If you have been to the airport or any public place since 9/11, we see dogs standing next to security people at the ready because of their ability to smell explosives. Police dogs have also been used for missing persons or finding the remains of a deceased person. Did you know that dogs can smell diseases and sense seizures before they happen? Dogs possess about fifty times more olfactory receptors in their noses compared to humans and the part of the dog’s brain that is devoted to analyzing smells is about 40 times greater than humans. Dogs also have a vomeronasal organ which enables them to detect pheromones, which are chemicals that transfer information to another member of either the same or another species.
There are humans that are also capable of smelling disease, they are called super smellers. Joy Milne a “super smeller” who is capable of detecting scents too subtle for most people to perceive and is also a retired nurse living in Perth, Scotland. Joy first noticed a “sort of woody, musky odor” from her husband about 12 years before his diagnosis of Parkinson’s disease. Tilo Kunath, an Edinburgh University neurobiologist became aware of Milne’s observations of smell during a lecture he gave in 2012. Milne’s husband Les had since passed away, but Kunath tested Milne by having her smell 12 shirts worn by a mixture of healthy volunteers and patients diagnosed with Parkinson’s. Milne correctly picked out the six shirts worn by those suffering from Parkinson’s disease. She also picked another shirt that was initially thought to be a normal volunteer, but eight months later it was later learned that the shirt the person belonged to was diagnosed with Parkinson’s!
Dogs can be trained to smell cancer, and many other diseases. For instance, the standard P.S.A. blood test for testing men for prostate cancer is probably only 50 percent accurate. Properly trained dogs can detect prostate cancer with better than 90 percent accuracy. Andreas Mershin is a physicist at M.I.T. who runs a lab called the Label Free Research Group. The lab, which has 100 million dollars’ worth of equipment is attempting to develop artificial olfaction (A.O.) and be at the forefront of a new approach to solving problems by inventing robots that can do what dogs can do naturally. One of Mershin’s mentors, Shuguang Zhang who runs the Laboratory of Molecular Architecture, has been researching olfactory receptors since 2003. He spent 8 years learning how to successfully create water-soluble receptors. Zhang and Mershin worked together to solve a 2007 request from DARPA, Defense Advanced Research Projects Agency, to develop a robot to detect I.E.D’s (improvised explosive device), as a result of the war in Iraq so the military wouldn’t have to use dogs. When DARPA tested the device from Mershin and Zhang, their years of hard work had paid off. The device called the Nano-Nose passed the sniff-off and was able to sense isolated odors in the lab. It even beat out dogs in a controlled environment, sniffing out odors in lower concentrations than canines could detect. Problems arose with the Nano-Nose in real life situations with multiple smells to sift through including outside smells.
Right now, the Nano-Nose is just a detector, and can’t interpret the data it collects. However, Mershin and Zhang want to make it smarter. Eventually, Mershin wants to see the Nano-Nose incorporated into your cell phone where it will become more than just a sensing device; it will become a true diagnostic tool. There is competition. Whereas Nano-Nose only uses about 20 kinds of receptors, a small Silicon Valley startup called, Aromyx who have stabilized only a few of the 400 human olfactory receptors and have their own ambitious plans by eventually putting all 400 olfactory receptors onto its EssenceChip, a 3x5 inch plastic plate dotted with small wells to hold its receptors. As they add receptors this method may be become finer and more detailed than the Nano-Nose.
Throughout history doctors have used odor to aid in their diagnosis. Typhoid fever produces an aroma of baked bread and scrofula (a type of tuberculosis), smells like stale beer. Ammonia on the breath is a sign of kidney failure. When someone has liver failure an odor of raw fish occurs. Gum disease caused by bacteria that release hydrogen sulfide produces an odor like rotten eggs. A fruity breath might be a sign of diabetes.
An Israeli company has a breathalyzer-type device that is up to 90% accurate for diagnosing lung cancer. After Joy Milne’s successful identification of the Parkinson’s patients, researchers delved deeper and found that it was the sebum – the oily secretion that coats everyone’s skin which produced the odor. Further investigation revealed that a few compounds, particularly hippuric acid, eicosane, and otadecanal, were found in higher concentrations on the skin of Parkinson’s patients. One can easily see where the future is heading in odor detection and health and how early detection could stave off more serious problems.
In May of 1914, Alexander Graham Bell, delivered a commencement address to some high school students in Washington D.C. The 67-year-old inventor of the telephone called upon the students to investigate the science of smell. It’s over a hundred years since that speech but it appears that we are getting closer to identifying a way of measuring smell and the implications will be far reaching. Not only will A.O. be able to diagnose disease earlier, but applications outside of medicine such as sensors in grain silos to determine grains that might be moldy, or sensors in a bioreactor to monitor it, along with yet unimagined ways will be the future application of this technology.