Potentially unsafe levels of toxic chemicals were found in e-cigarette vapers, according to a recently released study.

Researchers at Johns Hopkins Bloomberg School of Public Health tested e-liquids in vapers' refilling dispensers from 56 Baltimore-area daily e-cigarette users for a study published Wednesday in the peer-reviewed journal Environmental Health Perspectives.

After testing for the presence of 15 metals, researchers found significant levels of highly toxic arsenic in 10 of the samples. Significant levels (nearing or exceeding current health-based limits) of chromium, manganese, nickel and lead were found in about half of the samples. Aerosol metal concentrations were also highest for e-cigarettes with more frequently changed coils, study authors found.

Read more from USA TODAY:

Trying just one cigarette leads to a daily habit in majority of people, study suggests

New York state bans vaping of electronic cigarettes indoors, just like traditional tobacco products

These baby foods and formulas tested positive for arsenic, lead and BPA in new study

"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," said study senior author Ana María Rule, assistant scientist in the Bloomberg School's Department of Environmental Health and Engineering.

The Food and Drug Administration has the authority to regulate e-cigarettes and e-liquids.

The Johns Hopkins team is planning future studies on vaping and metal exposures. More research must be done to determine possible health effects.