Worker Health Study Summaries – Radiofrequency Heat Sealer Operators

Research on long-term exposure

Radiofrequency Heat Sealer Operators (Radiofrequency Heat Sealers)


Study Background

NIOSH studied radiofrequency heat sealer operators.

How the study was done

Approximately 9,000,000 workers are occupationally exposed to radiofrequency (RF) radiation. We wanted to determine whether working with radiofrequency (RF) heat sealers affects a worker’s reproductive health. A man’s reproductive health can affect his ability to father children or the time it takes for his partner to become pregnant.

NIOSH asked two groups of workers to be in their study. One group (the exposed group) was workers who sealed the seams of waterbed mattresses using RF heat sealers. The other group (the unexposed group) was workers with no known work exposure to RF radiation. This plan lets us compare the test results of workers exposed to RF radiation with the results of unexposed workers.

We planned to test at least 60 RF heat sealer operators. However, the largest water mattress firm withdrew its support for the study. Therefore, the final study had only 12 exposed and 34 unexposed workers.

At each work place, we measured the RF radiation reaching the heat sealer operators. We also measured the induced current flowing in the worker’s body, which is a measure of the amount of RF energy absorbed by the worker. We found that average worker exposures to RF radiation at different water mattress companies were similar to each other. These average exposures were less than the recommended occupational exposure limits for RF radiation. However, some individual RF heat sealer operators had exposures that were higher than these limits.

We had each worker privately collect a semen sample. We also collected a blood sample from each worker.

Many tests were done on the semen and blood samples. We counted the number of sperm in each semen sample. We measured how fast the sperm swam. We determined the percent of the sperm that were alive. We determined how many of the sperm looked abnormal.

We also measured four male hormones in the blood samples: testosterone, follicle stimulating hormone (FSH), luteinizing hormone and prolactin.

These tests tend to change from day to day in any given individual. Only very large changes in a man’s test results are known to affect his fertility.

What the tests mean

In the semen samples, the quality of the sperm and the liquid they swim in were tested. We also measured the levels of blood hormones important for male reproductive health. The types of changes seen in this study can be found in everyone and happen for a number of reasons. Some reasons have been related to health problems and others have not. Factors in everyday life, like sleep patterns and the use of certain medicines, can also change these test results.


We saw only two differences between the sperm of workers exposed to RF radiation and unexposed workers. The percent of live sperm was somewhat higher in workers exposed to RF radiation than in the unexposed group. The number of a type of damaged sperm (double-headed) was also higher in the unexposed workers than in the exposed group. These results are not what we expected to find. They may have occurred because of chance alone. Alternatively, the unexposed group might have had other exposures that caused these changes.

The average blood FSH level was significantly higher in workers exposed to RF radiation than in the unexposed group. However, this higher level was still in the normal range for this hormone. This increase did not appear to cause a decrease in the sperm count or in the quality of the sperm.


This study suggests that exposure to RF radiation at the levels measured in these workers did not cause damage to the sperm or male hormones. Since there were only 12 exposed workers in our study, we believe that this study should be repeated with a larger group of workers. However, the researchers believe mat there are probably no large effects resulting in sperm damage or changes in hormone levels in men exposed to RF radiation at the levels seen in this study.

If you or your doctor would like more information about this study, call our toll free number 800-356-4674. Say that you’re calling about the Radiofrequency Heat Sealer Operator Study.


Grajewski B, Cox C, Schrader S et al. (2000) Semen Quality and Hormone Levels Among Radiofrequency Heater Operators. Journal of Occupational and Environmental Medicine 42 (10): 993-1005.

Page last reviewed: April 8, 2020