A bizarre bezoar tale.

A bizarre bezoar tale

Bezoars, or stomach stones, are clumps of fruit and vegetable matter, drugs, hair, carpet fibers or other substances that can accumulate in the gastrointestinal tract. Animal bezoars were once treasured for their supposed medicinal properties, and it is said that a gold-framed specimen was included in the 1622 inventory of Queen Elizabeth I's crown jewels.

While modern society has dropped the bezoar fad, it has contributed to the phenomenon in a unique way. Surgeons at the University of Missouri in Kansas City recently removed a 7-centimeter-long, tan, egg-shaped bezoar from the stomach of a 35-year-old man who admitted to nibbling and swallowing pieces of polystyrene (Styrofoam) cups.

This case of "polystyrenomania' is apparently a medical first, but it also presents something of a chemical mystery: How did the polystyrene foam get transformed into the hard, glassy state of the bezoar? When University of Missouri chemist Eckard W. Hellmuth soaked polystyrene foam in stomach acids, nothing much happened.

Hellmuth suspects that butter fats, in combination with the great pressures exerted by the stomach muscles, loosen the bonds between polystyrene molecules and gradually reorient them into a glass. This is a physical process, he says, which changes the material's surface area in much the same way soap bubbles are transformed into a liquid without undergoing significant changes in density. His hypothesis, which he plans to test soon in the laboratory, is based on work by others showing that dairy products can reduce the amount of stress needed to initiate small cracks in polystyrene containers.