A federal probe of brain cancer deaths among workers at the huge Dow Chemical plant near here has had about the same impact locally as one of those tropical storms that are forever boiling up this time of year, out in the distant Caribbean.

It is worth watching, for there is always a chance it could alter forever the outline of this petrochemically busy coast. But nobody knows exactly how dangerous it is, how likely it is to hit them, and more importantly, what they can do to protect themselves. It is altogether too vague to cause anyone here even to consider a probable evacuation route.

Several patrons at the Lake Jackson Racquet Club one recent brilliant afternoon -- most of them Dow employers -- were aware that federal agents are studying brain cancer fatalities at the plant over the years.

"Sure, they told us all about the brain-cancer thing at the plant," said a shaggy young fellow. His eyes rolled up toward the ceiling.

"It was like less than one-half of 1 percent of the Dow workers who were ever affected by it. They came up, I think with the names of six individuals over 25 to 30 years -- I forget exactly, but something like that," he said.

"Listen," he said, identifying himself as a process-control engineer at the Dow Chemical Co., "you don't know Dow. If you spill just a little bit of Benzene, they want to know all about it. You have to do a long report: when and where it happened, how much, who was there at the time. Dow's motto is, 'We do it safely, or we don't do it at all'."

That motto and similiarly safety-conscious ones at other manufacturers along the coast have been called into question in recent months by investigators for the National Institute for Occupational Safety and Health, an arm of the new Department of Health and Human Services, and another federal agency, the Labor Department's Occupational Safety and Health Administration.

Alarmed by the discovery of 18 brain cancer deaths in nearly 20 years among 9,000 workers at a Union Carbide Chemical plant at Texas City, up the coast near Galveston, the NIOSHOSHA probers next turned to Dow's even bigger chemical complex near here, one of the world's largest.

Principally from studying death certificates and Dow's personnel records, they found 24 fatal brain cancers among as many as 44,411 past and present Dow workers between 1951 and 1977.

In a recent report, The Washington Post said the federal investigators regarded these findings as a "serious outbreak" of brain cancer at the two chemical plants.

And yet, to the understandable annoyance of many who still work at chemical plants, the federal investigators stopped short of indentifying any cancer-causing chemical or process that the victims may have shared.

"Ther is nothing so far to connect the workplace to these brain cancers," a Dow spokesman said here in late July, and it is a statement he stands by.

"Nobody's saying there is no problem," he stressed recently. "What we are saying is that we don't know whether there is a problem" that stems directly from any of Dow's workplace practices.

"Right now, we don't know if that's a little or a lot," said retired Dow employe Jake Willis, referring to the 24 deaths among 44,411 workers over 40 years, although the deaths happened in a 26-year period.

"Nobody has let that study make a real difference in how they approach life," continued Willis, who's still active in the affairs of Dow's largest union, Local 564 of the International Union of Operating Engineers, which claims 1,800 of the more than 7,500 workers at the sprawling Dow complex.

Then Willis backtracked, remembering that a friend of his from Dow has brain cancer, and that obviously concerns him. But then his friend also has cancer in both lungs, so it's not clear to Willis that this man's struggle for life is at all related to his work at a chemical plant.

"Really," Willis concluded, "those of us who've worked at Dow don't know anything so far that we could have avoided on the job that would have protected us from coming down with cancer."

Until it produces a bottom line that can be viewed as helpful and life-preserving to today's thousands of workers in chemical plants, all the NIOSHOSHA findings are destined to steep slowly on a distinctly low back-burner here.

I called NIOSH headquarters in Rockville, Md., to ask for the latest word. A spokesman there told me that a study of death certificates here in Brazoria County -- over what period, he didn't know -- showed that a third of the brain tumor victims were former Dow employes, while Dow people accounted for only 15 percent of deaths attributable to "other causes."

"Such evidence," he said, "suggests a twofold risk of developing brain cancer if Dow is your employer." But he said it would probably be another month before NIOSH released further evidence in the probe and he had no idea what that data would deal with.

"Shoot," said a Dow worker here. "That study has so many variables left open in it that these people might actually have contracted brain cancer from some form of shampoo in their homes."

Rather typically of its power and paternalism, Dow, which manufactures scores of chemicals here, promptly assigned its own epidemiologists to analyze the brain cancer data it was supplying to NIOSH and OSHA, and the company's report included what was known of the smoking and alcohol-drinking habits of the Dow workers who died of brain cancer.

Interestingly, Dow's study of the employe deaths concluded only that workers who were salaried when they left the company were three times more likely to have contracted fatal brain cancer than were those who had been hourly wage-earners. But it suggested "a further study of association with socio-economic variables is needed" to explain the apparently higher death risk among mostly supervisory people.

At a meeting of the Operating Engineers Local 564 in its brick hall a couple of miles from Dow's main plant, a popular local politician quickly focused on politics. He predicted dourly that the brain cancer studies at Union Carbide and Dow were the sorts of things that simply wouldn't happen in a Ronald Reagan Republican administration.

"Vague as this study may now seem," argued state Sen. A. R. (Babe) Schwartz of Galveston, "what frightens me more is that the people who are pooh-poohing its statistics are the same people who are were saying a few years ago that asbestos in chemical plants can't hurt people because it occurs in nature, the same people who said they couldn't afford to clean up these plants. It has taken every agency of the government to bring about these environmental changes. Because time and again we have seen that we can't rely on corporate consciences.

Cherry Bowers sat listening quietly and later said she was concerned as a "household executive" about the seemingly inconclusive early returns of the brain cancer study at Dow because her husband and her two sons all work there.

"Around a chemical plant," she said, "you're always concerned, even about things that may look too bad. I'm glad somebody from outside is studying this."