ST. LOUIS, MI -- One day in 1974, Jane-Ann Nyerges got home from school and found her mother sitting at the kitchen table, crying. The family lived on a farm near Remus where they raised livestock and Nyerges had thought it odd the chicken coop was empty as she walked up the driveway.

Inside, she learned why.

"Some men came and killed them all with baseball bats because they were sick," her mother said. "And we're sick, too."

That was 42 years ago. In the decades since, Nyerges suffered 10 miscarriages and multiple ectopic pregnancies that she blames on exposure to polybrominated biphenyl, or PBB, an insidious poison she and 9 million other Michiganders ingested in 1973 and 1974, when a distribution snafu at a Gratiot County chemical plant contaminated the state food supply.

That colossal screw-up -- accidentally switching a ton of Nutrimaster, a cattle feed supplement that boosted a cow's milk supply, with Firemaster, a toxic flame retardant -- caused one of the largest chemical poisonings in the western world. Researchers say that many in Michigan still have elevated blood PBB levels from consuming contaminated eggs, milk, butter, cheese and meat.

Six in 10 people tested for PBB in Michigan today -- including some born after the disaster -- have levels above the national average, according to researchers at Emory University in Georgia. Because PBB lives for decades in body fat and mimics the effects of estrogen, people directly or indirectly exposed have become prone to reproductive health issues and thyroid problems.

"Among the people in Michigan, a vast majority are above the national average," said Michele Marcus, an Emory public health professor who has lead the research into the long-term effects of PBB for the past 15 years.

Because PBB stores in fat, exposed mothers unwittingly passed it to children in breast milk. Emory researchers say daughters of women exposed after 1973 generally experienced their first menstruation a year earlier than normal, ended up shorter in stature as adults and have suffered increased pregnancy risks.

The rate of miscarriages among daughters of mothers exposed to high PPB levels was as high as 35 percent, Marcus said.

In male children, researchers found more genital abnormalities and other urinary and genital system problems. Exposed boys also matured more slowly.

Epigenetic researchers are studying whether PBB effects were also passed down from fathers exposed to the chemical and how the widespread contamination has affected the grandchildren of Michiganders exposed in the 1970s.

The long-term health consequences are poorly understood by doctors, which Marcus said has probably resulted in misdiagnosed illness causes.

"If these affects are being transmitted to future generations, it changes everything," she said. "It's a whole different equation."

"It's very important to understand if that's really happening."

Emory University graphic showing elevated PBB blood levels in Michigan.

Where did this stuff come from?

The PBBs came from Michigan Chemical Corp., a subsidiary of Velsicol Chemical, which operated a 52-acre plant on a bend in the Pine River in St. Louis; a town near the state's geographic center once known for its pure mineral spring water.

Today, St. Louis is known mostly for its toxic legacy -- a chemical past that scars the very land where the plant once stood. The factory was leveled after Veliscol closed up following investigation into the PBB incident, but the property has since become one of the largest and costliest Superfund sites in the country.

Under the grass, beneath a clay cap behind a chain link fence, are huge amounts of hazardous chemicals in concentrations that could pose a major health risk to humans and wildlife. Total cleanup is estimated to cost between $300 million and half a billion, paid for almost entirely by taxpayers.

"It's essentially going to be there forever," said Jane Keon, a local resident and founding member of the Pine River Superfund Citizen Task Force, which has advocated for cleanup and research on behalf of those exposed to Velsicol's PBB.

Although Velsicol exported its infamous contamination to nearly every refrigerator in Michigan, the company also did a number on the community that supplied its workforce. Production of PBB caused so much dust pollution that Velsicol moved its research lab to Alma College to find clean space to work. On the ecological end, natural topography meant the Pine River received the brunt of toxic drainage and erosion from the factory.

An aerial photo of the former Velsicol Chemical Co. factory along the Pine River in St. Louis

"It was a dangerous, dirty place to work and Velsicol was not interested in addressing any of those concerns," said Marcus Cheatham, officer at the Mid-Michigan Health Department.

After the strange livestock plague was traced to Velsicol PBBs, the company "cleaned up" by dumping waste in a pit across the river and the county landfill; both of which are now their own separate Superfund sites.

When the factory closed in 1978, workers had trouble landing new jobs because employers were leery of their exposure to hazardous chemicals. Velsicol, the main employer in St. Louis, destroyed not only the town's health and environment, but its economy and reputation as well.

Years of silent spring in St. Louis

While the company was going bankrupt in 1982, Veliscol and the U.S. Environmental Protection Agency signed an agreement that provided $20 million for cleanup, a pittance of the eventual cost. Nonetheless, a slurry wall was built around the perimeter and a cap was placed over the site. But there was nothing underneath to keep the buried chemicals out of the local water.

The encapsulation proved to be an utter failure. The slurry wall leaks in major areas and the EPA had to install a groundwater trench around the site that collects 20,000 gallons a week, which is shipped to Detroit for treatment.

In 1999, a 10-year, $100 million project began to remove 750,000 cubic yards of contaminated sediment from 36-acres of the riverbed across from the site.

Last summer, the EPA began digging up yards and replacing soil in the 9-block neighborhood bordering the site. Crews hauled away 50,000 tons of soil contaminated mostly with dichloro-diphenyl-trichloroethane, or DDT, a pesticide once widely used to control malaria, typhus, and the other insect-borne diseases.

Today, DDT is classified as a probable carcinogen and its use was banned after Rachel Carson's book "Silent Spring" exposed the hazard it posed to birds.

In 2014, a field study by a Michigan State University toxicologist determined that years of unexplained local bird deaths were being caused by eating worms and insects poisoned by soil filled with DDT, which was discovered in some of the highest tissue concentrations ever recorded in wild birds.

Bridgett Davis, whose North Street front door faces the fence, has seen many dead birds throughout her years in the neighborhood, including one in April. Last year, the EPA replaced her soil. Now, she says the buried plastic liner causes water to pool in neighborhood yards when it rains.

Her husband's grandfather worked at Velsicol. The young couple has two kids, an infant girl and a two-year-old boy. The neighborhood is inexpensive, she said.

Despite the contamination, "it's nice not having people across the street."

Among the older residents of St. Louis, the toxic legacy has become a fact of life. Many of their bodies are contaminated. Some are angered by it. Others shrug.

Everyone is happy to finally be drinking clean water, though. In October, St. Louis and nearby townships began tapping Alma for water after completing a $40 million project sparked by the 2005 discovery that St. Louis water was contaminated with para-chlorobenzene sulfonic acid, (p-CBSA) a DDT byproduct.

Redevelopment a distant hope

Taxpayers are funding the work now. Velsicol shed its liability for St. Louis long ago. The company is now owned by Arsenal Capital, a private equity firm. Chemtura Corp. now owns the patent on Firemaster, which is made with a slightly different chemical composition.

More St. Louis yard dig-ups are scheduled this year. The EPA plans to start in-situ thermal treatment (sticking electrified rods into the ground to boil off chemicals) at some point. Work on that could happen this year if EPA higher-ups allocate money for construction.

The city hopes to redevelop the site someday. A 12-year-old reuse plan on the city website includes designs for a park, amphitheater, sport fields and a commemorative area. Whether any of that comes to pass depends on time and money. The plans include the inevitable water treatment plant, a perpetual multi-million dollar annual expense.

The Pine River is there, but it's also not there. People fish, but throw their catch back. Signs between the Alma dam and the confluence with the Chippewa River 36 miles downstream warn about toxic fish. At Penny Park, directly across the river from the plant site, "No Swimming" signs warn people about the water.

Toxicologists are still studying exactly how much Velsicol contamination is getting into fish and animals downstream of St. Louis.

In the 1980s, instead of a typical Superfund sign, a judge ordered the property feature a marker that would last 300 years. Since then, carved in granite on a tombstone near the entrance were the words "Warning, Do Not Enter." After years of coaxing, the government allowed St. Louis to move the tombstone to the local historical society in 2013. Today, instead of a symbol of death, a granite bench declares the city's intent to someday reclaim the land for public use.

"We're so anxious for the plant site to start getting cleaned up," said Keon.

"We know it's going to take at least 20 years and some of us aren't spring chickens anymore."

Garret Ellison covers government, environment & the Great Lakes for MLive.com. Email him at gellison@mlive.com or follow on Twitter & Instagram