About particulate matter

This article is written with the intent of clarifying particulate matter, for not only is it an invisible health detriment that surrounds us at all times, it is also accompanied by somewhat confusing and contradictory advice and guidelines. For this purpose, we want to explain in an accessible way what particulate matter is, which guidelines there are, how you can measure it and what to do about it. (The quotes in this article are clickable, but they do lead to Dutch sources. These can be translated by your browser, or translation programs like google translate.)

A preview of what will be discussed:

Particulate matter is usually divided into relatively larger particulate matter (PM₁₀) and smaller particulate matter (PM_2.5) (and sometimes even smaller divisions like PM_1.0).
There are 3 important guidelines you can use to determine acceptable PM levels: the European guideline for particulate matter, the WHO guideline for particulate matter, or the European air quality index (EAQI).
The best solution against particulate matter is good ventilation. A detector can help herein by making clear whether air quality is sufficient, or whether it's subpar and action is required.
Finally, we advise to pay attention to these 3 aspects when looking to buy a PM detector:
1) A good particulate matter detector measures at least both PM₁₀ and PM_2.5.
2) The guideline norms that you intent to follow fall within the minimum and maximum values that the detector can measure.
3) Go for a detector that displays the results in µg/m³.

If there are things you find unclear and you want additional information, or, if you have other questions or comments, you can contact us here!

What exactly is particulate matter?

Particulate matter is nothing more than a collective name for all small particles that float in the air; they are sometimes also referred to as aerosols, particulates or fine dust. Particulate matter is usually divided into the larger PM₁₀ particles and smaller PM_2.5 particles. PM stands for particulate matter , and the subsequent number indicates the maximum diameter that particles have that fall under that term. PM₁₀ particles therefore have a diameter of 10 µm (10 µm = 10 micrometers = 0.01 millimeter) or smaller, and PM_2.5 particles have a diameter of 2.5 µm or smaller. This distinction is made because your body reacts differently to the larger PM₁₀particles than to the smaller PM_2.5 particles. This is reflected in the particulate matter guidelines, which we will return to later in the article.

In addition to PM₁₀ and PM_2.5 , you can also come across the terms PM₁ and PM_0.1. PM₁ particles are even smaller particles with a maximum diameter of 1 µm; and similarly with PM_0.1, which are particles with a maximum diameter of 0.1 µm (equal to 100 nm). PM₁ and PM_0.1 are also known as ultrafine particulate matter (or ultrafine particles). These particles are less common in the news because they are much more difficult to detect and observe. For this reason, no detailed guidelines have been drawn up for ultrafine particulates. However, that doesn't mean they are not dangerous! In fact, they may even prove to be more hazardous than ‘regular’ particulate (source: RIVM). It is therefore quite possible that ultrafine particles will be included in the guidelines in the future. (update: the Dutch health council now advices the government to take action against health detriments by ultrafine particles)

Extra information
Source: RIVM

In addition to the subdivision in size, particulate matter can also be subdivided into:
• Secondary inorganic aerosol This consists mainly of ammonium sulfate and ammonium nitrate. The secondary aerosol accounts for 40% of the particulate matter mass.
• Carbon and carbon containing substances In particular elemental carbon and organic compounds. This component contributes 25-30% to the mass of particulate matter.
• Sea salt aerosols Sea salt consists of 85% sodium chloride ('table salt') with small contributions of magnesium, calcium and potassium compounds. Seas salt contributes about 5-10% to the total particulate matter mass.
• Soil dust Soil dust mainly consists of oxides of silicon, aluminum, calcium, iron and potassium. This contribution is 4-7%.
• Metals The metals that are not part of the soil dust are released during various types of wear and tear processes and in the metal industry. This contributes around 5%.

How harmful is particulate matter?

"It is estimated that about 12,000 people die prematurely every year in the Netherlands due to inhaling particulate matter and other forms of air pollution"

In the Netherlands, several thousand people die a few days to months earlier every year, as a result of short-term exposure to high concentrations of particulate matter. This mainly concerns the elderly and people with heart, vascular or lung disorders. The average Dutch citizen loses 12 months of their life due to exposure to particulate matter (source: RIVM).

Long-term exposure to lower concentrations of particulate matter, even below the European limit values, also has adverse health effects. For the time being, there is no known concentration value below which there are no health effects. Particulate matter is therefore always harmful, but the consequences increase with increased concentration and exposure to particulates. Lifelong exposure can lead to permanent health effects such as a reduced lung function, worsening of respiratory and cardiovascular issues, and premature death.

Although the detrimental health aspects of particulate matter affect the lungs and respiratory tract the most, there is a range of effects all over the body. For example: it may cause Alzheimer's or dementia, negatively affects the eyes, and really the whole body.

"The average Dutch citizen inhales so much particulate matter per week that this is equivalent to smoking 2 packs of cigarettes per week"

Particulate matter standards

Many different guidelines have been drawn up, and the differences can be significant. This makes it confusing to know when the air quality is healthy, or at least acceptable; it can even obfuscates what to pay attention to when attempting to measure particulate matter yourself. Two PM guidelines are used in the Netherlands: the European particulate matter standards, which only deals with particulate matter; and the European Air quality index (EAQI), which shows the general air quality including particulates. There are also many international variants of PM specific guidelines as well as air quality indices.

European and WHO PM guidelines

Particulate matter is usually measured in micrograms per cubic meter (µg/m³), which is useful because particulate matter is often present in a couple of tens of µg/m³; the daily exposure guidelines are therefore also expressed in µg/m³. These standards indicate what the maximum amount of particulate matter in the ambient air should be, which is also referred to as the particulate matter concentration. In the Netherlands we use the European guideline for this. It has 2 different recommendations: the annual average, and the daily average. Please note that this is a guideline, and the associated legislation and regulation varies from country to country.

European PM standards

PM₁₀

PM_2,5

Annual average

40 µg/m³

25 µg/m³

Daily average

*Maximum number of violations per year:

50 µg/m³

*35

The above table shows the European guideline for particulate matter. The annual average indicates the maximum average particulate matter concentration when measuring over a year. So, when measuring over a year, the average particulate matter concentration must remain below 40 µg/m³ for PM₁₀, and below 25 µg/m³ for PM_2.5.

In the same way, the daily average indicates what the maximum average particulate matter concentration may be when you measure over 1 day. For PM₁₀this is 50 µg/m³, and for PM_2.5 no daily average limit has (yet) been established. However, these standards are more lenient in regards to the daily average, which is why the daily PM₁₀ limit may be exceeded for a maximum of 35 days per year.

The World Health Organization (WHO) believes that the guidelines should be a bit stricter. (Update 23-09-2021: WHO has further tightened their PM guideline based on new scientific insights. The annual average of PM₁₀ has gone from 20 to 15 µg/m³, and for PM_2.5 from 10 to 5 µg/m³.) The guidelines of the WHO can be found in the table below:

WHO PM standards update: 23-09-2021	PM₁₀	PM_2,5
Annual average	15 µg/m³	5 µg/m³
Daily average	50 µg/m³	25 µg/m³

In addition to the European and WHO guidelines, many countries have their own national guidelines. This may not be of particular interest to those living in the Netherlands, but it can make a difference when purchasing a particulate matter detector. This will be expanded upon later, but first there is still the Air Quality Index to touch upon.

"Good insulation in (new-build) houses has a downside: it leads to poor ventilation and thus to regular exceedance of particulate matter limits"

The Air Quality Index

In addition to the European particulate matter standards, the European Air Quality Index (EAQI) is also used in the Netherlands. It is similar to the prior used Common Air Quality Index (CAQI), although there are some differences. The European Air Quality Index is not actually intended for particulate matter specifically, but for an assessment of air quality in general. In total, there are 5 different substances on which air quality is assessed: PM₁₀and PM_2,5, as well as NO₂, O₃ and SO₂ (nitrogen dioxide, ozone and sulfur dioxide).

In the table you can see what the concentration assessments are for each substance. The scale runs from left to right (from light blue to purple): good, fair, moderate, bad, very bad, extremely bad. A small difference with the guidelines discussed earlier is that only the concentration of particulate matter (PM₁₀ and PM_2.5) over one day is considered: the daily average – an annual average is thus not included. For the other substances - NO₂, O₃ and SO₂ - the concentration per hour is considered.

The final assessment of the European Air Quality Index is equal to the worst of the five concentrations shown. Is SO₂ evaluated as bad, and all the others as good? Then the EAQI indicates that the air quality is bad. However, some measuring stations cannot measure all substances. In that case, only the substances that can be measured are assumed. Sometimes you’ll come across an AQI referencing a specific substance (also called IAQI). According to European legislation this is not allowed to be displayed as an AQI, but you may encounter this (especially outside Europe).

Comparing the EAQI and European particulate matter guidelines

If you compare the two European guidelines (the particulate matter standards and the EAQI) you will see that the limit of the daily average of PM₁₀(50 µg /m³) corresponds to moderate (moderate). The European particulate matter guideline does not (yet) have a daily average limit for PM_2.5, but if you take the WHO's limit (25 µg/m³), you will see that this is also only moderate (moderate). This means that even if the ambient air is below the standards of the European particulate matter standards, this does not equal healthy ambient air.

So, is there a particulate matter concentration at which health damage does not occur? Not according to the RIVM: 'Epidemiological studies cannot indicate a concentration value below which no health effects are found'. In other words: less particulate matter is always better, and even in the good (blue) part of the index, health drawbacks still occur. And that applies doubly to people with lung and respiratory issues.

Other countries have different AQIs. This can be confusing, as these have their own scale, with different substances included in the index, and different concentration limits. If possible, it is probably easiest to use the European variant, at least then you’ll know for sure that you’re doing (reasonably) well.

How to deal with particulate matter?

"Most exposure to particulate matter occurs indoors"

As an individual it is difficult to influence the outside air quality, the most you can do is to stay away from large particulate matter sources by avoiding carbon combustion such as with open fires, cars or industry. Additionally, it’s good to realize that particulate matter causes more damage during heavy breathing (e.g. sports) because it penetrates deeper into the lungs; breathing through the nose, on the other hand, has a mitigating effect. If you exercise in the city, it is therefore advisable to breathe through your nose as much as possible, especially along busy roads.

Fortunately, we have more control over the air quality indoors. For this, it is important to know where particulate matter comes from: what are the PM sources, and how to deal with them? Indoors, the largest particulate matter sources also come from (carbon) combustion processes: baking, candles, fireplaces, incense and smoking are all sources of particulate matter. But, other activities can also generate or shake up dust, for example vacuuming. The room itself is also important, because it determines how good the influx of fresh air is. In a small room with closed windows, particulate matter peaks will occur more quickly than in a large room with many open windows.

If you want to be sure of the effect that activities such as vacuuming or baking have on the room’s air quality, the best way is to use a PM detector. During the activity, you measure the spaces where the activity takes place and any adjacent spaces that are connected to it. Continue to measure even after the activity is over, as it can sometimes take a long time before the air quality is back to normal. This depends on the ventilation of the room.

Of course, you can also permanently have a particulate matter detector on. This allows you, for example, to check at the end of the day when there were peaks, and which activities were being carried out at that moment in time. In this way you keep expanding your knowledge on PM and which activities in your life cause pollution. Keep in mind that the air quality in different rooms can vary a lot. The most important rooms to keep an eye on are the rooms where you spend a lot of time, for example, the living room and bedroom, as well as rooms with significant PM sources, such as the kitchen (especially when it is connected to the living room).

"A fireplace emits as much particulate matter in 4 hours as a car trip from Brussels to Moscow"

Solutions

If you don't have a particulate matter detector yourself, make sure you regularly air the house: open windows and doors, especially during and after the activities mentioned earlier (such as with combustion processes: baking, smoking, candles). Ventilation works best if there are several (large) windows or doors that face each other. Especially in winter it is important to pay attention to this, because windows and doors are often closed for long periods when it’s cold. Ventilation also lowers the room’s humidity, which is beneficial for energy consumption: dry air heats up faster. Ventilation grilles and extractor hoods can also help with ventilation, but are not always sufficient on their own. Keep ventilation grilles free to allow a good open airflow. An extractor hood that directs air to the outside (exhaust air) works better than a recirculation extractor hood, the latter only removes part of the particulate matter before it blows back into the kitchen. It also requires you to replace the filter regularly, usually every 3 to 12 months, depending on use and product.

Even if you have a PM detector, ventilation is the most important thing. The difference, however, is that you can now see exactly when you need to ventilate, or when it is not so necessary. It may even happen that it is better to leave the room for a while, for example if the particulate matter concentration is far above the daily average limit, or if you are more susceptible to respiratory and lung complications. In addition, it is easier to identify particulate matter sources. This allows you to ventilate better during polluting activities, or you could adjust the activity to mitigate PM generation: e.g. smoking outside, limiting candle burning, or using less heat to bake your potatoes. PM detection simply makes the problem visible, allowing you to respond; it changes particulate matter from a silent ‘killer’ to a better known quantity. It also shows possible weaknesses in your ventilation system, for example, if it takes hours for the particulate matter peak to drop. Are you considering buying a detector? The next chapter expands on this, and here you can see the detector that AeroCount currently sells.

In general, the outdoor air is of better quality than the indoor air. But the reverse can also occur, especially if there are sources of particulate matter in your area, such as a busy road, a lot of industry or animal husbandry. You can see whether this is the case in your area on (Dutch) sites such as luchtmeetnet and samenmeten . AeroCount will also show regional PM values to those who use our products. It is good to consult these sources now and then, not only so that you’ll know for sure whether it is useful to open your windows to ventilate, but also to get a picture of the outside air quality in your location.

Please note that in large parts of the country there are very few detection points, and that a detector can only measure locally. Depending on the situation (wind direction, space ordering, PM sources, etc.), the air quality can be very different even a few streets away. AeroCount aims to expand the air measurement network, which is why our detectors are also suitable for outdoor use. This way you can not only immediately see whether it is useful to open the windows at home, but it is also possible to contribute to the citizen network (if you give permission for this).

Purchasing a detector: what to pay attention to?

Are you considering purchasing a particulate matter detector? Then there are a few things to keep in mind:

First of all, it is important that the detector can measure both PM₁₀and PM_2.5 . Of course, any additional measurement quantities are a plus.

Secondly, it is important that a particulate matter detector has a good range and accuracy (step size). In general, a detector has a good range if what you want to measure is within the minimum and maximum value that the detector can detect. So, if you want to check that the ambient air remains below the daily average standard of 50 µg/m³ (PM₁₀), the range should be, for example, from 0 to 60 µg/m³. Or from 40 to 60 µg/m³, as long as it's in between.

Extra information

Accuracy If you want to know the PM concentration to greater detail, it is useful to look at the accuracy (step size). For example, let’s take a detector with an accuracy of ±10 µg/m³. This means that if the detector indicates the concentration is 20 µg/m³, it can be expected to be within ±10 of that value: the actual concentration can be any value between 10 and 30 µg/m³. If you want the PM₁₀ concentration to never exceed 25 µg/m³, that would be difficult to see with this detector. Even with an accuracy of 5 µg/m³, you are only sure the actual value is below 25 µg/m³ when it displays 20 µg/m³. Using a PM detector with an accuracy of 1 µg/m³ makes it a lot more obvious when the 25 µg/m³ is exceeded. In general, the smaller the step size, the better, but this usually increases the price of the detector.

Finally, it is wise to buy a detector that displays the results in µg/m³. This applies to current measurement as well as to an average measurement over a day or year. This way you can check and decide yourself whether the particulate matter concentration is acceptable. Some detectors only give a good-moderate-bad rating, or a percentage or index from 0 to 100. You should avoid these, because it is not always clear what this rating is based on. Remember the many different international guidelines there are: you are not sure which guideline the detector is set to! For example, a product outside Europe can indicate that the particulate matter concentration is good, while it is bad according to the official European standards. You avoid this with results displayed in µg/m³. Another advantage is that if the guidelines are made more stringent in the future, you will still have the correct information (as an example: Europe is looking to change their guidelines to be in line with the WHO in the future, and the WHO themselves have also changed their guidelines as of September 2021). You can then simply compare the displayed concentration with the new guidelines. This is not possible with a good-moderate-bad or percentage display. Naturally, a good-moderate-bad qualification in combination with a display in µg/m³ is fine (although you should still be mindful of possible guideline changes).

Summary

A brief overview of the points discussed:

Particulate matter is usually divided into relatively larger particulate matter (PM₁₀) and smaller particulate matter (PM_2.5) (and sometimes even smaller divisions like PM_1.0).
There are 3 important guidelines you can use to determine acceptable PM levels: the European guideline for particulate matter, the WHO guideline for particulate matter, or the European air quality index (EAQI).
The best solution against particulate matter is good ventilation. A detector can help herein by making clear whether air quality is sufficient, or whether it's subpar and action is required.
Finally, we advise to pay attention to these 3 aspects when looking to buy a PM detector:
1) A good particulate matter detector measures at least both PM₁₀ and PM_2.5.
2) The guideline norms that you intent to follow fall within the minimum and maximum values that the detector can measure.
3) Go for a detector that displays the results in µg/m³.

Finally, if you are indeed looking to buy a detector, please consider the AeroCount PM Detector!

If you have any questions or comments about this article, please feel free to contact us!