When Ramirez collapsed (presumably from cancer-related kidney failure) and was put in an ambulance, the paramedics put an oxygen mask on her face. Oxygen molecules flooded her bloodstream, combining with the dmso in her system, the researchers hypothesized, to form high levels of dimethyl sulfone. The higher the concentrations of the ingredients required, the more efficiently chemical reactions will run; thus, with so much oxygen, no dmso was left untransformed.
Now the Livermore team needed to figure out the next step: how the relatively harmless dimethyl sulfone could have been converted to the extraordinarily harmful dimethyl sulfate. This is where we were afraid we might find a showstopper that would kill the theory, says Grant.
They conducted an experiment to see how much dimethyl sulfone could accumulate in the blood at normal body temperature. They dissolved the compound in a transparent liquid called Ringer’s solution, which is basically all the ingredients of blood minus red blood cells. We found we could load it up in the Ringer’s solution to an appreciable extent without any sweat, says Grant. (The autopsy, the researchers note, had found that Ramirez had a urinary tract blockage. That could have aggravated the buildup of dimethyl sulfone by preventing it from being flushed out of her system.)
When they cooled a vial of this Ringer’s solution crammed with dimethyl sulfone to room temperature (about 70 degrees), they were greeted by a good sign. The solution became supersaturated, and dimethyl sulfone began to form beautiful white crystals, says Whipple, who did the experiment with Grant. In real blood those crystals might have appeared manila-colored. Thus this process could have produced the crystals that had been observed in the syringe in the hospital, particularly since emergency rooms tend to be cooler than most rooms–about 66 degrees.
So far, so good. But how did the dimethyl sulfone convert to the nerve gas dimethyl sulfate? The Livermore chemists envision a reaction-- which hasn’t yet been observed–in which some of the molecules of dimethyl sulfone in Ramirez’s blood broke apart. What had been (CH3)2SO2 became CH3, CH3, and SO2. Sulfates (SO4) are common in the body, so the two CH3 molecules may have linked up with them to form (CH3)2SO4–dimethyl sulfate. But in her warm blood, the dimethyl sulfate was unstable and quickly fell apart into its hydrocarbon and sulfate components. There was not yet a sufficient amount of nerve gas to harm the paramedics.
When Susan Kane drew blood at the hospital, however, the cool temperature had slowed the breakdown of the dimethyl sulfate. Appreciable amounts of it built up in the syringe, and some of it vaporized out of the blood. This was the gas that poisoned the emergency room staff. Dimethyl sulfate doesn’t vaporize easily–the Merck Index lists its boiling point as 370 degrees. Nevertheless, according to Grant and other chemists, some fraction will still vaporize at room temperature. The crystals of dimethyl sulfone turned into dimethyl sulfate as well and vanished from sight. In the end, all of the dimethyl sulfate either vaporized or broke back down in the blood into its constituents. And thus the macabre chemistry of that night hid most of its traces from investigators.
It’s a really clever piece of detective work, says Oregon State toxicologist Frank Dost. It would seem to me that it would take a hell of a lot of dmso, but in that stage of fighting for her life, Ramirez may have really overloaded on it, he says. The Riverside Coroner’s Office apparently agrees–it released the Livermore report last November, hailing its conclusion as the probable cause of the hospital workers’ symptoms.
But the theory has provoked a backlash from other scientists. Several organic chemists have scoffed at the step-by-step change of dmso into airborne dimethyl sulfate. I’m pretty skeptical, says Hans Reich, an organic chemist at the University of Wisconsin at Madison. Reich doubts that dimethyl sulfone would split apart in the human body’s relatively cool environment. I have used it as a solvent up to at least 300 degrees, he says. Other scientists don’t see a match between the symptoms of the hospital staff and some of the symptoms of industrial workers who have been accidentally exposed to dimethyl sulfate. The stuff is like tear gas, says Jack de la Torre, a physiologist and professor of neurosurgery at the University of New Mexico. When you’re exposed to dimethyl sulfate vapors, the first thing that happens is it makes you start to cry. None of the hospital staff reported tearing or other eye irritation. Furthermore, many other known effects of dimethyl sulfate usually take several hours to hit, and yet the fainting spells and other symptoms at the hospital began to occur minutes after the supposed exposure.