CHICAGO - US health officials on Thursday reported another 180 cases of vaping-related lung illnesses and announced plans to start testing aerosols produced by e-cigarettes and vaping products as they search for the source of the nationwide outbreak that has so far killed at least 33 people in 24 states.
The US Centers for Disease Control and Prevention (CDC) also said it plans to start testing lung cells collected from people who became sick in the outbreak.
The CDC now reports 1,479 confirmed and probable US cases of the mysterious respiratory illness tied to vaping, up from 1,299 a week ago, an indication that the public health crisis has shown no signs of slowing.
Last week, the CDC and the US Food and Drug Administration said that while many patients became ill after vaping products containing THC, the psychoactive ingredient in marijuana, some had only used nicotine vape products. They said more than one root cause may be behind the outbreak, and urged people to stop vaping, especially products containing THC.
Investigators primarily have been testing the liquids in vape products. Testing the aerosol produced when the liquids are heated might show whether that causes a chemical reaction that produces a toxic substance.
"They might be able to see components that we don't see in the raw materials," said an official in the New York Health Department's Wadsworth laboratory, which has been testing product samples for the state.
Pathologists at the Mayo Clinic have likened the lung injuries to a chemical burn.
A preliminary report seen by Reuters of vaping product samples collected from Wisconsin patients and tested by the FDA showed that more than half contained THC.
Of the THC-containing products, two-thirds also tested positive for Vitamin E acetate, a cutting agent believed to be used to stretch the amount of THC oil, and an early suspect in efforts to determine the cause of the injuries.
A spokeswoman for the Wisconsin Department of Health Services said it is still not known whether vitamin E acetate is responsible for the lung injuries.
The results from Wisconsin appear to confirm an earlier FDA report. On Friday, FDA officials said it found Vitamin E acetate in 47% of the first 225 THC products that it had analyzed.
Wisconsin tested vaping liquids that were used by people with confirmed or probable cases within three months of developing symptoms. No vaping devices were tested.
Among the results, 14 products contained THC, nine of which also tested positive for vitamin E acetate, while another seven contained nicotine.
Some of the samples underwent more extensive testing, and no excessive levels of toxins were detected.