A new study found significant traces of metals such as lead leak from e-cigarette heating coils into the vapour.
Long-term exposure to lead, chromium, manganese and nickel can cause damage to the lungs, liver, heart, brain and immune system – as well as cancer.
Experts from Johns Hopkins University school of public health looked at vaping devices owned by 56 users.
They found that significant numbers had dangerous levels of the toxins leaking into their vapour.
The amount of lead found in the aerosols produced by the devices was, in some cases, more than 25 times greater than in the refill dispensers.
Almost half of the aerosol samples had lead concentrations higher than limits set out by the Environmental Protection Agency.
The researchers called on the US Food and Drugs Administration (FDA) to regulate the devices.
Senior author Ana Rule, from the school’s department for environmental health, said: “It’s important for the
FDA, the e-cigarette companies and vapers themselves to know that these heating coils, as currently made, seem to be leaking toxic metals, which then get into the aerosols that vapers inhale.”
E-cigarettes often use a battery operated electric current that passes through a metal coil to heat e-liquids, many of which contain nicotine, to create a vapour to inhale.
An estimated three million people in the UK and 10 million in the US use e-cigarettes.
Previous research suggested e-cigs are less harmful than traditional smoking products, which produce sinister toxins adverse to health.
In 2015, Public Health England (PHE) said vaping is 95% less harmful than tobacco.
But a bombshell report released in 2015 suggested that vapour from e-cigarettes damaged and killed human cells during lab tests.
Another study found vaping could increase the risk of heart attacks and strokes.
Dr Stuart Flint, a psychologist at Leeds Beckett University, recently accused health officials of being “irresponsible” for promoting vaping as a method to stop smoking.
Writing in a respected journal, Dr Flint said there is “very low-quality evidence” showing e-cigarettes can help people quit the habit.
He urged health organisations to wait until more research has been done before recommending the popular smoking gadgets to patients.
Without further research, prescribing vaping products to patients is “irresponsible, unethical and potentially harmful”, he said.
