An invisible problem:
Mankind is moving closer together, conurbations are becoming denser and cities are growing steadily.
This also means that air pollutants are concentrated in urban areas. Unlike wastewater or waste, we cannot perceive the increasing air pollution. This makes them one of the most underestimated health risks.
A person breathes about 10,000 litres of air every day.
For this reason, the World Health Organization has classified air pollution as one of the greatest health risks worldwide since 2014.
Even in cities with high outdoor air pollution, indoor air can contain up to 10 times higher concentrations of pollutants. More and more buildings are being equipped with artificial ventilation, which recycles the air to save energy. The fresh air rate is minimised for energy reasons. At the same time, this leads to the concentration of pollutants within the rooms.
Particularly in the age of increasingly energy-efficient buildings, air pollution found indoors is becoming an increasingly important issue.
Our cities today are still operated by a fossil-driven infrastructure. This continues to mean air pollution from urban combustion processes. By-products such as formaldehyde, nitrogen oxides and carbon dioxide accumulate in the city in particular.
Particles, sulphur dioxide and ozone also pose a danger. We are exposed to urban air pollutants on a daily basis.
Air pollutants are ubiquitous.
Volatile organic carbon compounds (VOCs) contain many representatives of synthetic substances that can cause serious respiratory disease. The most common are formaldehyde, benzene, naphthalenes, acetaldehyde, toluenes, tetrachloroethylene and many more.
Already in very low concentrations [µg/m³] (→ PDF) these substances can have a variety of health effects. These include Respiratory diseases, eye irritation, immunological and neurological effects as well as leukaemia, liver and testicular cancer.
The main sources of these indoor substances are poor building materials, paints and varnishes, furniture and cleaning products.
Fine dust particles have various effects on health.
For example, certain particle sizes can even write through the lung blood barrier.
A study (→ Link) shows that fine dust particles may even overcome the foetal placenta barrier, which can influence the cognitive development of children even before birth. In addition, scientific evidence shows that thyroid levels in unborn children may be associated with air pollution.
Thyroid is a known hormone that appears to have a critical influence on the cognitive development of unborn babies.
Increased concentrations of CO2 reduce cognitive performance and lead to headaches, dizziness and fatigue.
Particularly in offices, event and meeting rooms, increased CO2 concentrations are frequent.
Even at moderate concentrations of 1000-2500 ppm, cognitive performance deteriorates by up to 94% (→ Link).
Nitrogen dioxide irritates the respiratory tract and can cause or aggravate respiratory diseases. The sources are combustion processes such as gas stoves or outside air.
A meta-analysis (→ PDF) showed that an increased value of 28 µg/m² increases the risk of respiratory diseases by 20%.
Carbon monoxide is a colourless, odourless and tasteless gas. It is produced during combustion processes with insufficient oxygen supply.
Inhalation leads to smoke poisoning and in the worst case to death.
Due to the high health risk, there has been an obligatory limit value (→ PDF) of 10 mg/m33 (highest 8-hour average value of a day) since the year 2005
The main indoor sources are defective or inadequately maintained heating systems, gas heaters or exhaust air ducts.
The collective term nitrogen oxides (NOx) covers the nitrogen compounds nitrogen monoxide (NO) and nitrogen dioxide (NO2). These are particularly reactive nitrogen compounds that can lead to harmful environmental effects.
The health risk for asthmatics is particularly high because NOx has a bronchoconstrictive effect.
NOx, on the other hand, is more relevant for the environment, since nitrogen oxides damage plants (e.g. premature aging and caring growth). In addition, nitrogen dioxide (NO2) leads to overfertilisation and thus to acidification of soils.
The main sources in cities are from road traffic.
Fine dust is a mixture of solid and liquid particles of different size and composition.
Particulate matter is a source of danger both to the environment and to human health.
The deposition of fine dust on buildings can cause material damage and changes in surface properties (e.g. increased light and heat absorption).
Inhalation of fine dust particles, depending on size and penetration depth, may cause lung, heart and circulatory problems.
The most relevant source of particulate matter is road traffic (exhaust and tyre abrasion).
Sulphur dioxide is an air pollutant that results from combustion processes of fossil fuels.
Sulphur dioxide can irritate human mucous membranes, eyes and respiratory tract. Nowadays, the prescribed limit values are adhered to in Germany, which is why the health risk is very low.
Sulphur dioxide can have an acidifying effect on ecosystems: deposits can acidify both soil and water. Here, too, the danger in Germany has fallen sharply since the 1990s.
Ozone is a colourless gas that occurs naturally in the stratosphere and protects people from dangerous UV radiation.
Ozone in the troposphere is referred to as ground level ozone. Ozone is a pollutant in relation to humanity and the environment.
In humans it can lead to respiratory diseases and probably also to cancer.
In plants, ozone can damage the leaf organs.
A natural solution: Microalgae
Microalgae are capable of fixing and rendering harmless air pollutants such as carbon dioxide and carbon monoxide. Our current findings show that microalgae biofilms in particular are also capable of absorbing nitrogen oxides. We are currently working on the further development of our microalgae biofilter concept to also test the filtration of VOCs and SO2.
In biofilters, microalgae biofilms operate with low energy consumption and are suitable for cleaning off low concentrations. They thus offer enormous potential for urban and biological air purification. In addition, they can be attached to facades in a space-saving and effective way.