By focusing the most powerful X-ray beam in the Western Hemisphere on six of Ludwig van Beethoven's hairs and a few pieces of his skull, scientists have gathered what they say is conclusive evidence that the famous composer died of lead poisoning.

The work, done at the Energy Department's Argonne National Laboratory outside of Chicago, confirms earlier hints that lead may have caused Beethoven's decades of poor health, which culminated in a long and painful death in 1827 at age 56.

"There's no doubt in my mind . . . he was a victim of lead poisoning," said Bill Walsh, an expert in forensic analysis and chief scientist at Pfeiffer Treatment Center in Warrenville, Ill., who led the study with energy department researcher Ken Kemner.

Still a mystery, however, is the source of Beethoven's lead exposure, which evidence now suggests occurred over many years. Among the possibilities are his liberal indulgence in wine consumed from lead cups or perhaps a lifetime of medical treatments, which in the 19th century were often laced with heavy metals.

One metal that was clearly absent was mercury, Walsh said -- a detail that weakens the hypothesis floated by some that Beethoven had syphilis, which in those days was commonly treated with mercury.

"We found zero evidence of that," Walsh said, "so it was nice to exonerate him of that scurrilous possibility." Details of the findings are to be announced today in Argonne, Ill.

The work was done at Argonne's Advanced Photon Source, a $467 million high-tech facility that sends subatomic particles sailing around a circular half-mile-long track at velocities up to 99.999 percent of the speed of light.

When electrons are whipped around that tubular tunnel they emit X-rays that are 100 times as bright as the surface of the sun. Scientists can divert those rays toward tiny samples in need of analysis. As those X-rays hit atoms in a sample, they knock other electrons out of place, causing a brief release of energy whose signature is specific to the types of atoms present.

Many of the atoms in Beethoven's body were lead atoms, it turns out. The hair samples clocked in at 60 parts per million, or about 100 times higher than normal. The bone samples were also extremely high in lead, though technical problems kept the team from getting a precise number for those samples.

The hair samples were from an authenticated lock of Beethoven's hair purchased by a collector from Sotheby's several years ago. Preliminary studies completed on two of those hairs in 2000 suggested high levels of lead but were not definitive and left open the question of whether they were the result of short-term or chronic exposure.

Moreover, the method used at that time destroyed the hairs -- an approach the owner was not willing to repeat.

Argonne's X-ray technique is nondestructive. Moreover, it offered Kemner a chance to further his research, which aims to develop ways to clean up heavy-metal contamination. A major goal is to develop soil-dwelling bacteria that can consume dangerous elements and render them relatively harmless.

The hairs were the smallest things Kemner had ever analyzed with the X-ray beam. In part because of that success, he has since moved on to measuring heavy-metal levels in individual bacteria, which are 1/100th the diameter of those hairs.

The skull relics are the property of a California businessman who inherited them through various relatives from his great-great uncle, who was a doctor in Austria. The lead analysis has been complete for more than a year, Walsh and Kemner said in a telephone interview yesterday. But the two were sworn to secrecy until the businessman received the test results comparing the bone DNA to that in the hairs.

Those tests, recently completed, came back somewhat short of definitive, but the provenance of the bones is "absolutely clear," said William Meredith, a Beethoven scholar and director of the Center for Beethoven Studies at San Jose State University in California.

Beethoven developed serious health problems in his early twenties, which grew worse over time and reflected many of the symptoms of lead poisoning, including severe stomach problems.

The composer was deaf by his late twenties, a problem of questionable relevance because deafness has only rarely been associated with lead poisoning.

But with his many health problems, it is not hard to imagine that medicine itself may have done him in, Meredith said.

"He was diagnosed with lots of things, and he was prescribed lots of different treatments." If nothing else, he said, some medicines may have leached the metal from leaded glass medicine bottles.

Although the new work leaves the question of the lead's source frustratingly unanswered, it is an important contribution, Meredith said.

"There have been many doctors who have theorized about what ailed Beethoven," he said. "But this is actual science versus interpreting someone else's description of symptoms."

The source of the composer's exposure to lead remains a mystery. A strong X-ray beam showed that Beethoven's hair and skull samples contained high levels of lead.