A nationally known environmental health specialist testified today there is "a very high degree from the Galaxy Chemical Co. were responsible for some of the cancer deaths in the small northeastern Maryland valley where the firm was located.

Dr. Samuel S. Epstein added that, had Dr. Pietro U. Capurro failed to publicize his findings about the high cancer death rate in the Little Elk Valley, "it would have been an act of criminal neglience on his part."

Capurro's cancer death rate studies are the focus of the legal battle being aged here. The Galaxy firm and its owner, Paul J. Mraz, have sued Capurro for $2.1 million, claiming that the studies made by the Elkton pathologist defamed Galaxy by falsely sunking its emissions to cancer deaths.

The national publicity these studies attracted, Mraz's suit contends, eventually ruined Galaxy's business and forced the small chemical recycling plant to close down.

Epstein dismissed business questions as irrelevant when he was being cross-examined by Mraz's attorney, George W. Constable. "You, sir, talk of ethics in terms of money." Esptein said. "I talk of ethics in terms of human lives."

Earlier, Epstein had testified that, 'In my opinion, there is a very high degree of probability that the excess number of lymphomas" - cancers of the lymphatic system - "are directly attributable to the emission of high concentrations of carcinogens from Galaxy into the surrounding community."

Epstein added that he believed that the high cancer death rate in the area would probably continue over the next decade.

A two-year study of the cancer deaths in the Little Elk Valley, which was conducted by the Maryland Department of Health and Mental Hygiene, found that four area residents died of lymphatic cancer between 1969 and 1976 - a number much higher than would be expected in the valley's population of about 400.

Early in the case, Dr. William P. Radford, himself a nationally known epidemiologist, testified that he suspected that two paper mills that had operated in the valley - one of which occupied the same site as Galaxy - might be linked in some way to these cases of lymphatic cancer.

Radford had also started categories that Galaxy couldn't have been the cause of the lymphomas because there is a gap, or inclubation period, of at least 10 years between the time a person is exposed to a cancer causing agent and the time that the person dies of cancer.

In his testimony today, Epstein contradicted Radford, saying that the so-called "latency period" for lymphatic cancers "could be from two to 10 or two to 15 years. There is some indication of people getting it in less than two years."

At least six of the 30-odd chemicals that Galaxy processed during the 15 years of its existence are known to be carcinogens, or cancer causing agents, Epstein said, although he admitted on cross-examination that he did not know exactly what amount of these chemicals were processed or when they were processed.

Epstein nevertheless singled out one of these chemicals, benzene, as the possible cause of the lymphatic cancers. "There's no question at all that benzene is . . . a potent chemical carcinogen which produces leukemias," he testified.

Although the evidence linking benzene to lymphatic cancer is less strong, Epstein said, "to patently deny a connection is just not sensible."

Epstein, who occasionally stepped out of the witness box and paced before the jury as if it were a college class, pointed out several times that the level of chemcials measured in the air near Galaxy was far greater than the level measured near several major chemcial firms elsewhere in the country - 20,000 times greater, in the case of benzene.

In addition, Epstein pointed to the open pond or lagoon on Galaxy's property where the firm used to dump its residues before clean-up procedures were ordered by the state six years ago.

"When you take reactive chemicals - carcinogens, teratogena ( agents that cause birth defects) - and dump them in a pond and leave them there to evaporate, you're playing with dynamite, the dynamite of human lives," Epstein said, pointing his finger at the jury with a flourish to emphasize his point.

The cross-examination of Epstein was cut short at lunchtime today when Mraz's attorney, Constable, became ill and was driven to the Easton General Hospital in an ambulance. Constable was reported to be resting comfortably there yesterday afternoon.

Presiding Judge Thomas K. Everngam told both Mraz and Capurro's attorneys after the incident that the case would resume Wednesday Constable's associate is expected to continue the cross-examintion.