The Hidden Chemistry Behind Pleasant Smells
A forest is a pristine environment, but if you’re using cleaning and aromatherapy products full of chemically manufactured scents to recreate a forest in your home, you’re actually creating a tremendous amount of indoor air pollution that you shouldn’t be breathing in, according to Purdue University research. This groundbreaking revelation challenges everything most people believe about making their homes smell fresh and clean.
The problem isn’t just about masking odors anymore. Bringing that pine scent or other aromas indoors with the help of chemical products – yes, air fresheners, wax melts, floor cleaners, deodorants and others – rapidly fills the air with nanoscale particles that are small enough to get deep into your lungs. These nanoparticles form when fragrances interact with ozone, which enters buildings through ventilation systems, triggering chemical transformations that create new airborne pollutants.
The Shocking Nanoparticle Discovery
Between 100 billion and 10 trillion of these particles could deposit in your respiratory system within just 20 minutes of exposure to scented products. The numbers are staggering when you consider that most people don’t even know these invisible particles exist. Recent research from Purdue University’s tiny house laboratory revealed something that should make every homeowner reconsider their scented product choices.
The resulting atmospheric concentrations were over one million nanoparticles per cubic centimeter, which is comparable to concentrations emitted by traditional lighted candles, gas stoves, diesel engines, and natural gas engines. Think about that for a moment – your innocent-looking wax melt warmer is producing pollution levels similar to a diesel engine running in your living room.
When Air Fresheners Become Air Polluters
Emissions from volatile chemical products like perfumes, paints and other scented consumer items now rival vehicles as a pollution source in greater Los Angeles, according to a surprising new NOAA-led study. The scale of this problem extends far beyond individual homes, affecting entire metropolitan areas.
Common products like paints and perfumes are literally engineered to evaporate. Perfume and other scented products are designed so that you or your neighbor can enjoy the aroma. This intentional design feature means that every spritz of perfume or plug-in air freshener is deliberately releasing chemicals into your breathing space.
Volatile Organic Compounds: The Invisible Threat
Concentrations of VOCs indoors are up to 10 times higher than outdoors, and this holds true even near industrial areas with heavy pollution. Studies have found that levels of several organics average 2 to 5 times higher indoors than outdoors. During and for several hours immediately after certain activities, such as paint stripping, levels may be 1,000 times background outdoor levels.
Breathing VOCs can cause health issues such as eye, nose, and throat irritation, headaches, nausea, dizziness, and difficulty breathing. Long-term exposure can damage the liver, kidneys, and central nervous system, and some VOCs are linked to cancer. The health effects range from annoying to potentially life-threatening, yet most people remain unaware of the risks lurking in their laundry rooms and bathroom cabinets.
The Terpene-Ozone Reaction Problem
The researchers knew from their previous research that new nanoparticle formation was initiated by terpenes – aromatic compounds that determine the smell of things like plants and herbs – released from the melts and reacting with indoor atmospheric ozone. They’d found that activities such as mopping the floor with a terpene-rich cleaning agent, using a citrus-scented air freshener, or applying scented personal care products like deodorant inside the house resulted in pulsed terpene emissions to the indoor air within five minutes.
Cleaning agents often emit terpenes that react rapidly with ozone. These ozone-initiated reactions, which occur in the gas-phase and on surfaces, produce a host of gaseous and particulate oxygenated compounds with possible adverse health effects in the eyes and airways. Your body becomes an unwitting test subject in this ongoing chemical experiment happening right in your home.
Wax Melts: The False Promise of Safety
In a recently published paper, the pair found that scented wax melts, typically advertised as nontoxic because they are flame-free, actually pollute indoor air at least as much as candles. Since wax melts contain a higher concentration of fragrance oils than many candles, they emit more terpenes into indoor air. The marketing promise of “flame-free equals safe” turns out to be dangerously misleading.
They found that the new particle formation triggered by using scented wax melts indoors produced a median rate for particles of 29 billion per minute. That’s about 483 million particles per second. Every second you breathe near an active wax warmer, you’re potentially inhaling hundreds of millions of tiny particles.
The Surprising Kitchen Connection
A study led by Boor found that cooking on a gas stove also emits nanoparticles in large quantities. Just 1 kilogram of cooking fuel emits 10 quadrillion particles smaller than 3 nanometers, which matches or exceeds what’s emitted from cars with internal combustion engines. At that rate, you might be inhaling 10-100 times more of these sub-3 nanometer particles from cooking on a gas stove indoors than you would from car exhaust while standing on a busy street.
Most people worry about outdoor air pollution while unknowingly creating much worse conditions inside their homes. The irony is palpable – we close our windows to keep out dirty air, then fill our homes with products that create even dirtier air.
Fragrance Sensitivity: More Common Than You Think
Among the general population, across the four countries, 32.2% of adults on average report fragrance sensitivity; that is, adverse health effects from exposure to fragranced consumer products. Among vulnerable sub-populations, the prevalence of fragrance sensitivity is higher. For instance, 57.8% of asthmatic individuals and 75.8% of autistic individuals report adverse effects from fragranced products.
These numbers suggest that fragrance sensitivity isn’t a rare condition but rather a widespread health concern affecting roughly one in three adults. For people with existing health conditions, the risks become even more pronounced, creating a public health issue that extends far beyond individual preferences.
The Secondhand Scent Problem
The problem of widespread exposure gives rise to the problem of “secondhand scents”: indirect or involuntary exposure to fragranced products. Consequences of secondhand scents include, for example, restricted access in society, health risks, lost workdays and lost jobs, and negative effects in daily life and living situations. Just as secondhand smoke became recognized as a serious health concern, secondhand scents are emerging as the next frontier in public health awareness.
Consider how your choice of laundry detergent or personal care products doesn’t just affect your own health but also impacts everyone who shares your space – family members, coworkers, and even strangers in public places. The invisible cloud of chemical emissions follows us everywhere.
Children and Vulnerable Populations at Risk
Children, older people and individuals with respiratory conditions are at greatest risk of experiencing health problems associated with VOCs. Children breathe more air relative to their body size, which means they inhale a higher concentration of VOCs. The smallest members of our households face the greatest risks from our well-intentioned attempts to create pleasant-smelling environments.
People with respiratory problems such as asthma, young children, the elderly and people with heightened sensitivity to chemicals may be more susceptible to irritation and illness from VOCs. What seems like harmless home fragrance to healthy adults can trigger serious health problems for those with compromised systems.
The Building Design Blindspot
Indoor air quality is often overlooked in the design and management of the buildings we live and work in, yet it has a direct impact on our health every day. Modern buildings are designed to be energy-efficient with tight seals that prevent air exchange, but this efficiency comes at the cost of trapping pollutants indoors.
Our research shows that fragranced products are not just passive sources of pleasant scents – they actively alter indoor air chemistry, leading to the formation of nanoparticles at concentrations that could have significant health implications. These processes should be considered in the design and operation of buildings and their HVAC systems to reduce our exposures.
Simple Solutions for Cleaner Indoor Air
Open windows and add a fan to pull the indoor air outside while you’re using products with high VOCs. Increasing the amount of fresh air in your home will help reduce the concentration of VOCs indoors. Sometimes the most effective solutions are also the simplest ones – opening a window can be more beneficial than plugging in an air freshener.
The best way to address VOCs in the home is to completely eliminate the use of products and materials that contain VOCs – if they aren’t in the home, they can’t harm you. But, given the universal nature of VOCs, it’s nearly impossible to keep all VOCs out of the home. The goal isn’t perfection but rather conscious reduction of unnecessary sources.