Since the beginning of the COVID-19 pandemic, cleaning products have become more widely and frequently used, particularly in indoor settings. According to a new study led by Indiana University Bloomington, commercial disinfectants can significantly affect indoor air quality and health, particularly for workers who are repeatedly exposed to these chemical products.
The scientists have found that a group of molecules called “monoterpenes,” which are commonly added to cleaners and furniture polish to help remove oil and grease, can easily react with ozone – an outdoor pollutant which is the main ingredient of smog. When ozone enters buildings, it can turn monoterpenes into peroxides, alcohols, and other molecules which grow into airborne particles that can lodge into people’s lungs, irritating cells and, at high enough exposure, leading to health issues such as asthma.
In order to investigate in a realistic setting what happens with airborne reactions during a typical floor cleaning, scientists brought their lab instruments into a room with an air volume of 50 cubic meters, mopped the floor with a terpene-based cleaner, and monitored the molecules and particles as they reacted over the next 90 minutes.
By using a standard computer model, the researchers calculated how many dangerous nanoparticles would a person inhale during mopping. The result was staggering: during and after a simple cleaning procedure, an average person would breathe in about one billion to ten billion nanoparticles each minute – the equivalent to vehicle traffic on a busy street in a typical U.S. or European city.
Moreover, the researchers also detected short-lived molecules called radicals, such as hydroxyl and hydroperoxyl, which are known to drive chemical reactions that usually create particles outdoors. These findings suggest they can also form indoors, from reactions between monoterpenes and ozone. “The rate at which it occurs indoors is surprising,” said study co-author Colleen Rosales, a postdoctoral fellow at the University of California, Davis.
“I was absolutely amazed that mopping produced potentially harmful aerosols at similar rates to those generated by traffic on a busy street,” commented Nicola Carslaw, a professor of Indoor Air Chemistry of the University of York who was not involved in the study. “The people who should be paying particular attention to this paper are NIOSH, the National Institute for Occupational Safety and Health,” added Genn Morrison, an environmental scientist at the University of North Carolina, Chapel Hill. “There is a lot of particle formation during these cleaning events, even under conditions that we would consider very normal.”
Keeping ozone levels below one part per billion by reducing ventilation or using activated carbon air filters would help diminish the formation of these dangerous particles. So would avoiding cleaning products containing monoterpenes, or cleaning in the morning or evening, when ozone levels are lower.
Unfortunately, current regulations for the design and operation of buildings, and the use of various chemicals during cleaning processes, are rather scarce and fail to adequately protect the health of cleaning workers. This study, published in the journal Science Advances, can be an important step forward in solving these problems.