Fine particulate matter (PM₁ – PM₂,₅ – PM₁₀)

Description:

The term “dust” refers to a complex physicochemical mixture of liquid or solid particles suspended in the air. These are also known as PM (from the English: particulate matter) and, generally, as particles.

Particles with a very small diameter, which can reach the bronchi, are called“fine particles”or even “ultrafine particles.” The composition varies greatly among different fine particles. They can contain both organic and inorganic matter.

The different particle sizes—which can be measured, for example, using the air-⁠Q air analyzer—are referred to as PM₁₀, PM₂,₅, or PM₁.

Fine particles have a high potential to absorb trace gases. Thus, pollutants with relatively high boiling points (such as pesticides and plasticizers) accumulate very easily on fine particles and increase the health risk when the air contaminated with them is inhaled.

Limit values for PM₁, PM₂.₅, and PM₁₀:

Since the harmfulness of fine particles depends on their size, various limit values have been established. In general, the smaller the fine particles are, the deeper they can penetrate into the lungs and the bloodstream. This increases the danger they pose to people.

For PM₁₀ fine particulate matter (particles smaller than 10 µm), the Federal Environment Agency sets a daily limit value of 50 μg/m³ and an annual average of 40 μg/m³ for outdoor air. The daily limit value may be exceeded on no more than 35 days per year.

The smallest fine particles can penetrate even deeper into the respiratory tract. For this reason, since 2015, the annual limit value of 25 μg/m³ established by the World Health Organization (WHO) for PM₂.₅ (particles with a diameter of less than 2.5 μm) in outdoor air has also been applied as a reference value for indoor air.

To date, there are no standardized measurement methods for the even smaller fine particles in the PM₁ category, so there is still no legal limit for these particularly hazardous particles—since 100% of them reach the pulmonary alveoli. These very small particles are also referred to as ultrafine particles.

Consequences of a concentration that is too high:

It is difficult to accurately assess the health effects of fine particulate matter due to its heterogeneous composition. However, it is generally assumed that fine particulate matter is harmful to health. Unlike other pollutants, there are no actual threshold values below which no health effects are expected for fine particulate matter: any amount, no matter how small, is considered harmful.

Regardless of the type of fine particle, they irritate the respiratory tract and can cause inflammation there. Depending on their composition, the pollutants attached to fine particles can trigger allergic reactions or, as in the case of coal dust, destroy the pulmonary alveoli.

The smallest particles, in particular, can enter the bloodstream via the pulmonary alveoli, thereby causing long-term damage to the cardiovascular system. Certain substances can also increase the risk of a heart attack (for example, fine sulfur-containing particles) or have a carcinogenic effect (for example, asbestos).

In addition, irritation of the mucous membranes of the eyes, nose, and throat may occur. Damage to the central nervous system cannot be ruled out either.

Source of fine particles:

Natural emissions (such as those from soil erosion, the oceans, volcanoes, and forest and brush fires), as well as biogenic particles (such as viruses, fungal and bacterial spores, pollen, and excretions from house dust mites), are considered particularly common sources of fine particulate matter. However, human-caused air pollution is undoubtedly the main source of fine particulate matter.

In outdoor air, fine particulate matter originates primarily from emissions from industrial facilities, power plants, and motor vehicle traffic. Livestock farming also generates a considerable amount of ammonia, which forms fine particulate matter in the atmosphere through chemical reactions. Wood-burning heating systems in residential areas contribute to fine particulate matter pollution on cold days.

Through open windows and via shoes and clothing, these pollutants can also enter indoor spaces and thus the indoor air, affecting air quality. In addition, candles, tobacco smoke, open fireplaces, as well as cooking and frying, also contribute to fine particulate matter pollution.

In addition, pet allergens and chemicals from carpets and furniture can adhere to fine particles. These particles can also enter the indoor air when vacuuming or through office equipment such as printers, photocopiers, and computers.

Sensor used:

Fine particles are measured using optical scattering. An infrared LED and a detector are separated by a wall and never “see” each other directly. Only when a fine particle enters the LED’s beam does the detector detect a flash. The sensor counts these flashes and, based on their intensity, determines whether the particle is large (bright, PM₁₀) or very small (dark, PM₁).

The advantage of the sensor used is its very high measurement accuracy, comparable to that of very expensive particle counters. The disadvantage of this measurement principle is cross-sensitivity to water vapor or fog. These fine water droplets also produce a flash at very high relative humidity (> 90%) and are counted as fine particles.

Measure PM₁, PM₂,₅, and PM₁₀:

To determine the causes of dangerously high levels of fine particulate matter in indoor air, an indoor air quality monitor such as the air-⁠Q—which can measure different sizes of fine particulate matter (PM₁, PM₂,₅, and PM₁₀)—can be helpful. The air quality monitor can be ordered from the online store.