(Bloomberg) -- Vaping, already under scrutiny for health risks and deaths, was linked to a rare type of lung damage in a new case report.

Doctors investigating a patient’s breathing difficulties found damage that appears similar to an occupational health hazard, called hard-metal pneumoconiosis. The condition typically strikes workers involved in sharpening or polishing metal tools, physicians from the University of California, San Francisco wrote in a case history published in the European Respiratory Journal.

Controversy over the safety of e-cigarettes is raging in the U.S., where the deaths of as many as 47 people have been linked to a different severe respiratory illness. Health officials are studying whether the cause is vitamin E acetate, which is added to dilute THC, the euphoric compound in marijuana that some vapers are using.

The case report published Thursday is the first to identify the rare form of lung scarring in a vaper, but others may have gone unnoticed, the doctors wrote, advising people who want to quit smoking tobacco not to rely on e-cigarettes.

“The inflammation caused by hard metal would not be apparent to people using e-cigarettes until the scarring has become irreversible,” wrote Rupal Shah, an assistant professor at the university’s division of pulmonary, critical care, allergy and sleep medicine.

When researchers tested the patient’s vaping device, they found cobalt in the vapor it released, as well as other toxic metals such as nickel, aluminum and lead. Exposure to cobalt dust is rare outside a few industries, Shah said.

Michael R. Bloomberg, the founder and majority owner of Bloomberg News parent Bloomberg LP, has campaigned and given money in support of a ban on flavored e-cigarettes and tobacco and supports efforts to reduce global demand for tobacco worldwide.

To contact the reporter on this story: Marthe Fourcade in Paris at mfourcade@bloomberg.net

To contact the editors responsible for this story: Eric Pfanner at epfanner1@bloomberg.net, John Lauerman, Anne Pollak

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