RIVM conducts independent scientific research on the effects of different inhaled particles and substances on human health. Knowledge of inhalation toxicology helps RIVM to maintain its authority and scientific reputation, and is essential for providing policy advice on various topics. Collaboration in this area is crucial, as it fosters a strong knowledge network and enables the publication of scientific papers. To facilitate such collaboration, RIVM invests in its own measurement and exposure facilities.

Air pollution

Scientific research shows that even small amounts of hazardous airborne substances can cause adverse health effects. Studies on the topic are conducted globally, with a primary focus on fine particulate matter, ozone, and nitrogen oxides, but also on complex mixtures such as diesel emissions and wood smoke.

Epidemiological research examines the relationships between (estimated) exposure to a substance and negative health outcomes. This type of research does not necessarily prove that adverse effects are directly due to the exposure. To establish a causal relationship, toxicological research is required.

Fine and ultrafine particulate matter

Toxicological research on fine particulate matter helps to identify the components that contribute to harmful effects and the extent of these contributions. Such knowledge can help to pinpoint emission sources, supporting more effective policy decisions.

Ultrafine particles are a component of air pollution and will be receiving increasing attention in coming years. At present, ultrafine particles are excluded from air quality standards to a certain extent. RIVM has measured elevated levels of ultrafine particles around airports, including Schiphol. Emissions from the Rijnmond area also contain relatively high levels of ultrafine particulate matter. RIVM aims to address questions such as the comparative harmfulness of ultrafine and fine particulate matter (PM2.5). We also want to determine whether specific sources of ultrafine particulate matter affect the health impact. Various sources, such as wood smoke and wear from tyres and brakes, are under investigation.

RIVM conducts research on the health effects of air pollution components found both indoors and outdoors, including:

  • Fine particulate matter (PM10 and PM2.5)
  • Ultrafine particulate matter (PM0.1); very fine particles emitted by sources such as traffic and industry
  • Soot, brake dust and tyre particles
  • Nitrogen oxides (NOx)

This research aims to understand how these air pollution components affect the lungs, heart and vascular system. We also investigate the concentrations at which health risks arise. Findings from such research support the establishment of air quality standards and inform policy decisions.

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Microplastics

Microplastics are everywhere in the environment, yet the risks to human health and ecosystems are poorly understood. Microplastics are tiny, solid synthetic particles smaller than 5 mm. They do not dissolve easily in water, are resistent to degradation and can be present in the air. Microplastics can break down into even smaller particles and inhaled.

Microplastics, and even smaller particles such as nanoplastics, like nanomaterials, can vary in their chemical composition. This variability complicates their risk assessment. Insights gained from nanomaterial research can help to evaluate the potential health risks of microplastics and nanoplastics.

Nanomaterials and complex materials

It is well known that inhalation is the primary route of exposure to nanoparticles, both at work and through consumer products. Due to their miniscule size, these particles can spread throughout the body, potentially damaging systems such as the central nervous system, reproductive system, heart, vascular system and immune system.

RIVM plays a central role in the risk assessment of new substances. This makes it crucial for us to be sufficiently knowledgeable about the potential health effects of exposure to these materials. 
In recent years, we have gained extensive knowledge on simpler nanomaterials like cerium oxide, zinc oxide, and silica. Now trends are shifting towards the production of more complex and composite materials, referred to as advanced materials. These materials possess new properties and can be on the market already or still at the research and development stage.

There is no official international definition for advanced materials at present. Depending on the dimensions, some of these materials may also be classified as nanomaterials. Like ‘conventional’ nanomaterials, there is a risk of exposure via inhalation for both workers and consumers. However, little is known about emissions of these materials in different applications.

  • RIVM studies:
  • Behaviour of advanced (nano)materials in the lungs
  • Ability of advanced materials to cause inflammation or tissue damage
  • Advanced materials’ ability to spread through the body

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Source-oriented research

There is increasing interest in the contributions of different sources to the toxicity of air pollution. While past research focused primarily on combustion engines, current studies examine emissions resulting from wear and tear of tyres, road surfaces and brakes, aviation (e.g. emissions from turbine engines) and the petrochemical industry.

For policymakers, a source-oriented approach can be efficient and effective. Sectors such as aviation and shipping are significant sources of emissions of (ultra)fine particulate matter. Wood smoke is also under investigation, as this mixture is considered a nuisance and source of concern to citizens. Research is underway to determine the harmfulness of smoke from modern wood-burning stoves compared to older models. RIVM is also investigating the impact of practices such as burning overly damp wood or excessive quantities on the toxicity of wood smoke.

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Chemical substances

RIVM researches the health risks of inhaling various chemical substances:

  • Industrial chemicals
  • Solvents
  • Pesticides
  • Substances released during fires and other incidents

The research primarily focuses on:

  • Acute hazards from short-term exposure
  • Chronic effects of long-term exposure
  • Effects on the airways, lung tissue and immune system

This research is essential to support risk assessments for both workers and the general public.

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  • Risico's van stoffen (in Dutch)

Indoor environment

People are exposed to a range of substances in their homes. RIVM conducts various research on indoor air quality in houses and buildings. In 2022, RIVM started a pilot study of the indoor environment to investigate the effects of homes’ increased sustainability on indoor air quality.  In addition, RIVM is working on a method to assess the risks of combined exposure to multiple substances.

RIVM receives inquiries from various parties on these topics, and demand is only expected to increase. That means there is an ongoing need for experimental research, especially in the area of combined exposure.

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Alternatives to animal testing

RIVM is committed to finding alternatives to animal testing, also in response to policies in the European Union and the Netherlands. One such alternative is the use of in vitro tests, such as lung cell models, as part of an approach known as ‘Intelligent Testing Strategy’ (ITS). This approach focuses on screening and prioritising materials based on the potential hazards.
In addition, there is a strong focus on the use of ‘new approach methodologies’ (NAMs). These aim to reduce the reliance on animal testing and allow greater numbers of samples to be tested quickly. This, in turn, enhances our understanding of how various substances may adversely affect human health.

NAMs can also be part of a ‘Safe-by-Design’ strategy. By modifying certain properties of a nanomaterial or complex material, researchers can explore ways to enhance the material’s safety for human health and the environment. The introduction and further development of an Air-Liquid-Interface exposure system, along with the use of organ-on-a-chip techniques, may support these efforts. Additionally, there are test tube methods available for initial assessment of the reactivity of a substance or mix of substances in air, providing an early indication of hazardous potential.

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Distribution in the body

When substances are inhaled, this exposes the lung tissue. Whether this results in damage depends on the specific area of the lung and the extent of the deposition. Information on lung deposition is also essential to be able to apply results from animal testing to humans. RIVM uses computer models such as the Multiple Path Particle Dosimetry Model to make this conversion and has played a key role in its development.

For the development of in vitro models such as air-liquid-interface models, it is important to know how much of a substance actually reaches the cells. This too requires the design of new computer models.

RIVM investigates how (nano)particles deposit in the lungs and their distribution through the rest of the body. Understanding the fate of these particles in the body helps identify and test in vitro models for other organ systems. In addition, this information improves insight into the accumulation of particles in specific organs and the potential for long-term harm due to exposure to low doses of particles. Experience gained through this type of research is important for the development of OECD test guidelines and guidance on best research practices.

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