If "Blue Vinyl" does nothing else, it has already defied conventional wisdom about what you can and can't do on television. You can, in fact, talk about a deadly serious subject without being deadly dull. You can aggressively promote a political agenda and be entertaining. And you can do a program on home improvement that viewers might actually find useful. Of course, the two young filmmakers who spent five years on "Blue Vinyl" hope their work accomplishes much more than that. Even as their self-described "toxic comedy" about the PVC, or vinyl, industry has its premiere at 9 tonight on HBO, Judith Helfand and Dan Gold are on the go. They're crisscrossing the nation, showing their film to local environmental groups, trying to turn what might be the best TV program of the year into a grass-roots movement. This extraordinary film opens with a seemingly innocuous event. One day in 1996 Helfand's parents decide to have new siding put on their modest Long Island, N.Y., home. They choose vinyl, the "versatile plastic" used in everything from medical supplies and bathroom pipes to shrink wrap. Helfand clearly disapproves. A sweeter Jewish version of Michael Moore, she marches out to learn the truth about PVC, a scrap of blue vinyl siding (hence the film's title) clutched in her arm. Right beside her is Gold, whose incisive and whimsical eye would capture the top cinematography prize for "Blue Vinyl" at this year's Sundance Film Festival. When Helfand was 25, she was treated successfully for a rare cervical cancer. Like thousands of other "DES daughters," her mother had been given the drug diethylstilbestrol, or DES, to prevent miscarriage. Helfand's first solo documentary, "A Healthy Baby Girl," was an emotionally raw account of her cancer and an angry history of DES, a drug promoted to doctors for years even though its manufacturer knew it was ineffective. Toward the end of that film, Helfand is seen talking about DES with one of the workers installing vinyl siding on her parents' house. Though she didn't know it then, that was the genesis of "Blue Vinyl." While promoting "A Healthy Baby Girl," Helfand visited Lake Charles, La., home to a huge PVC facility. Activists there told her that the factory had contaminated the community's soil and ground water. Workers inside the factory, they said, were at even greater risk, because of high levels of vinyl chloride (the "VC" in PVC) handled there. In an interview earlier this year, Helfand said she remembered the vinyl siding on her parents' house, "and suddenly I became nauseated." Had her family just bought a product manufactured at this very facility? A product advertised as safe and beneficial - the way DES once was? She felt kinship with Lake Charles; more than that, she felt another film coming on. But it would be different from her previous one. With the help of Gold, whom she eventually made co-director, "Blue Vinyl" would be not as intense; there would be humor in it. It would be aimed at everyday Americans, not save-the-Earth types. And it would be practical, with a Web site for people to find alternatives to PVC (myhouseisyourhouse.org). "We wanted to alert people to a problem, but not in a way that makes them feel helpless," Gold said in a recent interview. So, in the tradition of Moore's classic "Roger and Me," they decided to make a documentary about the making of a documentary. Helfand would start out knowing nothing about PVC (or at least pretending not to); she would educate herself along the way (albeit interviewing mostly people opposed to PVC production or suing the industry); then she would talk her parents into symbolically removing their vinyl siding. Not surprisingly, the Vinyl Institute, the main trade group representing PVC makers, is not pleased with "Blue Vinyl." An industry publication quotes a spokesman as saying, "It's an attack on vinyl that's unsubstantiated by the facts." HBO's top executive for documentary films, Sheila Nevins, disputes that. "There aren't any false moves in it," she said. "No one likes to be criticized, but the truth is the truth." According to Gold, HBO's legal department required a briefing book documenting every claim in the film. It's 1,200 pages long. "They said, 'Give us two sources for everything, and if Greenpeace is one of them, give us three,' " Gold said. Doubtless the people at the Vinyl Institute were also unhappy about their portrayal in the film. Like General Motors in "Roger and Me," the institute is the comic foil of "Blue Vinyl," a paranoid, image-obsessed PR front for an industry that, it seems, must have something terrible to hide. The fun starts when Helfand and Gold request an interview with an official at the Lake Charles PVC plant. They are referred to the Vinyl Institute. We see Helfand on the speakerphone, getting nowhere with a PR person at the institute. Later she's handed off to a higher-up PR person, who insists on meeting off-camera to gauge the "comfort level." When the institute finally decides to send a spokesman, he shows up for the interview with a crew. They've been told to film the filmmakers filming the flack. No problem, says Gold - who then brings in a second shooter to film them filming him filming the flack. Helfand says she decided to include these and other Vinyl Institute high jinks because "they were so concerned with controlling the message ... We felt that was really revealing." All that makes for an amusing sideshow. Talking heads aside, what sets "Blue Vinyl" apart is how deftly it assembles the stories of everyday people to present the vinyl dilemma in all its troubling complexity. In Lake Charles, we see plucky citizen-activists forming a "bucket brigade" to monitor the town's air quality. The filmmakers tag along with Billy Baggett, a lifelong Lake Charles resident, attorney, inventor and one-man wrecking crew against the vinyl industry. He introduces them to the widow of Dan Ross, who worked at a PVC plant for 23 years and whose agonizing death led to a landmark lawsuit. Baggett also points them to Italy and Ceasare Maltoni, a highly excitable scientist who was the first to link vinyl chloride exposure to health problems, including an obscure type of liver cancer. There are more widows there, 150 of them. Many of them show up daily at a Venice courtroom to watch the trial of officials at the factories where their husbands worked. They are charged with manslaughter. On the other hand, there is the family at the Habitat for Humanity house-raising, funded by the Vinyl Institute. A mother sheds tears of gratitude for her new home, made mostly with PVC products. Helfand looks on sympathetically. And then there are Helfand's own parents. Though obviously good-natured and fond of their only child, they are perplexed by her determination to tear off their new siding. Besides supplying comic relief throughout the film, the parents are surrogates for the home audience. Convince them of the evils of PVC and you can convince anyone. That isn't easy given the persuasive reason why they, like most people, chose vinyl: It's cheap, durable and looks nice. Helfand runs herself ragged looking for environmentally correct alternatives to the blue devil. Her mother rejects them all. Even if they do settle on a compromise, it will be expensive, and Helfand will be stuck with a U-Haul full of used siding - which gives off deadly dioxins when burned. What then? It might all seem a little eco-freaky. But because Helfand is trying to please her mom, and honor the victims and widows to whom she feels bonded, it humanizes her quest. Eventually Helfand concocts a vinyl-recycling scheme. It's the kind only a filmmaker would dream up, but that's sort of the point. "Blue Vinyl" calls attention to a problem. Solving it is the viewer's job. Gold and Helfand have formed a production company to create more socially conscious films like "Blue Vinyl." Consumers rejoice; corporate PR people, you've been warned. You can reach Aaron Barnhart through the TV Barn Web site at www.tvbarn.com. Pro vinyl/anti vinyl The case against vinyl "Vinyl turns out to be the most environmentally hazardous consumer product on Earth. Vinyl is the source of more persistent toxic pollutants - dioxin in particular - than any other single product in the world." - Joe Thornton, Columbia University "Dioxin ... lasts a long time in the environment. It lasts a long time in our bodies. ... A little bit of dioxin goes a long, long way." - George Lucier, former director, environmental toxicology, National Institutes of Health The case for vinyl "Almost any field you can imagine, you will create dioxin ... The good news is that dioxin emissions to the environment have been declining for the past 30 years." - William Carroll, Vinyl Institute "Take a look at all the vinyl products that are going to be in this house ... You'll have a heck of a lot less maintenance and I think this house is going to look good for years." - Jim Kosinski, Vinyl Institute, at a Habitat for Humanity house-raising - From the HBO film "Blue Vinyl" @ART CAPTION:Documentary filmmaker Judith Helfand removes vinyl siding from her parents' Long Island home in a scene from her "toxic comedy" "Blue Vinyl." @ART CREDIT:HBO @ART:Photo