Raise your hand if bleach is your go-to cleaner when you want to get rid of dangerous cold germs and flu viruses, or when you want to sanitize your kitchen. After all, that's what science tells us to do.
Now raise your hand if you also use household cleaners with a bright lemon, orange or pine scent. Who doesn't? After all, they are in thousands of household cleaners, air fresheners and personal care products.
Called limonenes, these compounds that come from the skin of lemons and oranges are often the basis of many green household cleaning methods, or added as flavors or fragrance to foods, pharmaceuticals and cosmetic products.
By themselves, limonenes aren't toxic. But when they come into contact with light or air, they can oxidize and become irritating to eyes and skin.
Even though limonene can attach to surfaces as well as dissipate in the air, there's not enough limonene in the products we use day-to-day to be of any health concern.
But some workplace cleaning products can contain high concentrations, leading to strict regulations about safe usage.
Researchers from the University of Toronto and Bucknell University in Pennsylvania decided to see what might happen when limonene and bleach fumes, at concentrations likely to occur in indoor environments, were combined. The study was published Tuesday by the American Chemical Society.
The results weren't good: They found bleach fumes can interact with the limonenes in common citrus household cleaners to create potentially dangerous air particles that, when inhaled, can be harmful to people and pets.
Here's how the process works:
Bleach-based cleaning products discharge hypochlorous acid and chlorine gas, which can easily accumulate to relatively high levels if the environment is poorly ventilated. When those come into contact with sunlight, or even indoor lights, those compounds can split into elements small enough to create air particles called secondary organic aerosols or SOAs.
SOAs are a major component of fine particulate matter, the tiny particles in the air that reduce visibility and cause a smoggy haze when levels are high. If small enough, these particles are able to travel deep into our lungs, causing short-term health effects such as eye, nose and throat irritation, coughing, sneezing and shortness of breath.
The worsening lung function can seriously affect anyone with asthma and heart disease; in fact, studies have shown emergency room visits, hospital admissions and deaths go up when fine particle counts are high. That's one of the reasons many cities issue advisories when the air is expected to be especially bad.
Chronic exposure to fine particulate matter is associated with chronic bronchitis and increased mortality from lung cancer and heart disease.
In this study, which researchers are calling the first to analyze what would happen when limonene interacts with hypochlorous acid and chlorine gas, they found that the two reacted to release volatile compounds even in the dark.
But when indoor lights were turned on, the two compounds formed secondary organic aerosols at significant levels. Using sunlight increased the levels and sped up the reactions.
In all cases, the researchers concluded the results could "lead to negative health effects for indoor occupants," especially anyone who spends a good deal of time cleaning, those who use industrial strength cleaning supplies, and children and the elderly.
One suggestion to reduce risk: Open your windows when you clean with bleach and citrus-based cleaners.