When 3M bought Aearo Technologies in 2008 it became a giant in the military earplug market. Aearo's Combat Arms earplug was standard issue for U.S. soldiers in Iraq and Afghanistan.

A dozen years later, 3M is mired in one of the largest U.S. mass torts ever over the earplugs. More than 200,000 people — mostly veterans and active duty soldiers — say that Combat Arms earplugs were knowingly defective, imperceptibly loosening and leaking in noise.

Kevin Wilhelm, a Navy veteran, is one of them. Wilhelm said he now wears hearing aids almost constantly and is plagued by "nonstop" tinnitus — ringing in the ears, a common ailment among those suing 3M.

"I didn't know these earplugs were defective," he said. "I thought they were the best of the best."

Indeed, the Combat Arms earplugs were groundbreaking, offering hearing protection while allowing soldiers to hear commands even in war zones.

3M maintains that the earplugs were not "defectively or negligently designed" and did not cause injuries. "Plaintiffs' attorneys have created a false and baseless narrative regarding the product, and we will vigorously defend ourselves against such allegations," 3M said in a statement.

Several "bellwether" earplug suits are scheduled for trial in April in a Pensacola, Fla., federal court. Their disposition is likely to set the tone for a possible settlement of all Combat Arms claims.

If the verdicts go against Maplewood-based 3M, the damages could tally in the hundreds of millions of dollars, if not more, based on the outcome of other large mass tort cases in recent years.

In July, a federal judge shot down a key 3M defense strategy, which would have granted the company some legal immunity as a government contractor.

At the litigation's heart is the U.S. Army's request in 1999 to Aearo — before 3M owned it — to shorten the plugs so they would fit in a standard-issue military carrying case. The company did so, but plaintiffs claim Aearo's fix caused bigger problems.

Tests in 2000 at Aearo's Indianapolis laboratory indicated that the shorter earplug didn't always fit properly — and thus wasn't always effective — unless it was inserted in a particular way, according to internal Aearo documents filed in court.

Two Aearo sales managers said in court depositions that soldiers did not need to know of the earplugs' possible shortcomings.

Asked if it was "OK for Aearo/3M to conceal this information from the government," former Aearo vice president Martin Salon said in a deposition: "I suppose it is, if the product is working — in most cases. ... Nothing is perfect."

3M said that neither it nor Aearo concealed information about the earplugs.

The earplug battle comes as 3M is grappling with an even bigger legal war over PFAS, a class of chemicals. Hundreds of cities, states and individuals are suing the company for allegedly contaminating water and soil with PFAS.

The earplugs in question are the second version of Combat Arms, which were sold to the government from 1999 to 2015 when 3M abruptly discontinued the product. The 200,000-plus earplug claims against 3M were lodged after the company settled a whistleblower suit in 2018.

That suit was brought by rival earplug maker Moldex-Metric on the federal government's behalf, after an inquiry by the U.S. Army Criminal Investigations Command. The suit claimed Aearo knew about "dangerous design defects" in 2000.

In a 2018 report, the Army concluded that had the government known about tests Aearo had done in 2000 it may not have purchased Combat Arms earplugs. In the whistleblower settlement, 3M paid a $9.1 million penalty, but denied all claims and did not admit liability.

Auditory ailments are common occupational hazards in the military — and not only in combat. Hearing loss and tinnitus were the two most prevalent service-connected disabilities in 2019, according to the Veterans Benefits Administration.

Wilhelm, 57, said his tinnitus is so severe that he sleeps poorly and has developed anxiety and depression. The ringing "just grates and grates on you," he said. "You never get a moment's rest."

Wilhelm, a Michigan native, retired in 2012 after 30 years in naval aviation, rising from jet mechanic to the top enlisted rank of maintenance master chief, often working on aircraft carriers.

He said he had worn ear protection throughout his career, switching to Combat Arms plugs by early 2003. Four years later, he said he began to noticeably struggle with his hearing.

The "dual-ended" Combat Arms earplug was considered an advancement.

The dark-colored end of the plug was solid, and when inserted into the ear would block steady noise, from helicopters to armored personal carriers. The yellow end was attached to a filter and when plugged into the ear, it would allow speech to be heard, while still blocking "impulse noise" such as gunfire.

The Combat Arms earplug became a big seller as the U.S. went to war in Afghanistan and Iraq. Aearo/3M tallied over $30 million in Combat Arms Version 2 sales from 1999 through 2009, mostly between 2004 and 2008, court records show.

The earplugs appeared to be quite profitable, too. In a deposition, one 3M marketing manager acknowledged that a set of earplugs cost 85 cents to make and were sold to the military for $7.63 apiece.

Plugs were tweaked

In 1997, Army and Aearo officials met for the first time to discuss a dual-ended earplug at an Army proving ground in Maryland. Doug Ohlin and Elliott Berger were both there.

Ohlin, an audiologist, was the hearing conservation manager at the Army's Center for Health Promotion and Preventive Medicine. "Doug was the one that pretty much dictated how we were to provide hearing protection to the military," one former Aearo and 3M sales executive said in a deposition.

Berger, an acoustical scientist, founded Aearo's lab and had more than 20 years experience with the company when development began on the Combat Arms earplug. Well-regarded in hearing conservation circles, Berger worked for 3M until his retirement in 2018.

Ohlin said he chose the Combat Arms in 1999 because "it was the best game in town" — indeed one of the only games, court records show.

But the plugs turned out to be too long for the Army's carrying case and could interfere with the fit of a soldier's helmet. So, Ohlin told Aearo in 1999 to shorten them, and the first Combat Arm earplugs were shipped to the military that year.

In 2000, Berger supervised tests of the Combat Arms earplugs at Aearo's lab, including one to establish a Noise Reduction Rating, or NRR. The higher an NRR, the better the noise protection, and an NRR must be derived from a test with 10 subjects.

The initial test was stopped after eight subjects because the results were variable and the estimated NRR was an 11, Berger and a colleague wrote in a July 2000 internal Aearo memo known as the "Flange Report."

Other court documents said that an NRR of 11 is far below adequate, indicating the earplug would not stop sound as claimed.

A big part of the problem, Berger and his colleague found, was that because the plug had been shortened, it was difficult to fit deeply into some test subject's ears, especially those with medium and larger ear canals, the Flange Report said.

For a second test, Aearo scientists changed the plugs' fitting, pulling back the "flanges" of the yellow end sticking out of the ear. By folding the flanges, the plugs fit more consistently and deeper into the ear, the Flange Report said.

The second test achieved a Noise Reduction Rating of 22, much better than the first and in line with what was needed to sell the product.

Judge's ruling pivotal

The Flange Report was never shared with the Army, wrote U.S. District Court Judge Casey Rodgers, who is presiding over the Combat Arms suits in Pensacola. Plaintiffs claim neither Aearo nor 3M even discussed the contents of the report with the military.

3M disputes that, saying in a statement that "the issues outlined in the Flange Report regarding fitting were communicated to the military," and that the military was responsible for informing soldiers about the earplugs' proper fit.

Berger, in a deposition, didn't recollect providing test data to Ohlin. But he said this "entire development project was discussed with him and the issues from shortening [the earplug] to how it affected our testing were reviewed."

Ohlin died in 2013. He had retired from his Army post in 2007, and soon thereafter became a contract consultant for Aearo and then 3M.

Veterans and soldiers suing 3M claim they were never told they needed to roll back the earplug's flanges to receive proper hearing protection. "I would have adhered to that policy if I knew," Wilhelm said.

The judge's conclusions on the Flange Report were part of her July 24 order disallowing 3M's use of the "government contractor defense" — a blow to the company's legal plan.

That defense shields contractors from liability for defects in products designed and developed for the federal government. 3M has long said that the Combat Arms was designed in conjunction with the military.

However, Rodgers ruled that "the Army never issued a request for a design proposal for the new earplug." And there was no contract between the Army and Aearo when Ohlin said the plugs needed to be shortened, she wrote.

"No reasonable jury could conclude that Dr. Ohlin or the Army made Aearo do anything," the ruling said.

3M said it will continue to argue — and "ultimately prove" — that the company worked in close coordination with the U.S. military, and that the earplug's design "reflected the direction and feedback of individuals acting on the military's behalf."

Mike Hughlett • 612-673-7003