Thomas Gassert from the Harvard University School and V Ramana Dhara from Emory University have slammed Balaram in the latest edition of Current Science, India's most-respected science journal.
The Indian National Science Academy publishes the journal.
Balaram, the editor of Current Science, in a June 2010 editorial questioned the motivations of Gassert and Dhara for challenging a theory posited by pathologist S Sriramachari who worked with victims in Bhopal for years.
Suggestions that they are bed-fellows with Union Carbide are "far from the truth, and such a litmus test is counterproductive", they have now written in a letter to the journal.
"As a scientific journal, Current Science should focus on promoting good and vigorous scientific debate rather than alluding to false connections," Dhara said.
Balaram did not respond to queries sent by email and could not be reached by phone.
The debate revolves around whether it was Hydrogen Cyanide or methyl isocyanate (MIC) that killed thousands following leaks from a Union Carbide plant in Bhopal on the night of December 2-3, 1984.
Sriramnachari had written a paper for Current Science arguing that cyanide and not MIC may have caused many of the deaths. MIC can disintegrate into Hydrogen Cyanide at very high temperatures.
In a rejoinder to Sriraramchari's paper, Gassert and Dhara had argued that there was insufficient evidence to link cyanide to the deaths.