It’s been over a year since researchers with the U.S. Environmental Protection Agency started monitoring the air near a LaPlace plant that for decades has produced a chemical classified in 2010 as a likely carcinogen.

Several months into the monitoring, officials from the plant voluntarily pledged to reduce airborne emissions of the chemical, chloroprene, by 85 percent, and they’ve begun a $17.5 million installation designed to accomplish that.

But based on the monitoring results so far, environmentalists are saying the goal isn’t nearly ambitious enough.

Even if Denka Performance Elastomer LLC achieves it, they say, the air for miles around still will contain levels of chloroprene that far exceed those that the EPA says create an elevated risk of cancer.

For nearly 50 years, the chemical has been used to make neoprene, the basis of products like wetsuits, electrical insulation, coatings and orthopedic braces.

Regulators, who say there’s no hard proof showing immediate health risks, have accused environmentalists and activist groups of stirring up a panic over nothing.

In a recent appearance before the St. John the Baptist Parish Council, Chuck Brown, secretary of the Louisiana Department of Environmental Quality, accused Denka critics of “fear-mongering.”

Sorting out the truth is difficult, in part because the long-term effects of chloroprene exposure are still not well understood. The task of measuring risk is made more difficult by a profusion of other variables, including the proximity of the exposed person to the site, the amount of time chloroprene stays in the body and the tendency for chloroprene levels to spike and dip over time.

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As the data are gathered from six monitoring sites and scientists begin to pore over them, some of those who live in the neighborhood of the plant — along the Mississippi River, at LaPlace’s upriver end — continue to fret.

Kellie Tabb, 56, who lost her right lung to cancer, is among them.

"I'm scared. I'm scared I'm going to lose my other lung," Tabb said at a community meeting at a church in Reserve this month. "I'm thinking I have to move."

Assessing the risk

The EPA assesses the risk that an airborne toxin poses by trying to determine the likelihood that a person could get cancer as a result of exposure to it.

Ideally, the risk would be one in a million or less, but the EPA considers the “upper limit of acceptability” to be one in 10,000. In other words, at that level of exposure, over a lifetime — measured consistently over 70 years — one of every 10,000 people would get cancer who otherwise would not.

For chloroprene, the EPA considers that maximum acceptable level to be 0.2 micrograms per cubic meter.

The Denka plant has far exceeded that threshold at times. One EPA measurement, taken last year, showed a level of chloroprene in the air 765 times what the agency considers acceptable.

Although the levels have come down since, numbers from this month show one area was subjected to 88 times the concentration the EPA says puts residents at increased risk.

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A monitoring site near East St. John High School, which is about a mile from the plant and where more than 1,350 students are enrolled, detected chloroprene levels 33 times the concentration thought to increase chances of harm.

Although some of those numbers represent spikes rather than steady levels, members of the Louisiana Environmental Action Network — which has been involved in studying the monitoring results — say spikes are routine and can bring their own set of health problems.

According to the EPA, short-term exposure to high levels of chloroprene can cause headaches, dizziness, respiratory irritation, chest pains and hair loss, as well as gastrointestinal disorders, dermatitis, corneal damage and fatigue.

But it’s long-term exposure, and the increased risk of cancer, that’s of most concern. The EPA says studies suggest chloroprene causes an increased risk of lung, liver and kidney cancers, as well as leukemia and immune problems. Members of the environmental network say the initial data for long-term average exposure also are worrisome.

Over a year's time, data collected from all six monitoring sites show that residents have been exposed to an average of between 12 and 58 times the amount the EPA says is the “upper limit of acceptability.”

So even if plant officials were to reduce emissions by 85 percent, residents would still be exposed to between 1.8 and 8.7 times that threshold, according to calculations done by both The New Orleans Advocate and members of the environmental network.

Perhaps even more alarming are the EPA’s estimates of cancer risk by census tract, which the agency has been calculating based on industry emissions intermittently since 1996. On average, the risk runs at one in a million. But in St. John Parish, in the census tract that includes most of the Denka plant, the EPA estimates that the risk is 802 times higher.

The risk level decreases the farther one travels from the plant. But even 10 miles away, in Garyville, the EPA estimates the risk is still more than 53 times the average in the rest of the country.

The latest National Air Toxics Assessment study, done in 2011 and released in 2015, found that the approximately 43,000 people in St. John Parish have the highest potential risk of cancer in the country because of Denka-related air pollution.

The EPA didn't specifically say chloroprene from Denka would cause cancer in St. John. Instead, officials said in a memo that "more detailed assessments are needed" to "accurately characterize" health risks.

Robert Taylor, who founded the group Concerned Citizens of St. John and has been working with the environmental network, has for the past year been telling Parish Council members that the plant unfairly "poisons" his neighborhood, located directly behind the plant. But he's not just worried about himself.

"That plant right here is doing this to the whole parish," Taylor said.

State: No cause for panic

Although the EPA risk estimates are alarming, local and state officials have largely taken a "wait and see" approach as monitoring proceeds and as the plant continues its upgrades.

They note that chloroprene has been been produced at the same site in LaPlace for the past 48 years.

Department of Environmental Quality officials repeatedly have said that residents shouldn't panic, noting that, although chloroprene levels fluctuate, sometimes the sites show none at all.

The New Orleans Advocate calculated that at some of the monitoring locations, there is no detectable concentration of chloroprene in the air a third of the time.

"There is no smoking gun in St. John Parish," DEQ spokesman Greg Langley said. He pointed to an assessment by the organization’s toxicologist, Dr. June Sutherlin, saying that neither the Louisiana Environmental Action Network nor Concerned Citizens of St. John has "adequate monitoring data" to estimate "potential long-term exposure concentrations."

Brown, the department secretary, has told council and school district officials that the environmentalists are "fear-mongering."

Brown further called the 0.2 micrograms level "a guidance" from the EPA, rather than an enforceable threshold or "protective standard." Last year, he advised people to "detach" themselves "from that number.”

And Dr. LuAnn White, a toxicologist at Tulane University, pointed to data from the Louisiana Tumor Registry, collected by the LSU Health Sciences Center School of Public Health, which showed no higher incidence of cancer in the region than elsewhere in the state.

In the meantime, Jorge Lavastida, a spokesman and plant manager for Denka, told The New Orleans Advocate that the plant is "fully tasked and focused on" achieving requirements that will be set by the EPA and the DEQ in determining "what the right level of emission reduction should be."

The biggest change is expected to come by the end of the year, when the company will install a regenerative thermal oxidizer, which Lavastida said has proved effective in removing chloroprene emissions from plants in Japan.

Denka is also adding a vent condenser, installing a vacuum pump, replacing an older vacuum system and installing more than 1,200 feet of pipe that will redirect the chemical to be removed by combustion.

4 decades of neoprene

The Denka plant used to be owned by DuPont, which began producing neoprene there in 1969.

Nearly 30 years earlier, DuPont published an internal memo saying chloroprene could cause health problems. Marked "personal and confidential," the report — which is public but was first highlighted by the Louisiana Environmental Action Network and The Intercept — said clinical and experimental studies done over a period of years showed "exposure of concentrations of toxic vapors, gases or fumes" from the chemical might "eventually cause serious disturbance of health."

Among the complaints listed in that report were headaches, fatigue, gastric disturbance, dizziness, respiratory distress and "pain around the heart," or palpitation.

The report wasn't handed over to the EPA until 1991. It took another 20 years for the agency to classify chloroprene as a "likely" human carcinogen.

Since the EPA identified the potential danger caused by the plant last year and began monitoring the air, members of Concerned Citizens of St. John have been meeting with the environmental network every two weeks to to discuss the data. Many of them are convinced the plant has contributed to health problems.

Tabb, who has lived in St. John for 25 years, said that in addition to losing her right lung to cancer, she suffers from rapid heartbeat and shortness of breath.

Taylor, the founder of Concerned Citizens, and Marylee Orr, founder of the environmental network, said the anecdotal evidence of people with health problems in St. John is "overwhelming."

And it's not just cancer they worry about.

For example, Taylor called 911 last year when his wife, Zenovia, had trouble breathing while the air was thick with chemical odor. She suffers from multiple sclerosis, an autoimmune disease.

Lydia Gerard, a 62-year-old clerical worker, also has an autoimmune disease and regularly breaks out into hives for "no apparent reason." Her husband has kidney cancer.

St. John resident Donna Jackson, 71, survived brain surgery after a tumor was found.

Taylor complained that government is putting industry concerns ahead of citizens' health. He believes officials should order the plant to reduce production of chloroprene while the levels are monitored by the EPA to better assess the risk.

Because the risk from chloroprene exposure is measured over a lifetime, environmentalists fear more problems will surface as local residents get older.

"This is a pretty terrifying problem to find out about 40 years later," Orr said. "It’s tragic. So many are already experiencing terrible health problems."

Uncertain future

Langley, of the Department of Environmental Quality, said he is "optimistic" that initial drops in chloroprene emissions "will be reduced much further" once improvements to the plant are complete.

Although the plant has set a goal of reducing emissions by 85 percent, the EPA has yet to weigh in on whether that will produce "protective" air quality for St. John residents. The agency is expected eventually to decide what additional actions, if any, Denka needs to take.

Meanwhile, as residents wait for the EPA to act, some worry that the current monitoring program could be threatened by deep cuts to the agency’s funding proposed by President Donald Trump.

Among the programs that could be threatened, Orr said, is the Integrated Risk Information System, a database the EPA has been building of human health effects from potentially harmful substances. It was a database study that underscored the risks of chloroprene years ago.

"The threat is that there will be this huge void of information they won’t know," Orr said. "There will be no monitoring to know if numbers are going up or down."

Follow Della Hasselle on Twitter, @dellahasselle.