Hidden Camera Exposes Engineer’s 18-Month Cadmium Poisoning of Colleague

​For nearly a year and a half, chemical engineer Rong Yuan endured a terrifying medical mystery. Plagued by persistent vomiting, severe hair loss, and an inexplicable sour taste in her mouth, she made repeated emergency room visits while bewildered doctors struggled to find a diagnosis. At one point, her condition deteriorated so severely that she flew overseas in search of medical answers, suspecting she might be suffering from cancer.

​The true horror, however, was playing out right at her desk at Berkeley Engineering and Research (BEAR) in California.

​Her colleague, fellow metallurgist David Xu, was systematically lacing her food and water supply with cadmium—a highly toxic heavy metal known to cause extensive multi-organ damage. Investigators later discovered that the contamination levels in her water bottles reached up to 3.5 million times federal safety limits. The toxic exposure ultimately extended beyond the workplace; Yuan’s elderly parents, who occasionally consumed or cooked with water brought home from her office, also suffered severe poisoning.

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​Chillingly, Xu maintained a facade of supportive camaraderie as Yuan’s health unraveled. When she emailed colleagues in November 2018 to announce she was taking a sick day due to acute vomiting, Xu replied with casual indifference, writing, “You should work from home until you feel better. No reason to rush in,” before adding, “I think BEAR is moldy.”

​Growing increasingly suspicious of the recurring chemical odors and her sudden physical decline, Yuan took matters into her own hands by installing a concealed surveillance camera at her workstation. The camera captured unmistakable footage of Xu approaching her desk on multiple occasions to pour foreign substances into her water bottle.

​Yuan handed the footage directly to law enforcement, leading to Xu’s arrest in March 2019. While state regulators and investigators pointed to professional rivalry as a motive to eliminate a perceived threat to his standing at the firm, the subsequent legal proceedings sparked intense public debate.

​After posting a $2 million bail, Xu’s travel restrictions were eventually lifted. In late 2023, under a plea agreement overseen by the district attorney’s office, initial attempted murder charges were dropped. Xu pleaded no contest to a single felony count of poisoning and received a sentence of two years of probation, serving just one day of credited jail time. Furthermore, despite Yuan requesting nearly $500,000 to cover mounting medical and personal damages, the court ordered Xu to pay a mere $7,058 in restitution.

​Years after the ordeal first came to light, the psychological and physical fallout persists. Yuan continues to grapple with long-term health complications that prevent her from working full-time.