10.25.07
How We Smell – Olfaction
The sense of smell or olfaction is truly a survival mechanism. Through this sense, we can scope out potential mates, smoke, dangerous (spoiled) foods that might kill us, and assess our surroundings as pleasant or threatening. Smells can be uplifting like those of flowers or a baby’s skin, or depressing such as septic (uh oh – there’s a problem with the system).
The feeling of smelling comes from detecting an odorant molecule in the air at whatever part per million (humans, though not as sophisticated as animals, can still differentiate between thousands of scents). The molecules hit your sensory receptors in a handy area called the olfactory epithelium, located high up in your nose, which contains tiny sensory neurons and cilia. Proteins created when the molecules dissolve in the mucus activate a message sent to the brain: “Hey, process this smell, will you?” Smell is really an interaction in the body between inhaled odor molecules and receptors which generate an electrical signal.Some experts speculate that up to 78% of what you taste is really your sense of smell. Both smell and taste (gustation) are called the chemical senses because they’re all about detecting chemicals (and of course everything’s made up of chemicals naturally – even you). Recent gene studies have discovered at least 1,000 genes related to sense of smell – a large proportion of the total estimated 30,000 – 50,000 protein coding genes.
So how do those odor molecules actually make it to your nose in the first place? They need to be “volatile” which sounds scary as if they’re going to explode any moment or go on a rampage. It really just means that the thing which has the odor is constantly emitting or evaporating small amounts of molecules that in turn are tiny enough to enter the nose and dissolve in the mucus. According to the EPA, VOCs (volatile organic compounds) occur in much higher concentrations indoors than outdoors (up to 10X higher). Thousands of products give off VOCs from the magic marker in your kitchen drawer to the cleaning supplies under the sink to the carpet on the floor. Many common household products give off odors that may be undetectable to your nose, but nonetheless are present in the environment. Multiply this by all the cans, sprays, jugs and bottles of products and you begin to think….do I really want all this in my house? But that’s a topic for another time. To learn more about Indoor Air Quality by the EPA visit here.
