I melda Sanchez tries not to go outside if she doesn’t have to.

Dust from the nearby Martin Marietta batch concrete plant in Kirby cakes on her windows, settles on cars and powders the water she stores in a bucket in the garage. Sanchez, 63, blames it for a deep cough that tightens her chest.

“Even walking down to the street,” she said, “I feel out of breath.”

With more than two dozen such plants that supply wet concrete ready to be poured in the San Antonio area, and more than 1,300 across Texas, many residential neighborhoods like hers live with the dust they generate.

But it’s more than a nuisance. It contains tiny particles that can be hazardous to people’s health.

Crystalline silica, a mineral present in the cement and other materials at batch plants, has been linked to lung disease, chronic respiratory problems and silicosis.

Whether the concentration of airborne silica in neighborhoods such as Sanchez’s is high enough to endanger human health hasn’t been established. Plant operators do not monitor silica emissions. Nor does Texas’ environmental regulator.

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Toni Lott stands near property just off Highway 46 between Boerne and Borgheim where a company seeks to build a concrete batch plant. Parents from a nearby Montessori school and area residents have been fighting the plan.

Property is seen behind Toni Lott between Boerne and Borgheim where a company proposes to build a concrete batch plant. Parents from a nearby Montessori school and area residents have been fighting the plan.

For years, the Texas Commission on Environmental Quality said the material doesn’t need to be regulated at batch plants, and for that reason, the state historically did not require plant operators to monitor the air for silica.

That changed, at least on paper, in 2012 when the TCEQ inadvertently removed an exemption for silica. Technically, the plants have been required to eliminate silica from their emissions since then. But no plants in Texas are known to have done so, and the TCEQ has not enforced the requirement.

The industry maintains it’s impossible to produce concrete without releasing silica particles.

The matter will be back before the TCEQ on Sept. 22, when it is expected to decide whether to restore the exemption or impose limits on silica emissions that could affect a $10 billion industry.

For Sanchez and her husband, whose house is less than 250 yards from the concrete plant, the issue comes down not to money but to dust.

“Is someone going to do something about this?” she asked.

Concrete batch plants are popping up throughout Texas to meet demand spurred by development in the nation’s fastest-growing state.

The number of applications for air quality permits for batch plants rose 25 percent from 2014 to 2019, according to the Texas Tribune. Of the 27 permits in Bexar County, 12 were applied for in the last five years, according to the TCEQ.

The plants are operated by companies that include Martin Marietta Inc., a nationwide supplier of building materials based in Raleigh, N.C.; Alabama-based Vulcan Materials Co.; and Alamo Concrete Products Ltd.

Concrete batch plants combine cement, air and materials such as sand and gravel in large drums. The material is loaded into trucks, mixed with water and transported to construction sites.

The plants typically occupy at least an acre, with 40-foot silos that store cement and piles of sand and gravel. The sites and their supporting industries employ 100,000 people a year statewide, according to the Texas Aggregates and Concrete Association. The plants produce about 20 percent of all ready-mix concrete in the United States.

Most plants are within 30 miles of the construction projects they support since concrete’s quality can degrade when hauled long distances. With increasing development in towns and cities, plants are often located close to residential areas.

A company seeking to build a batch concrete plant must obtain an air quality permit that sets limits on emissions of various contaminants — including tiny solid or liquid particles known as particulate matter.

The Standard Permit for Concrete Batch Plants, which the TCEQ created for this industry, exempts certain types of particulate matter from monitoring.

For many years, crystalline silica was among those exempted. The exemption was based on a “protectiveness review” the TCEQ conducted in 2000 that examined contaminants such as nitrogen dioxide, sulfur dioxide and particulate matter.

The study concluded that at a distance of 100 feet from a plant, the minimum permissible distance from a neighboring property, the concentration of particulate matter would not exceed the state’s safety threshold.

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In 2012, while updating the standard permit, the TCEQ removed the exemption for crystalline silica.

The agency now says the removal was an oversight. It went unnoticed until last year, when residents in Tarrant County opposed the construction of a concrete batch plant. In the meantime, batch plants had operated as before, with no objection from the TCEQ. Some 700 plants obtained air quality permits during this period.

Without the exemption, concrete batch plants are not allowed to emit any crystalline silica, which is impossible under their current operating procedures, said Adam Friedman, an environmental lawyer in Austin who represented a group of residents living within 440 yards of the proposed Tarrant County plant.

“They are all emitting it,” Friedman said of the plants.

Other states regulate the facilities more rigorously than Texas does. In San Diego, the Air Pollution Control District requires companies to monitor and measure crystalline silica emissions. And some states require greater distances between the plants and sensitive areas than the 100-foot minimum in Texas. In New Mexico, concrete batch plants must be at least 1,320 feet from an existing park, recreation area or schoolyard.

Crystalline silica is found in the earth’s crust. A crystalline silica particle is one-hundredth the size of a grain of beach sand, making it easy to inhale.

At concrete batch plants, respirable crystalline silica can come from cement and fly ash, a powder used in producing cement. Once inhaled, the mineral can cause lung cancer, kidney disease and silicosis, an incurable lung disease.

The U.S. Environmental Protection Agency does not regulate crystalline silica and has never set exposure limits. But the Occupational Safety and Health Administration has. OSHA regulations limit workplace exposure to respirable silica to a maximum of 50 milligrams per cubic meter of air over an eight-hour day.

The agency strongly advises people who work around the substance to have chest X-rays every three years.

From 2005 to 2014, 1,167 people died of silicosis in the United States, according to the Centers for Disease Control and Prevention.

Many worry about crystalline silica’s effects on people living near plants that emit it. But it’s difficult to draw a causal link between the plants and respiratory problems among residents living in the vicinity.

Elizabeth Matsui, professor of population health and pediatrics at the UT Austin Dell Medical School and a leading expert in environmental exposures, said that compared to the “well-established” risk to workers exposed to crystalline silica, less is known about its potential harm to communities.

“But what we do know is communities that are in close proximity to those emissions are at a higher risk of high concentrations of silica in the air,” she said. “There are certainly concerns about potential health effects.”

For Krystal Henagan, those concerns are more than academic. She and her family moved into the Cedar Grove neighborhood on San Antonio’s Northeast Side in 2013, near a concrete plant, quarry and asphalt plant operated by Vulcan Materials.

Within three months, her 4-year-old son, Tanner, began suffering from what appeared to be severe allergies.

The family moved out at the end of 2013 because of concerns about the boy’s health. By then, he was on seven medications and had been diagnosed with asthma, allergies and breathing issues caused by limestone and silica respiratory irritants affecting his nose, sinuses and lungs.

“I cleaned and cleaned,” said Henagan, who now lives in Boerne, “and the dust just kept coming back.”

Tanner’s symptoms eased significantly after the family moved, his mother said.

No studies show with any confidence that a certain level of silica exposure is safe for communities, Matsui said..

But to conclude that the absence of strong evidence means there’s no health hazard would be “a threat to public health and in particular to vulnerable and disadvantaged communities,” she said.

Kirby residents whose homes are across a field from the Kirby Ready Mix concrete plant, operated by Martin Marietta Inc., live with the dust that the plant emits.

Dust from concrete batch plants does not respect property lines.

Martin Marietta’s Kirby Ready Mix plant sits just off Loop 410, a few hundred feet west of the scattering of homes where Sanchez lives. An open field is all that separates the plant from the neighborhood.

One of Sanchez’s neighbors, Teresa Vogel, 63, said she sometimes sees a cloud of dust moving across the field toward houses. The dust gets into her home and onto window sills and furniture.

“I know it’s bad, and it’s so close,” Vogel said, looking at the plant from her doorstep. “It looks a lot like caliche dust from gravel roads.”

Corey Williams, research and policy director at the nonprofit Air Alliance Houston, has studied the environmental effects of concrete batch plants for years.

“When you hear about communities with dust on their cars and windows, we’re concerned — the assumption being that they’re probably breathing it in,” he said.

A sign was placed on Highway 46 between Boerne and Borgheim by people opposing a proposed concrete batch plant nearby.

Williams is among environmental activists urging the TCEQ to do more research on crystalline silica. He and others believe the “protectiveness review” conducted in 2000 was inadequate in that regard.

They note that the review examined particulate matter as a whole without assessing its components, including crystalline silica. Since the safety limits for crystalline silica and particulate matter overall are different, they contend the study cannot be relied on in making decisions about regulating silica.

“Crystalline silica has a much lower threshold than just particulate matter,” Williams said.

The TCEQ sets limits for particulate matter in the air based on two sizes of particulates: those 2.5 micrometers or smaller and those up to 10 micrometers.

A micrometer is one-millionth of a meter. Plastic wrap is about 10 micrometers thick.

For the larger particulates, the TCEQ limit is 150 milligrams per cubic meter of air over 24 hours. For the smaller ones, the limit is 35 milligrams per cubic meter.

The TCEQ’s protectiveness study predicted that at 100 feet from a batch plant, concentrations of particles in both categories would remain below those safety limits.

But the limit for crystalline silica is a fraction of the limit for other particulate matter. So if silica accounted for as little as 2.9 percent of smaller particles in the air 100 feet from a batch plant, that would exceed the safety threshold for silica.

Williams said the issue wasn’t explored thoroughly in the protectiveness study, and he noted that batch plants are not required to monitor silica concentrations in the air.

The TCEQ, meanwhile, recently estimated crystalline silica levels for concrete batch plants and said they don’t exceed the agency’s limit for the substance, but Williams said such estimates are not a substitute for field-based studies.

Texas counties lack zoning powers, which limits their ability to regulate development in unincorporated areas. That means concrete companies can often build batch plants in places where county officials would prefer not to have them — near schools, parks and residential neighborhoods.

Incorporated municipalities legally can adopt zoning laws, but some have not. Boerne is in that category.

An aerial photo shows property behind a Montessori school just off Highway 46 between Boerne and Borgheim where a a company wants to build a concrete batch plant. Parents from the school and area residents have been fighting the plan.

When Vulcan Materials Co. planned to build a concrete plant across from the Hill Country Montessori School in Boerne in 2018, the Boerne to Bergheim Coalition for a Clean Environment sued to block an air quality permit. The lawsuit failed, but the coalition is appealing. Construction has not started on the plant.

Boerne resident Toni Lott, a member of the coalition, said the TCEQ’s protectiveness review did not consider proximity to homes in its analysis.

“There’s no reason for a concrete plant and its emissions to be so close to people,” said Lott, who transferred her special needs daughter from Hill Country Montessori to a school in San Antonio out of concern that the Vulcan plant would generate hazardous dust. “Not only is that going to affect your property value, but beyond that it can damage your health permanently.”

The TCEQ’s failure to enforce the limit on silica emissions — after the exemption from it was removed — came to light in November, when a judge at the State Office of Administrative Hearings recommended that the TCEQ reject an application for an air quality permit for a batch plant in Tarrant County.

The administrative law judge determined that the proposed plant “was not proven to be safe in respect to crystalline silica, and the TCEQ commissioners agreed,” said Friedman, the lawyer representing opponents of the plant.

The judge’s decision was consistent with a limit of zero for silica emissions — per the letter of the standard air quality permit. TCEQ officials said in court that the exemption for silica had been removed inadvertently and that the agency had carried on as if it was still in place.

The TCEQ said in a statement in advance of its Sept. 22 meeting that it intends to reinsert the exemption in the standard permit, because the agency has already addressed “emission rates and distance limitations for concrete batch plants.”

“The commission originally determined that permits issued to concrete batch plants meeting the requirement of the standard permit were protective of human health and environment,” the TCEQ said.

The exemption’s proponents, including the Texas Aggregates and Concrete Association, see its omission as an administrative error having nothing to do with safety.

“The science is still very sound from back when the TCEQ first did their original study on this particular standard permit,” said Josh Leftwich, president and CEO of the industry association. “To suddenly say in 2021 that this protectiveness is not there for these plants, that’s just not accurate.”

Although the TCEQ has said concrete batch plants that received permits since 2012 can continue to operate without monitoring silica, Williams believes they may be vulnerable to a challenge for not following the letter of their permits.

If the TCEQ were to reverse course and put limits on crystalline silica emissions, all concrete batch plants in Texas likely would have to meet the new requirements eventually. Plant operators must renew their air permits every 10 years.

How much that would affect the industry depends on how tight a limit the TCEQ imposed. Research may find that the limit for crystalline silica emissions doesn’t need to be zero.

“There are so many communities affected by this issue,” Williams said. “And because it’s such a technical issue, it may take a while for people who are not environmental professionals to fully understand what’s being proposed and make their concerns heard.”

Elena Bruess writes for the Express-News through Report for America, a national service program that places journalists in local newsrooms. ReportforAmerica.org. elena.bruess@express-news.net.

Elena Bruess joined the Express-News as the environment and water reporter in June 2021 through Report for America. Previously, she covered water issues for Circle of Blue in Michigan and wrote about COVID-19 in Chicago as a reporting fellow for the Pulitzer Center. She has a master's in science journalism from Northwestern University and a degree from the University of Iowa's undergraduate writing program. She is originally from northeastern Iowa, but also grew up in central Greece.