New York, Feb 24 (IANS): E-cigarette users are exposed to increased concentrations of potentially harmful levels of metals that are linked to elevated oxidative DNA damage, a new study has found.

For the study, published in the journal BMJ Open Respiratory Research, researchers found that the biomarkers, which reflect exposure, effect, and potential harm, are both elevated in e-cigarette users compared to the other groups and linked to metal exposure and oxidative DNA damage.

"Our study found e-cigarette users are exposed to increased concentrations of potentially harmful levels of metals -- especially zinc -- that are correlated to elevated oxidative DNA damage," said the study's lead researcher Prue Talbot from University of California in the US.

Zinc, a dietary nutrient, plays key roles in growth, immune function, and wound healing. Too little of this essential trace element can cause death; too much of it can cause disease. Its deficiency, as well as its excess, cause cellular oxidative stress, which, if unchecked, can lead to diseases such as atherosclerosis, coronary heart disease, pulmonary fibrosis, acute lymphoblastic leukemia, and lung cancer.

Electronic cigarettes consist of a battery, atomizing unit, and refill fluid. Metals in e-cigarette aerosols come mainly from the metal components in the atomizer-- nichrome wire, tin solder joints, brass clamps, insulating sheaths, and wicks -- as well as the e-fluids that the atomizers heat.

For the study, researchers have examined and quantified urinary biomarkers of effect and potential harm in relation to metals in e-cigarette users.

According to the study, a biomarker is a quantifiable characteristic of a biological process. Biomarkers allow researchers and physicians to measure a biological or chemical substance that is indicative of a person's physiological state.

Previous e-cigarette studies with humans have examined biomarkers of exposure -- for example, nicotine or nicotine metabolites -- but none have studied biomarkers of potential harm or shown how this harm correlates with metal exposure.

The biomarkers studied by the researchers were 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage; 8-isoprostane, an indicator of the oxidative degradation of lipids; and metallothionein, a metal response protein.

All three biomarkers were significantly elevated in e-cigarette users compared to the concentrations in cigarette smokers, the researchers said.

"Pregnant women, especially, should not be encouraged to use e-cigarettes," Talbot said.

"Excess of zinc in their bodies can lead to nausea and diarrhea. Given the recent deaths and pulmonary illnesses related to e-cigarette usage, everyone should be made aware of the potential health risks linked to e-cigarette usage," Talbot added.