Saray says she is lucky not to have become really sick, whereas others have become visibly ill. “Last week, they made us work when it was raining, and I got water in my mouth and I felt dizziness and nausea,” Ana Flores said of exposure to wet tobacco leaves — the plants’ nicotine often dissolves in rain and dew. At 16, she is spending her third summer in the tobacco fields. “I didn’t throw up, but other people did.”

For years, public health experts and federal labor officials have sought to bar teenagers under 16 from the tobacco fields, citing the grueling hours and the harmful exposure to nicotine and other chemicals, but their efforts have been blocked. Three years ago, Hilda Solis, then the labor secretary, proposed declaring work in tobacco fields and with tractors hazardous — making that type of work illegal for those under 16. Opponents of child labor note that Brazil, India and some other tobacco-producing nations already prohibit anyone under 18 from working on tobacco farms.

The Obama administration withdrew Ms. Solis’s proposed rule after encountering intense opposition from farm groups and Republican lawmakers. Agricultural organizations said the move would hurt family farms and make it harder for young people to learn farming skills.

The administration killed the proposal in April 2012, when the president was running for re-election, saying it would not pursue these regulations for “the duration of the Obama administration.” But some proponents still hope to revive the tobacco part of the proposal once this year’s midterm elections are over.

Image Cured tobacco hangs in a barn in Deep Run, N.C. Credit... Travis Dove for The New York Times

In the meantime, public health experts say hundreds of children under 16 like Saray continue to work in America’s tobacco fields. Dr. Thomas A. Arcury, an expert on tobacco and migrant workers and a professor at the Wake Forest Baptist Medical Center, said tobacco work was particularly harmful to children, pointing to nicotine poisoning, pesticides and dehydration.