E-cigarettes are a toxic replacement for tobacco products, according to a recent study.

Researchers at the University of Rochester said the emissions from e-cigarette aerosols and flavorings damage lung cells by creating harmful free radicals and inflammation in lung tissue. The study suggests that the harm begins when the device's heating element is activated, and that that some flavored e-juices (particularly cinnamon) create more stress and toxicity on lung tissue.

The heating element is designed to turn a liquid solution (known as an e-liquid or "juice") into an aerosol that mimics cigarette smoke. The inhaled vapors contain heavy metals and other possible carcinogens in the form of nanoparticles -- tiny particulate matter that can reach farther into lung tissue, cell systems, and blood stream.

"Several leading medical groups, organizations, and scientists are concerned about the lack of restrictions and regulations for e-cigarettes," Irfan Rahman, who led the study, said in a statement. "Our research affirms that e-cigarettes may pose significant health risks and should be investigated further. It seems that every day a new e-cigarette product is launched without knowing the harmful health effects of these products."

During the study, Rahman and his colleagues observed in the laboratory that human lung cells exposed to e-cigarette aerosols released various inflammation biomarkers. Mice exposed to e-cigarettes with classic tobacco flavoring also demonstrated signs of pulmonary inflammation.

Rahman's laboratory also recently reported in the journal Environmental Pollution that toxic metals and oxidants from e-cigarettes raise safety concerns as well as potential pollution hazards from second-hand exposures and disposal of e-cigarette waste. Another recent study connected e-cigarette vapors to a higher risk of respiratory infections in young people.

In a joint statement issued Jan. 8, 2015, the two leading cancer organizations in the United States -- the American Association for Cancer Research and American Society for Clinical Oncology -- said that e-cigarettes should be subject to the same Food and Drug Administration (FDA) restrictions as tobacco until more is known about possible adverse health effects. Insufficient data also exists on the value of the tool for smoking cessation.

The biggest concern is for e-cigarette users under age 18.

Health experts believe e-cigarettes entice some young people to start smoking and will make it socially acceptable again.

Rahman's study notes that manufacturers typically don't disclose all materials and chemicals used to make e-cigarettes and e-juices. Without that information or long-term use studies, consumers have limited information about the potential dangers for human health and the environment, he said.

The findings are detailed in the journal PLOS One.