Particulate matter, an elusive problem - but what is particulate matter?

• 1. How does particulate matter affect your health?
• 2. How is particulate matter formed?
• 3. What makes particulate matter so dangerous?

1. How does particulate matter affect your health?

In the Netherlands, 11,000 people die prematurely every year because of air pollution. 4 times out of 5, particulates are the cause. Particulate matter leads to human suffering. And don't underestimate the social costs. If you convert the loss of healthy life years into euros, then the particulate matter problem in the Netherlands represents a cost of between 10 to 15 billion euros per year. So it's not surprising that TNO has been researching this issue for years. We are developing technologies to map particulate matter and to combat it at its source.

“Not all particulate matter is harmful as such. It only becomes a problem when it’s ultrafine”

Ultrafine and therefore dangerous

“Particulate matter is a catch-all term for everything floating in the air that is smaller than 10 micrometers”, explains Paula Bronsveld. “Direct emissions of particles into the air, we call primary particulate matter. These include man-made particles such as PAHs and metals. Secondary particulate matter is created by chemical reactions of gases in the atmosphere, such as ammonium nitrate from a combination of ammonia from intensive livestock farming and nitrogen dioxide from other sources.

Not all particulate matter is harmful in itself. It only becomes a problem when it’s ultrafine - less than 0.1 micrometer - or consists of substances that are very harmful to humans. When exposed to it, it can pass through the respiratory tract and into the bloodstream.”

2. How is particulate matter formed and where does it come from?

The largest contribution to particulate emissions in the Netherlands comes from households (mainly due to wood burning), industry and agriculture. Other sources include maritime and inland waterway navigation, road traffic and construction. Different sources cause different particulate mixtures. And some mixtures are more harmful than others.

Bronsveld: “Particulate matter containing metals carries an increased risk to health, especially if the particles are ultrafine. Major sources of metals are wear emissions from road traffic and industrial emissions. Certain organic components in, for example, wood smoke, also pose health risks. Fine particulate mixtures containing harmful substances such as soot and PAHs can also be produced by other combustion processes.”

3. What makes particulate matter so dangerous?

The effect of particulate matter on health depends on what is triggered in the body when exposed to it. This depends on the reactivity of the particulate matter. So you don’t just look at the mass, but also at the shape and size of the particles and at the composition of the particulate matter.

Bronsveld: “The smallest particles, ultrafine particulate matter, are the most dangerous. Not only because they penetrate far into the body due to their small size, but also because they’re often ignored when combating particulate emissions, simply because they are so small. Whereas a hundred fine particles, due to their small size, have a much larger reactive surface area in relation to a much smaller number of larger fine particles that together are of equal mass. This makes the reactivity far greater for a mixture containing many small particles than for a mixture with many large particles.”

Health benefits

TNO uses proprietary technology to measure particulate emissions, and has developed mathematical models to predict dispersion and exposure. For the Ministry of Infrastructure and Water Management, for example, we collect data on the emissions of particulate matter from diesel vehicles. We have also researched how the particulate emissions from fireplaces and stoves can be reduced.

Bronsveld: “We are now even better at analysing air filters and determining the composition and reactivity of particulate matter. Collecting this information will give us the opportunity to combat particulate emissions more effectively than we do currently. This requires a 5-step plan with which we can achieve greater health gains than we are already doing in the Netherlands.”