Scientists Find Most 'Offensive' Odors for Stink Bomb

It can cause shortness of breath, nausea and panic and has now been perfected into two devastating varieties: human waste and rotting garbage.

Odors, that is.

In a recently concluded project funded by the U.S. Department of Defense, the ingredients for the mother of all stinkbombs have been tested and approved by researchers at the Monell Chemical Senses Center in Philadelphia.

The malodorous molecules are not harmful, but are expected to terrify the senses and cause instant fleeing. Department of Defense spokespeople working in the Nonlethal Weapons Program say the tool could prove useful in crowd control and 'other situations' (imagine, for example, foul-smelling vapors driving terrorists from cave networks).

"These were the two that most people had an extreme reaction to — our testers said these were probably the worst thing they ever smelled," said Pam Dalton, a Monell researcher. "When we asked them how long they would sit in a room that smelled like this they said not at all."


While most odor specialists spend their time recreating pleasant smells, Dalton and her colleagues devote their efforts to recreating — even amplifying — the less-than-pleasant ones. The team analyzed a variety of awful smells ranging from that of burning hair, rotting flesh and wet human waste and determined the responsible chemicals inside the vapors.

The team then mixed these chemicals to recreate the stench and exposed individuals from a range of international backgrounds to the smells to gauge their physical and emotional reactions.

"Foul odors cause you to take shallow breaths so you become short of breath. You also can feel nauseous," explained Dalton. "And then there is the subjective reaction."

The worst smells, said Dalton, had some screaming in revulsion. But, it turns out, not all rank odors are as universally offensive as others. The smell of burnt hair, for example, wasn't unbearably unpleasant to testers of South African origin. And other testers showed a peculiar tolerance for the smell of vomit.

Vomit: Dieter’s Deterrent

Incidentally, getting the right chemicals for the vomit odor wasn't difficult. Dalton said her team simply bought the bottled scent from a proprietor who had created the smell for a company specializing in dieting gimmicks. The idea, said Dalton, was to insert the smell into a dieter's refrigerator to discourage snacking.

"I don't think it ever made it into development," she said.

To recreate one of the most successfully repulsive smells — human waste — the team mixed a chemical called skatole with fatty acids and sulfurs. To create the runner-up odor of rotting garbage, the team combined a variety of sulfur compounds. The research was described in today's issue of Chemical & Engineering News.

Pinpointing and creating the smells is one step, delivering them is another, and that part of the project will be left to researchers at the DOD. Past experience shows this is no easy task.

Dalton says, when a stinky spray was provided to fighters in the French Resistance during World War II, the device backfired and left the odor-wielding soldiers as smelly as their victims.