Smokers are known to have higher levels of bacteria and bacterial infections in their respiratory tracts, and a new study shows that cigarettes are crawling with hundreds of types of germs, HealthDay News reported Dec. 2.

Among the germs detected in cigarettes are some known to cause respiratory disease, lung and blood infections, and other illnesses. However, researchers said that it remains unclear whether these germs survive burning or are the cause of smoking-related illnesses.

Researchers said that bacteria could be drawn unharmed into the lungs along with cigarette smoke, since only the tip of the cigarette burns.

“Right now, we’ve just taken the first step to identify what’s there,” said lead researcher Amy Sapkota of the University of Maryland School of Public Health. “Now we need to figure out if they are impacting human health.”

The study was published in the journal Environmental Health Perspectives (PDF).