Have We Learned Our Lessons from PBB?

Michigan cattle contaminated by toxic PBB in 1973 were slaughtered and buried in landfills.

A story in the Detroit Free Press last week revived memories of one of the nation’s worst chemical disasters.  It happened in Michigan 45 years ago.  And researchers are still trying to figure out what the legacy is for human health.

Sometime in May or June of 1973, the Michigan Chemical Company accidentally shipped a fire retardant with the brand name of Firemaster to Farm Bureau Services, a supplier for thousands of Michigan farmers, in place of Nutrimaster, a cattle feed containing magnesium oxide.  Firemaster was a brand name for PBB, used to reduce the flammability of plastics and electrical circuits.  Customers incorporated Firemaster in, among other things, auto dashboards and casings for telephones and hair dryers. 

The mistake apparently happened at a time when Michigan Chemical ran out of preprinted bags and hand-lettered the trade names of the two products in black.  The similarity of product names or even smudging of the letters was all it took to make the first link in a disastrous chain of events.

Farm Bureau Services sold the mislabeled feed to, among many others, dairy farmer Fred Halbert of Battle Creek.  Halbert purchased 65 tons and after one week of feeding it to his cows in the fall of 1973, noticed the animals were sick.  They lost appetite, lost weight and produced 25 per cent less milk.  When Halbert stopped feeding the Firemaster pellets to the cows, they showed signs of recovery. 

In October 1973, the state Department of Agriculture’s head diagnostician inspected the herd and at first suspected lead poisoning.  When tests for lead proved negative, the department sought help from Michigan State University and laboratories in Wisconsin, Iowa and New York to isolate the contaminant in the feed.   Not until May 1974 did the department determine, with help from Halbert’s son Rick, a chemical engineer, that PBB was the poison.   The department then tested feed and farm products across the state.  In the first six weeks after the identification of PBB, the state seized 621 tons of feed, quarantined 388,000 chickens, destroyed 13,000 tons of butter and cheese, and imposed a quarantine on 34 dairy herds with 4100 contaminated animals.  By 1975 the state had quarantined more than 500 farms and condemned for slaughter over 17,000 cattle, 3,415 hogs, 1.5 million chickens, and 4.8 million eggs.

Before the controversy died away, PBB spawned intensive coverage by the national news media, a made-for-TV movie, a special episode of a popular network drama, and bitter charges of government and industrial coverup and incompetence from the affected farmers and families.

Manufactured for only five years, PBB was so new and poorly-understood that the U.S. Food and Drug Administration did not even set a safety standard for the chemical in food until after it was determined to be the source of Michigan’s previously mysterious farm scourge.

Dennis Swanson, an employee of the Department of Natural Resources, inspected the facility that produced PBB not long after its mistake was exposed.  A plant executive told him the company had been monitoring its inventory carefully.  But upon entering the building, Swanson spotted what looked like gravel covering the floor, a material that had literally fallen through the cracks from the second floor of the building.  “I scooped it up,” he said, and took it back for laboratory analysis. It turned out to be pure PBB.   Swanson also took three samples of water from the Pine River, which flowed past the plant, and captured some catfish.  When analyzed, they all tested positive for PBB. 

The Company’s negligence was causing two environmental disasters simultaneously.  Locally, PBB – and, it was later discovered, DDT – smothered the bed of the Pine River for miles downstream, and the plant site itself was seriously contaminated. 

The attention of state officials, the national news media and Michigan citizens was concentrated on the fact that PBB had entered the state’s food chain, entering the body of anyone who drank milk or ate chicken or beef from the affected farms. Millions of citizens took PBB into their systems.

But what were the health effects of PBB?

Scientists knew almost nothing about this angle, since the chemical had entered commerce so recently.  It was clear that some dairy herds were severely affected. 
As a precaution, the state ordered the slaughter of the most highly-contaminated cattle, hogs and chickens.  Burial of the PBB-tainted animals touched off another controversy.  The burial finally went ahead, but only in the teeth of local resistance.

In an age when other issues were commanding public attention and chemical manufacturers had spent considerable sums trying to remake the image of their products, falsely reassuring messages about PBB’s impact on human health were passed along in the 1980s and 1990s by the same news outlets that had trumpeted PBB as a catastrophe in the 1970s.

Largely through federal funding from the Centers for Disease Control and Prevention, the state for more than two decades maintained a study group of over 3,500 persons from the most highly exposed farm families in the state.  Researchers reported in 1995 that women from the group with higher levels of PBB in their blood had an increased risk of developing breast cancer.  A second study published in 1998 revealed higher risks of digestive cancer and lymphoma among members of the group with higher PBB blood levels. A third study suggested that girls born to women who had the highest levels of the chemical in their blood reached menarche six months earlier than those whose mothers had been less exposed.  This raises the question of whether PBB’s effects may include damage to reproductive health in the second or later generations of the most exposed families. 

Tragically, some of the chemicals that replaced PBB in commerce also proved to be a threat to the environment and human health and have been banned or are being phased out. Known as PBDEs, these chemicals have been shown to persist in human blood and tissue and may pose a variety of serious health impacts.  

Our regulatory system has repeatedly allowed into commerce chemicals that threaten our health.  Last week’s PBB story is a reminder of how such misguided policies can have lasting, multigenerational impacts that could be avoided through precaution.