Ultrafine particles: what they are, health risks and how to measure them accurately

At first glance, the air around us may seem clean, but beware, it hides an almost imperceptible danger: ultrafine particles (UFP). With a size so small they are hard to detect, they are one of the greatest threats to public health caused by air pollution.

Their origin lies in combustion engines and industrial processes. However, measuring their presence is not easy. Ultrafine particles float irregularly in the air, with concentrations that vary throughout the day, often eluding traditional surveillance systems.

But their microscopic size doesn’t make them harmless—on the contrary, they are highly aggressive. Being so small, they penetrate deep into our lungs, reaching the alveoli, and from there can enter the bloodstream. Continuous exposure to these tiny particles has been linked to increased respiratory issues, cardiovascular diseases, and even higher mortality.

In the battle against air pollution, size does matter—and ultrafine particles are the proof. Combating them requires their inclusion in environmental regulations. Advanced technologies such as those from Kunak, capable of detecting and measuring their concentration in real time, provide essential support. Because only through constant monitoring can we reduce the risk they pose to our health.

What are ultrafine particles?

Ultrafine particles are a type of particulate matter with an aerodynamic diameter of nanometric proportions: less than 0.1 micrometers (µm) or 100 nanometers (nm). Due to their extremely small size, they exhibit different physical and chemical properties compared to larger suspended particles (PM₁₀ and PM_2.5), such as a greater surface-to-volume ratio, higher ability to penetrate the human body, and increased tendency to aggregate or react with other atmospheric pollutants.

In addition to the size difference PM₁₀ (≤10 µm), PM₂.₅ (≤2.5 µm)and UFP (≤0.1 µm), airborne particles are differentiated by:

Penetration

• UFP (≤0.1 µm): Reach alveoli and bloodstream. Greater health risk.
• PM_2.5 (≤2.5 µm): Remain in bronchi and alveoli.
• PM₁₀ (≤10 µm): Trapped in upper respiratory tract like nose and throat.

Suspension time

• UFP: Stay airborne from minutes to hours, can aggregate or deposit quickly.
• PM2.5: Remain for days or weeks.
• PM10: From hours to days.

Origin

• UFP: High-temperature combustion and exhaust gas emissions.
• PM_2.5: Industrial and combustion sources.
• PM₁₀: Construction, agriculture, and natural erosion phenomena.

Main sources of ultrafine particles

Although ultrafine particles can be generated from natural sources such as volcanic emissions (ash and gases that condense upon cooling), marine aerosols formed by breaking waves in rough seas, or forest fires, their main source of emission stems from anthropogenic activities. Among these, vehicle traffic (especially diesel engines) and industrial processes stand out as the most significant sources in terms of volume and human exposure.

These human-origin sources present two critical characteristics:

• Continuous and concentrated emission: unlike natural sources (sporadic or seasonal), anthropogenic activities release UFPs constantly, reaching high concentrations in urban environments, port areas, and regions near airports.
• Potential for atmospheric reactivity: UFPs interact with other primary pollutants such as nitrogen oxides (NOx) and sulfur dioxide (SO₂), leading to the formation of secondary pollutants (e.g., particulate nitrates and sulfates). This chemical transformation capacity increases their impact on both air qualityAir quality refers to the state of the air we breathe and its composition in terms of pollutants present in the atmosphere. It is considered good when poll...
  Read more (contributing to smogSmog, beyond that dense fog Smog is a mixture of air pollutantsAir pollution caused by atmospheric contaminants is one of the most critical and complex environmental problems we face today, both because of its global r...
  Read more that accumulate in the atmosphere, especially in urban areas. This phenomenon is character...
  Read more and PM₂.₅ formation) and public health, by facilitating their penetration into the respiratory and circulatory systems.

As a result, anthropogenic UFPs represent a high-priority challenge for air pollution control policies, given their persistence, synergistic potential with other pollutants, and proven adverse effects on ecosystems and human health.

How do ultrafine particles affect human health?

Ultrafine particles represent a significant risk to human health due to their ability to cross primary biological barriers (pulmonary alveoli, nasal epithelium), their high chemical reactivity, and their potential to induce oxidative stress and inflammation.

Unlike larger suspended particles (PM₁₀ or PM₂.₅), ultrafine particles penetrate these critical biological barriers, triggering adverse effects at the level of:

Inhalation and respiratory effects

When inhaled, ultrafine particles exhibit a 90% alveolar retention efficiency. Their high surface-to-volume ratio facilitates the absorption of previously adsorbed toxic compounds (heavy metals, aromatic hydrocarbons). After depositing in the alveoli, they cross the alveolar-capillary barrier through translocation, entering the bloodstream and distributing systemically to target organs and distant tissues.

Cardiovascular and neurological impact

In the cardiovascular system, ultrafine particles reduce the bioavailability of nitric oxide (NO), promoting vasoconstriction and the formation of atherosclerotic plaques. In this way, they increase the risk of arterial thrombosis by activating platelet aggregation and raising levels of the protein (fibrinogen) involved in blood clot formation.

At the genetic level, ultrafine particles contribute to DNA fragmentation and induce mutations in pulmonary epithelial cells exposed to them. They also cause epigenetic modifications (changes in genes due to environmental exposure) associated with chronic diseases and developmental alterations in fetuses.

Due to their ability to easily penetrate the human body and their cumulative effects, ultrafine particles not only damage the lungs and heart but also directly affect the brain, increasing the risk of developing neurodegenerative diseases such as Alzheimer’s and Parkinson’s, as well as cognitive impairments in children exposed to them.

Special risks for vulnerable populations

Children, the elderly, and people with pre-existing respiratory and cardiovascular conditions are the most susceptible to ultrafine particle exposure. Children are more vulnerable due to their incomplete lung development and higher respiratory rate. In older adults, their lower antioxidant capacity and pre-existing comorbidities make them more vulnerable. For pregnant women, breathing ultrafine particles in the environment increases the risk of placental inflammation, which can lead to premature birth and low birth weight in newborns.

In summary, the evidence of the risks that ultrafine particles pose to public health leaves no doubt: it is necessary and urgent to implement their monitoring (currently absent in most environmental regulations and policies) to measure and control their presence and concentration in the air at all times. In addition, mitigation techniques can be employed, such as installing filters in indoor spaces, stricter regulations on vehicle emissions, and promoting a transition to clean energy sources.

Environmental impact of ultrafine particles

Ultrafine particles pose an environmental challenge with two critical aspects: on one hand, they deteriorate air quality, and on the other, they interact with the global climate system. Their small size and high reactivity make them agents with disproportionate effects relative to their mass, acting directly on:

Air pollution and climate change

Ultrafine particles are a highly problematic component of air pollution due to their high atmospheric mobility. Their nanometric size allows them to disperse over long distances and persist in suspension for extended periods. In addition, they play an important role in atmospheric reactions by acting as active surfaces for the formation of secondary pollutants: PM_2.5 suspended particles, gaseous precursors (NOx, SO₂), and tropospheric ozoneTropospheric ozone (O3) or ground-level ozone is a gas found in the lowest layer of the Earth's atmosphere, the troposphere, which extends up to 10 kilomet...
Read more.

Ultrafine particles interact with climate processes through radiative effects (scattering of solar radiation, absorption of radiation when forming black carbon particles); they modify cloud properties by acting as condensation nuclei; and alter the reflectivity and persistence of existing clouds. Lastly, they cause significant global damage to ice and snow masses by altering their albedo, accelerating melting processes, especially in polar and glacial regions.

For all these reasons, controlling UFPs is essential through strengthened implementation of monitoring systems that allow for their detection, measurement, and atmospheric modeling, as well as for their capture and filtration. These measures must be inseparable from coordinated policies on air quality and climate.

Accumulation in urban and rural environments

Ultrafine particles accumulate differently in urban and rural environments:

Urban environments

• Greater accumulation due to local emissions such as vehicle traffic, airplanes, and industry.
• Faster deposition because of the high presence of impervious surfaces like asphalt or building facades.
• Distribution in heterogeneous spatial patterns, with higher incidence in hotspots such as main roads, port areas, and airports.

Rural environments

• Development of atmospheric transport that travels long distances.
• Very different deposition depending on surface type, with preference for vegetative cover.
• Persistence in soil due to lower disturbance.

Ecosystem alteration

The presence of ultrafine particles in the environment causes ecological impacts with differentiated effects on:

Flora

• Blockage of plant stomata reduces gas exchange.
• Disrupt photosynthetic function, decreasing it by up to 20% in polluted areas.
• Promote bioaccumulation of adsorbed heavy metals (lead and cadmium) in plant tissues.

Fauna

• Direct toxicity in pollinating insects, causing oxidative stress (e.g., in bees) and reduced biodiversity.
• In heavily affected bird populations, such as urban birds, cause respiratory damage similar to human COPD.
• Amphibians are impacted by endocrine disruptions.

Soils

• Alteration of soil microbiota by reducing nitrogen-fixing bacteria.
• Cause changes in physicochemical properties such as pH and conductivity.
• Accumulate in the surface layer (0–5 cm), limiting leaching functions.

Water

• Enter aquifers through urban runoff.
• Damage phytoplankton by inhibiting growth.
• Cause harm that spreads throughout aquatic food chains.

Current technologies for measuring ultrafine particles

Accurate measurement of ultrafine particles is a challenge due to their tiny size, complex dynamics, and the limitations of available technologies.

Limitations of conventional systems

The main current techniques for the detection and characterization of ultrafine particles are based on condensation particle counters (CPC), optical nanoparticle counters (OPC-Nano), diffusion charging sensors (DISC), electron microscopy (SEM/TEM), and scanning mobility particle sizers (SMPS).

These are conventional systems that face limitations such as their high operational cost, reduced sensitivity below 10 nm, lack of adequate spatial representativeness, and measurement accuracy affected by environmental interferences.

Solutions based on next-generation sensors

However, emerging innovations such as Kunak’s compact stations are overcoming these barriers thanks to the use of advanced technology that enables continuous and real-time monitoring. In addition, their ease of installation and maintenance offers high spatial resolution, making it easier to implement more effective regulation of these invisible but omnipresent particles.

Why is it crucial to measure ultrafine particles?

While PM₁₀ and PM_2.5 are monitored and regulated by current international and national standards, ultrafine particles pose a greater challenge due to their multifaceted impact, difficulty of detection, higher toxicity, and adverse influence on atmospheric processes. With their unique characteristics and atmospheric dynamics, they represent an invisible risk that demands more advanced technological and policy solutions to overcome the limitations of conventional equipment.

Emerging standards and regulatory demands

Unlike PM₁₀ and PM_2.5 particles, which have been regulated for decades, ultrafine particles have until recently lacked specific standards for their monitoring, despite their proven toxicity. This is due to the technical limitations for their detection and correct measurement in situ. Moreover, because they are light but numerous, they are beyond the control methods based on particle mass.

However, in 2021, the World Health Organization (WHO) included for the first time explicit recommendations to monitor ultrafine particles, based on their harmful ability to penetrate primary biological barriers (alveoli, placenta) and to induce oxidative stress.

In this regard, the WHO provides guideline values to monitor particle number concentrations in vulnerable environments such as urban areas. It does so based on particle size, exposure peaks near locations like airports, highways, and industrial zones, and with a preventive approach, without defining a numerical range due to the current lack of conclusive data.

Europe is leading the technical and legal standardization of ultrafine particles, but still faces challenges to resolve within Directive 2008/50/EC. Although focused on PM_2.5 and PM₁₀, this directive includes amendments under discussion to ensure ultrafine particles are incorporated into regulatory procedures.

Relevance for cities, ports, and industries

Ultrafine particles are a critical indicator of air pollution caused by anthropogenic sources, especially in areas with a high density of emissions such as cities. Urban traffic alone can generate up to 80% of ultrafine particles, alongside productive activities like construction and heating systems using fossil fuels and biomass.

To these emissions we add those from port facilities, which—through machinery and shipping traffic—release ultrafine particles, heavy metals (vanadium, nickel), and black carbon. Industrial combustion processes and manufactured nanomaterials also contribute to the presence of ultrafine particles in the atmosphere.

Sustainability strategies to reduce and control emissions of ultrafine particles into the atmosphere are based on:

• Transport and Urban Mobility: Limiting diesel-powered vehicles, especially in low-emission zones, can reduce ultrafine particle presence by up to 30%. Electrification of vehicles and port machinery and the use of advanced filters (GPF/DPF) also contribute.
• Capture Technologies: Hybrid industrial electrofilters used in cement plants can reduce ultrafine particle emissions by more than 90%. Ports implement dust suppression systems.
• Urban Planning: Creating green corridors and implementing real-time air monitoring are proven allies in reducing ultrafine particles.

How Kunak helps accurately measure ultrafine particles

The environmental challenge posed by ultrafine particles can be addressed using Kunak’s technology, designed to overcome key obstacles such as limited scalability and incompatibility with large-scale monitoring networks caused by the complex physical behavior of UFPs.

Key features of our stations

Kunak’s technology enables the precise measurement of ultrafine particles with advanced sensors integrated into patented smart cartridges. These are low-maintenance, highly reliable, and easily deployable in complex, saturated environments such as port facilities, urban areas, or the chemical industry.

 

The sensors integrated in Kunak AIR stations can detect particles from 7 nm to 2.5 µm, enabling the monitoring of UFPs, PM₁₀, and PM_2.5 in real time with a single device, maintaining accuracy despite environmental factors like humidity and temperature, thanks to advanced correction algorithms.

Use cases and benefits for your projects

Kunak has succeeded in adapting the precision achieved in the laboratory to any environment. The robustness, scalability and compliance with current regulations make its monitoring networks a strategic ally for industry and urban environments. They enable informed decision making, based on the analysis of sensor data, which reduces environmental impact and health damage while promoting a transition to clean air.

Cemex

The measurement of ultrafine particles using Kunak technology has proved essential for Cemex cement factory in Monterrey, Mexico. The technical accuracy developed, using advanced sensors equipped with high-precision lasers to measure UPF, PM_2.5 and PM₁₀ concentrations, identifies emission sources and their propagation patterns in real time. Properly determining and measuring these direct emissions contributes to improving the company’s ESG or environmental, social and corporate governance, as well as improving its operational efficiency, optimising filtering systems and production schedules among other factors; also, by reducing emissions, it prepares the company to comply with regulations when they are finally implemented.

Balearic Islands Port Authority (APB)

The Kunak sensors installed in the ports managed by the Balearic Islands Port Authority (APB) make it possible to monitor atmospheric pollution with a special focus on particulate matter (including UPF together with PM_2.5 and PM₁₀) as well as nitrogen oxides, sulphur dioxide and VOCs. These are the main emissions from ships and their heavy fuel and from logistics operations. Such monitoring reinforces compliance with regulations, minimises the impact of port activities as well as the berthing of large vessels. With the data provided, it supports better port management.

Bilbao

The control of air pollution generated by urban and industrial traffic in a city of complex geography such as Bilbao has prompted the deployment of a dense network of air quality monitoringControlling air quality is an essential task in order to enjoy optimal environmental conditions for healthy human development and to keep the environment i...
Read more throughout the city that measures suspended particles (including PUFs), CO, NO, NO₂, O₃, H₂S and VOCs and ambient noiseImagine waking up every morning at 5:00 a.m. to the relentless roar of a motorway just metres from your window. Experiencing such high-intensity noise is n...
Read more. This allows high spatial resolution for detailed mapping of pollution hotspots. Urban environment monitoring facilitates regulatory compliance, traffic management and urban planning, as well as early warning of potential public health risks.

Frequently Asked Questions (FAQ) on ultrafine particles

What are ultrafine particles (UFPs)?

Ultrafine particles (UFPs) are microscopic air pollutants with a diameter of less than 0.1 microns (100 nanometres), equivalent to one-thousandth the thickness of a human hair. They are invisible to the human eye and can penetrate deep into the lungs and even reach the bloodstream.

Where do ultrafine particles come from?

Ultrafine particles are generated by physical and chemical processes mainly from direct emissions such as diesel engine combustion, industrial processes, heating, aircraft and biomass burning. They can also cause chemical reactions in the atmosphere when combined with other pollutants in the air.

How do ultrafine particles affect health?

Due to their tiny size, ultrafine particles can travel long distances inside the human body and reach organs far from the lungs and vital organs such as the brain, heart or liver. In doing so, they cause inflammation, oxidative stress, respiratory and cardiovascular diseases and neurological damage.

How can ultrafine particles in air be measured?

The measurement of ultrafine particles requires specialised equipment that measures the concentration in real time. Some are based on electrical mobility such as the spectrometer (SMPS) and mobility analyser (DMAS). Another technical range uses condensation for measurement such as the condensation particle counter (CPC) or the nanoparticle counter (NPC). Systems based on optical techniques have optical particle counters (OPC) that use laser light scattering, and time-of-flight size spectrometers for detection.

Are ultrafine particles regulated by current legislation?

At present, ultrafine particles are not specifically regulated by any international or European legislation. However, the WHO, in its new air quality guidelines, recognises that ultrafine particles are more harmful than PM_2.5 due to their high lung penetration capacity, but does not set limits due to lack of conclusive data.

Conclusion

Ultrafine particles go unnoticed by the naked eye, but their effects on our health make them impossible to ignore. Increased respiratory and cardiovascular diseases and neurological damage await us if industrial efficiency is not optimised and current regulations are not updated to include these dangerous particles for health and the environment. On-site solutions exist, they require advanced technology such as Kunak’s to anticipate the risk of exposure. The affordable cost and accuracy means that breathing ultrafine particles is no longer an intractable environmental problem.