Air Quality Monitoring

PurpleAir sensors detect and measure the presence of particulate matter, which includes tiny particles of dust, smoke, pollen, and other solid or liquid droplets suspended in the air. The size of particulate matter is a critical factor in determining its potential health effects, with smaller particles generally posing a greater risk. The basic classifications of particulate matter include:

• PM10 (Inhalable Coarse Particles): These particles are larger than 2.5 micrometers but no larger than 10 micrometers. They can be inhaled into the lungs and may cause respiratory issues. PM10 includes particles like dust, soot, and pollen. 

• PM2.5 (Fine Particles): These particles are 2.5 micrometers or smaller in diameter. They are small enough to penetrate deep into the lungs and even enter the bloodstream. PM2.5 includes particles from sources such as combustion and is among the most commonly measured and reported air pollutants due to their widespread presence and significant health impacts.

• Ultrafine Particles: These are the smallest particles, typically less than 0.1 micrometers in diameter. They are capable of penetrating deep into the lungs and potentially entering the bloodstream. Ultrafine particles are most commonly emitted through combustion from natural or human sources.

PurpleAir provides real-time, publicly accessible data on their map, allowing individuals and communities to monitor air quality in their areas. The active monitors in Richmond will display an Air Quality Index (AQI) and color on the map, which the key at the bottom left of the screen can help decode.

• Gray: No data is being received from this PurpleAir sensor

• Bright Green: 0 - 50 — Air quality is satisfactory, and air pollution poses little or no risk with 24 hours of exposure.

• Yellow: 51 - 100 — Air quality is acceptable. However, there may be a risk for some people with 24 hours of exposure, particularly those who are unusually sensitive to air pollution.

• Orange: 101 - 150 — Members of sensitive groups may experience health effects with 24 hours of exposure. The general public is less likely to be affected.

• Bright Red: 151 - 200 — Some members of the general public may experience health effects with 24 hours of exposure. Members of sensitive groups may experience more serious health problems.

• Purple: 201 - 300 — Health alert: the risk of health effects is increased for everyone with 24 hours of exposure.

• Maroon: 301+ — Health warning of emergency conditions: everyone is more likely to experience health effects with 24 hours of exposure.

PurpleAir sensors use a fan to draw air past a laser beam. The reflection of the laser light by the particles is measured, and this information is used to determine the number and size of particles. The number of particles counted, along with assumptions about their density, is then used to estimate the mass concentration of particulate matter in an area.

Particulate matter comes from both natural and human-made sources. Primary sources release particles directly into the air, while secondary sources involve chemical reactions that form particles in the atmosphere.

Primary Sources:

• Burning fossil fuels (coal, oil, natural gas)

• Construction and demolition activities that generate dust and debris

• Agricultural activities like tilling fields, livestock management, and the use of fertilizers and pesticides

• Traffic on paved and unpaved roads

• Mining, smelting, and manufacturing

• Wildfires

Secondary Sources:

• Gaseous pollutants like sulfur dioxide and nitrogen oxides, emitted from power plants, vehicles, and other sources

• Ammonia, a common byproduct of agricultural and industrial activities

Indoor* Sources:

• Cooking, especially frying and broiling (gas stoves produce more than electric)

• Smoking or vaping

• Burning candles and incense

• Dust

• Some building materials

*Please note that the PurpleAir sensors only measure outdoor air quality.

Particulate matter (PM) pollution can have a significant impact on human health, causing both short-term and long-term health issues. Vulnerable populations like children, the elderly, and those with pre-existing conditions are particularly susceptible.

Short-Term Effects:

• Respiratory irritation, including irritation of the eyes, nose, throat, and lungs, which can cause coughing, sneezing, and shortness of breath. 

• Exacerbation of existing respiratory illnesses like asthma and COPD, leading to increased hospital visits and emergency room trips.

• Increased risk of cardiovascular issues, such as heart attacks and irregular heartbeats, especially in individuals with heart conditions.

• Weakened immune system, which can make individuals more vulnerable to respiratory infections.

Long-Term Effects:

• Decline in lung function and an increased risk of developing chronic bronchitis.

• Higher risk of heart disease, stroke, and other cardiovascular problems.

• Can lead to premature death, especially in individuals with heart and lung diseases.

• Exposure during pregnancy can negatively affect fetal development and increase the risk of low birth weight and premature birth.

• Research suggests potential links between PM exposure and other health issues like cancer, diabetes, and neurological disorders. 

Particulate matter (PM) pollution can have many negative effects on the environment.

• PM is a major component of smog and haze, reducing visibility and impacting scenic views.

• Some forms of PM, such as black carbon (soot), absorb sunlight and contribute to global warming.

• PM can alter soil chemistry, affecting nutrient availability and potentially harming plant growth and ecosystem health.

• PM can settle on buildings, monuments, and other surfaces, causing soiling and discoloration. 

• PM can contribute to the greenhouse effect, trapping heat in the atmosphere and contributing to global warming.

• Some forms of PM can affect weather patterns, potentially leading to changes in precipitation and other climate-related effects.

• How does air quality vary seasonally and spatially across Richmond, particularly between historically underserved areas and other parts of the city?

• Is there a measurable relationship between temperature and PM2.5 levels, especially during extreme heat events?

• Are there identifiable pollution patterns tied to land use, wind direction, or proximity to point-source emitters?

• How well do satellite-based measures of air quality (e.g., aerosol optical depth) correspond with ground-based measurements from our network of low-cost PurpleAir sensors?

According to Xerces Society, "Community science (sometimes referred to as 'participatory science' or 'citizen science') is a form of research that provides everyone—regardless of their background—an opportunity to contribute meaningful data to further our understanding of key issues."