Category: outdoor

The Hidden Threat in Our Air: Why Measuring Indoor Ultrafine Particles (UFPs) Is a Modern Regulatory Maze

Sotirios Papathanasiou1 Comment

We have spent decades obsessing over PM2.5 —the fine particulate matter small enough to lodge itself in our lungs. We draft laws around it, track it on our phones, and buy home monitors to avoid it. But while our regulatory gaze has been fixed on particle mass, an invisible, almost weightless army of much smaller particles has been slipping through the cracks: Ultrafine Particles (UFPs).

Known technically as PNC0.1, these aerosols have an aerodynamic diameter of 100 nanometers or less. To put that in perspective, they represent a negligible fraction of total ambient mass, yet they often make up over 90% of the total particle number concentration (PNC) in our atmosphere. Because they are so unbelievably small, they don’t just settle in the lungs—they have the unique physical ability to cross into the bloodstream, posing distinct and severe health risks.

Yet, when we step inside our homes, we enter a measurement blind spot. In our current study across two Spanish cities—Granada and Almeria—we exposed a frustrating reality: meeting current PM2.5 standards provides a completely false sense of security when it comes to UFP exposure, and our current measurement tools and guidelines make it nearly impossible to tell if the air we breathe inside is actually safe.

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Review: AirGradient Open Air

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Having had the opportunity to get the AirGradient Open Air (Model O-1PST) at the ASIC 2025 conference in Thailand, complete with its unique engraving, I’ve spent some time with this device, and it’s clear that AirGradient is pushing the boundaries of accessible and reliable outdoor air quality monitoring. This device presents a compelling alternative to existing solutions, particularly for those seeking transparency and robust performance.

Technical Specifications O-1PST

  • WiFi 2.4GHz IEEE 802.11 b/g/n-compliant
  • Bluetooth LE: Bluetooth 5, Bluetooth mesh
  • Status LED
  • Plantower PMS5003T for PM2.5 + ENS210 for T/RH
  • SenseAir S8/S88 CO2 NDIR Sensor
  • Sensirion SGP41 TVOC/NOX Module
  • Enclosure: ASA Plastic, UV Resistant and Weather Proof
  • Mounting Options: Wall or pole mounting options
  • 4m USB-C to USB-A Cable
  • USB-C Power Connector 2A/5V
  • Certifications: CE, RoHS, REACH, FCC

Sensor Selection: A Thoughtful Approach

The Open Air features a well-considered suite of sensors designed for accurate and insightful data. For PM2.5 measurements, it utilizes the Plantower PMS5003T, a sensor known for its reliability and found in other popular monitors like the PurpleAir (though it’s important to note the PMS5003T is a similar but not identical variant).

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Unveiling Urban Health: The ISGlobal Ranking of Cities and its Healthy Urban Design Index (HUDI)

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In an era where urban populations continue to swell, understanding the intricate relationship between city design and public health is fundamental. The Barcelona Institute for Global Health (ISGlobal) has emerged as a leading voice in this field with its “ISGlobal Ranking of Cities” and the innovative “Healthy Urban Design Index (HUDI).” This comprehensive tool sheds light on the health impacts of urban exposures like air pollution, noise pollution, and access to green spaces across nearly 1,000 European cities.

The ISGlobal Ranking of Cities is more than just a list; it’s a dynamic project aimed at quantifying the health burdens attributable to urban and transport planning. It evaluates various environmental exposures and their associated mortality, presenting cities from the highest to lowest mortality due to these factors. You can explore the tool directly on the ISGlobal Ranking of Cities website.

At the heart of this initiative is the Healthy Urban Design Index (HUDI). The HUDI is a composite score that meticulously assesses the extent to which the configuration of European cities supports the health and well-being of their inhabitants. It examines 13 key indicators across four domains: urban design, sustainable transport, environmental quality, and green space accessibility. These indicators include factors such as urban compactness, housing density, walking and cycling infrastructure, public transport availability, air pollution levels, capacity to mitigate heat, and accessibility of green spaces. Each city receives a score between 0 and 10 for each indicator, culminating in an overall HUDI score.

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Top 5 Smartphone Air Quality Apps: 2025 Guide [Updated]

Sotirios Papathanasiou1 Comment

In today’s world, where air pollution is a growing concern, it’s essential to stay informed about the quality of the air we breathe. Fortunately, a variety of smartphone apps can provide real-time air quality data, helping you make informed decisions about outdoor activities and protect your health. Here are five of the top-rated apps to keep you breathing easy:   

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Particle Sizes, Infiltration, and the Indoor/Outdoor Ratio

Sotirios Papathanasiou1 Comment

Particle Sizes

Particle size plays a significant role in determining how particles behave indoors and their potential impact on human health. Fine particulate matter (PM2.5), with diameters of 2.5 micrometers or less, is a major concern due to its ability to penetrate deep into the respiratory system. An important subset of PM2.5 is ultrafine particles (UFPs), which have diameters less than 0.1 micrometers and are primarily emitted from combustion sources. These UFPs can even be transported to the brain via the olfactory nerve, potentially causing neurological effects. Particles in the 0.1 to 2.5 micrometer range can originate from indoor sources like soot or from the infiltration of outdoor particles. Coarse particles, larger than 2.5 micrometers, are mainly generated by mechanical processes like resuspending dust. These size distinctions are crucial because they influence a particle’s ability to penetrate indoors, remain airborne, and affect human health. For instance, the high surface area to mass ratio of UFPs makes them efficient at transporting harmful chemicals deep into the lungs. Understanding the sources and behavior of different particle sizes indoors is essential for developing effective strategies to mitigate their potential health risks.

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Dust Devils of Doom: Sand Storm & Haboob and Their Invisible Assault on Human Health

Sotirios Papathanasiou1 Comment

Recently, I met Dr. Karin Ardon-Dryer and she is my new favorite scientist/superstar because of her research and her charismatic way to share important information to the public. She was able to captivate everyone in the room with her presentation Effect of Dust Particles on Human Health at Miami University.

Sand storms, often romanticized in movies and documentaries, pose a far more significant threat than just a dramatic backdrop. These swirling giants of dust wreak havoc on air quality, carrying not just coarse sand but also microscopic fine particles with serious implications for human health. While sand storms are often associated with arid regions far from home, their reach extends farther than you might think, impacting even areas within the United States. Arizona, New Mexico, Texas, and even eastern California are some of the states that experience poor air quality from such meteorological phenomena.

Haboob vs Sandstorm vs Dust Storms 

  • Haboob (Arabic for blasting/drifting) is a strong wind carrying a mass of dust and sand that has been lifted from the ground in very dry areas such as deserts.
  • Sandstorm is a windstorm especially in a desert, that blows along great clouds of sand.
  • Dust storms carry much smaller particles, which can be carried higher and further than sandstorms. 
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Ventilation Challenges and Pathogen Spread in High-Polluted Environments

Sotirios Papathanasiou3 Comments

Indoor air quality (IAQ) is a crucial aspect of human health and well-being. However, achieving adequate ventilation in homes and other indoor spaces can be challenging, particularly when outdoor air pollution levels are elevated due to smoke from wood-burning stoves. This article explores why poor ventilation in polluted environments poses a heightened risk of pathogen spread.

Factors Hindering Ventilation in Polluted Environments

Wood-burning stoves, used for heating and cooking, release particulate matter (PM), nitrogen oxides (NOx), and carbon monoxide (CO) into the atmosphere. These pollutants can accumulate in extended areas, especially under certain weather conditions. Normally, warm air rising from the ground carries pollution upwards, dispersing it into the atmosphere. However, during the winter, a warm layer of air can settle over a city like a lid, trapping cold air and pollutants near the ground. This phenomenon, known as a thermal inversion, occurs when a warm air mass above restricts the upward movement of cold, denser air, trapping it along with pollutants close to the surface. Thermal inversions are particularly prevalent in cities like Los Angeles, Mumbai, Granada, and Mexico City, where cold, dense air gets confined within mountain basins or valleys.

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Warming Up your Vehicle in Winter is Dangerous for your Health & Illegal (US Version)

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As we face the frigid temperatures brought by polar vortexes in the US, the last thing anyone wants is to enter a freezing cold car. However, it is important to note that in many states, warming up your vehicle by letting it idle is actually illegal.

Regardless of the duration, idling is considered an automatic misdemeanor in most states. Surprisingly, even using the automatic start feature on your car can be against the law in some states. The penalties for idling vary depending on the jurisdiction. For example, in Washington D.C., you could face a $5,000 fine if your car idles for just three (3) minutes. However, some states are more lenient, like Pennsylvania, where idling is allowed for up to twenty (20) minutes when the temperature is below 40ºF (4ºC).

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Outdoor Air Quality Monitors 2023Q4

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What’s new? Well, some clean up of discontinued monitors and some updates. In this list you will find ambient air quality monitors for experts who want to supervise and monitor air pollutants in cities and industrial sites, and commercial outdoor air quality monitors for homeowners who want to check the air quality outside their houses/apartments. 

Air pollution can cause a range of health problems, including respiratory and cardiovascular diseases (CVD), and even premature death. By monitoring ambient air quality, governments and individuals can take steps to reduce exposure to harmful pollutants and protect public health.

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How Easy is for Wildfire Smoke to Travel Across States and Countries

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The animated image below was created by Mark Parrington and was originally publish on his Twitter account on June 6th, 2023.

I believe it is an eye opening animation as it reveals how easy air pollution travels across states and countries. We call this pollution Cross-Border Air Pollution.

2023 Canadian Wildfires and Smoke
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