What is PM1?

Particulate matter (PM) less than 1 micron in size is called PM1 (sometimes PM1.0). PM1 is considered especially dangerous due to its extremely small size.

The smaller the diameter of a particle, the more harm it can typically cause. Tiny airborne particles like PM1 are small enough to penetrate lung tissue and get into the bloodstream. PM1 can then circulate throughout the body and cause systemic health effects.

Click here to see why particle size matters.

Despite its smaller diameter, the typical PM1 particle has a larger physical surface area than other fine particulates like PM2.5. This makes PM1 more likely to carry heavy metals, chemicals, and volatile organic compounds (VOCs) on its surface and cause even greater harm when inhaled.

Unlike PM2.5, PM1 is not regulated, and monitoring technology for PM1 is limited. Research is still being conducted to better understand the specific harm that PM1 causes in contrast to other particulate pollutants like PM2.5 and ultrafine particles (UFPs).

What are the sources of PM1?

Like PM2.5 and UFPs, most PM1 pollution results from fuel combustion and industrial activity.

Some sources of PM1 are naturally occurring, such as mineral fragments and aerosols from sea spray.¹ But by far, the majority of airborne PM1 originates from human activity, such as:

• emissions from factories and other industrial activity
• vehicle exhaust
• tire particles from vehicle use
• smoke from wildfires or indoor wood-burning

Because human activity makes up the bulk of PM1 sources, densely populated urban areas, especially those with busy roadways or industrial facilities, are especially prone to PM1 pollution as well as other types of particle pollution.

A 2019 study in Atmosphere looked at particulate matter in the air around four preschools and eight industrial facilities in Poland. Researchers found a close correlation between PM1 and PM2.5, suggesting that nearly 75 percent of ambient PM2.5 particles fall into the PM1 size range below 1 micron.²

The study also found that airborne carcinogens like cadmium, chromium, and nickel were commonly found on PM1 particles near urban areas and industrial plants. Concentrations of these carcinogens ranged from 10 nanograms per cubic meter (ng/m3) to 800 ng/m3 in samples of ambient PM1 within a kilometer of industrial plants.

A study of PM1 in Delhi, India from October through November 2020 also illustrates this prevalence around urban areas well, finding average concentrations of PM1 from 200-300 micrograms per cubic meter (µg/m³) throughout the study.³

How does PM1 affect our health?

Because of its association with PM2.5, PM1 is known to have similar health effects on the lungs and heart. Emerging research has also found that PM1’s size and ability to carry toxic chemicals on its surface increases the range of its possible health consequences.

A 2020 study in Scientific Reports found trace levels of the following chemicals and heavy metals on PM1 particles measured near the city of Harbin, China, a city that largely relies on coal for heating during cold seasons:⁴

• sulfates
• nitrates
• ammonium
• zinc
• lead
• chromium
• nickel
• cadmium
• cobalt

All of these elements and compounds, especially heavy metals like lead and cadmium, have documented long-term health effects like heart disease and cancer.⁵

Some studies have also found that exposure to PM1 has similar effects on the heart and lungs as PM2.5 and ultrafine particles (UFPs).

A 2017 study in The Lancet Planetary Health on PM1’s health effects looked at emergency room visits at 28 hospitals in 26 Chinese cities in correlation with PM1 and PM2.5 monitoring data.⁶

With average PM1 concentrations across all 26 cities measured by researchers at 42.5 µg/m³, study data suggested that emergency room visits increased significantly for every rise in PM1 of 10 μg/m³, with effects lasting up to 2 days after the initial spike in PM1 concentrations.

A similar 2020 study measuring PM1 levels in 65 Chinese cities found that every rise in PM1 of 10 μg/m³ increased an individual’s risk of heart disease by 0.29 percent.⁷ With average PM1 levels of 27 μg/m3 across the 65 cities, the study noted that this effect was much more severe for PM1 than for either PM2.5 or PM10.

Another 2020 study in the journal Hypertension investigated a possible link between PM1 and high blood pressure, studying nearly 10,000 Chinese children between 5 and 17 years old during 2012 and 2013.⁸ Nearly 50 percent of the children were regularly exposed to tobacco smoke, and at least 10 percent lived in homes that used coal for indoor heating.

Researchers concluded that every PM1 increase of 10 μg/m3 increased the risk of high blood pressure in children by 61 percent, especially in children younger than 11 and in overweight or obese children.

Can PM1 be measured by air quality monitors?

PM1 monitoring technology is limited. Most air quality monitors that measure PM are only capable of monitoring PM2.5 and PM10. This lack of PM1 monitoring technology is partially due to PM1’s small size, but also due to its movement in the air.

Some of the smallest PM1 particles experience Brownian motion, an erratic movement in the air due to collisions with other airborne molecules.⁹ This means that PM1 behaves more like a gas than a solid particle, and gases require much different monitoring techniques than particles for accurate measurement.

AirVisual Series air quality monitors include laser-scattering PM sensors that measure particulate matter in ambient air ranging from 0.3 to 10 microns in real time. This includes measurements of PM1, PM2.5, and PM10.

Weatherized outdoor sensors are ideal for use near major PM1 sources in dense urban environments, such as near factories or busy roadways with high vehicle traffic volumes.

Tips to reduce PM1

Here are some tips to help reduce PM1 emissions from some of its most common sources:

• Commute by walking, bicycling, taking buses or trains, or using rideshares to reduce reliance on personal vehicles.
• Replace gas-powered cars with electric or hydrogen-fueled vehicles to help reduce or eliminate personal carbon emissions.
• Replace diesel-powered vehicles or machinery with those that use more fuel-efficient power, such as natural gas or electricity.
• Equip home energy systems with solar power to reduce energy grid use of power plants fueled by coal or other dirty fuels.
• Reduce reliance on indoor combustion sources, such as fireplaces, scented candles, ovens, and stoves. Make sure to ventilate properly if you do decide to use these sources.
• Limit or stop smoking cigarettes, vapes, or cigars.

The takeaway

PM1 measures particulate pollutants smaller than 1 micron. Like other fine particles, it can cause damage to the heart, lungs, and other organs in the body, but also carries toxic carcinogens on its surface that can result in even further harm, including increasing the risk of cancer.

Due to its small size, PM1 also behaves differently in the air than other particles and can be tricky to monitor. Highly accurate PM1 sensors can help to clarify the relationship between PM1 and other airborne pollutants and measure the effect that air filtration has on this specific pollutant.