# particulate matter

Fine dust is part of the airborne dust . The current definition of particulate matter goes back to the introduced in 1987 National Air Quality standard for P articulate M atter (abbreviated as PM-Standard) represented by the US Environmental Protection Agency ( Environmental Protection Agency ). The original definition of fine dust was based on the Johannesburg Convention from 1959 and provided an aerodynamic diameter of 5 µm as the separating particle diameter . As an air pollutant , fine dust has a negative impact on health, causally on mortality, cardiovascular diseases and cancer, and probably causally on respiratory diseases.

## Categorization

The PM categorization introduced with the US standard represents a fundamental change in the assessment of immissions : While the total immissions were previously considered, the focus is now on the inhalable portion of the immissions. This takes into account the fact that fine particles are only partially retained by the mucous membranes in the nasal / pharynx or by the hairs in the nasal area , while coarse particles do not burden the respiratory tract thoracic airborne dust.

### PM 10

In the first version of the American guideline, the PM 10 standard was defined, for which a limit value has also been observed in the EU since the beginning of 2005 . In contrast to the definition usually given, PM 10 does not represent a sharp division of the immissions with an aerodynamic diameter of 10  micrometers (10 µm); Instead, an attempt was made to simulate the separation behavior of the upper respiratory tract : particles with an aerodynamic diameter of less than 1 µm are fully included, for larger particles a certain percentage is assessed, which decreases with increasing particle size and finally reaches 0% at approx. 15 µm. From a technical point of view, this corresponds to the application of a weighting function (in the technical language separation curve or separation function) to the immissions (in practice this is achieved through a size-selective inlet on the measuring devices). The designation PM 10 is ultimately derived from the course of this weighting function , since at approx. 10 µm exactly half of the particles are included in the weighting.

### PM 2.5

In 1997, the American National Standard for PM was 2.5 adds that the lungs ( alveoli (also called fine dust)) fine equivalent. The definition is analogous to PM 10 , but the weighting function is much steeper (100% weighting <0.5 µm; 0% weighting> 3.5 µm; 50% weighting at approx. 2.5 µm). This much sharper separation can no longer be achieved during the measurement through a special inlet; impactors or cyclones are used for this in practice .

### "Ultra-fine dust"

In addition, ultra-fine particles (UP or UFP, “ultra-fine dust”) are defined as particles with a thermodynamic diameter of less than 0.1 µm. The thermodynamic diameter describes a spherical particle with an identical diffusion behavior as the considered particle.

### Scientific discussion

Glass fiber strips for the detection of fine dust using individual samples

In addition to the PM standard, which divides according to particle size, dust can also be classified according to its nature, origin or other criteria. So while with PM the size-dependent effectiveness is in the foreground, other models break down, for example, under the aspect of material and structural toxicity or according to the causer. A sufficiently complete consideration can only be achieved by including several models. A collection and evaluation concept based purely on a PM would therefore be at least incomplete (and / or misleading) due to the principle involved; likewise any discussion that is limited to the concept of fine dust, while it is about the discussion of air pollutants or air pollution control .

A report in Die Zeit in 2005 with reference to the expert Joachim Heyder provided more details :

"Describing this finest universe just by its weight is not a brilliant idea."

Heyder himself, until the end of 2004 head of the Institute for Inhalation Biology at the GSF - Research Center for Environment and Health , describes the current findings as follows:

"The smaller the particles, the more dangerous they are for people"

Die Zeit continued:

“The weight of individual particles hardly reveals anything about their toxicity. Rather, it is their content and shape, i.e. the chemistry and physics of the particles, such as their size and shape, that determine the degree of danger. "

A general problem of fine dust assessment is therefore the measurement methods used , which often concern the weight of the particles and can be strongly influenced by the moisture content of the particles depending on the weather. Furthermore, with the usual measuring methods there are often deviations in the range of up to 30%, and sometimes even up to 50%. These deviations can initially be avoided by only determining the dry mass of the fine dust, which in turn neglects the effect in the air depending on the condensation . The effect of condensation and agglomeration of particles is greater, the smaller the individual particles are. This is the reason for the expansion of the measuring process from PM 10 to PM 2.5 . A qualitative analysis , however, requires a minimum amount of sample substance, which is often not available with the previous recording methods.

## Emergence

### Main causer and type of sources

Fine dust can come from both natural and anthropogenic (human) sources. Which source dominates in which place depends on the respective local conditions.

The main causes of natural dust pollution (including fine dust) are:

Agriculture also contributes to fine dust emissions. Their average share in European PM 10 emissions was around 9% around 2001, around half of which can be attributed to animal husbandry.

Sources of fine dust emissions from private households are mainly wood heating systems and open chimneys , since the combustion of solid fuels leads to significantly higher fine dust emissions than the combustion of liquid or gaseous fuels.

Dust also arises as a result of the erosion of cement-bound asbestos made of Eternit , which was previously used as roofing material, facade panels, for molded parts such as flower boxes and fences.

In closed rooms, the smoke from tobacco products , laser printers and copiers are sources of fine dust pollution. Emissions of 2 billion particles per printed page are not uncommon with laser printers.

Fine dust can also arise from gaseous precursor substances such as sulfur dioxide, nitrogen oxides, nitric acid, ammonia or organic trace substances. Such secondary particles make up 30% to 50% of the urban background pollution .

Since May 26, 2011, EU citizens have had the opportunity to see exactly who is polluting air in their environment. The European Commission and the European Environment Agency have published new maps in the European Pollutant Release and Transfer Register that show on a scale of 5 × 5 km where emission sources such as road and air traffic etc. a. Emit fine dust. So far, such values ​​were only selectively, e.g. B. for individual industrial plants.

### Situation in Germany

The main causes of the anthropogenic share of fine dust in Germany were still incompletely listed around 2001 (according to the Federal Environment Ministry and supplementary sources):

This resulted in a total of around 205,000 t / year. This figure was incomplete in many ways. For example, fine dust from opencast mines such as open-cast lignite mining was ignored and the proportion of road traffic was initially only partially taken into account: there was no wear from tires , brake pads and road asphalt. Tire wear caused roughly 60,000 t / year (of which PM 10 share around 10%, i.e. around 6,000 t / year) and brake wear 5,500 to 8,500 t / year (mainly PM 10 ) ( Federal Environment Agency 2004). No estimates are known of emissions from the road surface.

In cities, the share of traffic in particulate matter emissions was an estimated 20 percent. The national mean it was around 30 percent. A statement about the absolute conditions could not be derived from this, since the total pollution in urban areas, especially during the winter months, is often strongly dominated by fine dust from heating systems for private, public and commercial purposes.

The Federal Environment Agency points out that on New Year's Eve, fine dust pollution rises explosively from an average value of 22 µg to over 1000 µg per cubic meter of air. It is therefore advisable to limit the fireworks for health reasons. In total, the New Year's fireworks in Germany produce an amount of fine dust in the order of 15% of the fine dust generated annually in road traffic.

In 2005, at 24,000 tonnes, most of the fine dust emissions came from small combustion systems , which today are mainly operated with wood and are subject to the regulation on small and medium-sized combustion systems (1st BImSchV). Oil and gas together contributed only two tons. The fine dust emissions from pellet heating systems were two to eight times lower than that of burning logs, but still a thousand times that of natural gas heating systems. From 2000 to 2005, reductions in particulate matter by means of lower-emission forms of wood combustion were nullified by an increase in wood combustion systems. The fine dust emissions from wood-burning systems exceeded the emissions from road traffic (incineration only) of 22,700 tons. Particularly in weather conditions that limit the air exchange in the air layer close to the ground due to low wind movements in connection with a temperature inversion (cold air on the ground, warm air above), the disposal of vegetable waste by incineration outside of waste disposal facilities leaves the air pollution with fine dust above the current level EU daily mean increase beyond. According to the Federal Association of Chimney Sweepers, around four million chimney, tiled stoves and other fireplaces for solid fuels across Germany do not comply with the required limit values.

## Osh

Conventional values ​​for the inhalable fraction, thoracic fraction and respirable fraction as a function of the aerodynamic diameter according to DIN EN 481

In the area of ​​occupational health and safety, fine dust is regarded as part of the overall dust load, which, in Germany , is defined and monitored in accordance with the Technical Rules for Hazardous Substances (TRGS), like other hazardous substances. Measuring devices that comply with DIN EN 481 should be used to measure dust exposure. This standard defines conventions for the dust fractions , the respirable fraction , the thoracic fraction and the inhalable fraction .

Unless explicitly stated otherwise for a substance , the general dust limit value has been in effect since February 14, 2014 , as defined in TRGS 900 , which is 1.25 mg / for A dust and 10 mg / m³ for E dust .

In the early 1970s , fine dust based on the Johannesburg Convention was included in the list of MAK values ​​maintained by the Senate Commission for the testing of harmful substances .

## reduction

### European Union

Fine dust pollution (PM10) in Europe.

In Europe, limit values ​​for fine dust were set for the first time with Directive 80/779 / EEC of July 15, 1980 (implemented in German law with the Ordinance on Immission Values - 22nd Federal Immission Control Ordinance). This guideline has evolved over the years:

1. Since January 1, 2005, the daily mean value to be observed for PM 10 has been 50 µg / m³ with 35 permissible exceedances in the calendar year. (In Austria, from January 1, 2005 to December 31, 2009, only 30 exceedances per year are allowed)
2. Since 2005 the annual mean value for PM 10 has been 40 µg / m³.
3. Since January 1, 2010, the daily mean value to be maintained for PM 10 may still be 50 µg / m³, the originally planned only 7 permissible exceedances in the calendar year are due to Directive 2008/50 / EC of May 21, 2008 (Annex XI) originally permissible 35 exceedances have been corrected.
4. Since 2010 the annual mean value for PM 10 should only be 20 µg / m³. This has also been eased by Directive 2008/50 / EC, so that the annual mean value for PM 10 40 µg / m³ has continued to apply since 2010 .

If limit values ​​are exceeded, a clean air plan or action plan must be drawn up. Different strategies are pursued in the individual European countries:

• In London , the city toll introduced in 2003 reduced traffic, but fine dust pollution (emissions) remained practically constant. As of July 2005 the fee has been £ 8  . In 2007 the toll zone was enlarged.
• In Italy there are driving bans that apply generally, only on Sundays or alternately to vehicles with even or odd number plates.
• In Austria there are subsidies for particulate filters in diesel vehicles and subsidies for biodiesel . There are also air rehabilitation areas - e.g. B. in parts of the Inn valley in Tyrol or in the greater Graz area as well as fine dust speed limits on various motorways.
• In Germany , the installation of particle filters was subsidized by taxes. In 2008, several municipalities introduced environmental zones that vehicles with high levels of particulate matter are not allowed to enter. Other municipalities are planning to introduce environmental zones over time. The use of particulate reduction systems will be promoted for trucks from 2009 by classifying them in a cheaper toll category for appropriately equipped vehicles.

The particulate filter of the wall-flow principle provide for their high filtration efficiency (> 95%) for total particulate matter an effective way to reduce the particulate emissions are. Bypass filter , even partial flow deep-bed filters, called filter especially the harmful fine particles (PM 10 and smaller) with over 80% of the Total particle mass with up to 40%. Since diesel soot in particular has a carcinogenic effect, particulate filters are useful for diesel engines despite their low overall effect on fine dust pollution.

Switching from vehicles with internal combustion engines to zero-emission vehicles such as electric vehicles or fuel cell vehicles would significantly reduce particulate matter emissions from road traffic. Many cities, such as Stuttgart , therefore already recommend switching to electric vehicles or e-scooters . In the goods segment, it makes sense to shift traffic to modes of transport such as rail and inland waterway vessels , some of which also generate fine dust from combustion, but less from abrasion.

In view of the frequent exceeding of limit values ​​in German cities, many politicians argue that EU Directive 1999/30 / EC should not be complied with and that the limit values ​​should therefore be increased.

The Association of the Automotive Industry considers regular street cleaning in the main roads to be more efficient than solving the fine dust problem by introducing diesel soot filters. According to a study commissioned by the Berlin Senate, 13 to 16 percent of particulate matter pollution should come from deposits on the streets. In order to permanently remove fine dust from the inner cities by machine cleaning the streets, sweepers are required to retain fine dust. From the point of view that smaller particles are systematically more dangerous for humans, the expert Heyder postulates that an assumed or classic sweeper that only reduces particles in the middle and upper range would be quite suitable for ensuring compliance with the limit values but the health would still have no particular effect. As part of the EUnited Municipal Equipment organization , based in Brussels and Frankfurt, a quality seal for street cleaning vehicles has now been defined, which includes the words "PM 10 2008 - Certified" and thus defines a standard in the industry for equipping municipal services. A planned update of the test guidelines up to PM 2.5 is still waiting for an associated EU directive on air pollution control.

Ongoing discussions about the best measure have highlighted the following problem points:

• Fine dust accumulates in the standing air layers.
• In principle, “clean” vehicles can also generate fine dust from brake, clutch and tire abrasion and whirling up, especially if there is already a layer of fine dust close to the ground or the road has been scattered.
• According to the Technical University of Vienna, rail vehicles generate a high level of fine dust pollution by grinding quartz brake sand.
• For reasons of capacity, it is not considered possible for a larger proportion of commuters to switch to public transport only on days with a high concentration of pollutants.
• Instruments to promote the formation of car pools have not yet been developed (e.g. exemptions from the inner city toll for vehicles with multiple occupants). The (automated) control of the occupancy rate is not desired (video surveillance).
• Free public transport campaigns (including SMS- based) have limited success with little effect on the overall exposure.
• The fine dust pollution from wood heating has increased in some regions in the last few years (while pollution from other heating sources tends to decrease to an independent extent).

### Germany

On May 31, 2006, the federal government passed an ordinance on the labeling of low-emission vehicles (labeling ordinance) in accordance with Section 40 (3) of the Federal Immission Control Act. It was intended to help reduce particulate matter pollution, which at the time was often felt to be too high in cities. For this purpose, the ordinance provided for a nationwide uniform labeling of cars, trucks and buses with stickers according to the level of their particulate matter emissions. In addition, a new traffic sign "Umweltzone" has been introduced, which signals a driving ban due to particulate matter. Since then, only vehicles with a specific sticker on the windshield are allowed to drive in such a zone . The GTÜ (Society for Technical Monitoring) in Stuttgart offers a service on its website that can be used to determine which particulate matter sticker is available for which vehicle. However, the effectiveness and legality of the measures were questioned. It is currently also criticized that measures unilaterally geared towards motor vehicle traffic do not take sufficient account of the polluter pays principle, since the fine dust emissions from industry and private combustion plants are not taken into account.

Since measurements on direct-injection gasoline engines have shown that the fuel consumption savings go hand in hand with a considerable increase in fine dust emissions, a political dispute arose when the limit values ​​for the "Euro 6" pollutant standard applicable from 2014 were set. In 2011, manufacturers' associations allegedly campaigned for the limit value to be set higher than for diesel engines. This plan met with harsh criticism from environmental lobbyists. In a survey by the opinion research institute YouGov , 64% of the 961 respondents spoke out in favor of driving bans with high levels of particulate matter in German city centers.

### Fine dust reduction indoors

To this day, particulate matter pollution from tobacco smoke in indoor spaces is often ignored, although it far exceeds all limit values ​​(see section Milan study ).

Other indoor sources of fine dust include laser printers, copiers, candles, cooking activities and vacuum cleaners without filters. In a study by the DAAB and the Society for Environmental and Indoor Analysis (GUI), Mönchengladbach from 2005, a significant increase in fine dust in the indoor air of rooms with smooth floors was found. That would speak in favor of using carpets indoors to reduce exposure to fine dust and thus also the amount of allergenic substances in the room air. According to the measurement results, the arithmetic mean value of the fine dust concentration in rooms with smooth floors is 62.9 μg / m³, well above the legal limit of 50 μg / m³. In households with carpeted floors, the mean value is 30.4 μg / m³, which is well below the limit value. According to a ministry spokesman, the Lower Saxony Ministry of Justice exchanged all 4,033 laser printers in 2012 for low-emission inkjet printers " for the precaution and reassurance of employees " after increased fine dust levels were ascertained in the Burgwedel district court .

### Other countries

Seoul has the highest particulate matter pollution of all 31 OECD capitals . The further expansion of local public transport (see Seoul subway ) is intended to bring about a decline in motor traffic ; In addition, the government wants to give incentives to use less polluting vehicles and to install emission-reducing technology .

### WHO

In view of the health hazards posed by fine dust, the World Health Organization recommends the following limit values ​​for fine dust in its WHO air quality guidelines:

1. Annual mean PM 10 20 µg / m³
2. Annual mean PM 2.5 10 µg / m³
1. Daily mean PM 10 50 µg / m³ without permissible days on which an exceedance is possible.
2. Daily mean PM 2.5 25 µg / m³ without permissible days on which it may be exceeded.

The guideline values ​​of the WHO are thus well below the legally effective limit values ​​of the EU.

## Effects on health

Today, particulate matter is essentially blamed for the health effects of air pollution . At least this does not apply to the natural fine dust from sea salts, as they are considered water-soluble. The effects of the remaining fine dust are the intensification of allergy symptoms , an increase in asthmatic attacks, respiratory problems and lung cancer as well as an increased risk of otitis media in children and impairments of the nervous system. Effects on cardiovascular diseases (e.g. heart attack ) are also assumed. The extent of the impact of particles on the airways depends not only on their chemical composition but also on the size of the particles: the smaller a particle, the deeper it can penetrate the lungs.

Industrial plant for extracting welding fumes

Fine dust sometimes reaches the lungs because the filtering effect of the nasopharynx is insufficient for fine particles with a diameter of less than 10 micrometers. Thus ultrafine particles pass (diameter less than 0.1 microns) up to the alveoli and from there are only very slowly or not removed ( pneumoconiosis ). New studies suggest effects of fine dust on brain function. A connection between particulate matter and lower birth weight is also discussed.

The transfer of fine dust into the blood has not yet been scientifically clarified. While the Ministry for the Environment and Nature Conservation, Agriculture and Consumer Protection of the State of North Rhine-Westphalia assumes that only ultra-fine dusts enter the bloodstream via the lungs, the Swiss Federal Office for the Environment ( FOEN ) even allows this option for PM 10 .

Epidemiological studies have shown an increase of the PM 10 concentration in the outside air by 10 µg / m³ with a highly significant result that the morbidity - measured by the number of hospital admissions due to respiratory diseases - increases by 0.5 to 5.7%, and mortality (the risk of death) increases by 0.2 to 1.6%. The 2001-2004 conducted particulate matter cohort nstudie NRW studied 4,800 women over 60 years and has shown that the stay in an environment with traffic-related air pollutants such as nitrogen dioxide (NO 2 ) and PM 10 -Feinstaub to increased mortality due to cardiovascular diseases cause can.

According to an EU study, 65,000 people die prematurely in the European Union every year from fine dust. Studies by the World Health Organization (WHO), the Ludwig Maximilians University of Munich (LMU) and from the Ruhr area independently come to the conclusion that the current fine dust pollution increases the mortality rate. On average, the studies indicate a reduction in lifespan of around ten months for Germany.

According to calculations by the Federal Environment Agency, an average of around 47,000 premature deaths per year are due to excessive fine dust pollution, for example from acute respiratory diseases or lung cancer.

The Greek health scientist and statistician John Ioannidis criticizes that "prematurely deceased" is a "very problematic measure". Better is the measure of  disability-adjusted life years , in which one counts how many years one has to live with a disability due to a corresponding illness. The mathematician and epidemiologist Peter Morfeld also agrees . He regards such figures as dubious and believes that such calculations are aimed primarily at the public and politicians. They wouldn't have much to do with science .

Because of the linear relationship, there is no harmless concentration of fine dust. For the population of the European Union, the overall exposure to the extent of air pollution (with nitrogen oxides, fine dust and ground-level ozone) results in an average life expectancy that is reduced by almost a year.

A current meta-study shows that concentrations below the applicable EU limit values ​​are dangerous and can lead to lung cancer , especially adenocarcinoma .

In Europe, the increased health risk associated with the increasing use of wood firing, which is being promoted as a “sustainable” form of energy use in connection with renewable energies , is discussed above all .

According to WHO statements, the average lifespan of all Europeans is shortened by an average of 8.6 months and in Germany by 10.2 months as a result of the fine dust. The EU Commission is assuming around 310,000 deaths across Europe, which occur prematurely every year as a result of fine dust pollution.

A study from 2018 shows a connection between fine dust (PM 2.5 ) and ozone (O 3 ) and Alzheimer's disease . 203 residents of Mexico City were examined. It was u. a. examined the incidence of tauopathies and beta amyloid . Exposure to particulate matter and ozone on the USEPA - limits may risk Alzheimer associated according to the study with an increased.

Recent research has shown that the PM 2.5 content of fine dust is particularly hazardous to health, as particles of this size can get into the alveoli. They are no more than the size of bacteria and therefore cannot be seen with the naked eye. Due to the small size of the particles, their long residence time in the atmosphere (days to weeks) and the atmospheric transport distance of up to 1000 km, PM 2.5 is also of international relevance.

A current assessment of the health effects of fine dust by the World Health Organization (WHO) has shown that increased PM 2.5 exposure is related to serious health effects (e.g. cardiovascular diseases). The EU Commission therefore set maximum values ​​for PM 2.5 of 25 µg / m³ in 2015 as part of the “Clean Air for Europe” program.

As it became known in 2019, tiny soot particles that are inhaled by the pregnant woman end up in the circulation of a fetus . According to an empirical study , the dirtier the air, the higher the pollution . Apparently the placenta cannot protect the fetus, as scientists from the University of Hasselt (Belgium) under the leadership of Tim Nawrot found out.

### Dust of natural origin

Sea salts contribute an average of 5 µg / m³ to PM 10, for example on the North Sea island of Norderney . Since they are water-soluble, they are not considered to be relevant to health and therefore do not have to be taken into account in the EU limit values. On the contrary, staying in such air is used as a cure for various respiratory diseases.

After the eruption of Eyjafjallajökull in 2010 , the effects of dust from volcanoes were also examined in more detail. According to the World Health Organization and British trade associations, adverse effects on health cannot be completely ruled out: volcanic ash contains traces of harmful substances such as fluoride or sulfuric acid and can also be allergenic and irritating due to its mineral character .

### Milan study

In 2004, Italian scientists from the National Cancer Institute in Milan compared the particulate matter pollution of a low-emission diesel car when idling with the pollution caused by cigarette smoke. In a garage with a volume of 60 m³, the researchers initially operated a Ford Mondeo turbodiesel for half an hour with the doors and windows closed while idling while determining the particle concentration. The garage was then thoroughly ventilated for four hours and the experiment repeated with three cigarettes, which were burned within 30 minutes. The fine dust pollution in the car experiment was 36 (PM 10 ), 28 (PM 2.5 ), and 14 (PM 1 ) µg / m³, in the cigarette experiment it was 343 (PM 10 ), 319 (PM 2.5 ) , and 168 (PM 1 ) µg / m³. Both findings turned out to be highly significant ( p <0.001 ). According to the conclusion of the scientists, their investigation confirms the high level of fine dust pollution caused by cigarette smoke in closed rooms. In their study, the authors point out that in another, comparable experiment, the fine dust emissions of a diesel engine that was not reduced in exhaust emissions were many times higher even when idling (300 µg / m³ after dilution with 90% air).

In 2019, doubts about the harmfulness of fine dust (and nitrogen compounds) were expressed by 112 pulmonologists. In particular, the undersigned doctors saw “currently no scientific justification for the current limit values ​​for fine dust and NOx”. They criticized the fact that the data used so far were “interpreted in an extremely one-sided way, always with the objective that fine dust and NOx must be harmful. However, other interpretations of the data are possible, if not much more likely. "

In November 2018, on the other hand, the German Society for Pneumology and Respiratory Medicine presented a position paper that detailed the proven health effects of air pollutants on the respiratory tract , the cardiovascular system , the metabolism , the fetus during pregnancy and potentially also on the neurological development in childhood and old age is considered. One of the conclusions of the authors: “Negative health effects also occur below the European limit values ​​currently valid in Germany. So far, no effect threshold could be identified for the scientifically well-studied pollutants, below which the risk to health is excluded. ”The risk from exposure should therefore be kept as low as possible.

In response to the publication of the pulmonologists and the subsequent media response, the International Society for Environmental Epidemiology (ISEE) also made it clear in a detailed statement that recent studies have already proven the harmful effects of air pollutants below the existing limit values.

## Physical Properties

The physics of dust particles in the atmosphere and their numerical simulation are based on the law of mass , momentum and energy conservation . The number, size distribution and composition of particles in the air depend on their entry into the atmosphere ( emission ), the discharge through dry or wet deposition , chemical reactions, physical effects such as coagulation and condensation as well as air movement.

At first, meteorological-chemical models were used for modeling , which had been developed to simulate the behavior of gases in the air. They are known as Chemical Transport Models (CTM). With the help of so-called aerosol modules, it was possible to improve the CTMs and also to better simulate the behavior of particles. CTMs adapted in this way are also known as aerosol chemistry transport models (ACTM).

### Fine dust transport by air

Fine dust particles settle slowly due to their small size. The steady rate of descent with an assumed laminar flow around the particle results from the equilibrium of gravity, buoyancy and frictional force

${\ displaystyle u = {\ frac {d ^ {2} \ cdot \ Delta \ rho \ cdot g} {18 \ cdot \ eta}}}$

( Sinking speed , particle diameter , density difference , gravitational acceleration , air viscosity ) ${\ displaystyle u}$${\ displaystyle d}$${\ displaystyle \ Delta \ rho}$${\ displaystyle g}$${\ displaystyle \ eta}$

By inserting a micrometer particle with a density of 1000 kg / m³ into this equation, one obtains a rate of descent in air ( viscosity about 20 · 10 −6 Pa · s) of about 3 · 10 −5 m / s or 10 cm / hour. In a turbulence-free horizontal flow at a speed of 1 m / s, the particle would lose only 2 m in height over a distance of about 70 km. Smaller particles sink much more slowly, while larger particles with a diameter of 10 micrometers would sink 10 m in one hour.

Dust also follows the streamlines of the air, it is transported with the wind. Under certain conditions, particulate matter can also be transported across continental borders. Dust from outside is also introduced into so-called “environmental zones”.

### Particle size distribution and coagulation

Very small particles with a diameter of less than 0.1 µm result from incomplete combustion or are formed from gaseous precursors . When they meet, they often stick together and form larger particles. As a result, the number of ultrafine particles in the air usually decreases rapidly. This process is known as nucleation , coagulation or agglomeration. Because of their very low mass, ultra-fine dust particles only make a very small contribution to the total mass of the dust, although they are by far the most common particles in the air. The particle number concentration is typically in the range of 5,000 to 50,000 / cm³. A mean particle concentration of 13,000 / cm³ (median 11,500 / cm³) was measured at a measuring station in the Ruhr area, which represents the urban background. At a comparison station on a busy road, the particle number concentration was 25,500 / cm³ (median 18,000 / cm³).

The volume spectrum of dust particles in the atmosphere usually shows a three-peak distribution , so three modes can be recognized. The smallest particles show a peak around the particle radius of 0.018 µm, the nucleation mode. These particles coagulate with other particles within a few hours or days and are thus removed from the air. The nucleation mode can be missing if new nucleation aerosols are not constantly being replenished.

With the somewhat larger particles, the distribution has a further maximum around the particle radius 0.1 µm, the so-called accumulation mode. The gap between nucleation and accumulation mode arises from the fact that one small and one medium-sized particle coagulate more easily than two small ones. These larger fine dust particles with diameters of 80 nm to 1 µm arise from the coagulation of smaller particles or the accumulation of gases. Their length of stay in the atmosphere is comparatively long at several days. Most of them are removed from the air by wet deposition . Such particles can be transported over several thousand kilometers as long as no precipitation falls along their trajectory . If the dilution of the particles is additionally hindered by an inversion layer, high fine dust concentrations can occur at a greater distance from the point of origin.

The third maximum, the dispersion mode, consists mainly of coarse dust blown up from the ground. Such coarse particles with a diameter of more than 1 µm are usually caused by wind erosion or mechanical abrasion .

Fine dust particles are subject to downward sedimentation and diffusion , which allows them to move from high to low concentration. From this consideration it can be deduced that for the meeting of two particles the coagulation rate J is proportional both to the sum of the radii of both particles and to the sum of their diffusion coefficients .

${\ displaystyle J = 4 \ cdot \ pi \ cdot (R_ {1} + R_ {2}) \ cdot (D_ {1} + D_ {2}) \ cdot n_ {1} (\ infty) \ cdot n_ { 2} (\ infty)}$

(Coagulation rate , particle radius , diffusion coefficient , number of particles ) ${\ displaystyle J}$${\ displaystyle R}$${\ displaystyle D}$${\ displaystyle n}$

Radius and diffusion coefficient work in opposite directions. Small particles have a large diffusion coefficient, but they are unlikely to meet due to their small diameter. The influence of diffusion is small for large particles. With two small particles the sum of their radii is small, with two large particles the sum of their diffusion coefficients. The product of the sums remains small in both cases. For two differently sized particles, the coagulation rate is proportional to the product of the larger radius of the large and the higher diffusion coefficient of the small particle. The coagulation rate is therefore highest with particles of very different sizes.

## Law

### European Union

According to Directive 80/779 / EEC, the member states were obliged to comply with the following limit values ​​from April 1, 1983:

• 80 µg / m³ for the median of the daily mean values ​​of airborne dust measured during the year;
• 130 µg / m³ for the median of the daily mean values ​​of airborne dust measured in winter;
• 250 µg / m³ for the 98 percent value of the cumulative frequency of all daily mean values ​​of airborne dust measured during the year; it is only permitted to exceed it once on a maximum of three consecutive days.

The European Court of Justice ruled in 1991 that the Federal Republic of Germany had not implemented the directive in time; however, the limit values ​​were observed. The Federal Republic of Germany cited that the Federal Immission Control Act of March 15, 1974 already ensured protection. In addition, the TA Luft has been adapted accordingly. However, the Commission did not see sufficient provisions in this. Among other things, the court objected to the fact that the scope of the TA Luft did not correspond to the nature of the directive. In particular, "the threshold value from which environmental impacts are to be regarded as harmful is not specified".

Directive 96/62 / EC, passed in 1996, prescribes measurement and information obligations also for fine dust. The European Court of Justice has condemned France and Spain in infringement proceedings for violating this rule.

Directive 99/30 / EC, adopted in 1999, sets the following limit values ​​for the period from January 1, 2005:

• 50 µg / m³ for the 24-hour mean value of PM 10 , 35 exceedances are permitted per year;
• 40 µg / m³ for the annual mean value of PM 10 .

Directive 99/30 / EC also stipulates that the following tightening of the limit values ​​should come into force on January 1, 2010, if they are not changed beforehand:

• still 50 µg / m³ for the 24-hour mean value of PM 10 , however only 7 exceedances per year are allowed;
• 20 µg / m³ for the annual mean value of PM 10 .

This planned tightening was repealed by Directive 2008/50 / EC on May 21, 2008 (Annex XI).

The competent authorities must take countermeasures with action plans at short notice if the limit is exceeded. You are obliged to draw up air pollution control plans if future limit values ​​are significantly exceeded.

The limit values ​​are exceeded in several European metropolitan areas. In 2005, Stuttgart became the first German city to exceed the limit for the 35th time on March 13th. In Austria, particulate matter pollution is greatest in Graz : in 2003 the permissible limit value of 50 µg / m³ was exceeded on a total of 135 days instead of the maximum permissible 35 days. Because of the fine dust allegedly imported from Eastern Europe, on February 8, 2010, the maximum permitted speed on motorways and country roads in Belgium was temporarily reduced to 90 km / h and in Brussels to 50 km / h. On February 9, 2010, a fine dust alarm was also given for the Ile-de-France (“Paris metropolitan area”).

### Switzerland

In Switzerland the limit value for PM 10 for the annual mean value is 20 µg / m³. In densely populated regions and along busy traffic axes, this value was exceeded in the year 2000 and in the winter of 2005 on the Mittelland (Switzerland) .

The limit value for PM 10 as a 24-hour mean value of 50 µg / m³ may not be exceeded more than three times a year. However, this can only be met in a few years and in a few cantons .

The constant exceeding of limit values ​​causes many Swiss people to doubt the credibility of limit values. The daily mean fine dust value was exceeded many times over in February 2006, for example in Lausanne with 223 µg / m³. As an immediate measure, the speed limits on the motorways were reduced to 80 km / h in eleven cantons from February 3 to February 8, 2006 . In certain cantons the lighting of chimneys has been prohibited.

A doctoral thesis by Peter Straehl ( Carcinogenic air pollutants in Switzerland , 2003) shows that around 300 cancer cases per year are caused by "particulate air pollutants" in Switzerland. The reduction of related emissions by z. B. low-emission truck engines will not be implemented at the proposed pace, but in step with the more slowly falling EU standards. On the other hand, construction machines are no longer allowed to be sold in Switzerland without a particle filter. Old machines built before 2000 must be retrofitted by 2015.

After the drought and heat in Europe in 2018 , the Migros Aare cooperative announced shortly before New Year's Eve that it would now permanently stop selling fireworks . In Switzerland, fireworks release 320 tonnes of fine dust per year, which corresponds to 2 percent of annual emissions.

### United States

The 24-hour mean value for PM 10 may not exceed 150 µg / m³ at most once a year (based on a 3-year average). The limit value of 50 µg / m³ for the annual mean was lifted in December 2006 because there was no evidence of health problems after long-term exposure.

For PM 2.5 , the limit value for the mean over three years is 15 µg / m³. In addition, the mean value in the 98th percentile of the 24-hour values ​​for three years must be 65 µg / m³.

The national environmental protection agency, the US Environmental Protection Agency, issued the PM 2.5 limits in 1997, against which industrial organizations and states sued and won in 1999. However, this judgment was overturned in 2001 by the Federal Supreme Court and found that the environmental authority was constitutionally empowered to set limit values ​​and did not need to consider the resulting economic costs. In 2002, a court found that the environmental protection agency had neither exceeded its discretion nor acted arbitrarily.

## Metrological recording of fine dust

The measurement of fine dust can be done on the emission side by means of a two-stage cascade impactor . The first stage is used for coarse separation, while the second stage collects the PM 10 fraction and the final filter collects the PM 2.5 fraction . On the immission side , a gravimetric method is described as a reference measurement method: air containing dust is sucked through a size-selective inlet and passed through a filter . This is then balanced.

In official immission measurements, gravimetric methods serve as a reference method, but also to determine the 24-hour values. Usually, however, these values ​​are only available with a delay of a few days to several weeks, as the loaded filters (or filter magazines) must first be brought from the measuring station to a laboratory and weighed there.

Since the public should be informed hourly at least about the current pollution of the ambient air with the fine dust fraction PM 10 , continuously working methods are also used in the official measuring stations, based e.g. B. on

• Radiometric dust measurement (attenuation of beta radiation when passing through a filter sample),
• the so-called TEOM principle (detuning of the resonance frequency of a flexural oscillator due to fine dust particles),
• Light scattering (so-called aerosol spectrometer).

For the detection of fine dust in the indoor air come among other things

for use. Measured variables are particle mass concentration, particle number concentration, particle surface concentration or particle volume concentration. In order to check the reliability of measurements, corresponding VDI guidelines were developed in Germany in the 1980s by the Air Quality Commission .

## literature

Books:

Essays:

• Joachim Heinrich, Veit Grote, Annette Peters, H.-Erich Wichmann: Health effects of fine dust: Epidemiology of long-term effects. In: Environmental Medicine in Research and Practice , 7, No. 2, 2002, pp. 91–99.
• Working group 'Effects of fine dust on human health' of the Air Pollution Control Commission in VDI and DIN: Assessment of the current state of scientific knowledge on the health effects of particles in the air. In: Environmental Medicine in Research and Practice , 8, No. 5, 2003, pp. 257–278.
• German Allergy and Asthma Association V. (DAAB) Society for Environmental and Interior Analysis (GUI), Mönchengladbach: Study on fine dust pollution in the interior. 2005.
• J. Junk, A. Helbig: The PM10 dust pollution in Rhineland-Palatinate. New legal regulations for fine dust and first measurement results. In: Hazardous substances - keeping the air clean , 63, No. 1/2, 2003, p. 43.
• Christopher Neumaier: The “fine dust ghost” 2005. Real danger or social construction of a risk? In: Christine Pieper, Frank Uekötter (Ed.): From the benefit of science. Contributions to a precarious relationship . Stuttgart 2010, pp. 255-266.
• T. Pregger, R. Friedrich: Investigation of fine dust emissions and reduction potentials using the example of Baden-Württemberg. In: Hazardous substances - keeping the air clean . 64, No. 1/2, 2004, pp. 53-60.
• M. Struschka, V. Weiss, G. Baumbach: Fine dust - emission factors and emissions in small and medium-sized combustion plants. In: Immissionsschutz. (Berlin) 9, No. 1, 2004, , pp. 17-22.
• H.-Erich Wichmann: Fine dust: Air hygiene problem No. 1 - a current overview. In: Environmental medicine in research and practice . 10, No. 3, 2005, pp. 157-162.
• Vera Zylka-Menhorn: Fine dusts - tiny things with a great effect. In: Deutsches Ärzteblatt . 102, No. 14, 2005, pp. A954-A958.
• G. Invernizzi et al. a., Particulate matter from tobacco versus diesel car exhaust: an educational perspective. In: Tobacco Control . 13, 2004, pp. 219-221 doi: 10.1136 / tc.2003.005975 .
• Thomas Gabrio, Gerhard Volland, Irma Baumeister, Josef Bendak, Annemarie Flicker-Klein, Monika Gickeleiter, Georg Kersting, Valentina Maisner, Iris Zöllner: Measurement of fine dust in interiors. In: Hazardous substances - keeping the air clean . 67, No. 3, 2007, pp. 96-102.
• Peter Bruckmann, Thomas Eikmann: Fine dust and human health. In: Chemistry in Our Time . 41, No. 3, 2007, pp. 248-253, doi: 10.1002 / ciuz.200700419 .
• Thomas P. Streppel: Individual legal protection options in air quality law. In: Journal for European Environmental and Planning Law (EurUP). 2006, p. 191.
• Manfred Santen, Martin Wesselmann, Ursula Fittschen, Ruth Cremer, Peter Braun, Anja Lüdecke, Heinz-Jörn Moriske: Investigations into exposure to fine and ultra-fine particles in inhabited interiors. In: Hazardous substances - keeping the air clean . 69, No. 3, 2009, pp. 63-70.
• Thomas Gabrio: Fine dust in office buildings. In: Hazardous substances - keeping the air clean . 70, No. 3, 2010, pp. 63-69.
• Wolfram Jörß, Volker Handke, Lukas Emele, Margarethe Scheffler, Vanessa Cook, Jochen Theloke, Balendra Thiruchittampalam, Frank Dünnebeil, Wolfram Knörr, Christoph Heidt, M. Jozwicka, JJP Kuenen, HAC Denier van der Gon, AJH Visschedijk, RN van Gijlswijk, Bernhard Osterburg, Birgit Laggner, Rainer Stern: Air quality 2020/2030: Further development of forecasts for air pollutants taking climate strategies into account. UBA texts 35-2014. Federal Environment Agency (ed.). Dessau-Rosslau. July 2014. . ( Online (PDF))
• Beate Ritz , Barbara Hoffmann, Annette Peters: Effects of fine dust, ozone and nitrogen dioxide on health. In: Deutsches Ärzteblatt. Volume 116, Issue 51-52, December 23, 2019, pp. 881-886.

Diverse articles:

Wiktionary: Fine dust  - explanations of meanings, word origins, synonyms, translations

Measurement and prediction:

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