A contaminant of some synthetic fuels, such as liquefied and gasified coal, can cause serious birth defects -- extra heads and extra eyes -- in crickets.

The new finding raises the question of what effect the contaminant might have on humans and whether it is economically feasible to remove it from the fuels. It has "raised a considerable concern in the Department of Energy," the scientist who made the discovery, Dr. Barbara Walton of the government's Oak Ridge National Laboratory in Tennessee, said Yesterday. Her report appears in the April 3 issue of the weekly journal Science, out today.

The next step, Walton said, is to learn whether the chemical contaminant produces the same effect in other animals, including those closer to humans.

Then, researchers must learn whether the contaminant, if risky to human offspring, can be readily monitored and removed from synthetic fuels or their waste products.

Walton's research is financed by the Energy Department's environmental division. The Energy Department and a new federally financed Synthetic Fuels Corp. direct various parts of what is becoming a multibillion-dollar program to learn how to make large quantities of fuel from coal. President Reagan revealed his interest in the program this month when he overruled an Office of Management and Budget plan to cut $5.3 billion from oil shale and coal conversion programs.

Scientists are still unsure of the chemical identity of the responsible contaminant, Walton reported. But is is apparently one or more of several impurities found in acridine, a common component of the wastes produced in either gasifying or liquefying coal.

When Walton exposes cricket eggs to minute amounts of acridine, some developed extra heads or eyes, extra antennae and other defects.

Complete purification of the acridine at the Oak Ridge laboratory eliminated this effect. One question, said a government scientist who did not want to be identified, is "could we do the same kind of purification on a large commercial scale, if it proved necessary? All this really says is that we've got some work to do on synthetic fuels, and that's not really unexpected."

The Energy Department will make a scientific review of the Oak Ridge results to determine if they seem valid and merit more study.

"Certainly the control technology is available" to remove any guilty impurities, once they are identified, said Dr. Robert Lewis, an Energy Department environmental official. "The question then would become one of cost, and that would be part of the whole process of technological assessment, which we do here all the time."