Monitoring for invisible, toxic pollutants like benzene along the fencelines of industrial sites can help reduce pollution and protect workers and nearby communities. Benzene is a carcinogen and prolonged exposure can also lead to blood disorders, threaten the immune system, and increase the risk of leukemia.
Following a lawsuit by community groups, the Environmental Integrity Project and allies, U.S. oil refineries since 2018 have been required by the Environmental Protection Agency (EPA) to monitor benzene levels at their fencelines and take steps to reduce emissions if calculated values exceed an “action level.”
The EPA has also required several chemical plants and other facilities to begin fenceline benzene monitoring programs through enforcement actions. The agency in April 2024 issued new rules that will require approximately 218 chemical plants to monitor for up to six pollutants—benzene, 1,3-butadiene, ethylene oxide, vinyl chloride, chloroprene, and ethylene dichloride— starting in June 2026, and the first year of data will be published in June 2027.
This dashboard makes it easier to understand monitoring results and identifies plants that must take action to reduce benzene concentrations. It also identifies gaps in current regulations. For example, while levels at some plants have decreased over the past several years, levels at other plants have remained high. Despite the need for enforcement in these cases, action level exceedances are not violations under current regulations. These gaps need to be closed in order to better protect downwind communities exposed to dangerous levels of toxic air pollution.
Continue down the page for additional information.About the Dashboard
Number of Refineries Exceeding Action Level at the End of Each Year
Map of Refineries and Chemical Plants
Annual average net benzene concentrations (or rolling average delta C values) over nine micrograms per cubic meter (highlighted red) exceed EPA’s action level and require clean up. The 2-week net benzene concentration, or delta C value, accounts for benzene in the ambient air that may not be directly attributable to the facility because it might be drifting onto their fenceline from neighboring facilities or other offsite sources. For more information about how the 2-week net benzene concentration is calculated, see the About page. For more information about what qualifies a potential health threat, please see the Public Health Thresholds section of the About page.
Refineries and Chemical Plants with Fenceline Benzene Monitoring Data
Refinery Monitoring Requirements
By 2018, refineries across the U.S. started measuring two-week average benzene concentrations at locations around their fencelines, using a network of monitors. The first year of data was submitted to EPA by June 2019. Companies have 45 days after the quarter ends to submit their reports to EPA. After receiving those reports, EPA waits 30 days before making them available to the public on its WEBFIRE Report Search and Benzene Dashboard . For more information about the regulatory requirements of the program, see 40 CFR 63.658 .
Chemical Plant Monitoring Requirements
In early 2024, EPA finalized fenceline monitoring rules for a subset of chemical plants that produce commodity chemicals, elastomers, and resins while emitting hazardous air pollutants into surrounding communities. The rules will require chemical plants to conduct fenceline monitoring for six pollutants: benzene, 1,3-butadiene, chloroprene, ethylene dichloride, ethylene oxide, and vinyl chloride if they emit, manufacture, store, or otherwise use these chemicals. Plants will begin monitoring by June 2026, with the first year of data to be published in June 2027. However, the 2024 rules do not cover many chemical plants that emit the same pollutants.
EPA Action Level
How the action level is calculated for a particular facility is best summed up in the EPA’s Office of Inspector General’s report on the subject:
“A refinery must continuously measure concentrations at each of its monitors over two-week periods and report those concentrations to the EPA at the end of each quarter. These two-week periods are referred to as sampling periods. After each sampling period, a refinery must determine whether its annual average concentration for the most recent 26 two-week sampling periods is over 9 µg/m³. The concentration that a refinery uses to determine whether it is over the action level is referred to as the delta concentration, or delta c. The delta c accounts for benzene in the ambient air that may not be directly attributable to the refinery. The delta c is determined by subtracting the lowest benzene concentration measured by any of a refinery’s monitors from the highest benzene concentration measured by any of a refinery’s monitors for each two-week sampling period. If the refinery’s average delta c for the preceding 26 two-week sampling periods is above 9 µg/m³ the refinery has exceeded the action level.”
Example: If during a two-week sampling period, the highest monitor reading is 12 micrograms per cubic meter (µg/m³), and the lowest monitor reading is 0.8 µg/m³, the benzene Δc value (or delta value) would be 11.2 µg/m³. The annual rolling average Δc is then calculated using the 26 most recent sampling periods. When this annual rolling average Δc is greater than 9 µg/m³, the facility has exceeded EPA’s action level threshold.
The regulations also allow refineries with site-specific monitoring plans approved by EPA to make further downward adjustments to exclude benzene that comes from specific sources, including plants outside the refinery’s boundary and certain sources within the refinery that are exempt from the regulation (such as benzene storage tanks). These adjustments allow some refineries to avoid triggering the EPA action level that requires cleanup of the plant’s emission sources, even when their monitors report very high benzene levels. Unlike refineries, chemical plants do not have site-specific monitoring plans.
Public Health Thresholds
Long-term Health Risk
Even relatively “low” benzene levels can harm health. The California EPA, for example, has determined that continuous or repeated eight-hour exposures (i.e., workplace exposures) to three or more micrograms per cubic meter of benzene over about eight to nine years could increase the risk of noncancer health effects, such as damage to blood cells and a weakened immune system. The risk from benzene exposure increases with prolonged and additional exposure, especially among sensitive populations like pregnant people and young children.In addition to the noncancer health impacts of benzene exposure, the pollutant is also a known carcinogen that can increase the risk of developing leukemia. EPA estimates that breathing benzene at a concentration as low as 0.13 micrograms per cubic meter over a lifetime could result in up to one additional cancer diagnosis per one million people exposed. As benzene levels rise, those risks increase. By EPA’s estimate, the additional cancer risk at a concentration of 3 µg/m³ over a lifetime, for example, would be 6 to 23 in a million. The California EPA has published a higher unit risk that suggests that long-term exposure to as little as 0.03 micrograms per cubic meter can increase cancer risk by one in one million. At 3 µg/m³, the additional cancer risk based on California EPA’s estimate would be 87 in a million.
Short-term Health Risk
Exposure to high levels of benzene over shorter periods of time can also lead to adverse health effects. Short-term exposure can cause headaches, dizziness, and irritation to the eyes, skin, and respiratory tract. It could also decrease blood cell counts, including in vulnerable groups like pregnant people and young children. The U.S. Agency for Toxic Substances Disease Registry (ATSDR) estimates that exposure to benzene concentrations above 29 micrograms per cubic meter for 1-14 days can increase the risk of noncancer health effects like a weakened immune system.Health Risk Levels
Potential health risks are estimated based on many factors, including the length of exposure, concentration, how people are exposed, type of health effect, age, and other vulnerabilities. There are many uncertainties and assumptions that go into calculating risk and different government agencies have established different thresholds that estimate when a chemical poses an increased health risk to human health. Some risk levels for benzene include:California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) Reference Exposure Levels (RELs): An estimated concentration at or below which there would likely be no noncancer health effects anticipated for the specified exposure duration.
U.S. Agency for Toxic Substances Disease Registry (ATSDR) Minimal Risk Levels (MRLs): An estimate of daily exposure to a substance that would likely not increase the risk of a noncancer health effect over the specified exposure duration.
U.S. Environmental Protection Agency Cancer Risk Levels: EPA publishes cancer potency estimates known as “unit risks” (in units of risk per µg/m3), which can be converted into exposure concentrations associated with certain levels of risk. For benzene, EPA has published a range of unit risks which suggest that long-term exposure to 0.13 to 0.45 micrograms per cubic meter creates a cancer risk of one in one million. The California EPA has published a higher unit risk that suggests that long-term exposure to as little as 0.03 micrograms per cubic meter can increase cancer risk by one in one million.
U.S. Environmental Protection Agency Noncancer Risk: The reference concentration for inhalation exposure (RfC) is a concentration that, with continuous inhalation exposure, is likely to be without an increased risk of noncancer health impacts.
Methodology and Data
Some of California's major refineries provide access to real-time air monitoring data along the fence lines. Links to the data from these refineries can be found on the California Air Resources Board’s website . Note that many of these refineries track multiple air pollutants.
Chemical plants post monitoring reports to their own websites biweekly and are not available on EPA’s WebFIRE report search. Those reports can be found here:
Some refineries or chemical plants section off parts of the facility and provide multiple reports (e.g. the refinery and the refinery dock). EIP has counted these “sub-refineries” as separate facilities, consistent with how the refineries report to EPA or chemical plants report on their websites.
EIP downloads the reports as they are made available (every three to four months for refineries and biweekly for chemical plants) and compiles the data in an online database. There may be a lag between when EPA makes data available and when this website is updated. However, our goal is to keep the database as current as possible.
Data Limitations
The benzene monitoring data is collected at facility perimeters and are not direct measures of benzene within a community, residential neighborhoods, or homes. How much benzene drifts into surrounding areas can vary, in part due to meteorological variables like wind.The fenceline monitors are passive samplers that measure average benzene concentrations over a two-week period. Concentrations over shorter periods during the two-week periods could have been much higher or lower.
Because of the two-week sampling periods and delayed reporting, benzene concentrations shown do not reflect real-time benzene concentrations.
Previous Reports by EIP
Environmental Justice and Refinery Pollution: Benzene Monitoring Around Oil Refineries Showed More Communities at Risk in 2020, April 2021Monitoring for Benzene at Refinery Fencelines, February 2020
Contact Us
What is the action level?
EPA’s “action level” for benzene, which is used to require cleanup efforts, is not the same as the actual levels of benzene monitored at the fencelines of industrial plants. The actual levels of benzene measured at the fenceline are usually higher than the adjusted levels that EPA allows companies to compare to the “action level.” This is because EPA allows companies to subtract out benzene that companies claim (rightly or wrongly) has drifted onto their facilities from off-site pollution sources, like neighboring facilities, or onsite sources like benzene storage tanks that are not regulated under the current rule. In other words, EPA allows companies to not count what they regard as background levels of benzene, referred to as the 2-week delta C (Δc), or the 2-week net benzene concentration.
Example: If during a two-week sampling period, the highest monitor reading is 12 micrograms per cubic meter (µg/m³), and the lowest monitor reading is 0.8 µg/m³, the 2-week benzene Δc value (or net 2-week benzene concentration) would be 11.2 µg/m³. The annual rolling average Δc (or annual rolling average net benzene concentration) is then calculated using the 26 most recent sampling periods. When this annual rolling average Δc is greater than nine micrograms per cubic meter, the facility has exceeded EPA’s action level threshold.
Choose a plant from the list below to see if it has exceeded the benzene action level. Plants highlighted red are currently exceeding the action level, and plants highlighted gold have exceeded the action level in the past.
The line graph shows the annual rolling average Δc for benzene, starting a full year after the plant began monitoring. The red line represents the 9 µg/m³ action level.
Dropdown Key:
Facilities that are currently violating the action level threshold are highlighted in red .
Facilities that have violated the action level threshold in the past are highlighted in gold .
Facility Information
Annual Rolling Average Net Benzene Concentration Over Time
While the action level for benzene cleanup isn’t a health-based threshold, measured benzene concentrations can be compared to health-based thresholds to better understand potential risks to workers and people who live their daily lives near refineries and chemical plants.
Choose a facility to view a line graph of the two-week average benzene concentrations measured over time. Facilities highlighted green have had monitors measure values higher than 29 µg/m³ – high enough to pose short-term health risks with as little as 1-14 days of exposure. Plants highlighted blue have at least one monitor that has a long-term average concentration over 3 µg/m³ – high enough to pose longer-term health risks with prolonged exposure. Each of these health threshold levels are shown on the graph, the short-term depicted as dashes and the long-term as dots.
To view additional information about a specific two-week period, choose a sampling period end date to view the benzene concentrations in a bar graph, a map of the facility and monitoring locations, and the wind direction and speed during that period. Wind data come from NASA's POWER (Prediction of Worldwide Energy Resources) database and may provide insight into where benzene comes from and where it may impact off-site communities. For more about NASA's POWER data, click here.
Dropdown Key:
Facilities that have posed a short-term threat to public health are highlighted in green .
Facilities that have posed a long-term threat to public health are highlighted in blue .
Facilities that have posed both short and long-term threats to public health are highlighted in brown .
Benzene Concentrations Over Time by Monitor
On the map below, clicking on a monitor will reduce the line graph above to show the clicked monitor's recorded concentrations over time, and highlight the clicked monitor on the bar graph below. To restore the graphs, click on the reset button below.
Map of Concentrations from Selected Period
Bar Graph of Period Concentrations
Wind Direction Map from Selected Period
Use the dropdown below to select up to 15 facilities.
After selecting a facility, a button will appear that allows you to gather the data from our database.
After you choose to gather data, a progress bar will appear in the bottom right corner.
You will receive a message when your data is ready to be downloaded.
If you need access to data for a large amount (15+) of facilities, please contact us at
info@environmentalintegrity.org
.
Dropdown Key:
Facilities that have posed a threat to public health are highlighted in purple .
Facilities that have violated the action level are highlighted in orange .
Please note that all facilities that have exceeded the action level threshold have also posed (or currently pose) a potential threat to public health.