The Lemony-Fresh Scent of Death
What’s in a Smell Anyway?
There were two rogue ants in the bathroom to begin with. Scuttling along the back of the sink, they seemed so innocuous that they were easily ignored. Within a day, dozens of their comrades would be running a trail from behind the cabinet, along the edge where the bathtub meets the floor, and into a small crack in the far corner of the tile work that surrounds it.
As the Santa Ana winds strengthened over the following days, bringing dry, searing heat to southern California, more and more ants began to find their way into the house. Driven inside by the roasting sun outside, or just in search of food made scarce by the continuing drought, they came in their thousands. The trusty barrier of cinnamon dust that runs under the steps by the kitchen door had been breached, and the colony had somehow established a masthead inside the house.
The initial battles were a one-sided war of attrition. As the ants appeared in a new room, running a trail from one crack to another, the scouts were squashed, the trails cleaned up with detergent. Barriers of natural ant repellents: baking soda, cinnamon, cloves, and cayenne pepper, were deployed around known points of entry. Eventually though, we would go to sleep. The ants would not.
By Day Three, we were on the run. Even as our rudimentary defenses had held in the bathroom, pushing the enemy back into its bastions below the walls, the ants had established multiple inroads into the kitchen. From a staging post behind the dishwasher, they were able to reach the cabinetry, and the boxes of sugar within. They had reached their goal; our defenses had fallen, and the rest of our food seemed within their grasp.
Sometimes, the only way out of a corner is to fight. Our failed defenses had been based on a desire to avoid collateral damage. To minimize unnecessary exposure of ourselves and our pets to harmful chemicals by using more natural methods — at worst, some detergent to clear up the ants’ own chemical trails. But now, the unnecessary had become necessary. We would strike back mercilessly with the most effective means at our disposal. Nothing short of total victory would be enough to save our home from the invasion, and we would not rest until the ants were driven out entirely, by any means necessary.
In the 1960s, American farmers were struggling to keep up with the food demands of a booming population following the end of World War II. Innovations in intensive farming, aided in part by new chemical fertilizers, promised to dramatically increase productivity. However, intensively farmed crops were more vulnerable to losses from pests and infection. Widespread spraying of DDT had been largely effective in wiping out malaria in Europe and North America, but questions were already beginning to be asked about its safety and effects on the environment. In fact, DDT’s harmful effects on wildlife and human health turned out to be so pervasive and-long lived that the US passed an outright ban in 1972 on its use in agriculture.
A solution to this problem presented itself in the chemistry of Pyrethroids, synthetic variants of the molecule Pyrethrum which is found in the petals of the Chrysanthemum plant. Powdered Chrysanthemums have been used as an insecticide for over 2000 years, and are still commercially produced in mountainous areas of Kenya and Tanzania. Pyrethrum and its variants are lethal to many insects; the chemical binds to voltage-gated sodium channels in the insect’s nervous system. This causes the channels to lock open, allowing unlimited amounts of sodium ions to flow into the nerve cell — in effect, the insect’s nervous system is instantly fried by global hyperactivity, just as if they had been put into an electric chair.
From the 1970s onward, pyrethroids became the predominant choice for agricultural insecticides, and are still the most common insecticide for domestic and food use today. They are naturally broken down by sunlight, so are less likely to accumulate in the environment than organochlorides such as DDT. Pyrethroids are also much less harmful to humans and other animals: our nervous system’s sodium channels are sufficiently different to insects’, such that pyrethroids do not bind to- and lock them open until we are exposed at many thousands of times the concentrations of pyrethroids used in commercial insecticides. We also have a class of enzymes called glucuronidases in our liver that rapidly break down toxins like pyrethroids.
Despite having a much safer profile than older pesticides like DDT, pyrethroids still present a number of hazards that mean they need to be used with great care; indiscriminate spraying for agricultural use would cause the death of many helpful insects such as bees, and soil-dwelling invertebrates. Chronic human exposure to pyrethroids has been linked to a number of health issues, including endocrine disorders and cancer. In domestic situations, pet cats are especially vulnerable to pyrethroid poisoning, as they lack glucuronidases in their livers to break down these chemicals.
The hardware store was busy — it seemed that we were not the only ones experiencing a bout of weather-related insect infestation, along with the traffic from multiple emergency HVAC repairs that were necessary after three days of 100-degree temperatures in a row.
A group of people were crowded around the section that contained pesticides, insecticides, herbicides, and all the other deadly chemicals one might want to maintain a biology-free environment. A store attendant was waiting by the shelves, ready to help another poor homeowner work out how best to repel an invasion of ants, spiders, roaches, or rats. Two different brands of aerosolized chemical warfare agents claimed to kill ants dead on contact. The attendant asked me if I had any questions.
Which of these will work best, and how much cancer will they give me?
He assured me both brands would be very effective for killing ants, before quickly turning away to find a different customer to help. I picked up the brand that came with 25% extra free, and had a fresh, floral scent.
The widespread introduction of scented additives to cleaning products is often traced to the invention of Pine-Sol in 1929 by Harry A. Cole. A chemist from Jackson, Mississippi, Dr. Cole used the plentiful pine oil available from local forests as an antibacterial ingredient for his new cleaning product. Dr. Cole’s invention would go on to enjoy decades of success as the biggest selling household cleaner in the world — a status that owes as much to its pleasing ‘fresh pine scent’, as it does to its effectiveness as a cleaner.
The runaway success of Pine-Sol was a game-changer for the household cleaning products industry. Previous products had been largely unadulterated, functional products, such as bleach, soap, or carbolic acid. The introduction of a product that not only left surfaces clean, but allowed the home to smell clean afterwards unleashed a wave of floral, woody, and citrus perfume additives for cleaning products onto the market. Cleaning product manufacturers quickly discovered that the smell of a product alone can be enough to generate brand loyalty, even if the product itself is inferior to a rival in terms of cleaning power — truly any marketer’s dream!
However, unlike active ingredients such as the pyrethroids, the ingredients that constitute the scent in household cleaning products are a mystery to the consumer, as are any health risks associated with them. Due to its historical reliance on distillates of plant-based ingredients, much of the accumulated knowledge in the perfume industry has traditionally been considered trade secrets, as methods for growing and processing plants are readily copied. This secrecy has persisted into the modern era, where fragrance manufacturers make few disclosures about the nature of chemicals in their products, yet neither the FDA or EPA has any authority to regulate perfumes and fragrances. Just as with pyrethroids, the chemical constituents of perfumes are almost entirely synthetic derivatives of naturally-occurring chemical families found in plants. However, without the history of safety testing and public disclosure that all insecticides, herbicides, or cleaning chemicals have undergone, the chemical constituents and specific health hazards of the various fragrances in cleaning products are unknowable.
The day of our fightback came with a fresh wind and cooler temperatures. With windows open and a cool sea breeze to clear out the house air, all remaining foodstuffs were removed from the kitchen. Open packages were discarded and the remainder stored in the garage. The cat and dog were confused by the reassignment of their feeding and water stations to the yard, and then by their own exile to the same. It was time for war to begin.
Poisoned bait traps were deployed to areas where the pets could not reach them — behind baseboards, under the crawlspaces, and behind the dishwasher. With the areas that we could not readily reach baited to attract ants who would take the baited poison back to their hive and kill the colony, it was time to take on the foot soldiers.
Sometimes, claims on cleaning products can seem inflated. In this case, kills on contact was almost an understatement. The battle was over almost as soon as it had begun. As each edge under a door, along a baseboard, under the edge of a cabinet, was briefly sprayed, every ant instantly stopped still as if frozen to the ground.
After the slaughter was over, every surface was cleaned over with soapy water to remove residual insecticide and insect remains. Small amounts of the pyrethroid chemicals would persist inside the cracks and joints that were the ants’ entrances for weeks to come, protected by the darkness inside, ready to kill any insect that dared try to re-enter our home. All the cabinets and floors were cleaned with detergent, removing the last of the ants’ chemical signals for directing each other to our food. It was over. They were gone.
Days later, there are no more signs of ants inside the house. Everything has been returned to its rightful place, and neither of our pets has shown any sign of being adversely affected by the insecticide. All that remains in a hint of the Fresh Floral Scent of the insecticide spray.
I know that by now, both of the two active pyrethroids in the spray will have dried down, dissipated, and been chemically broken down by heat and light. If I were still concerned, I can easily look up their chemistry online, and the history of studies that have been performed on them to analyse their safety and long-term effects on humans and animals. I can even visit the EPA’s website to learn more about these insecticides, or to report a problem with their use.
Yet the fresh floral scent remains. What chemicals did the manufacturer use to get the smell of fresh-cut roses and lilies almost exactly right (yet completely wrong)? How were they able to tweak the formulation such that the scent would be released slowly, still detectable after several days with windows wide open? Are any of the perfume ingredients known to be harmful to human or animal health? Did the fragrance come from processed flowers or herbs, or (more likely) a petrochemical production plant? We will likely never know.
In conflict, the biggest loser is often the battlefield.
