FEDERAL agencies are currently investigating the possibility that two pesticides the Buildings and Grounds Department regularly uses may cause birth defects in experimental animals.

Last December, the HEW Commission on Pesticides and their Relationship to Environmental Health suggested that Carbaryl-an insecticide sprayed to combat the elm leaf beetle-was a potential health hazard to man. It apparently causes bone malformations in litters of mice and beagle dogs.

But the Commission's report emphasized that the birth defect experiments used large doses of Carbaryl and that the experiments were still inconclusive concerning effects on people.

However, the Commission recommended that Carbaryl use "be immediately restricted to prevent risk of human exposure." Last year, a Harvard contractor sprayed some 25 gallons of Carbaryl, and elm sprayings are again scheduled for early June and possibly later this summer.

The HEW Commission delivered a similar warning against several forms of the herbicide 2,4-D. The particular salts of 2,4-D used to kill crabgrass here were not condemned, but the Commission urged further research into their possible side effects.

The manufacturer of the other major herbicide used on Harvard's lawns states that the fertilizer mix (containing the compound polychlordicyclopentadiene) is "toxic to fish and wildlife." The label warns that birds and small children may be harmed for brief periods after the mix is applied.

MOST biologists here are not very worried about B and G's herbicide program: the questionable chemicals are used in very small quantities and the evidence of direct danger to humans is inconclusive. The current furor over herbicides focuses on the massive acrial sprayings in Vietnam, where huge doeses of herbicides sometimes drift into drinking water supplies.

However, B and G's insecticide program has received mixed reviews.

"There is a great difference between hard pesticides and biodegradable ones," Ernest Mayr, professor of Zoology in the Museum of Comparative Zoology, noted recently.

"The important thing is that they stopped using hard pesticides here." B and G phased out its use of DDT in 1968.

But of Harvard's four major insect spraying projects, the ivy moth program has come in for particular criticism.

This small black and white moth known as the Eight-Spotted Forester ( Alypia Octomaculata ) emerges in early May, Several generations of its caterpillars fatten themselves on the University's ivy each summer.

"This bengn little Lepidopteran was not known to be a pest anywhere else in the world," commented Carroll M. Williams, Bussey Professor of Biology.

So why did the plague come to Harvard?

Williams and other biologists suspect that over the past 40 years chemical sprays have killed the moth's natural parasites more thoroughly than they controlled the moths.