“Smell is a potent wizard that transports you across thousands of miles and all the years you have lived”.
- Helen Keller (Blind and deaf educator, 1880–1968)
My children often smile indulgently on our visits to the local library, not because they accept my love of reading (they are avid readers also), but because they find it amusing when I tell them that the library we frequent in Mumbai reminds me of the University department I studied at miles away in Canada more than a decade ago. How? Not because of the books, but because of the smell of the room. They probably think I am quirky, but as researchers have long recognized, smell can trigger many memories, some good, some bad. Many of us instantly recognize the “foreboding” smell of a hospital or the “warm and fresh” smell of a bakery.
The role of smell in our lives
Humans can reportedly distinguish about 10,000 different smells, each encoded by a different gene and each recognizing a particular smell. Smell is so subjective that no two humans smell anything exactly the same; after all, a person's perceptions (including how they perceive smells) are based on experiences that they have had throughout their life. Several factors determine how we smell a smell: genes, skin type, diet, age, gender, pregnancy, the weather, and even the time of day. When we are hungry, our sense of smell becomes keener. Many a time, foul odours are an indicator of safety issues (e.g. leaking gas or sour milk). Insects and animals communicate their requirements and emotional states to other animals (and sometimes, humans; think “skunk”) through changes in their body odours. Doctors have reported encouraging success in diagnosing lung cancer by benefiting from the ability of dogs to detect very low concentrations of the alkanes and aromatic compounds generated by the tumours. It is said that a baby recognizes and bonds with its mother through her smell. Indeed, our memory of smells is so potent that performing an undesirable or boring task in a scented room decreases the performance of other similar tasks in the presence of the same smell in a different place and at a different time. As the website of a leading ambient air scenting and scent marketing company reports, smells have also be used in a “deliberate and controlled manner”. Technicians at New York City’s Sloan-Kettering Cancer Centre are known to spray vanilla-scented oil in their MRI rooms, to help patients cope with the claustrophobic effects of the testing. I know someone who would leave his unwashed socks lying about in his room just to deter people from entering it (and it worked).
As any Grade 2 student can tell you, humans are endowed with five senses—the sense of sight, sound, taste, touch, and smell. Of these, the sense of smell is often ignored, except perhaps when we suffer from a bad cold and miss smelling the aromas of the food we eat (scientists say 80 percent of the flavours we taste are dependent on our sense of smell). The sense of smell is a stepchild of sorts in the environmental sense as well. Take for instance, air pollution. The health effects of air pollution are keenly felt. The smog that envelopes cities is rightly blamed as causing many health issues, such as asthma and other respiratory tract infections. Airlines are forced to cancel flights due to heavy smog, thus causing major inconvenience to passengers and throwing travel schedules out of gear. Noise pollution has also made headlines in the past, particularly during festivals. High noise levels can contribute to cardiovascular effects in humans. In animals, noise can interfere with reproduction and navigation. We understand these effects as clearly as night and day.
“Odour Pollution” and What it Means for Us and the Environment
But smell is not something we associate easily with environmental issues. This omission is deleterious to health—not just ours but also that of other creatures. Take, for instance, the bee. Recent studies suggest that commonly used pesticides (such as lindane, organophosphorus insecticides and neonicotinoids) block that part of the brain that bees use for learning, rendering some of them unable to perform the essential task of associating scents with food. In 2013, scientists discovered that reactive pollutants in diesel destroyed key chemicals in the smell of oilseed flowers, thus destroying the bees’ ability to smell and identify the flowers. The team zeroed in on the highly reactive nitrogen oxides (NOx) as the pollutant of concern; NOx chemically alters the bees’ sense of smell by removing key chemicals the bee uses to recognize the flower by its distinctive scent within as little as a minute of exposure. The researchers suggest that these effects could make it harder for bees to forage among flowers for food, thereby threatening their survival and reducing the pollination of crops and wild plants. Typically, crops bear flowers that may only be pollinated during a short period. If such a crop is not pollinated during that time, the flowers will eventually be shed and the next generation of seeds and fruit will not develop. More than 50 percent of the world’s needs for fat and oil is derived from oilseeds such as cotton, sunflower, coconut, groundnut and oil palm, all of which are dependent to some extent on bees for pollination. The Food and Agriculture Organization (FAO) reported an interesting experiment in Russia. Crop areas of the white clover plant (an excellent forage crop for livestock) were covered during blooming, so that no bees could enter. Only one gram (!) of seed could be harvested in the covered area. Conversely, uncovered bee-pollinated areas of the same size reported an average harvest of 331 grams of seeds. A report from India mentions a 100 percent increase in the coconut harvest because of bee pollination.
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