Worker Health Study Summaries – Acid Mist Exposure among Steelworkers

Research on long-term exposure

Acid Mist Exposure among Steelworkers


Study Background

NIOSH studied acid mist exposure among steelworkers.

The NIOSH studies helped us learn more about the hazards of exposure to acid mist. This information could help workers exposed to acid mist around the world.

The Larynx Cancer Study

This study was on cancer of the larynx. The larynx is the voice box in the throat.

This was an incidence study. This study followed the people exposed to acid mist to see if they developed cancer of the larynx.

We studied past workers at three plants so there would be enough people in the study. If a study didn’t include enough people, a real association between exposure and present disease may be missed.


Many of the workers in this study answered questions for the study by mail or over the telephone. Relatives answered for deceased workers.

However, even if you did not answer the questions, the results apply to your health, too. Nine men out of 879 men in the survey group had cancer of the larynx.

Smoking and Drinking

In the survey, NIOSH asked whether the worker smoked cigarettes or drank alcohol.

We asked this because excessive smoking and drinking can cause cancer of the larynx. We needed to see if more cases developed than we would expect from smoking and drinking alone. Additional cases could be caused by exposure to acid mist.

Expected Number of Cases

The first part of the study was to find out if nine cases of cancer of the larynx were more than expected. We estimated how many cases were expected based on rates of disease in the general population.

Based on the U.S. general population, only about 4 cases would have been expected. This number takes smoking, drinking, and other factors into account.

Larynx Cancer Findings

The result of the study was that steel pickling workers were 23 times more likely to get cancer of the larynx than men in the general population.

Even though pickling workers have a higher risk for cancer of the larynx, that does not mean that a lot of workers will get it.

This is a fairly new finding. Before we can be sure it is true, it must be confirmed in other studies. However, there are already some other studies that show similar results.

The Lung Cancer Study

This was a mortality study. This study followed the people exposed to acid mist to see if they died of lung cancer.

Information for the study came from work records, death certificates, and the survey questions about smoking. We asked about smoking because it is known to cause lung cancer.

Everyone at all three plants was included in the study, even if they didn’t answer the survey.

Lung Cancer Findings

Steel pickling workers were 1.4 times more likely to die of lung cancer than the general public.

This number takes smoking into account. This is considered a small increase in risk.

This means that the excess lung cancer was not just due to smoking. The acid mist may also have caused it.

However, there are three reasons why we are unsure about the lung cancer result:

  • The risk was not very high and may have been due to chance.
  • Acid mist may not reach deep into the lungs.
  • There haven’t been other studies of this problem, so we haven’t been able to confirm our results.


Based on past results of our studies, we cannot predict your risk of larynx or lung cancer. However, your exposure to acid mist may have increased your risk of larynx cancer and lung cancer.

There are ways to protected yourself from the effects of acid mist. They are listed on this web site, “Other Information for Workers Exposed to Acid Mist”.

Please take the time to read these materials. If you have any questions, do not hesitate to call the NIOSH toll free number: 800-356-4674. Say that you are calling about the acid mist study.

Other Information for Workers Exposed to Acid Mist

Exposure and Dose

The chance of developing a disease due to exposure to a hazardous chemical is greater the more you have been exposed.

Exposure means that the chemical (like acid mist) is present in the environment and can be taken into your body.

Dose describes how much of the chemical has been taken into your body. It is a combination of the concentration of the chemical in the environment and the length of time that you are exposed to it. Usually people are exposed to acid mist by breathing it.

Measuring Exposure

Exposure to acid mist should be routinely measured by your employer. This includes taking air measurements, especially personal air samples.

Exposure Limits

The federal Occupational Safety and Health Administration (OSHA) sets legal exposure limits.

NIOSH is a federal agency that does research on occupational health and recommends the appropriate standards.

The American Conference of Government Industrial Hygienists is not a government agency. However, it recommends voluntary guidelines called threshold limit values.

Sulfuric Acid Exposure Limits

OSHA has set a limit of 1 milligram per cubic meter of air (1 mg/m3) averaged over 8 hours. ACGIH has made the same recommendation. NIOSH has recommended this level averaged over 10 hours.

According to information available to NIOSH, levels of sulfuric acid in the study plants averaged 0.2 mg/m3, which is less than these limits.

Health Hazard Information

Health effects depend on: how much of a chemical you were exposed to, and whether the exposure was over a long or a short period of time.

When someone is exposed to a high concentration over a short time, they may get sick right away. Other diseases may develop when exposure at a low concentration occurs over a long time (usually years).

Sulfuric acid mist irritates the skin, eyes, nose and throat, and lungs. Exposure to high concentrations can cause severe damage at all these sites.

Exposure over many years could cause difficulty breathing or erosion of the teeth.

The NIOSH studies indicate that acid mist may cause larynx and lung cancer.

Reducing Your Exposure to Acid Mist on the Job

While the levels of acid mist now are generally lower than in the past, you should avoid all unnecessary exposure to acid mists.

Follow safe job practices especially those listed on JSHA’s (Job Safety and Health Analysis). Suggest any changes in JSHA’s you feel would improve the safety and health of you and your co-workers.

Know where Material Safety Data Sheets (MSDSs) are kept. Read and understand MSDSs for materials you are handling. If you are unsure what a MSDS says or how it applies to your job, it is important that you ask for assistance.

Obtain and use respiratory protection. Respirators are required on those tasks where exposures cannot be controlled adequately by ventilation or work practices alone. You may want to use a respirator for other jobs or tasks where you may be exposed.

Be sure you have received training in the proper use of the respirator.

Be sure you understand and follow the instructions on the proper use and care of the respirator and other safety gear.

Report broken acid mist controls immediately. Also report any problems with other chemical ventilation systems. Do this by informing your departmental supervisor directly or by completing an Unsafe Condition Report.

You may also contact the Safety and Industrial Hygiene Department or your AE3F representative.

Access to Your Records

You have a legal right to examine and copy the results of air testing under OSHA regulations 29 CFR 191020.

You have a legal right to examine and copy all medical records your employer keeps on you under OSHA regulation 29 CFR 191020.


Cancer of the larynx can be treated if caught early. If you have warning symptoms, you should go to a doctor.

Hoarseness is a common symptom. Other symptoms include: a change in your voice, a lump in your throat, or trouble breathing. See a doctor if these symptoms don’t go away in 3 weeks.

Symptoms of lung cancer include shortness of breath, chest pain, and coughing a lot.

Even if you have any of these symptoms, that does not mean you have a serious illness.

Many less serious conditions could have these symptoms. However, you should have your health checked by a doctor to be sure.

This is especially true if the symptoms don’t go away. Give your doctor a copy of the NIOSH materials.

Smoking and Drinking

Workers who smoke or drink can greatly reduce their risk of lung and larynx cancer by quitting.

Smokers are about 75 times more likely to develop larynx cancer and 9 times more likely to die of lung cancer than nonsmokers.

People who drink alcoholic beverages are about 2 to 3 times more likely to develop larynx cancer than non-drinkers.

In comparison, workers exposed to acid mist are 1 to 2 times more likely to die of lung cancer and 2½ times more likely to develop larynx cancer.

Sources of Information

If you or a family member would like to ask questions about any information on this web site, call the NIOSH toll-free number: 800-356-4674. Say you’re calling about the acid mist studies.

Sources of Information at the Plant Include:
  • Your supervisor
  • Your Plant Medical Department
  • Your plant Health and Safety Committee
  • Members of the Safety and Industrial Hygiene Department
  • Your union representative
  • Material Safety Data Sheets (MSDSs)
Program to Help Workers Quit Smoking

American Cancer Society
105 McKnight Dr. Middletown, OH 45044

Other Sources of Information and Service Include:

Center for Occupational Health
Holmes Hospital Eden and Bethesda Ave.
Cincinnati, OH 45267-0458

Greater Cincinnati Occupational Health Center
10475 Reading Rd, Suite 405
Cincinnati, Ohio 45241

National Cancer Institute’s toll-free telephone number for fact sheets on different types of cancer and information on sources of cancer diagnosis and treatment in your area: 800-4-CANCER.

Steelworker’s Letter for their Medical Record

November 1991

Steelworkers: See your doctor if you have any symptoms of lung or larynx cancer. We don’t recommend that you make a special trip to the doctor if you don’t have symptoms. However, we suggest that when you do see your doctor, bring a printout of “For Your Medical Record” with you.

Letter for the doctor of a steelworker.

Dear Doctor:

The bearer of this letter was an employee at one of three steelmaking plants that was studied by the federal National Institute for Occupational Safety and Health (NIOSH). The investigation consisted of two parts: 1) a retrospective cohort mortality epidemiologic study that evaluated many causes of death but primarily focused on lung cancer, and 2) an incidence study of laryngeal cancer.

The studies concluded that workers at these plants are probably at increased risk of developing laryngeal cancer and possibly also lung cancer due to occupational exposure to acid mist. The acids involved could have been sulfuric, hydrochloric, nitric, or hydrofluoric acid. However, the main acids used were sulfuric and hydrochloric acid. The purpose of this letter is to inform the personal physician of plant employees of this increased risk. These studies analyzed the risk for the group of workers; we cannot determine the risk for individual workers.

For both studies, work histories and vital status were obtained on employees. The difference between a mortality study and an incidence study is that in a mortality study, observed cancer refers to those who have died of the disease, whereas in an incidence study, observed cancer refers to those who have developed the disease, but may or may not have died of it. Mortality and incidence rates in the study group were compared to those expected based on rates for the general US population.

One advantage of these studies was that cigarette smoking and alcohol consumption behavior were obtained from a large segment of the study population by questionnaire. Expected rates of disease were adjusted to account for these two risk factors. This means that the expected rates were altered after taking smoking and drinking into account. The result was that, adjusted for smoking and alcohol, the workers were 23 times more likely to develop laryngeal cancer than the general population. Adjusted for smoking, they were 1.4 times more likely to die of lung cancer. These figures are relative risks. Therefore, even after taking smoking and drinking into account, these workers experienced a moderate excess of laryngeal cancer and a modest excess of lung cancer.

Both of these findings are relatively new and need to be confirmed in other studies. The evidence for the laryngeal cancer finding is considered to be stronger for three reasons: 1) the increased relative risk was higher and was statistically significant even after adjustment, 2) most acid mist particles probably only reach the upper respiratory tract (including the larynx), and 3) several other epidemiologic studies lend support to the results of the NIOSH study.

The evidence for lung cancer is weaker because: 1) the risk was not very high even though the increase after adjustment for smoking met the criteria for statistical significance used to identify diseases to be considered for notification, 2) fewer particles will reach the lung (although some will), and 3) there is less supporting epidemiologic evidence for the lung cancer finding However, there were far more cases of lung cancer than laryngeal cancer (this is because the absolute risk of lung cancer (or rate in the general population) is higher than the absolute risk of laryngeal cancer).

If your patient is still employed at the steelmaking plant, he or she may receive medical examinations at the plant. Your patient could provide you with the results of examinations done by the employer.

NIOSH does not currently recommend screening for lung cancer for asymptomatic patients because it has not been established that such screening is beneficial to those screened. Symptomatic patients should be evaluated. This letter only addresses the health effects reported in the NIOSH studies. Exposure to acid mist is known to have other health effects as well.

If your patient is a smoker, strongly encourage him or her to quit. Smoking is strongly associated with both laryngeal and lung cancer. Encourage your patient to reduce alcohol consumption. Consumption of alcoholic beverages is associated with laryngeal cancer, although not as strongly as smoking.

To put these findings in some perspective, it should be noted that smoking and drinking alcoholic beverages are known risk factors for laryngeal cancer.

NIOSH can provide copies of the epidemiologic studies on acid mist.

The references for the studies are:

Beaumont JJ et al., JNC3 1987, 79:911-21;

Steenland K et al., Am J Ind Med 1989, 16:347-54.

Steenland K et al., Brit J Ind Med 1988, 45:766-76;

We can also provide the document prepared by NIOSH to support the recommendations made here. This is called the Worker Notification Profile-Acid Mist Exposure in Steelworkers.

If you have any questions or would like to receive any of these materials, call NIOSH at 800-356-4674; say you’re calling about the acid mist studies.

Page last reviewed: April 8, 2020