It's gotten to be pretty routine. An EPA official goes up to Capitol Hill and straight-facedly insists that the agency is all about transparency and science, and Democratic senators respond by calling it a lie.

But this morning, it wasn't EPA chief Stephen Johnson who made the trip. This time the EPA sent Assistant Administrator for the Office of Research and Development George Gray instead. Why couldn't Johnson make it? Gray didn't seem sure, but explained to an angry Sen. Barbara Boxer (D-CA) that Johnson had been having back problems. In March, Boxer implied that Johnson had planned an official trip to Australia in order to avoid having to attend in Congressional hearings in April. Maybe all that flight time wasn't good for his back.

But the Democrats didn't hold up on Gray. Sens. Sheldon Whitehouse (D-RI) and Boxer went round and round with him, as he continued to insist that "transparency is key" to the EPA's decision process and that the administrator's decisions were based on science. Boxer was most direct, saying at the end of his testimony that Gray's insistence that only science had been considered "is a big lie.... You've tried to defend the indefensible, and you have failed as far as this senator is concerned."

Gray proved himself a fine substitute for Johnson, however. When the senators pressed him on why Johnson had gone along with the White House and overruled the recommendation of the agency's Clean Air Scientific Advisory Committee in setting a higher level for smog-forming ozone in the air, Gray wanted everyone to understand that it was "actually a very good example" of the "way in which the uncertainty of science plays an important role in decisions." Gray counseled that "science does not give us a single or precise answer."

But Whitehouse didn't seem to be buying it. "The people that you chose to be the experts unanimously supported this recommendation.... These were the best scientists in the country and you ignored them." Gray responded that Johnson hadn't "ignored" them -- he'd just come to a different conclusion. He did allow, however, that in addition to "scientific considerations," there had been "science policy considerations," which are a "part of moving the scientific process forward." But the EPA wouldn't discuss it's communications with the White House, he said, saying that it was important to keep "discussions with the rest of the federal family" private.