Most vacuum cleaners, regardless of age or price, are a significant source of dangerous ultrafine particles and also help spread toxic bacteria, according to a new study. The study would seem to indicate that a high-efficiency air purifier that is effective against tiny ultrafine particles is perhaps the only line of defense against the effects of vacuuming on indoor air quality. And the study found that vacuum cleaners contribute to indoor air quality problems not just by generating particle pollution but also by spreading bacteria.

The study was conducted by researchers at Queensland University of Technology in Brisbane, Australia. The results were first published by the American Chemical Society late last year. The research team included Professor Lidia Morawska, co-author of the book “Indoor Environment: Airborne Particles and Dust.” Her past research has focused on an array of air quality topics including the effects of laser printers on IAQ.

The vacuum-cleaner study examined more than 20 vacuums from 11 manufacturers, ranging from new up to 22 years old and in various price ranges from $100 to almost $800. The study found a wide variability in emissions from the 21 vacuums. In the end, the study concluded that emissions levels were not directly attributed to price, age or other factors.

Perhaps even more concerning, the researchers found that all of the vacuums they tested emitted a wide range of ultrafine particles, the smallest and more harmful particles in air pollution. Ultrafine particles, defined as those smaller than 0.1 microns in diameter, generally represent about 90 percent of all the pollutants in the air. These tiny particles are small enough to be inhaled and absorbed directly into the bloodstream, and result in increased allergies and asthma, heart attacks, strokes and even cancer.

The study noted that many vacuums not only redistribute ultrafine particles that have settled onto surfaces, but the vacuums generate substantial levels of additional ultrafines particles on their own as a result of using motors with carbon brushes. Past studies have shown that vacuum motors generate ultrafine particles containing copper and carbon. Carbon ultrafine particles can irritate allergies and ultrafine carbon particles can be toxic, the researchers noted.

Meanwhile, the study found that vacuum cleaners can also be a problematic source of bacteria emissions. Vacuum cleaner dust bags can trap and hold live bacteria for up to two months, they said. Vacuum emissions include salmonella and other bacteria that “have potential to spread infectious or sensitizing aerosols,” they concluded.