In the spring of 1981, an aide in the office of Vice President Bush placed a call to Edwin Johnson, director of the Environmental Protection Agency's office of pesticide programs. Johnson was deciding whether to allow Texas rice farmers emergency use of a pesticide called Super Tin.

Super Tin contains triphenyltin-hydroxide, a chemical that some studies have linked to impairment of the human immunological and reproductive systems. The chemical is registered for use on some crops, but EPA has refused to register the chemical for use on rice because of what it says is inadequate data on the potential hazards.

Bush's aide told Johnson that Texans who had met with the vice president, who is a former Texas congressman, were awaiting EPA's decision.

"He asked me to keep him posted on what was happening," Johnson recalled. "I called him back a couple of times."

About the same time, in late May, John (Jacko) Garrett was calling and writing his brother-in-law, White House chief of staff James A. Baker III, on the same subject. Garrett and his father own 1,500 acres of rice in Danbury, Tex.

Baker said he asked his deputy to buzz top EPA officials.

On June 5 the EPA granted Texas as a number of other southern states the exemption they were seeking.

The use, on an emergency basis, of unregistered pesticides such as Super Tin has spurted since the late 1970s. While it isn't common for officials as high as George Bush and Baker to take an interest in emergency exemptions, the EPA is feeling increasing pressure from senators, members of Congress and governors.

A former EPA official who asked not to be identified explained, "The agency is under extreme pressure from Congress and state governments to grant these exemptions. Normally, EPA will do everything it can to accede."

The number of statewide exemptions granted by the EPA jumped from 199 in fiscal 1978 to 489 for the first three-quarters of 1982. Strychnine and heptaclor, both banned, have been approved this year for some uses.

In Hawaii, where heptaclor is legal through the end of this year, its use on pineapple crops led to that state's widely publicized recall of dairy products found to be contaminated with the chemical.

Emergency use of permethrine has been granted for a wide variety of crops, despite an EPA scientist's controversial memo this spring, in which he called permethrine "a remarkably clear tumor inducer or carcinogen." The EPA is reassessing a recent agency study that came to an opposite conclusion.

"We've got more permethrine exemptions than you can shake a stick at," said Don Stubbs, head of the Office of Pesticide Programs emergency response section.

The number of local exemptions also remains near record levels. Under this program, state agriculture departments allow communities with "special local needs" to spray unregistered pesticides. Banned pesticides cannot be used, and EPA has 90 days to turn thumbs down on the state's action.

The agency's thumbs, however, rarely go in the down position.The agency rejected only 10 of the 1,324 state-granted local declarations during fiscal 1981.

Likewise, during fiscal 1982's first three quarters, EPA turned down only 16 statewide requests, and reversed a number of those on appeal.

Theoretically, the EPA can approve an emergency exemption only when farmers or ranchers can demonstrate that approved pesticides are inadequate to deal with the problem.

EPA acknowledges that its emergency criteria can be stretched. "Certain companies may be anxious to try products early so they foster the sense of emergency when it really isn't there," said Ann Lindsay, an assistant to EPA's Johnson.

Pesticide companies, often facing what they consider unreasonable EPA registration delays, acknowledge that they prod state farm groups to use all political means at their disposal to encourage EPA to issue exemptions.

Jimmy Whatley, corporate director of research and development at Griffin Chemical Co., a Super Tin manufacturer, said it isn't Griffin that is getting the exemptions, "But we do assist in them, I can guarantee that."

The exemptions, some of which are granted annually, generally restrict use of unregistered pesticides in a number of ways. Yet nagging questions about their safety sometimes remain.

During the Carter administration, Johnson rejected a California request for emergency use of DuTer, another brand name containing triphenyltin-hydroxide, on rice. That emergency involved a slightly different rice plant disease than the one claimed by Texas, and the California request was turned down in part because that rice disease could be controlled by burning.

DuTer, too, is registered for use on some crops, but not rice. Johnson told California that a number of questions concerning chemical residue levels in rice, meat and milk remain unanswered.

This year, Texas and other states again asked the EPA for the green light on DuTer. Agency officials had in hand a letter to Rep. George E. Brown Jr. (D-Calif.) from G.C. Bryars, then president of Thompson-Hayward Agriculture and Nutrition Co., a DuTer producer since bought by Uniroyal. Bryars' letter acknowledged that previous studies showed triphenyltin-hydroxide to have negative effects on human reproductive and immunological systems, but he said the pesticide had been used for years on pecans, potatoes, peanuts and sugar beets without documented ill effects to humans.

Johnson also had a copy of another letter to Brown, from Richard Rominger, director of California's Department of Food and Agriculture.

Rominger wrote, "My scientific advisers indicate that after considering the data which are available on DuTer, as to its inadequacies and its high level of toxicity, it will be difficult to maintain a posture of continued registration for any use."

Of the exemptions for triphenyltin-hydroxide, which were granted again in 1982, Johnson said, "There are some uncertainties involved, I won't deny that. But the uncertainties seem fairly minimal when you look at the exposures that might result."

Johnson acknowledged that politics plays a role in exemption decisions, but he said politicians are supposed to convey their constituents' concern to administration policy makers.

"These aren't clear-cut decisions," he said. "They are subjective weighings of benefits and risks."

An EPA toxicologist said, "There have always been political decisions around here. We're seeing a few more of them under the Reagan administration."

Politicians, however, particularly those from farm states, often focus on the economic health of their crop and livestock-producing constituents rather than on the potential physical harm to consumers.

For example, 17 southern senators wrote to EPA Administrator Anne M. Gorsuch earlier this year asking for a conditional registration for ferriamicide to combat fire ants.

Ferriamicide is made from Mirex, a pesticide that was withdrawn from use in 1977, after it was shown to cause cancer in laboratory animals.

The agency has this request on hold. But in 1978, after being swamped by political pressure, it issued an exemption for ferriamicide. A federal court blocked that exempotion.

Some argue that these so-called "back-door" registrations are increasing because EPA officials are afraid to disappoint agricultural chemical companies, who have been hard-hit by the recession.