PCBs: a study of breast cancer among workers 

from three manufacturing plants

Overview 

The National Institute for Occupational Safety and 

Health (NIOSH) is a government agency that strives 

to improve worker health and safety. At NIOSH, 

we studied the risk of breast cancer associated with 

exposure to polychlorinated biphenyls (PCBs) 

among female workers from three capacitor 

manufacturing plants. These plants were located in: 

● New Bedford, Massachusetts

● Hudson Falls, New York

● Bloomington, Indiana

Overall, we found no increased risk of breast cancer 

among these workers compared to women in the 

general population. This is consistent with what 

other studies have found. However, we did find 

that the more PCBs the nonwhite female workers 

were exposed to, the more their risk of breast cancer 

increased.

This fact sheet contains health information that 

may be important to you. Our records indicate 

you, or a relative of yours, worked at one of these 

manufacturing plants during the time when PCBs 

were used in the production process. 

Background about PCBs 

PCBs, also known as dielectric fluid, are oily 

and clear to light-yellow in color. They have no 

smell or taste and were used for many commercial 

purposes. At these manufacturing plants, PCBs 

were used in capacitors because they do not burn 

easily and hold an electrical charge well. 

The main sources of PCBs were the metal 

capacitor boxes that were made at the plants. In a 

heated vacuum chamber, the capacitor boxes were 

filled with PCB and then welded shut. Any spilled 

PCB was washed off each box and the unit was 

sent to quality control for testing.

Workplace PCB exposure can happen if the 

chemicals are:

● Absorbed (absorbs quickly through skin; high 

level exposure can cause skin conditions, 

such as acne or rashes)

● Breathed in (when heated, more vaporizes 

into the air)

● Ingested (if hands are not washed properly 

before eating)

Why we did this study 

In 1977, PCBs were banned in the United States 

because they were found to harm the environment. 

Many studies have found PCBs may also be bad 

for our health. Some laboratory tests have found 

PCBs may affect our hormones. Some of these 

hormones are related to breast cancer. 

We did this study to see if working with PCBs 

could increase a woman’s chance of getting breast 

cancer. We wanted to know if women who worked 

at these plants for at least a year had a higher 

risk of breast cancer than women in the general 

public. We also wanted to know if female workers 

exposed to more PCBs were more likely to have 

breast cancer than those exposed to less.

Figure 1: States where manufacturing plants were located.

IN MA

NY
How we did the study 

Using work site records, we found 5,752 women 

worked at these plants for a year or more (5,390 

white and 362 nonwhite).We determined the 

number of female workers with breast cancer by 

using a health survey, which we sent to female 

workers and family members of deceased 

workers. We also searched death certificates and 

state cancer registries (Indiana, Massachusetts, 

and New York, as well as California and Florida, 

which are common retirement destinations).

Worker PCB exposure was not measured 

regularly, so we don’t know exactly how much 

PCB each person was exposed to. We estimated 

PCB exposure for each worker based on work 

history data. This included worker job titles 

and descriptions, length of employment, plant 

layouts, and general air samples that were taken 

in the 1970s. For each worker, we accounted for 

all jobs worked while at the plant. For each job, 

we accounted for the time period and the length 

of time in each job. From this, we estimated the 

overall PCB exposure for each worker. 

What we found

We received 3,141 completed surveys (80% 

were from workers, 20% were from families 

of deceased workers). Of those who filled out 

the surveys, we found 145 women from these 

plants have or had breast cancer before 1999; 

131 women were white and 14 women were 

nonwhite (see figure 2). “Nonwhite” included 

women who said their racial background was 

something other than white (Caucasian), such 

as: multi-racial, African American, Portuguese 

(Cape Verdean), and others. 

When we compared the number of breast cancer 

cases among workers of all races from these three 

plants to what would be expected in the general 

public, there was no increase in breast cancer risk. 

When we separated the data by race, we found the 

more PCBs the nonwhite workers were exposed 

to, the more their risk of breast cancer increased. 

This finding is based on a small number of cases; 

more research is needed to confirm this. Most of 

the nonwhite women worked at the Massachusetts 

plant. The women from the Massachusetts plant 

had higher PCB exposure than the women who 

worked at the plants in New York and Indiana. 

The differences in exposure are likely due to 

differences in the work and housekeeping practices 

and the dielectric fluid used.

We did not see an increased risk in breast cancer 

with increasing PCBs exposure among the white 

women. 

Number of breast cancer cases among 

workers who filled out the survey

total surveys received

cases of breast cancer

2859

131

282

14

whites nonwhites

3000

2500

2000

1500

1000

500

0

Figure 2: Number of breast cancer cases among all workers 

(white and nonwhite) for whom surveys were recieved
What you should do 

Women from these plants should follow American 

Cancer Society and National Cancer Institute 

recommendations and continue doing regular 

breast self-exams and getting mammograms. 

These are routine practices that all women should 

do. Breast cancer is caused by many things and is 

most treatable when found early.

See the enclosed step-by-step information to learn 

how to do a breast self-exam. 

If you have questions or concerns about breast 

cancer, talk with your doctor. He or she can tell 

you about other routine tests, such as clinical 

breast exams. 

If you have questions about this study, please call 

1-800-CDC-INFO (1-800-232-4636).

What we are doing next 

We are planning a study to see if workers 

from these same three plants have a higher 

risk of developing other types of cancers when 

compared to men and women from the general 

public. This will help determine if a link exists 

between PCB exposure and certain cancers. It 

will be different from other studies done over the 

years because it will use cancer registry data and 

will look at all types of cancer. 

Additional information 

PCB levels in the body decrease over time. If you 

were exposed many years ago, your current levels 

may not be any different from those of the general 

public. Most people have low levels of PCBs in 

their body from environmental exposures. 

Many of the state health departments have done 

studies on PCBs in the environment and in 

communities. If you would like to learn more 

about these studies, contact your state health 

department:

● Indiana State Department of Health: call 

(317) 232-3413 or visit www.in.gov/isdh.

● Massachusetts Office of Health and Human 

Services: call (617) 624-5757 or visit www.

mass.gov and search “Environmental Health 

Investigations.”

● New York State Department of Health: call 

1-800-458-1158 or visit www.health.state.

ny.us/environmental/pcb/index.htm.

For more information about how you can prevent 

breast cancer, contact:

● The National Cancer Institute at 1-800-4- 

CANCER or visit www.cancer.gov/

cancertopics/wyntk/breast/page1.

● The American Cancer Society at 1-800-ACS2345 or visit www.cancer.org/.

Centers for Disease Control and Prevention 

(CDC) is the federal agency that promotes health 

and quality of life by preventing and controlling 

disease, injury, and disability. NIOSH is part of the 

CDC. To learn more, visit www.cdc.gov/niosh or 

call 1-800-CDC-INFO.