Porter Ranch Community
Air Monitoring Project

What is it?

Benzene is a colorless, highly flammable liquid with a sweet gasoline odor.

Why measure it?

Benzene is a cancer-causing chemical and is second only to diesel exhaust as a cancer-causing pollutant in the LA Basin. While the bulk of benzene in the air comes from vehicle exhaust, it is important to measure the concentration in ambient air to identify and control emissions from industrial sources including refineries.

How might it affect my health?

Short-term inhalation of high levels of benzene can cause dizziness, lightheadedness, and headaches as well as lung irritation. The long-term effects of benzene exposure are related to anemia and effects on the bone marrow. Benzene is classified as a cancer-causing chemical in humans based on workers with long-term occupational exposure as well as on animal studies.

What concentration of benzene is typically found in air in the South Coast Air Basin?

The average concentration of benzene found in the LA Basin is 0.40 ppb, with concentrations ranging from 0.02 to 1.77 ppb.

The California EPA's Office of Environmental Health Hazard Assessment (OEHHA) has information on benzene. In addition, the CDC has 'ToxFAQs' fact sheets for benzene.

What is it?

Toluene is a colorless liquid that smells like paint thinner.

Why measure it?

Like the other components of BTEX (benzene, ethylbenzene and xylene), is a major contributor to ozone formation in the LA air basin.

How might it affect my health?

Exposure to low to moderate levels of toluene can irritate the nose, throat and eyes, lungs, and cause headaches. Long-term daily breathing of toluene by workers has been associated with hearing and color vision loss. Toluene is the ingredient in airplane glue and paints that led to wide-spread abuse when inhaled causing nervous system damage.

What concentration of toluene is typically found in air in the South Coast Air Basin?

Toluene concentrations typically equal 1.11 ppb on average in the LA Basin. Concentrations ranged from 0.1 to 6.15 ppb.

The California EPA's Office of Environmental Health Hazard Assessment (OEHHA) has information on toluene. In addition, the CDC has 'ToxFAQs' fact sheets for toluene.

What is it?

Ethylbenzene is a colorless liquid that smells like gasoline. It evaporates at room temperature and burns easily.

Why measure it?

Like the other components of BTEX (benzene, toluene and xylene), ethylbenzene contributes to the formation of ozone.

How might it affect my health?

Breathing very high levels of ethylbenzene can cause throat and eye irritation and dizziness. Breathing lower levels over long periods of time causes hearing and kidney damage in animals. The World Health Organization has identified ethylbenzene as a possible human carcinogen based on animal studies.

What concentration of ethylbenzene is typically found in air in the South Coast Air Basin?

The average concentration of ethylbenzene in the LA Basin is 0.23 ppb. The maximum concentration reported equaled 4.75 ppb.

The CDC has 'ToxFAQs' fact sheets for ethylbenzene.

What is it?

Xylene is a colorless, flammable liquid with a sweet odor.

Why measure it?

Like the other components of BTEX (benzene, toluene and ethylbenzene), xylene is a major contributor to ozone formation in the LA air basin.

How might it affect my health?

Exposure to high levels of xylene for short periods of time can irritate the eyes, nose, throat, or skin. Both short- and long-term exposure to high levels of xylene may cause effects on the nervous system such as headaches, dizziness, confusion, and lack of muscle coordination.

What concentration of xylene is typically found in air in the South Coast Air Basin?

There are three forms of xylene which are measured in the LA Basin air and all function similarly. Meta- and para-xylene concentrations were on average 0.77 ppb in the LA Basin, while ortho-xylene concentrations were 0.19 ppb on average.

The California EPA's Office of Environmental Health Hazard Assessment (OEHHA) has information on xylenes. In addition, the CDC has 'ToxFAQs' fact sheets for xylenes.

What is it?

Methane is a colorless and odorless gas.

Why measure it?

Methane is flammable in high concentrations, between 5% and 15% (equivalent to 50,000 to 150,000 ppm). Measurements conducted by South Coast AQMD staff and other agencies in the Porter Ranch community show that methane levels are far below the concentrations where flammability would be a concern.

How might it affect my health?

Methane is considered to be biologically inert, but can cause health effects when levels are high enough to displace oxygen in the air, which can pose a suffocation hazard. However, this is generally only a concern in confined spaces (such as the inside of a tank), rather than in outdoor environments or typical indoor environments, where oxygen is readily available.

What concentration of methane is typically found in air in the South Coast Air Basin?

Methane is not considered an air toxic, as it is not on the California Toxic Air Contaminants list, nor the California Proposition 65 list, nor is it on the U.S. EPA Hazardous Air Pollutants list. However, methane is considered a climate pollutant (i.e. greenhouse gas), and is primarily regulated through state and federal regulations.

The CDC has 'ToxFAQs' fact sheets for methane.

The UV DOAS (UltraViolet Differential Optical Absorption Spectroscopy) analyzers detect gases on a real-time basis using beams of ultraviolet light. The system identifies gases by examining the wavelengths of UV light that have been absorbed by the gases present in the light beam. The instruments have a spectral library of gases covering the concentration range of the analyzer. It also includes libraries of potential interfering gases such as oxygen and ozone. Data from each UV instrument are averaged at approximate five-minute intervals.

The TDL (Tunable Diode Laser) analyzers detect methane gas on a real-time basis using beams of infrared (IR) light. If methane gas is present in the air, it will absorb at certain known wavelengths of the light. TDL air monitoring systems use a very narrow band of wavelengths to detect gases and thus are typically designed to detect only a single gas such as methane.

Gas chromatographs (GCs) are fixed-point analyzers which record data in one-hour intervals. GCs are able to separate compounds in the gaseous phase in order to quantify them.

A system setup to continuously measure weather parameters such as wind speed, wind direction, temperature, humidity and Barometric pressure. MET stations are particularly useful in pollutant source identification and the effect of weather events, such as fog or heavy winds, on the system performance.

The detection limit, also known as the "minimum detection limit (MDL)", is the smallest concentration level that the equipment can measure with high accuracy. The three factors that make MDLs vary are compound, path length, and ambient conditions.

"Below detection limit (BDL)" means the concentration level is unknown to the instrument. Information about the equipment Argos Scientific is using can be found in the "Resources" tab under "Instruments."

A 1 hour average is a data point produced from the data in the previous hour. Whereas, a 5 minute average is a data point from the previous 5 minutes of data collected.

The data displayed on this website is the raw data from the instruments in the field which are updated in near real-time. The data, as displayed, has not yet been through a rigorous quality control process required for the data to be considered final. However, a number of automated checks are done to provide a preliminary quality check. Data are considered preliminary for one quarter (90 days), at which point they are reviewed, finalized, and submitted to the South Coast AQMD.

The fenceline monitors send UV or infrared light beams across a path to a reflector which sends the light back to the source. When compounds in the air pass through the beam of light, some of the light is absorbed. The wavelength at which the light is absorbed and the amount of light absorbed determines which compounds are being detected and quantifies how much of it is in the air. The greater the absorption of light, the higher the concentration of that compound.

Note that open-path monitors cannot distinguish between a widely dispersed, low-concentration plume and a narrow, high-concentration plume. Rather, the monitors detect average concentrations across the entire distance from the source to the reflector.