Glossary

The Port Cares About Air website reports on many parameters. This glossary tells you what all those parameters mean, and will help you understand the data better.

AQI Definitions

The AQI is divided into six categories and each category is assigned a color to help visualize the information on the Current AQI map.

	Good (0 to 50). Air quality is considered satisfactory, and air pollution poses little or no risk.
	Moderate (51 to 100). Air quality is acceptable; however, unusually sensitive people should consider limiting prolonged outdoor exertion.
	Unhealthy for Sensitive Groups (101 to 150). The following groups should limit prolonged or heavy outdoor exertion: People with heart disease, pregnant women, children and older adults, people with lung disease, such as asthma
	Unhealthy (151 to 200). Everyone may begin to experience some adverse health effects (e.g. difficulty breathing and throat irritation), and members of the sensitive groups may experience more serious effects. The following groups should avoid prolonged time outdoors: People with heart disease, pregnant women, children and older adults, people with lung disease, such as asthma.
	Very Unhealthy (201 to 300). This would generate a health alert suggesting that everyone may experience more serious health effects. The following groups should avoid all outdoor physical activity: People with heart disease, pregnant women, children and older adults, people with lung disease, such as asthma. Everyone else should avoid prolonged or heavy outdoor activity.
	"Hazardous" (greater than 300). This would trigger a health warnings of emergency conditions. The entire population is more likely to be affected. Everyone should avoid all physical activity outdoors.

Black Carbon (BC)

Black carbon (BC) is a component of fine particulate matter (e.g. – PM2.5). It consists of pure carbon in several linked forms, and is formed through the incomplete combustion of fossil fuels, biofuel, and biomass burning. Black carbon is one of the main types of particulates comprising both anthropogenic (man-made) and naturally occurring soot in the atmosphere. BC is considered a surrogate for diesel particulate matter (DPM) by many air quality regulatory agencies in urban air basins.

Fine Particulate Matter (PM2.5); (e.g., soot, smoke)

Source: Primarily formed by burning of wood, diesel and other fuels; and by industrial plants.

Health Effects: nose and throat irritation, cardiovascular and respiratory problems.

Environmental Effects: fine particulates are the major cause of reduced visibility (haze) in parts of the United States. In addition, particles can acidify lakes and streams; damage sensitive forests and farm crops; and stain and damage stone and other materials.

Monitoring: The particulates are filtered through an inlet that only allows particulates smaller than 2.5 micrometers to enter. These particulates are then collected on a tape for a specified duration and compared to a baseline tape using Beta radiation.

Coarse Particulate Matter (PM10); (dust, smoke)

Source: agriculture (plowing, burning off fields); paved and unpaved roads, wind erosion.

Health Effects: nose and throat irritation, cardiovascular and respiratory problems.

Environmental Effects: Particles can acidify lakes and streams; damage sensitive forests and farm crops; and stain and damage stone and other materials.

Monitoring: The particulates are filtered through an inlet that only allows particulates smaller than 10 micrometers to enter. These particulates are then collected on a tape for a specified duration and compared to a baseline tape using Beta radiation.

Data Averaging Periods

1-hour averages – These averages are the mean of samples collected within a one-hour period.

24-hour samples – This average is the mean of samples collected within the most recent 24 hours.