To the Editor:

The emerging technology of electronic cigarettes poses important questions for public health officials. Much remains to be learned about the risks of e-cigarettes to health, as well as their possible benefits, particularly for those smokers who have not been able to quit using deadly conventional cigarettes. All of us in public health are concerned about any use of e-cigarettes by children and adolescents.

“Some E-Cigarettes Deliver a Puff of Carcinogens” (“The New Smoke” series, front page, May 4) refers to the Food and Drug Administration’s recent proposed rule to extend the agency’s authority to include e-cigarettes. However, I’d like to clarify the assertion in the article that the F.D.A.’s focus is largely on what gets added to these products rather than the emissions in the product vapor.

The proposed rule is a critical first step to bring an end to the completely unregulated e-cigarette marketplace. When it is finalized, e-cigarette companies will be required to report the levels of harmful and potentially harmful chemicals or chemical compounds delivered by their products. But we cannot enact a rule on reporting or restricting e-cigarette emissions until this foundational rule-making is completed, which is one of our highest priorities.

The F.D.A. is committed to the science-based regulation of these products to better protect public health. Where the science does not exist, we are able to finance the research to answer key questions related to e-cigarette safety and consumer behavior, including four studies that will focus on the contents of e-cigarette vapor.