Many common home appliances use heating coils or brushed electric motors. However, heat causes chemical changes in specific components, and mechanical action causes physical changes. Korean researchers discovered that both can release ultrafine particles. These particles are so minute that thousands of them could fit across the width of a human hair. Their investigation was published on 15 October 2025 in the Journal of Hazardous Materials.
Small Devices, Big Pollution: The Toxic Particles Hiding in Your Electric Home Appliances
Researchers have identified small household appliances—specifically those using brushed motors and heating coils—as significant sources of ultrafine particles. These invisible pollutants can reach concentrations 10 to 100 times higher than typical indoor levels.
Background
The team of researchers, led by environmental engineer Changhyuk Kim, selected common small appliances sold in the South Korean market. These include air fryers, toasters, and hair dryers. The researchers operated these devices under normal conditions and use cases. They then measured the particles released into the air using real-time aerosol instruments.
Offline analyses, such as transmission electron microscopy, were used to determine specific particle morphology and chemical composition. Human lung deposition modeling was performed using the Multiple-Path Particle Dosimetry model to understand where the emitted ultrafine particles would deposit in the lungs and throughout the respiratory tract.
Main Findings
Results revealed that most emitted particles were ultrafine or smaller than 100 nanometers. Hair dryers emitted ultrafine particles in the nucleation mode or a size range of less than 25 nanometers. Both air fryers and toasters emit ultrafine particles in the Aitken mode or a size range of between 25 and 100 nanometers. Brushed motors had higher emission rates.
Devices with brushed motors and heating coils released 10 to 100 times more particles than those with brushless motors or those without heating elements. Emission rates were highly dependent on operating temperature. The concentration of ultrafine particles spiked as the temperature increased. This suggests that higher temperature settings increase exposure.
The chemical and physical analyses of these particles revealed significant levels of heavy metals like copper, iron, aluminum, silver, and titanium. These metals come from the internal components of the devices. Moreover, because of their ultrafine size, these particles tend to remain suspended in the air for long periods and penetrate deep into the human body.
Simulation models further showed that the particles bypass the upper respiratory defenses and deposit predominantly in deeper in the lungs in the alveolar region where gas exchange occurs. Moreover, once in the alveoli, the heavy metals in these particles can then enter the bloodstream. They can also interact with lung tissue to generate oxidative stress.
Explainers
Many cheap or older motors use carbon brushes that rub against moving parts to create electricity. This friction acts like a pencil eraser rubbing on paper and shedding tiny bits of carbon and metal into the air. On the other hand, when the metal coils inside appliances get red-hot, the metal itself starts to degrade and shed microscopic and airborne metallic flakes.
The findings show that ordinary home appliances can be hidden sources of air pollution indoors and specific heavy metal exposure. However, there is a workaround. Appliances with brushless motors are better options. Using toasters or air fryers under a stove vent or near an open window with outward ventilation can minimize exposure to ultrafine particles.
FURTHER READING AND REFERENCE
- Ryu, G., Kim, J., Ha, Y., Chae, S., Yang, E., and Kim, C. 2025. “Physicochemical Characteristics and Health Impacts of Ultrafine Particles Emitted from Small Home Appliances Equipped with Heating Coils and Brushed Motors.” Journal of Hazardous Materials. 498: 139796. DOI: 1016/j.jhazmat.2025.139796