The Michigan Department of Environment, Great Lakes, and Energy sends investigators into neighborhoods across the state to look into noxious odors reported by residents. These scientists don’t measure with tools — they use their noses.
“I got a call today that somebody was smelling some suspicious odors in the Vine neighborhood," said Michael Cox, who works for EGLE. He’s an investigator in its air quality division based near Kalamazoo.
Cox took me on a mock investigation, mimicking an average day on the job outside Chenery Auditorium in Kalamazoo’s Vine neighborhood.
“We're going to want to see — obviously fill out this form that I have here with the date, what the temperature might be, sky conditions, wind speed, wind direction," he said.
Cox’s job is to identify noxious odors in residential areas around Southwest Michigan. Working in the field without scientific instruments, his most important tool is his nose — his sense of smell his only means of locating stenches reported to EGLE by residents, like those from industrial facilities or construction sites.
“Noting these things down will give you an idea which way the odor might be coming from," Cox said. "So you can kind of get a sense as to what it might be or where it might be coming from.”
For a typical complaint, Cox walks a loop through the neighborhood around the address where it was reported. He also tries to identify the type of odor using an "odor wheel" that correlates descriptors like "rotten" and "earthy" with potential odor sources.
“You have this whole array of different odors and what categories they fit in," he said. "So when you observe an odor, what category does that fit in, you know?"
EGLE investigates reports filed by residents on its online MiEnviro portal and its 24/7 hotline (800-292-4706).
The making of a sensory analyst
But how effective is this method of sniffing out noxious odors?
“A sensory assessment is appropriate for an odor complaint and it probably is the most appropriate first response," said Doug Williams. Before retiring, he spent almost 26 years as a chemist at Kalsec, a Kalamazoo company that manufactures food and beverage flavoring.
Williams said sensory analysis is a well-developed science. But, he added, the validity of sensory analysis hinges on training.
“You do have to refresh and go back to the standards and remember them and test on them to keep your edge as a panelist," said Williams.
He said Kalsec trials its flavorings through a panel of six to twelve analysts who are screened for their sensitivity to taste and smell, then trained for months. Sensory analysis can be done by individuals, too, like experienced perfumerists and flavorists.
“If you're a perfumerist though or a flavorist, you could go a couple of years under some sort of apprenticeship to develop and then take the advanced tests which involve recognition of dozens if not hundreds of standard compounds," he said.
Williams recalls a particularly skilled flavorist who sat at a machine evaluating odors sent to him by scientists through a "sniffer cone."
"He named every compound that came out of a complex mixture analysis," he said. "As it came out, he knew it right away and it was just a delight to watch somebody who was that well-trained."
EGLE investigators go to an "odor school" every two years, Cox told me, and apprentice with working investigators before going into the field on their own. But unlike their counterparts at Kalsec, they primarily identify odors using descriptors rather than by chemical compound.
Air quality division director Chris Ethridge said his department would like to provide more training to investigators or send multiple investigators into the field, but resources in his department are limited.
“Many times we don't have the luxury to be able to send two staff out," he said.
Measuring sensation
Since EGLE investigators aren’t expected to identify chemicals, WMU atmospheric chemist Steven Bertman suggested using instrumental analysis. He advocates for methods that can break down air samples into their individual chemical ingredients, like mass spectrometry or gas chromatography.
“Many agencies have mobile labs like a trailer that they pull," said Bertman. "They've got this instrumentation and they can set up and measure in a specific spot.”
But EGLE investigators can’t use scientific equipment to investigate odors because doing so would deviate from the agency’s methodology, which requires them to use sensory analysis alone. Ethridge says it’s been that way for his entire 27 years at EGLE.
“We have a very specific methodology that we follow now," he said. "We're always mindful to make sure that we're following our approved methodology.”
According to a spokesperson for EGLE, Rule 901, which covers noxious odors, was codified as a part of the Michigan Air Pollution Control Rules in 1980. Since then, the rule — and the agency’s procedure for investigating it, limited to sensory analysis — has not changed at all.
"I guess I would call it the Dark Ages method, right? Because what if that person has a cold or is congested or ate hot chilies for lunch and, you know, can't smell a thing?" WMU's Bertman responded. "It seems very unscientific and very subjective.”
Ethridge said that changing EGLE procedure is an arduous process that requires legislation from state representatives or a lawsuit that challenges current procedure. Making changes to approved methodology also runs the risk of undermining EGLE’s past investigations.
“It gives the accused the opportunity to punch holes into our authority and basically be able to weaken the assertion or weaken our violations," he said.
Instrumental measurement can be used to determine what threat a stench poses to public health. Bertman said that’s a crucial responsibility of EGLE. But odor, as a sensation, remains particularly subjective, setting it apart from how air quality or chemical emissions are measured.
“Some people's poo is another person's rose, right?" said Bertman. "You know, everyone's got a different take on thing the smell of different things.”
