Aerosol indoor pollution also occurs during cooking

Few people think about what happens to the air the moment they turn on the stove. The smell of garlic in oil, steam rising from a pot, the faint smoke from frying onions – it all feels cosy and homely. In reality, however, a chemical symphony is playing out at that very moment, whose effects on health are surprisingly serious. Indoor air pollution is a problem that receives far less attention than urban smog, even though the average person spends approximately 90% of their time inside buildings.

Research repeatedly shows that indoor air quality can be up to five times worse than outdoors – even in cities with heavy traffic. One of the main culprits behind this situation is an activity that virtually everyone engages in: everyday cooking. Indoor aerosol pollution generated during food preparation is now one of the most significant, yet most overlooked, health risks in the modern home.

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What exactly is produced during cooking and why is it a problem

When food is heated to high temperatures, a whole range of substances are released that mix with the air in the room. These include ultrafine particles, volatile organic compounds, nitrogen dioxide, carbon monoxide, and various polycyclic aromatic hydrocarbons. These substances are not visible to the naked eye – and that is precisely what makes them insidious. While smoke from burning food is immediately noticeable, most harmful emissions are produced during seemingly normal cooking without any visible sign.

Particularly dangerous are so-called PM2.5 particles – ultrafine aerosols with a diameter of less than 2.5 micrometres. They are so small that they penetrate deep into the lungs and from there can pass directly into the bloodstream. According to the World Health Organization, long-term exposure to these particles is among the leading causes of cardiovascular and respiratory diseases. And cooking is one of the largest producers of these particles in enclosed spaces.

A British study from 2022, conducted by researchers at the University of Birmingham, found that frying a steak in a pan can, within a few minutes, raise PM2.5 concentrations in a kitchen to levels comparable to those on a busy road in central London. That is a figure worth reflecting on – especially when we consider that while outdoors we are generally moving around, in the kitchen we stand directly at the source of emissions and inhale them from close proximity.

The method of food preparation plays a crucial role. Frying in oil, grilling, and baking at high temperatures produce significantly more aerosol particles than boiling in water or steaming. Vegetable oils heated above their smoke point release aldehydes and other toxic compounds, some of which are classified as potentially carcinogenic. Oils with a lower smoke point – such as virgin olive oil or butter – are therefore more problematic at high temperatures than, for example, rapeseed or avocado oil.

It is worth noting that even seemingly innocuous actions such as toasting bread or preparing popcorn in a microwave generate measurable amounts of volatile organic compounds. As American chemist Joseph Allen of the Harvard T.H. Chan School of Public Health puts it: "The air we breathe at home is not a neutral background – it is an active environment that constantly reacts to our behaviour."

How cooking-related air pollution affects the health of the whole family

The effects of aerosol pollution from cooking are not merely a theoretical risk – they manifest as specific health problems that people often attribute to other causes. Headaches after spending extended time in the kitchen, irritation of the eyes and mucous membranes, fatigue, or worsening of asthmatic symptoms can all be a direct consequence of prolonged exposure to emissions from food preparation.

Children are particularly vulnerable, as their lungs are still developing, as are elderly people with impaired respiratory function. Research repeatedly links high PM2.5 exposure in households to a higher incidence of childhood asthma and chronic obstructive pulmonary disease in adults. A study published in the scientific journal Environmental Health Perspectives confirmed that children living in households with inadequate kitchen ventilation have a statistically higher risk of developing respiratory diseases than their peers in better-ventilated environments.

But the health risks do not end with the lungs. Ultrafine particles entering the bloodstream can contribute to inflammatory processes in blood vessels, increase the risk of hypertension, and in the long term place strain on the heart. This is precisely why the topic of indoor air quality is increasingly attracting the attention of cardiologists and preventive medicine – not just pulmonology.

The situation is further complicated in modern, well-insulated flats and houses. Energy-efficient buildings, which are today the standard in new construction, are excellent in terms of heat loss, but at the same time significantly restrict natural ventilation. Air is exchanged more slowly in them, harmful substances accumulate, and without active ventilation or air purification, aerosol concentrations can reach alarming levels. Paradoxically, therefore, the better insulated a house is, the more important it becomes to consciously attend to indoor air quality.

Consider a specific scenario: a family in a block-of-flats apartment cooks a hot dinner every evening. The kitchen window is closed because it is cold outside. The extractor hood is either absent, or clogged with grease and functioning only nominally. Within an hour of cooking, PM2.5 concentrations in the flat climb to levels at which an outdoor meteorological station would issue a warning. Yet no one in the family notices anything – the air looks no different, has no unusual smell, and is not visibly smoky. This invisibility is precisely what makes indoor aerosol pollution so treacherous.

What to do about it: practical steps towards healthier air at home

The good news is that there are specific and relatively accessible measures that can significantly improve air quality in the kitchen. This does not require any radical lifestyle changes – it is more a matter of consciously establishing everyday habits and equipping the home appropriately.

The first and most important step is a functional and regularly cleaned extractor hood. Research shows that an extractor hood positioned directly above the hob and venting air genuinely outside the building (rather than simply recirculating it through a filter back into the room) can reduce PM2.5 concentrations by 60 to 90%. The key word, however, is "functional" – clogged filters and a weak motor drastically reduce effectiveness. Regular maintenance of the extractor hood should therefore be as much a matter of course as washing the dishes.

Ventilating through windows remains a cheap and effective alternative or complement to an extractor hood, even if it is not always practical throughout the year. Experts recommend ventilating not only during cooking, but also for at least 15–20 minutes after it has finished, because concentrations of harmful substances in the room continue to rise for a while after the hob is turned off before they begin to fall.

Choosing the right oil and cooking at an appropriate temperature is another simple measure. Using oils with a higher smoke point for frying, avoiding overheating fats, and favouring gentler cooking methods – braising, steaming, or slow cooking – significantly reduces the amount of pollutants released. Switching to induction cooking also eliminates emissions from gas combustion, which is another source of nitrogen dioxide in the kitchen.

Air purifiers with HEPA filters deserve a chapter of their own; they are capable of capturing ultrafine particles and significantly improving the overall air quality in a room. Modern devices are quiet, energy-efficient, and easy to operate. For households with children, people with asthma, or elderly residents, they can be an investment that pays off not only in terms of comfort, but also health.

It is also worth mentioning the choice of appropriate cookware. Damaged non-stick surfaces made from Teflon or other synthetic materials can, at high temperatures, release fluorinated compounds whose safety is the subject of expert debate. Alternatives include cookware made from cast iron, stainless steel, or ceramic, which are more materially stable and, when used correctly, do not release unwanted substances into the air or food.

It is also useful to keep an eye on current developments in the area of measuring indoor air quality at home. Smart air quality sensors are now available on the market that display real-time concentrations of PM2.5, CO2, and volatile organic compounds. For many people, the first glance at the data from such a device during cooking comes as a genuine surprise – and at the same time serves as the most effective motivation for changing habits.

The topic of indoor aerosol pollution is slowly but surely entering broader public awareness. Organisations such as the European Environment Agency and the WHO are increasingly emphasising that protecting health lies not only in combating outdoor smog, but also in caring for the air we breathe at home – every day, with every meal. Cooking is a fundamental human activity, and the intention of this message is not to suggest that people should stop cooking. Rather, it is about an awareness that even seemingly mundane everyday rituals have an impact on health – and that small changes in approach can have a surprisingly large effect on how we feel and how long we remain healthy.