Measuring PM in tunnels
The Importance of Measuring PM1.0, PM2.5, and PM10
Particulate matter (PM) pollution in road tunnels poses a serious health risk due to limited ventilation and high vehicle traffic. Monitoring PM1.0, PM2.5, and PM10 in these enclosed spaces is essential to protect public health. Our research highlights the importance of real-time PM monitoring to reduce exposure risks, raise awareness, and create safer environments for everyone on the road.
What is in the air?
PM10 – Dust, pollen
PM2.5 – Exhaust, combustion
PM1.0 – Ultrafine particles
Where It Comes From?
Combustion engines
Brake & tire wear
Resuspended dust
Atmospheric reactions
Who's at Risk?
Tunnel Users
Tunnel workers
Pedestrians & cyclists
Daily commuters
PM1.0 provides the biggest health risk due to having the deepest lung penetration.
Cleaner Air Starts Below Ground
Air pollution is a major global health concern, and particulate matter (PM) is one of its most dangerous elements. Road tunnels, with their enclosed design and heavy traffic, often trap high levels of PM – far more than what’s found in open urban air. These particles, from vehicle emissions, brake wear, and dust, pose serious risks to both workers and the public, especially as tunnels increasingly welcome pedestrians and cyclists. Real-time PM monitoring in tunnels is a vital step toward safer, healthier environments underground.
Sources, Characteristics and Dangers of PM in tunnels
The composition and size distribution of PM in tunnels is influenced by multiple factors:
Combustion Emissions
Diesel and gasoline engines emit fine and ultrafine particles, including soot and organic compounds.
Non-Exhaust Emissions
Mechanical wear from tires, brakes, and road surfaces contributes significantly to PM10 and PM2.5 fractions.
Resuspension
Vehicle-induced turbulence lifts settled dust back into the air.
Particulate Formation
Volatile organic compounds (VOCs) and nitrogen oxides (NOx) can undergo chemical reactions to form secondary aerosols.
PM1.0, in particular, is dominated by combustion-origin ultrafine particles, which are biologically more reactive
and capable of deeper penetration into the human body.
Measurement Technologies and Strategies
Real-time measurement of particulate matter concentrations in road tunnels and underground railway structures is crucial for maintaining safe air quality. It enables compliance with occupational health standards such as OSHA and the EU Directive 2008/50/EC, supports the timely activation of ventilation or filtration systems, and informs decisions on traffic regulation or tunnel closure during pollution peaks. Additionally, this data is valuable for epidemiological studies and health risk assessments.
Technologies commonly used include
Optical Particle Counters
Estimate size and concentration based on light scattering.
Gravimetric Samplers
Measure mass concentration over a period
Beta Attenuation Monitors
Provide continuous measurements with
high accuracy.
Laser-based LIDAR systems
Map particle concentrations spatially within.
Human Health Impacts of PM Exposure
PM10 Upper Respiratory Effects
Exposure to air pollution can increase symptoms such as coughing, wheezing, and shortness of breath, contribute to chronic bronchitis, and worsen existing conditions like asthma. These effects can reduce respiratory health and lead to higher rates of hospital admissions, highlighting the serious impact of poor air quality on public health.
PM2.5 Deep Lung Damage
PM2.5 particles are small enough to penetrate deep into the alveolar region of the lungs, where they can cause significant health effects. These include inflammation of lung tissue, altered heart rate variability, and an increased risk of myocardial infarction. Prolonged exposure is also associated with the development of chronic respiratory and cardiovascular diseases, and over time, has been linked to a reduction in life expectancy.
PM1.0 Cellular-Level Damage
PM1.0, composed mainly of ultrafine particles, is of particular concern because it can cross the alveolar-capillary barrier and enter the bloodstream. It is associated with oxidative stress, DNA damage, neuroinflammation, endocrine disruption, and adverse fetal development. Emerging evidence suggests PM1.0 may be more toxic than larger particles due to its high surface area, chemical reactivity, and ability to penetrate deep into body tissues.
Occupational and Public Exposure in Tunnels
Tunnel workers, such as maintenance staff and traffic operators, face increased health risks due to prolonged exposure to high levels of particulate matter. Commuters, cyclists, and pedestrians using tunnels also experience repeated low – to medium-level exposures. Personal exposure depends on factors like the duration of time spent in the tunnel, proximity to emission sources, tunnel design and ventilation, and the type and volume of traffic. Protective measures should prioritize vulnerable individuals, including children, the elderly, and those with preexisting health conditions.
French Alps Road Tunnel Case Study
Discover how the TunnelTech PM Monitor was evaluated during a five-week trial in a 12.87 km road tunnel in the French Alps. The case study compares the monitor’s performance against a reference TEOM analyser, demonstrating accurate, continuous measurement of PM2.5 and PM10 in a demanding tunnel environment while highlighting how particulate levels frequently exceeded WHO guideline values.
Conclusion
Measuring PM1.0, PM2.5, and PM10 in tunnels is a public health imperative. Tunnels represent unique microenvironments where high PM concentrations converge with dense human exposure. By understanding the sources, behaviour, and health impacts of PM within these confined spaces, stakeholders can better protect both workers and the general population. Investing in robust monitoring and mitigation strategies not only enhances tunnel safety but contributes to broader urban air quality goals.
Monitor Particulate Matter with Confidence
Measure PM10, PM2.5 and PM1.0 continuously with the TunnelTech PM Monitor. Real-time particulate monitoring helps optimise tunnel ventilation, improve air quality, protect road users, and support compliance with air quality standards—all with a rugged, low-maintenance instrument built specifically for tunnel applications.
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