The 1973 Michigan PBB Disaster: The clerical error that quietly poisoned an entire state.
In 1973, a simple mistake occurred in a loading bay at the Velsicol Chemical plant in St. Louis, Michigan.
Two products, Nutrimaster, a cattle feed supplement, and Firemaster, a toxic flame retardant containing PBBs, were packed in identical plain brown bags.
A worker loaded the wrong bags onto a truck.
The toxic flame retardant was delivered to the Michigan Farm Bureau as cattle feed.
For nearly a year, the PBBs were mixed into livestock feed and distributed across the state.
Cows began to sicken and die.
Farmers lost entire herds.
State officials initially dismissed the problem.
It was only after farmer Rick Halbert paid for private testing that the truth emerged: the animals — and the food chain — were contaminated with flame retardant.
The response was unprecedented.
Over 30,000 cattle, 1.5 million chickens, and thousands of other animals were slaughtered and buried in special pits.
The poison had already entered the human food supply.
Decades later, studies show that millions of Michiganders still carry traces of those PBBs in their blood.
A single bag swapped in error.
A state quietly poisoned.
And a lasting reminder that the most dangerous mistakes are often the ones that look ordinary at the time.