It may seem to the casual observer that the National Football League is impervious to an uncertain future.

After all, it has become a driving force in the American economy; a sport which has eclipsed all others, fueling billions of dollars in gambling and spawning fantasy leagues that fascinate tens of millions of Americans.

The league has $6 billion worth of TV contracts, gleaming new stadiums built with taxpayer dollars and a sweetheart deal with the federal government that allows it to skip paying any corporate income taxes while paying its commissioner $30 million a year.

The NFL rules.

But the throne it sits on relies on a player pipeline that begins in the high schools and carries forward with "student-athletes" in colleges and universities that function as an NFL minor league.

And that pipeline is starting to get tested as the danger and prevalence of concussions in the sport becomes more evident.

So despite its obvious strength, the future of the NFL is more tenuous that it appears, and in the hands of mothers in Florida, Texas and other incubators of would-be future talent.

In the past, the NFL has acted much like the cigarette companies, by introducing junk science to downplay the health risks associated with its product. To do this, the league formed a Mild Traumatic Brain Injury Committee which authored scientific papers that made football concussions sound benign.

"There was no evidence of worsening injury or chronic cumulative effects of multiple (mild traumatic brain injuries)," one paper read.

And even though the group didn't study the impact of concussions on younger football players, it suggested that high school kids had little to worry about.

"It might be safe for college/high school football players to be cleared to return to play on the same day as their injury," one report said.

We know now that this is dangerously wrong, due in part to the investigative reporting of journalists Mark Fainaru-Wada and Steve Fainaru, whose work was showcased this month in a PBS-aired Frontline report entitled "League of Denial."

They documented the mental health problems experienced by frequently concussed former NFL players, problems that include early onset dementia, as well as depression leading to suicide.

The league's strategy has shifted from denial to damage control. This fall, the NFL paid $765 million to settle 263 lawsuits filed by more than 4,500 former players who claimed that playing pro football had left them brain impaired.

The list includes 276 former Miami Dolphins.

And while the lawsuit settlement is a fraction of the league's $10 billion in annual revenue, it's a recognition of the dangers of the sport and the league's responsibilities in making it safer through rule changes and fines against abusive players.

The effect is trickling down to the game's farm system, too. This year, two class-action suits have been filed against the NCAA by college players who say they received brain injuries from playing football in school.

And last week, a poll commissioned by HBO Real Sports and conducted by the Marist College Institute for Public Opinion found that 33 percent of responders said the link between head injuries in football and the long-term effects of brain trauma would make them less likely to allow their sons to play football.

"For almost one in five Americans — 16 percent — the risk of long-term brain injury due to youth football participation would be the deciding factor in whether or not to allow their son to play football," the report said.

That's far from the tipping point, but if a critical mass of moms say "no" to youth football, the pyramid under the NFL crumbles.

Two years ago, the Florida High School Athletic Association developed a concussion action plan which required players to be removed from the remainder of the game after a suspected concussion, and not to return to play in future games until they had been evaluated and cleared to play by a health care professional.

Remarkably though, the FHSAA, which requires reports within 24 hours for displays of unsportsmanlike conduct during high school games, doesn't collect information on the number of high school kids who receive concussions while playing high school sports.

"We're involved in trying to increase awareness, but we don't keep statistics," said FHSAA spokesman Corey Sobers.

That's good news for the NFL. For now, Florida remains a fertile incubator for the next generation of brain-injured NFL players.

But the foundation has started to crumble.

Frank Cerabino writes for The Palm Beach Post. Distributed by the New York Times News Service.