinitrotoluene (DNT).
DNT causes liver and bile duct cancers in rats. We were concerned that DNT might cause these cancers in people who worked with DNT. Thus, we looked at the risk of these cancers in workers exposed to DNT.
How the DNT Cancer Study Was Done
NIOSH examined the job titles of all employees who worked at the arsenal for at least five months between 1949 and January 1980.
If a job title indicated that an employee worked on the single-base explosive line that used DNT, we determined that he had worked with DNT.
We studied two groups: those who worked with DNT for at least a day, and those who never worked with DNT. If we did not know whether an employee had worked with DNT, we excluded him from the study.
Then we obtained the death certificates of workers who had died. We counted the number of workers who died from each disease.
Next we calculated the number of deaths from each disease that we would expect to find in the workers, based on how often people die of these diseases in the whole U.S. population.
We also compared the risk of death of DNT-exposed workers to the workers who were not exposed to DNT.
If the number of deaths in the DNT-exposed workers is higher than the expected number, then DNT may be the cause.
What the DNT Cancer Study Found
NIOSH found an increased risk of liver, bile duct, and gall bladder cancers in workers exposed to DNT. Compared to the general public, we found 6 deaths from these cancers, but expected only 2 or 3.
The risk was almost 4 times higher in DNT-exposed worker than in unexposed workers.
All but one of the deaths occurs in workers hired prior to 1955. This suggests that possible high exposures to DNT before 1955, may have led to a high risk of these cancers.
These cancers are very rare. Only 6 out of 4,989 workers, or about 1 in 800 workers exposed to DNT, developed these cancers during the study.
This is the first study that has shown an increased risk of liver, gall bladder, and bile duct cancers in workers exposed to DNT. We believe that this study adds some support to the theory that working with DNT causes these cancers.
NIOSH believes that DNT may cause cancer in people. If you worked with DNT, your risk of liver, gall bladder, and bile duct cancers may be higher than normal. However, we believe that your risk of developing these cancers is still very low. Read the fact sheet, Steps to Protect Your Health, for more information about these cancers.
If you have any questions, or would like a copy of the technical reports, please call 800-356-4674.
Steps to Protect Your Health
Symptoms of Bile Duct and Liver Cancers
Jaundice may be a sign of these cancers, which may be caused by exposure to dinitrotoluene (DNT). That is, the whites of the eyes and skin may turn yellow.
- The urine may look greenish or darker than normal.
- There may be itching along with the jaundice.
- The jaundice may be painless. However, deep, constant pain in the right upper belly may occur with the jaundice. There may be pain without the jaundice.
- Loss of appetite may be accompanied by loss of weight.
These symptoms do not necessarily mean that you have bile duct or liver cancer. Other less serious diseases have these symptoms.
However, they need to be evaluated. If you develop any of these symptoms, please see your doctor right away. These cancers should be treated at a center where there are specialists who treat these diseases.
The National Cancer Institute Hot Line can direct you to the nearest center for diagnosis and treatment of these cancers. Their toll-free number is 800-4-Cancer. The American Cancer Society has free information on the treatment and diagnosis of various cancers. Call them at 800-227-2345.
Symptoms of Heart Disease
If you work with nitroglycerin (NG) and experience dizziness, headaches, or nausea while on the job, notify the plant physician. These symptoms may indicate overexposure to NG.
If you work with NG and notice chest pains or palpitations away from the job, it might be a symptom of a heart attack or other heart disease. Call your doctor immediately.
If you cannot reach your doctor, call 911 or the emergency medical services number in your area.
Exposure to DNT and NG
If you still work with DNT or NG, work with your employer or union to reduce your exposure.
NG and DNT are absorbed through the skin. Protect your skin from exposure to these chemicals.
The Arsenal examines the hearts of workers exposed to DNT yearly and NG every six months. This should help protect you from the heart disease caused by NG and DNT.
The NIOSH recommended exposure limit (REL) and the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for all DNTsis 1.5 mg/m3.
While the OSHA ceiling PEL for NG is 2 mg/m3, the NIOSH REL is 0.1 mg/m3 for any twenty minute period.
Stayner L, Dannenberg A, Bloom T, et al. (1993). Excess Hepatobiliary Cancer Mortality among Munition Workers Exposed to Dinitrotoluene. Journal of Occupational Medicine 35 (3):291-296. (Study Report).
Stayner L, Dannenberg A, Thun M, et al. (1992). Cardiovascular mortality among munition workers exposed to nitroglycerin and dinitrotoluene. Scandinavian Journal of Work, Environment, and Health 18:34-43. Study Report).