Border Air Quality Data - About the HAP Monitor Values Report

What Does the Report Tell Me ?

The border air quality data HAP Monitor Values Report displays measurements of hazardous air pollutant (HAP) concentrations recorded by monitoring sites within approximately 65 miles (100 kilometers) of the U.S.-Mexico border. The report shows a yearly summary of the measurements at individual monitoring sites, and descriptive information about the sites.

Hazardous air pollutants are substances that are known or suspected to cause serious health problems. Section 112(b) of the Clean Air Act currently identifies a list of 188 pollutants as HAPs. Some of those are further subdivided for air monitoring procedures, resulting in about 200 HAPs that may be monitored for their ambient concentrations in air.

Each row of the HAP Monitor Values Report displays air pollution levels measured at a single monitoring site in a single year. The same site may appear in multiple report rows if it has more than one monitor or if you include multiple data years in the report.

Air monitoring data usually are incomplete for the latest year available in this report. Therefore, comparing reported values for the latest year with prior years may not be meaningful.

How Can I Customize the Report ?

Sort Order

You can use the SORT buttons in each report column to change the order of rows in the report. The default sort order is monitoring site ID, which arranges rows in order of state, county, and monitoring site.

The reporting software automatically adds year as a secondary sort key for most report columns. If a report includes data for multiple years, rows having identical values for the primary sort key, which you choose with the SORT buttons, are arranged in ascending order by year.

Detail or Summary

This is always a detail report. Omitting optional report columns does not change the level of summarization. A row of the report always displays data for a single monitoring site for a single year.

Report Width

This report potentially can include nearly 40 data columns if you select all optional columns. Viewing such a "wide" report in a browser requires horizontal scrolling, and printing the full report width probably is not possible.

What Do the Report Columns Mean ?

Row #

Sequence number of report rows (lines). Sequence numbers are not associated with particular rows; they simply enumerate the rows of a report from first to last. Thus, choosing an alternate sort order for a report would change the sequence numbers associated with particular rows.

Pollutant Values

# Obs: Number of days in the year for which values (observations) were reported.
1st Max, 2nd Max, 3rd Max, 4th Max: The four highest values for the year. Each value is a 24-hour average.
Mean: Arithmetic average of all 24-hour values for the year.

If a monitoring site reports a pollutant concentration that is less than the minimum detectable level for the measurement procedure used, a value equal to one-half the minimum detectable level is substituted for the reported concentration in the AQS database. Pollutant values given in this report - maximum and mean values - reflect the half-minimum-detectable substitutions.

Units

The units of measurement for pollutant concentration:

ppbC = parts per billion carbon
To convert from ppbC to parts per billion by volume (ppb), divide pollutant concentration by the number of carbon atoms in the pollutant molecule. In other words, ppbC = ppb * (number of carbon atoms).
µg/m3 = micrograms per cubic meter
ng/m3 = nanograms per cubic meter

Concentrations in micrograms or nanograms per cubic meter have been adjusted to standard pressure (760 millimeters of mercury, or 101.3 kPa) and temperature (25 degrees Centigrade, or 298 kelvins), except for measurements derived from fine particulate matter samples - those which include "(PM2.5)" in pollutant name. Fine particulate samples are not adjusted; they are reported using the "local conditions" of pressure and temperature at the time and place of measurement.

Pollutant

The name of the hazardous air pollutant for the row of data.

Year

The calendar year to which data pertain - the year in which pollutant concentrations were measured. The report includes this column only when you select multiple years.

Monitor ID

The AQS database identification code for a monitor. An AQS monitor ID has the following parts:

FIPS state code (2 digits)
FIPS county code (3 digits)
FIPS is the acronym for Federal Information Processing Standards, which defines codes used in most U.S. government information systems.
AQS site code (4 digits) - an arbitrary code that identifies a particular monitoring site within a county
AQS parameter code (5 digits) - identifies the hazardous air pollutant measured
AQS monitor number (1 or 2 digits) - a sequence number that distinguishes among monitors for the same pollutant at the same site, also known as parameter occurrence code (POC).

For example, AQS monitor ID 06-073-0006-45202-1 is a toluene monitor in San Diego, CA (06 = California, 073 = San Diego County, 0006 = a monitoring site in the city, 45202 = toluene, 1 = an air sampler at the site).

Monitor Type

The administrative classification of an air monitoring station. This value indicates what type of agency established the monitor or what monitoring program it is associated with. A monitor with several roles may have multiple monitor types. Values are:

SLAMS (State and Local Air Monitoring Stations)
NAMS (National Air Monitoring Stations)
PAMS (Photochemical Assessment Monitoring Stations - detailed study of ozone and its precursors)
Unofficial PAMS (site certification pending)
Other
Industrial
Index Site
Non-EPA Federal (operated by a Federal agency other than EPA)
Trends Speciation (Speciation Trends Network for fine particulate matter)
Tribal
Unknown

Measurement Scale

The geographic extent of air quality measurements made at the site. Measurements made elsewhere within that geographic scope should be equivalent. Values are:

Microscale
Middle Scale
Neighborhood
Regional Scale
Urban Scale

Dominant Source Type

The class of air pollution sources that normally produce most of the air pollution measured at the site. Values are:

Area - small stationary sources (homes, offices) and diffuse sources (agriculture, wildfires)
Mobile - vehicles of all types
Point - stationary sources (factories, power plants)

Monitoring Objective

The primary reason for measuring air pollution levels at the site. When an objective pertains to a specific city, urbanized area, metropolitan statistical area (MSA), or consolidated metropolitan statistical area (CMSA), the name of the area is given in parentheses. Typical monitoring objectives are:

General/Background concentration
Population Exposure
Highest Concentration

Site Address

Address where the monitoring site is located.

City

Name of the city, town, village or other municipality in which the site is located. Blank if the site is not located within such a jurisdiction, or if no value was provided.

City Code

The 5-digit FIPS code for the city, town, village or other municipality (a "named populated place") in which the monitoring site is located. Blank or zero if the site is not located within such a jurisdiction, or if no value was provided.

County

Name of the county (or equivalent jurisdiction) in which a site is located.

County Code

Code for the county (or equivalent jurisdiction) in which a site is located, consisting of 2-digit FIPS state code and 3-digit FIPS county code. FIPS is the acronym for Federal Information Processing Standards, which defines codes used in most U.S. government information systems.

State

Postal abbreviation for the U.S. state in which a site is located. The nation of Mexico has the "state" abbreviation MX. [ Details ]

Border Region

Name of a section of the U.S.-Mexico border area in which the site is located. A border region is usually encompasses adjacent U.S. and Mexican urban areas. A border region is the smallest geographic area that you may select for border air quality reports.

Land Use

The prevalent land use within 1/4 mile of the site. Values are:

Agricultural
Blighted Area
Commercial
Desert
Forest
Industrial
Military Reservation
Mobile
Residential
Unknown

Location Type

A general characterization of the setting where the site is located. Values are:

Rural
Suburban
Urban and Center City
Unknown

Latitude/Longitude

Coordinates of the site location, in degrees. Negative values of longitude indicate locations west of the prime meridian. Blank if no value was provided.

Locational Accuracy

The estimated accuracy (uncertainty) of the site location, in meters, as specified by latitude-longitude coordinates. Blank if no value was provided.

Locational Method

The method used to determine the site location, as specified by latitude-longitude coordinates. Blank if no value was provided.

Distance to City Center

Distance in miles to the city central business district. Direction may be given also, as a compass point: N for north, NE for northeast, etc. Blank if the site is not located in a city, or if no value is available.

City Population

Population (in year 2000) of the city, town, village or other municipality in which the site is located. Blank if the site is not located within such a jurisdiction, or if no value is available.

Urbanized Area

Name of the urbanized area in which the site is located. Blank if the site is not located within such a jurisdiction, or if no value was provided. The U.S. Census Bureau defines an urbanized area as a place (city) and the adjacent densely-settled surrounding territory that together have a minimum population of 50,000 people.

UA Code

The 4-digit Census Bureau code for the 1990 urbanized area in which the site is located. Blank or zero if the site is not located within such an urbanized area, or if no value was provided.

MSA (Metropolitan Statistical Area)

Name of the MSA in which the site is located. Blank if the site is not located within an MSA, or if no value was provided.

A metropolitan statistical area consists of one or more counties having a combined population of at least 100,000 people, containing a city or urbanized area with a population of at least 50,000 people. (In New England states, the population threshold is 75,000 and MSAs comprise cities and towns rather than counties.) An MSA may contain more than one city larger than 50,000 population, and it may include counties in multiple States.

MSA Code

The 4-digit FIPS code for the metropolitan statistical area (MSA) in which the site is located. Blank or zero if the site is not located within a metropolitan statistical area, or if no value was provided.

CMSA (Consolidated Metropolitan Statistical Area)

Name of the CMSA in which the site is located. Blank if the site is not located within a CMSA, or if no value was provided.

A consolidated metropolitan statistical area consists of one or more MSAs that have a combined population of at least one million people. The constituent MSAs are called primary MSAs (PMSA).

CMSA Code

The 4-digit FIPS code for the consolidated metropolitan statistical area (CMSA) in which the site is located. Blank if the site is not located within a consolidated metropolitan statistical area, or if no value was provided.

AQCR (Air Quality Control Region)

Name of the AQCR in which the site is located. Blank if no value was provided.

An air quality control region is a group of counties within a state (or multiple adjacent states) that share common geographical or pollutant concentration characteristics based on a common pollutant source.

AQCR Code

The 3-digit AQS code for the air quality control region (AQCR) in which the site is located. Blank if no value was provided.

Site Established

The date (day, month, year) when the monitoring site began measuring air pollutant concentrations. This date pertains to the entire site, and not necessarily to a specific pollutant (monitor).

Site Terminated

The date (day, month, year) when the monitoring site stopped operating. No value is displayed if the site is still operating.

Site Detail

You can view a complete listing of all hazardous air pollutants reported by a monitoring site by clicking on the "See All HAPs" link in each row. A Site Detail report is displayed in response to your click. It shows annual summary values of every HAP reported by the site for the year associated with the row of the main report in which you clicked. The Site Detail column is included in reports whose rows pertain to distinct monitoring sites. It is not available if report rows represent larger aggregations, such as a county or a state.