The History of PBBs in Michigan

What happened in Michigan in 1973?

In early 1973, polybrominated biphenyls (PBBs) were sold under the trade name FireMaster. The St. Louis, Michigan plant—the Michigan Chemical Company (also known as the Velsicol Chemical Corporation) – produced these PBBs. The same plant also produced magnesium oxide (a cattle feed supplement) that was sold under the trade name NutriMaster. A shortage of preprinted paper bag containers led to the plant accidentally sending 10 to 20 fifty-pound bags of FireMaster (PBBs) to Michigan Farm Bureau Services in place of the NutriMaster cattle feed supplement. The bags were shipped to feed mills and used in the feed for dairy cattle. PBBs contaminated other livestock as well.

Map showing number of PBB contaminated farms by Michigan countyThe mix-up was discovered in April 1974. By that time, PBBs were in the food chain through contaminated milk and dairy products, beef, pork, lamb, chicken, and eggs.

As a result of this incident, over 500 contaminated Michigan farms were quarantined (Figure 1). Many farm animals were destroyed, including approximately:

  • 30,000 cattle
  • 4,500 pigs
  • 1,500 sheep
  • 1.5 million chickens

Also destroyed were over:

  • 800 tons of animal feed
  • 18,000 pounds of cheese
  • 2,500 pounds of butter
  • 5 million eggs
  • 34,000 pounds of dried milk products

What did the Michigan Department of Health and Human Services (MDHHS) do about the PBB incident?

Some people in Michigan were exposed to PBBs from eating these foods during the time between the distribution of the feed and the destruction of contaminated animals, dairy, eggs, and meat products, 

The Michigan Department of Public Health (now the Michigan Department of Health and Human Services (MDHHS)) responded by first testing the blood of the Michigan residents who were most likely to have been exposed to PBBs. They found that most Michigan residents who had contact with PBB-contaminated food had very low amounts of PBBs in their blood. However, tests showed that some people who lived and worked on the quarantined farms had higher amounts of PBBs in their blood.

Map showing number of long-term PBB study enrollees by Michigan county

To study any possible long-term health effects on Michigan residents, the Michigan Long-Term PBB Study began in 1976. MDHHS coordinated this study. They worked with federal partners in U.S. Public Health Service to enroll and follow a group of over 4,000 people (Figure 2). They monitored the group’s health over time. The people in this study were mostly farm families and neighbors—including their children—who ate the most contaminated products. They completed health and exposure questionnaires and had their blood tested for PBBs and other chemicals in the environment. Children born between 1976 through 1993 to mothers in the study were also enrolled. Information on cases of cancer and deaths were recorded.

Velsicol Chemical Worker Studies

Michigan Long-Term PBB Study

The Velsicol Chemical Corporation owned the Michigan Chemical Company. This factory, located in St. Louis, Michigan made PBBs. Factory workers and their families were also invited to join MDHHS’s Michigan Long-Term PBB Study in the late 1970s. As workers’ participation in the Michigan Long-Term PBB Study declined and other worker-related studies were started by new research groups, MDHHS discontinued efforts to recruit more factory workers and their families to participate in the Michigan Long-Term PBB Study. After 1990, the Michigan Long-Term PBB Study no longer included the workers’ group. MDHHS continued to work with the St. Louis, Michigan community to discuss concerns about health effects related to PBBs and also the factory. MDHHS has also evaluated environmental data from the Velsicol Burn Pit Superfund Site (Former Burn Area [Velsicol Burn Pit Superfund Site] Public Health Assessment). In 2013, the workers and their families were invited to join the PBB study run by Emory University.

1977 Health Hazard Evaluation

In 1977, 184 people who worked at the St. Louis factory took part in a Health Hazard Evaluation conducted by the National Institute for Occupational Safety and Health (NIOSH). This evaluation included medical examinations of the employees. A walk-through of the factory was done to look at how people may have been exposed to the many chemicals made or used there. The medical exams looked for abnormal health findings related to the employees’ contact with these chemicals, including PBBs.

The people who worked at the factory had a variety of health effects including abnormalities of the liver, kidney, skin, brain, eye, and adrenal glands, which are small, triangular-shaped glands located on top of both kidneys. Adrenal glands produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other body functions. NIOSH concluded that “… at least a portion of the Velsicol employees suffered adverse health effects because of chemical exposure encountered at the St. Louis, Michigan plant” (NIOSH 1979).

It is difficult to know if these health effects were caused by the employees’ exposures to specific chemicals found in the plant or if there were other factors influencing these effects. A summary of the evaluation, including health effects experienced by the people who worked at the factory can be found in the fact sheet, “Technical Summary of Velsicol Corporation Workers’ Chemical Exposure and Health Issues”.

General Population Studies

The Environmental Sciences Laboratory at Mount Sinai in New York was one of the leaders in environmental health research in the 1970s. Their laboratory supported the NIOSH Velsicol employees’ evaluation. In 1977, the State of Michigan asked Mount Sinai researchers to conduct a survey of the distribution of PBB levels in the blood and fat of the general population of Michigan and to evaluate potential health effects. This survey had several findings. The median measurable levels of PBBs for those living across the state of Michigan in 1978 was 0.6 parts per billion (ppb) in serum. Thirty percent of individuals had no detectable level of PBBs. Residents of the lower peninsula had higher levels of PBBs than those in the upper peninsula. In general, PBB blood and fat levels were highest in the six counties in southwest Michigan where meat and dairy products had been the most contaminated (Wolff et al. 1982). Michigan dairy farmers had higher measurable levels of PBBs than other farmers living in Wisconsin, who had lower non-measurable amounts of PBBs (Wolff et al. 1979). Chemical workers were highest in serum PBB levels when compared to farm residents and consumers (Wolff et al. 1978).