An atmospheric chemist?
It’s a reasonable question to ask why an atmospheric chemist is working on detector dogs. The short answer is that detector dogs are (in my view) self-propelled biological air pollution sensors. So, who else would you want?
The slightly longer answer is that the processes necessary for detector dogs to work are fundamentally the same as in air pollution. In fact, every step of the process for a molecule of odor to get from its source to the detection in the dog’s nose is governed by the atmospheric chemistry and physics that are foundational to air pollution work. Most researchers in detection dog assessment come from the dog side; one of the reasons I was able to contribute so much to this field is that I come from the air pollution side and brought that understanding to the table.
The fundamental processes that must take place in order that a chemical (or odor) be detected by a nose (be that human, canine, or other) are the same no matter what the chemical is. To think otherwise is to deny the basics of chemistry, physics, and biology. In most cases we do not know what exactly the chemical is that the dog identifies as its target odor, it is most likely that complex odors are a “chord” of various chemical “notes” that allow the dog to identify the target. What this means is that when a dog is said to be detecting a narcotic, or a bomb, or an accelerant, the actual chemical being detected by the dog’s nose is most likely not the narcotic, bomb, or accelerant, but rather another chemical, often a breakdown product or byproduct. This has been expertly shown in the case of cocaine, for example.
However, in all cases, a series of steps must take place for an odor chemical to be detected by a nose. First, the chemical must evaporate from the source, then it must move through the atmosphere, and lastly it must enter the nose and activate a receptor. All of these happen no matter what the source material is. The understanding of these processes is foundational to understanding detector dog work. I began studying detector dogs because these same processes are what drive air pollution work, and I understood these and was able to directly contribute to detector dog evaluation. Thus, in my view, detector dogs are simply biological air pollution detectors. Like in air pollution the concentration of the pollutant (or odor) will be highest nearest the source. This is the principle by which dogs follow an odor plume to source. Understanding diffusion and movement in the air is key to understanding and assessing performance of any detector, and those processes are the same for air pollution or odor (which is simply a subset of air pollution).
My academic studies in toxicology included biochemistry, physiology, and pharmacology. Thus, I have a solid background in the foundational sciences to better understand olfaction. As I began working with detector dogs, I undertook a significant amount of study and research into olfaction and how various chemicals (odors) interact with the receptors in the nose and how that influences detection limits, in other words, how “stinky” a particular molecule is and how variations in molecular structure influence its ability to be smelled. I have also studied training methods and other factors important to detector dogs’ ability to do the work they do. I am quite familiar with these areas of study, and with the literature surrounding them.
I have worked on Human Remains Detection (AKA “cadaver dogs”) assessment and training and studied the volatile odor components from human remains and published this work in the top two peer-reviewed forensic science journals, namely the Journal of Forensic Sciences and Forensic Sciences International. The paper on human remains detection dog capability also included work on training methods and time-dependent analysis of training methods.
I have also published peer-reviewed work on wildlife detector dogs including detailed assessments of their capabilities. This includes such tests as using GPS data from the dogs to accurately determine the distances at which dogs could detect their target and follow the odor to source. Lastly, I have worked extensively with volunteer Search-and-Rescue programs on assessing performance of detector dogs, and on science-based training methods. The principles behind all detector dog work are fundamentally the same and the principles apply to all detector dogs. This means, regardless of whether a dog is used to detect human remains, narcotics, explosives, or anything else, the training processes, evaluation approaches, assessments, and other aspects are the same.
In law enforcement detection dog work, I have seen dogs described as a “narcotics dog,” or an “explosives dog.” While these are useful categories for us, what we are really describing is a dog trained to find specific narcotics or specific explosives. There is no reason you could not train a dog to find both cocaine and TNT. To the dog these are simply two odors they are trained to detect.
In Nevada where I live, Search and Rescue operations are under the command of the Sheriff of each county and my county (Washoe) has three sworn officers who are assigned full-time to manage the operations. Much of the technical work is done by volunteers who are highly trained and are part of the Sheriff’s office as volunteers. I am very familiar with this process as I was a volunteer in the Washoe County, Nevada, Sheriff’s office for many years as part of Search and Rescue.
In particular, Human Remains Detection (HRD) dogs serve law enforcement frequently and assist in criminal cases more often than not. These days of mobile phones, GPS, and even satellite communications means that there are fewer calls to find truly lost people who don’t know where they are and thus may end up deceased. The more common need for HRD dogs is for criminal cases to locate homicide victims, and I have had extensive experience in this. I have assisted in training for law enforcement dogs and even worn a bite suit for patrol/protection dog training with the Elko County, Nevada, Sheriff’s office.
Olfaction remains something of a mystery to many people, but we actually do understand a lot about it. For one, all mammalian olfactory systems operate fundamentally the same way, and even other animals (including insects) have been shown to have olfactory systems that operate on the same principles as those of mammals. I argue that the main reason people think olfaction is a mystery is the lack of any independently measurable standard. In vision, for example, we can measure with machines the wavelength of light at about 700 nm that corresponds to the color red. In sound, we can measure the frequency with machines and find that middle C on a piano is about 262 Hz. These measurements can be made independently of a human and we accept these measures as correct even if a colorblind or tone-deaf human does not agree.
There are people with anosmia who cannot smell anything, and I think it can be argued that there are people with better and worse senses of smell, just as there are people with better or worse vision and hearing. We just cannot measure the sense of smell as precisely. Again, we still understand a lot about olfaction even if we have no machine-readable standard. We know some chemicals cannot be smelled at all, for example methane (aka “natural gas”), which is why we add an odorant (often methyl mercaptan) so that humans can detect a gas leak. We know some chemicals smell very strongly (in other words can be detected at very low concentrations in air. Methyl mercaptan can be detected at about 1.5 parts per billion (ppb) in air which is around 500-1000 times less than the levels typically added to gas piped into homes. Many people, myself included, have experienced smelling skunk miles before seeing the dead skunk on the side of the road. Skunk odor compounds and methyl mercaptan share a common molecular structure in that they are both what we call mercaptan (or thiol) compounds. That is a structure that has sulfur and hydrogen (sometimes written as -S-H) bonded to an organic (i.e. carbon-based) structure. Other chemical structures such as aldehydes, organic acids, and amines also have very strong and distinctive odors. We also know that other compounds such as simple hydrocarbons and organo-halogen compounds have almost zero odor. The major components of air, nitrogen and oxygen, also have zero smell, which is a good thing from the perspective of our sense of smell. What is more important than that simple fact is that we understand why those compounds to not activate mammalian olfactory receptors. Thus, the science of smell and olfaction is deeply rooted in the chemistry of the odor compounds, and as a person with an extensive atmospheric chemistry background, I am uniquely suited to understand this process.
