Acute Health Effect

A health effect that occurs over a relatively short period of time (e.g., minutes or hours). The term is used to describe brief exposures and effects which appear promptly after exposure.
Ambient Air

A variety of local, state, federal and international organizations share common goals of protecting humans from toxic air pollution by creating ambient air quality standards. Not all organizations use the same set of standards, nor do all organizations measure the same chemicals.

Air quality standards for individual pollutants typically refer to an upper "safe" limit for concentration in the air. Concentrations above the set limit for a specific chemical may pose health risks. Health risks may be considered "acute" (immediate effects from single exposure event) or "chronic" (effects from multiple exposures over longer periods of time) depending on the degree of concentration detected and the length of time of an exposure.
Chronic Health Effect

A health effect that occurs over a relatively long period of time (e.g., months or years).
Exposure Limit

An exposure limit is the concentration of a gas that a person can be exposed to without endangering their health. Typically exposure limits are published for short-term and long-term exposures to gases. The short-term exposure limit is called the acute exposure limit and the long-term exposure limit is called the chronic exposure limit.
°F - Degrees Fahrenheit

Degrees Fahrenheit is a measure of temperature. Water freezes at 32 degrees Fahrenheit (°F) and boils at 212 °F.
µg/m3 - Micrograms Per Cubic Meter

Micrograms Per Cubic Meter is a technical term that is commonly used to show how much of a chemical is in the air. Micrograms per cubic meters is the specific weight of a gas or particle (measured in micrograms) in a specific volume of air (measured in cubic meters). One microgram weighs 0.000000002 pounds.
MPH - Miles Per Hour

Miles per hour is a measurement of speed. A gas particle moving at the speed of thee miles per hour will be transported a distance of three miles in a given hour.
PPB - Parts Per Billion

PPB is a technical term that is commonly used to show how much of a chemical is the air. In the case of PPB, it is an abbreviation of one part per billion and denotes one part per 1,000,000,000 parts. To put this in perspective it is the same as one drop of water diluted into 250 drums of water.
Raw Data

Raw data is collected information that has been reviewed, processed or undergone any types of quality assurance or quality control review. It may contain errors and should be viewed as provisional and is subject to significant change. Data that has been screened using standard quality assurance and quality control protocols will be available in the data archive section of the website.
Toxic Air Contaminant (TAC)

An air pollutant, identified in regulation by the California Air Resources Board, which may cause or contribute to an increase in deaths or in serious illness, or which may pose a present or potential hazard to human health. Health effects to TACs may occur at extremely low levels and it is typically difficult to identify levels of exposure which do not produce adverse health effects.

Tracer pollutants are used in air monitoring when a gas that is easy to detect is used to show the presence of other gases that are difficult to measure using current technology. For example Sulfur Dioxide is often used to show the presence of gases that contain sulfur are in the air.