Photo by Al Braden
By Dr. Neil Carman, Clean Air Director, Lone Star Chapter
Earlier this year, after a significant delay, the US Environmental Protection Agency (EPA) formally proposed a new annual standard for fine particle particulate matter of 2.5 microns or less. The EPA ambient PM 2.5 standard proposal should be strengthened, but it is welcome news that, after years of delay, the EPA is proposing to do something that could lead to improvements for millions of Texans that are breathing dirty and dangerous air. Depending on the final standard that is adopted, Texans living in Austin, San Antonio, Dallas-Fort Worth, Houston, Beaumont-Port Arthur, El Paso, and the Rio Grande Valley could see improvement in air quality and improved health outcomes as a result over the next three to five years.
Before the standard is finalized, there is a recent opportunity for public input, which concluded included virtual public hearings between February 21 and 23. Recently, the Lone Star Chapter published a blog about the proposed standard and how you can get involved here. But why is this issue so important to Texas? Let’s dive in.
What is particle pollution and what is PM 2.5?
Toxic particle pollution became a known public health threat in 1994 when public health scientists at the Schools of Public Health at Harvard and Johns Hopkins began to link higher levels of soot particles—PM 10 (particulate matter with a size of 10 microns or less) — on bad air days in large cities with higher rates of heart attacks, asthma, breathing problems, hospital admissions, and premature mortality rates.
Epidemiologic studies found that even small increases (1%-5%) of PM 10 particle pollution from day-to-day as measured by urban monitors were found to trigger thousands of people to suffer premature heart and respiratory problems leading to increased hospital visits and mortalities.
After epidemiologists published more evidence of PM 10 harm by 1995, the Clinton EPA appointed a new Clean Air Science Advisory Committee (CASAC) of scientists to review the scientific evidence associating tiny combustion particles with serious health problems, especially in large cities like New York City, Chicago, Houston, and Los Angeles.
The Clinton CASAC panel focused on evidence that tinier pollution particles smaller than the PM 10 particles were able to penetrate deeply into ultra sensitive lung tissues—millions of tiny alveolar sacs—impacting the lungs and direct access to the bloodstream.
Since 1988, however, only larger particulate matter ten microns in size (PM 10) were regulated by EPA with the City of El Paso and El Paso County violating EPA’s new daily PM 10 standard of 150 micrograms per cubic meter (mg/m3).
El Paso was ordered by EPA to pave more alleys and streets and to conduct more cleaning to reduce the PM 10 pollution inside the city as part of its compliance plan to meet the 1988 PM 10 National Ambient Air Quality Standard (NAAQS).
By 1995, EPA air quality standards revisions were needed to address the more dangerous microscopic particles than PM 10. Prior particle regulations in the 1970s and 1980s had focused on the largest total suspended particulate matter (TSP) until 1988.
As a result of a 1995-96 health effects review and CASAC’s expert panel recommendations for new rules, the EPA set new NAAQS for the smaller and more toxic fine (meaning tiny) particle PM 2.5 pollution.
In 1997, as a sign of landmark Clean Air Act progress, the Clinton EPA set the first NAAQS for fine particles 2.5 microns in size called PM 2.5. Fine particle standards were adopted as three-year averages of an annual 15 mg/m3 and daily 65 mg/m3 limits.
Where is PM 2.5 most prevalent in Texas?
In Texas, PM 2.5-monitored cities like Houston and the polluted Ship Channel indicated they were in compliance after three years of monitoring data was reviewed by TCEQ and EPA in 2004. (While all areas in Texas have been able to meet the annual and 24-hour standard, there are days and hours when PM 2.5 directly impacts Texans.)
A particular concern is disproportionate impacts since Texas has dozens of communities of color and low-income communities located close to and downwind of large industrial plants emitting large quantities (tons a year) of toxic soot particles. Freeways are also often close to these frontline neighborhoods.
These communities have faced decades of living with highly toxic air pollution burdens from ~2,000 large industrial plants and tens of thousands of smaller plants, since Texas has long ranked #1 in the number of major Clean Air Act polluting plants and #1 in particle emitting smokestacks. The myriad of dirty industry has tended to be far less regulated despite emitting harmful chemicals into the local air supply due to laxness in the state air permitting rules and toxicology guidelines.
Invisible tiny PM 2.5 particles are often called soot due to mainly being poor combustion byproducts from burning fossil fuels. As an incomplete combustion of carbon compounds, most PM 2.5 particles contain unburned carbon—known as volatile organic compounds (VOCs). They include human carcinogens called polycyclic aromatic hydrocarbons (PAHs) such as benzo-a-pyrene (BAP), the first PAH to be identified as a carcinogen in the 1960s in tobacco smoke.
In fact, in 1996, California Air Resources Board’s (CARB) Medical Advisory panel of physicians, public health scientists, and toxicologists recommended that CARB declare fine particles PM 2.5 carrying as many as one dozen PAHs as known human carcinogens in recognition of their toxicity similar to the carcinogenicity of diesel smoke containing PAHs.
What are the leading sources of PM 2.5?
PM 2.5 particles are emitted by sources small and large, including construction sites, unpaved roads, agricultural fields, industrial smokestacks on large heaters and boilers, flares, industrial fires, vehicles, urban fires, highways (road dust from rubber and concrete fires), and outdoor burning such as sugar cane debris in South Texas where fuel is placed on the plant material.
Tiny PM 2.5 particles can even form in the atmosphere as secondary pollutants due to complex chemical reactions such as concentrated sulfur dioxide turning into PM 2.5 sulfates and nitrogen oxides forming PM 2.5 nitrates. These pollutants are emitted in large volumes from coal-burning power plants, industrial facilities (oil refineries, chemical plants, carbon black, Portland Cement kilns, etc.), and diesel engines.
PM 2.5 is also produced by common indoor activities. Some indoor sources of fine particles are tobacco smoke, cooking (e.g., frying, sautéing, and broiling), burning candles or oil lamps, and operating fireplaces and fuel-burning space heaters (e.g., kerosene heaters).
What has the EPA done in the past to help regulate PM 2.5?
To address unburned fuels from vehicles in 1998, EPA adopted new ultra-low sulfur gasoline and diesel rules for refineries to meet under the 1990 Federal Clean Air Act amendments to bring urban smog and pollution levels down. EPA next adopted ultra-low benzene gasoline and diesel to be produced by all refineries, since benzene is a known human carcinogen and unburned benzene vapors were easily measured inside vehicles traveling on crowded urban freeways.
Vehicles in the 1980s and 1990s still emitted visible black smoke from tailpipes and cleaner engines had been required by EPA to achieve lower tailpipe pollution including less soot particles. Today tailpipe smoke is rare except in diesel vehicles.
Back in May 1997, in a meeting with the EPA Dallas Region 6 Administrator, Jane Saginaw, I recall and remember how she stated (more or less): “The public needed to strongly support the new 8-hour ozone NAAQS and fine particle PM 2.5 NAAQS or they might not happen.”
Nonetheless, 1997 changed everything in addressing health concerns about fine particle PM 2.5 pollution in Texas, and EPA had also approved the first 8-hour ozone standards as part of sweeping efforts to reduce urban and industrial air pollution in the US.
Two major NAAQS standards were approved in 1997 and constituted a significant step toward cleaner air in polluted cities.
First, EPA’s 1997 PM 2.5 standards mandated TCEQ to set up a new fine particle air monitoring network in cities that initially ran once every six days and later the network ran 24/7.
In Texas, the EPA’s new fine particle standards were too weak to trigger nonattainment in 1997 for the annual and daily limits.
In 2012, since EPA is required by the Clean Air Act to determine every five years if the NAAQS need to be revised, EPA revised them with new PM 2.5 standards for a more stringent annual 12 mg/m3 down from 15 mg/m3 and daily 35 mg/m3 down from 65 mg/m3. Yet PM 2.5 monitoring of Texas communities again revealed they were in attainment with the 2012 PM 2.5 NAAQS.
Second (and less known to the public), as part of the new 1997 PM 2.5 standards, EPA required states to start tracking industrial air emissions of fine PM 2.5 particles in two ways with the goal of obtaining reductions in PM 2.5 emissions.
- Major source plant air permits began to list PM 2.5 limits (pounds per hour and tons per year) to start demonstrating compliance with PM 2.5 NAAQS standards, and
- PM 2.5-emitting plants were to report annual PM 2.5 emissions via TCEQ’s industrial Point Source Emissions Inventory (EI) reporting system due every March for the previous year.
Third, TCEQ began to seek PM 2.5 reductions in plant permit renewals and require air pollution controls for fine particle pollution - a great public benefit. Stack emissions testing for pollutants including PM 2.5 was a critical way TCEQ required plants to verify compliance with smokestack limits in permits. Stack testing was vital since no stack PM 2.5 monitors exist today beyond the surrogate opacity monitors that are merely a crude measurement of smoke particle emissions in percentages from 0%-100%.
Fourth, new air dispersion modeling protocols were developed to model airborne impacts of fine particle PM 2.5 and, as a result, permit applications had to contain new PM 2.5 air modeling to demonstrate attainment around the plant’s fence lines.
Air permitting became more complex with a need to submit detailed information on estimated PM 2.5 fine particle emissions from all industrial processes in new plants and existing plants involving thousands of facilities in Texas.
For example, in 2020, 1,720 Texas industrial plants (or 90%) reported PM 2.5 emissions (for a total of 28,754 tons) in the annual industrial Emissions Inventory of 1,917 listed plants. Since 2016, industrial PM 2.5 emissions decreased from 32,000 tons to 28,754 tons, a 10% decline.
So what is the EPA actually proposing in this latest announcement?
On January 6, 2023, EPA proposed to strengthen the current primary (health-based) annual fine particle PM 2.5 standard from 12.0 micrograms per cubic meter (mg/m3) to within the range of 9.0 mg/m3 to 10.0 mg/m3.
EPA is also seeking public comments on revising the annual level to as low as 8.0 mg/m3 or as high as 11.0 mg/m3.
This proposal comes after EPA’s independent scientific advisory committee recommended setting the soot standard between 8-10 mcg/m3.
Notably, the draft does not propose strengthening the 24-hour standard, which is critical for protecting against dangerous short-term spikes in air pollution and provides the basis for the air quality index that millions use to determine the quality of the air they breathe on any given day. However, the EPA is seeking comments on whether they should lower the 24-hour standard.
What would a new annual standard of 9 or 10 or a new 24-hour standard of 25 mean for Texas?
Although EPA is not proposing changes to the primary 24-hour standard for PM 2.5 at 35 mg/m3, EPA is seeking comment on whether the daily standard should be revised from 35 mg/m3 to as low as 25 mg/m3. Note California has used 25 mg/m3 for a daily PM 2.5 standard for years.
Fortunately, Texas has a fairly robust system of monitors for PM, with roughly 80 monitoring sites around the state. Still, additional monitors in areas of West Texas, such as in Midland-Odessa, are still needed to better assess the impact of flaring and diesel trucks utilized in the oil and gas fields.
After analyzing 24-hour levels across Texas where many cities fall between 26 mg/m3-34 mg/m3 over a three-year average, a new 24-hour limit of 25 mg/m3 would likely identify new nonattainment areas.
Among populated areas where a lower 24-hour standard would spur the most action include:
Four cities with 3-year averages of peak daily fine particles that exceed 25 mg/m3 and are above 30 mg/m3 include Houston, Brownsville, Mission, and Laredo.
However, EPA is mainly seeking more stringent health standards for the annual PM 2.5 limit of 12 mg/m3 over a three-year mean after being revised in 2012 from annual standard of 15 mg/m3 to 12 mg/m3, and the daily standard was tightened from 50 mg/m3 to 35 mg/m3. The PM 2.5 monitor data shows that all 254 Texas counties and urban areas were to meet the 2012 revisions, but many counties are not likely to meet new 2023 standards. According to data provided by the US EPA in the release, and a map that can be found here. Three counties - Harris, Hidalgo, and Webb - would not meet a standard of 10.0 mg/m3.
And the facts don’t lie. Currently, Harris County’s three-year average of 11.1 mg/m3, Hidalgo County at 10.6 mg/m3, and Webb County at 10.4 mg/m3 do not meet a proposed annual PM 2.5 standard of 10.0 mg/m3.
A standard of 9.0 mg/m3 would cause areas of South, North, and Central Texas to also fail: Cameron, Bowie, Travis, Dallas, and Tarrant counties do not meet 9.0 mg/m3 over three-years.
Five more counties would join the above three counties as likely nonattainment areas as follows with a tighter annual particle standard. Cameron County @ 9.7 mg/m3, NE Texas Bowie County @ 9.6 mg/m3, Travis County @ 9.5 mg/m3, Dallas County @ 9.1 mg/m3 and Tarrant County @ 9.2 mg/m3 do not meet a proposed annual PM2.5 standard of 9.0 mg/m3.
A standard of 8.0 mg/m3 would likely cause additional areas of West, Central, Southeast, and South Texas to fall in non-attainment: El Paso @ 8.9 mg/m3, Bexar @ 8.7, Nueces @ 8.6, Jefferson @ 8.3, and Orange @ 8.2.
Five Texas Sunset Advisory Commission reviews of the air and water agencies since 1984-85 have systematically painted serious weaknesses in how the primary environmental agency, what is now the TCEQ, regulates air pollution in all 254 counties.
Fortunately, EPA sets the NAAQS for states to comply with and the standards have been a significant benefit in achieving more rapid air pollution reductions in Texas than would be the case without EPA’s air standards.
While we call on the US EPA to set a strong standard of 8.0 or 9.0 and a 24-hour standard of 25.0, even a lowering of the annual standard to 10.0 would benefit Texans in Houston and South Texas, leading to healthier and longer lives. Reducing soot pollution would save lives and billions of dollars in healthcare costs.