Cable documentary tests the boundaries of TV and 'real life.'

Are we all becoming actors in a universal television soap opera? We are living in a television environment. Even if we don't own a television set, what is aired affects us directly, because television has become more than just a communications system spilling out information and entertainment. It is as much an integral part of our physical environment as, say, smog in some areas. And in the case of many people, as much a part of their intellectual environment as school.

A new generation of young people, nourished on television, seems to be growing up slightly confused about the boundaries between real life and television fantasy-life. American TV today isn't helping at all - it is increasingly blurring the line between TV and reality, as in the case of the ''reality entertainment'' shows such as ''Real People.''

Even TV news is beginning to blur the line. The recent CBS documentary ''The Plane That Fell From the Sky'' recruited some of the actual passengers to reenact their terrible experience. The result was to make it even more difficult for viewers to separate fact from reenactment.

As the human memory of actual events fades, the vividness of television reality too often takes over and is perceived as the only reality. Thus, without consciously applying for the role, many of us have become actors in an endless electronic drama.

One of television's earliest examples of the confusion of real-life/television-life reality was broadcast on public television in 1973. ''The American Family'' on PBS was a 12-hour documentary about the William C. Loud family of California. Millions of viewers were witness to sad facts surrounding disintegration of the family: the apparent generation gap between father Bill and all five of the Loud youngsters, the emerging homosexuality of son Lance, and the breakup of the Louds' marriage. The whole family became pop celebrities. Every crisis in their lives seemed to happen on camera. Or was it the camera that encouraged those actions to happen?

Now, 10 years later, the same filmmaking team, Susan and Alan Raymond, who photographed the first series while living with the Louds for seven months, has come up with a sequel: ''American Family Revisited - the Louds Ten Years Later'' (HBO, Thursday 8-9 p.m, check listings for repeats throughout the month).

Utilizing excerpts from the original series, the Raymonds flash forward to all seven members of the family as they are today. Bill has remarried; Pat is a single, socially active literary agent in New York; all of the children are on their own, although all seem to keep in touch with both parents. None of the youngsters have married.

One of the girls, Michelle, says she believes the experience of living through their parents' breakup has given them all a feeling ''for the value of a good marriage.''

All of the participants in ''The American Family'' drama seem to have ambivalent feelings about the experience of having allowed themselves to be on camera. At one point Mrs. Loud says that they lost dignity and honor in what she describes as a ''humiliating'' experience. But later she says, ''I'm glad I did it.''

The father says: ''I have no remorse for having done the series, but I didn't learn anything from it.''

Son Grant, now 29 and still a singer although he has switched from rock to ' 20s music, says, ''We're all more guarded about what we give away. . . .'' Then he proceeds to give away his most intimate feelings to the camera.

Perhaps the most revealing comment comes in the form of a self-question from son Lance: ''Was that really life or is what I remember really life?''

Ten years after, the characters in ''The American Family'' are still playing out the roles they created in the original series.

I wonder if they will ever again be able to snatch back the Loud persona from the television series that devoured them.