Vaping is often marketed as a less damaging alternative to smoking, but a new study raises more questions about just how harmful vapes can be to the body – even when the vapes are free from nicotine.

Researchers from Anglia Ruskin University in the UK looked closely at how a common brand of nicotine-free e-cigarette interacted with human lung tissue cells in the lab, finding that oxidative stress was still occurring.

Oxidative stress occurs when the natural reaction of cells to oxygen becomes imbalanced, causing malfunctions and wear and tear to the cells. This stress was spotted together with increased inflammation and blood vessel breakdown – a combination often associated with lung injuries.

"Nicotine-free vape fluid has been demonstrated to have the same chemical composition as nicotine-containing fluid except for the absence of nicotine," says biomedical scientist Havovi Chichger from Anglia Ruskin University.

"Our findings indicate that nicotine-free vape fluid exposure causes similar pro-oxidant and pro-inflammatory effects on human microvascular endothelial cells."

By comparing nicotine-free products with e-cigarettes from the same brand that did have nicotine in them, the researchers found that the absence of the addictive substance didn't necessarily make the vapes much better for lung tissue.

In the cells exposed to nicotine-free vape fluid, the team identified an unusual abundance of a particular protein called ARF6, which looks to be responsible for lung tissue damage in the lab.

This protein hasn't been connected to smoking or lung injuries in the past, but it is known to be involved in making sure the body's blood vessels are working correctly.

The findings around ARF6 should help future investigations into the health impacts of vaping, which have often focused on the damage done by nicotine.

Dozens of countries have now banned e-cigarettes with nicotine in them, but these precautions may be missing the mark.

"Further investigation is vital to identify the link between the vaping of nicotine-free e-cigarettes and the potential development of lung injury in future years," says Chichger.

There's plenty of scope for future study here, and the researchers are particularly keen to investigate how vapes increase the risk of Acute Respiratory Distress Syndrome (ARDS), a problem often seen in smokers and caused by blood vessel damage in the lungs.

A recent study – also using vapes without any nicotine in them – highlighted that just a single use of a vape could have an impact on the performance of blood vessels and blood circulation, suggesting the potential damage goes way beyond the lungs.

With the numbers of people using e-cigarettes now thought to be in the tens of millions, more and more concerns are being raised about the health consequences – even if vaping turns out to be the better of two evils compared with smoking, which remains contentious due to limited long-term data.

"Vaping is a significant health concern considering the rising numbers of smokers, especially young teenagers, and research into its health impact is still at an early stage," says Chichger.

The research has been published in Microvascular Research.