Ultrafine particles from toasters, air fryers and hair dryers: children face the biggest burden

Small appliances shape much of everyday life, from hectic breakfasts to drying hair before bed. But behind the familiar hum and warmth, scientists are now tracking a haze of ultrafine particles that can be inhaled deep into the lungs - and modelling suggests children receive the greatest relative dose.

When comfort appliances become micro-polluters

Indoor air can feel safer than traffic smog or motorway exhaust. However, many modern homes concentrate heat sources, electronics and limited airflow. Researchers at Pusan National University in South Korea have highlighted this issue by showing that ordinary devices - including toasters, air fryers and hair dryers - may release billions of ultrafine particles every minute.

Under controlled laboratory testing, a basic toaster running empty (with no bread inside) released as many as 1.73 trillion particles per minute. On the worktop it appeared harmless; on a particle counter it looked more like a small, local industrial emitter.

"These appliances generate clouds of particles under 100 nanometres wide – small enough to evade the body’s natural filters and reach deep into the lungs."

The team assessed widely used consumer products rather than specialised equipment: standard hair dryers, popular air fryers and everyday toasters. Emissions differed greatly between models. Traditional hair dryers using brushed DC motors produced 10 to 100 times more particles than comparable models with brushless motors. Toasters and air fryers also produced pronounced surges, particularly at higher temperature settings.

Unlike outdoor pollution, which can disperse in open air, these emissions can accumulate in enclosed kitchens, bathrooms and bedrooms. People also tend to stand very close to the device and often breathe more heavily while cooking, drying hair or cleaning - all while keeping windows closed for comfort or to save energy.

What exactly are ultrafine particles?

Ultrafine particles (UFPs) are smaller than 100 nanometres in diameter. By comparison, a strand of human hair is roughly 700 to 1,000 times thicker. Their tiny size is crucial: particles at this scale can bypass nasal hairs and mucus, penetrate deep into the bronchial passages, and settle in the alveoli where oxygen and carbon dioxide are exchanged.

• They are not confined to the airways; many can pass through cell membranes.
• Some enter the bloodstream and can reach organs such as the heart or brain.
• There is no clearly defined “safe threshold” for long-term exposure to UFPs.

Because they are both invisible and odourless, they are easy to dismiss. With no smoke, no smell and no immediate irritation, exposure can remain unnoticed.

Inside the machines: where the particles come from

The Pusan team went beyond simple particle counts. They dismantled devices, isolated key parts and examined the chemistry of the emitted material. Across multiple products, two components repeatedly emerged as primary sources: heating coils and brushed electric motors.

Heating elements subjected to high temperatures gradually break down. Repeated heating cycles can shed minute fragments of the element’s material. Brushed motors - still widely used in lower-cost hair dryers and other small appliances - create microscopic wear debris as the brushes make contact with the commutator.

"Chemical analysis revealed a cocktail of metals in the emitted particles: copper, iron, aluminium, silver and titanium, all at nanometre scale."

These metals were traced to parts such as coils, wiring, brushes and structural components. At the nanoscale, they present a large reactive surface area and may drive oxidative stress within cells. The study’s laboratory testing indicates cytotoxic and inflammatory responses, with repeated long-term exposure potentially linked to DNA damage.

Design choices that change the air you breathe

One of the most notable findings is just how far apart similar-looking products can be. Two hair dryers may appear nearly identical on a shelf and come in near-matching packaging, yet their particle outputs can differ by a factor of 100.

This variation points to substantial room for engineering gains. Brushless motors - already common in higher-end devices and some cordless tools - generate far fewer particles. Improvements such as alternative alloys, protective coatings or redesigned heating coils could also reduce heater-related emissions. Despite this, manufacturers seldom measure these outputs, and almost never publish them.

From kitchen air to the bloodstream: what the health models show

To connect laboratory measurements to what happens inside the body, the Pusan researchers used computational models of human respiration. These simulations estimate where particles of different sizes are likely to deposit in the airways of adults and children.

The modelling suggested that a large share of UFPs produced by these appliances ends up in the alveoli. From there, a fraction may cross into the bloodstream. Once circulating, particles may reach the heart, liver or brain and contribute to wider systemic inflammation.

"Children inhale more air per kilogram of body weight, have narrower airways and breathe faster, so the same room concentration leads to a higher dose reaching their lungs."

For a child positioned close to a toaster or hair dryer - particularly if the source is near face height - the estimated dose per kilogram of body weight was higher than for an adult sharing the same room. The study associates chronic low-level exposure with risks including:

• ongoing airway inflammation and a gradual reduction in lung function;
• worsening of asthma and other respiratory conditions;
• increased cardiovascular strain driven by systemic inflammation;
• possible disruption of normal immune responses.

The wider nanotoxicology literature is broadly consistent with this picture. Even when a single exposure appears minor, routine daily use over years could elevate baseline inflammation and interact with existing health issues such as allergies, viral infections or heart disease.

Regulation lagging behind the living room

In many countries, outdoor emissions from vehicles and industry are tightly regulated. Authorities monitor PM2.5, PM10 and nitrogen oxides, issue public alerts and set limits. Indoors, rules more commonly focus on ventilation standards or specific chemicals such as formaldehyde from building products. By contrast, ultrafine particle emissions from household appliances are largely unaddressed.

The researchers at Pusan argue that this mismatch is increasingly difficult to justify. Most people spend the bulk of their time indoors - particularly children, older adults and those working from home. Appliances such as toasters and hair dryers operate close to faces, not through distant stacks.

"The study calls for emission limits for small appliances, laboratory testing protocols and health-focused labels that highlight low-emission designs."

The policy options proposed include:

• standardised testing methods for UFP emissions under realistic conditions of use;
• maximum emission caps by appliance category, comparable to energy efficiency schemes;
• labelling that identifies “low ultrafine particle” performance to support informed purchasing;
• public advice on ventilating during and after using high-heat appliances.

Approaches like these would move some of the burden away from individual behaviour and towards product design. In practice, engineers would need to treat particle emissions as a headline performance measure rather than an obscure by-product.

What households can do right now

New regulation and redesigned product ranges take time, and manufacturers are unlikely to overhaul lines overnight. In the meantime, households can still reduce exposure through practical changes - without discarding every appliance.

• Run toasters and air fryers beneath an active cooker hood or close to an open window.
• Do not lean directly over a toaster slot or air fryer basket while the unit is heating.
• Dry hair in a room with good airflow rather than a closed, steamy bathroom.
• When replacing devices, choose models with brushless motors where this is stated.
• Clean vents and filters so dust and particles do not build up inside appliances.

These actions will not eliminate emissions, but they can lower peak concentrations and cut the time spent breathing the densest plume. For people with asthma, COPD or cardiovascular disease, that day-to-day reduction may be meaningful.

Bigger picture: ultrafine exposure from multiple sources

The toaster example fits a broader indoor pattern. Candles, incense, frying on gas hobs, 3D printers, laser printers and even some vacuum cleaners can also produce ultrafine particles. Any single source may seem limited in isolation. In a well-sealed modern home, however, the combined effect can create a persistent background cloud that is rarely noticed.

Health scientists increasingly describe lifetime risk in terms of a “cumulative particle load”. Indoor emissions from consumer products add to ambient urban pollution, any second-hand smoke exposure, and contact with particles at work. Lung tissue is affected by the total burden, regardless of which source contributed each particle.

A promising next step is real-time monitoring in homes. Affordable particle monitors already reveal PM2.5 spikes from frying or burning candles. Instruments that can capture the ultrafine range more accurately could make invisible emissions visible on charts - and add pressure for quicker action from regulators and manufacturers.

For now, the findings from South Korea point to a practical shift in thinking: the soft click of a toaster, the reassuring roar of a hair dryer and the whirr of an air fryer are not only the soundtrack of daily routines. They can also coincide with a plume of nanoscale debris circulating through the room and towards the lungs of anyone standing closest - especially the smallest people in the household.