Some Juul flavors could lead to lung irritation, new study says

A new study is prompting more concerns over the nation's largest e-cigarette company as investigators probe whether Juul made health claims without government approval.

Connecticut's attorney general is accusing Juul of marketing itself as a "smoking cessation device" without approval from the U.S. Food and Drug Administration.

Recently released research from Yale and Duke universities found an unexpected chemical reaction in some Juul e-cigarette flavors that could lead to lung irritation.

When the vape juice is heated, the study discovered a type of chemical called "acetals" in Juul's popular creme brulée flavor. Acetals prompt the respiratory system to become inflamed, and they aren't listed on the label.

Juul told ABC News that the study created a measurement of exposure that would never be found in real-world use.