Dangerous levels of the pesticides flumetralin, endocrine, pendimethalin, and trifluralin are in tobacco smoke, according to researchers from the Colorado School of Mines.

UPI reported April 18 that scientists using electron momochromator-mass spectrometry analysis identified the chemicals, two of which are classified as human carcinogens. They said the substances could negatively affect early development, reproduction, and hormonal processes.

All of the pesticides have been approved by the Environmental Protection Agency for use on tobacco. The study found that the chemicals survived the burning of tobacco leaves to retain about 10 percent of their original potency.

The research appears online in the journal Analytical Chemistry.