The towering fire at the Dow Chemical plant this summer released enough of the potent cancer-causing chemical ethylene oxide to match nearly a decade’s worth of typical emissions at the plant, a new company estimate indicates.
The ethylene oxide emissions were one of at least 17 chemicals — as well as tiny particles that can irritate the respiratory system — that Dow officials say were sent into the air during the explosions, large fireball and raging blaze in mid-July at the complex north of Plaquemine and also to much lesser extent in the weeks-long aftermath, as the company tried to clear the smoldering equipment of lingering chemicals.
In a new report, however, Dow officials told state regulators that they are still investigating what caused the conflagration inside the company’s Glycol II Unit that burned for a day and half between July 14 and July 16.
“Dow is continuing its investigation of this event and will provide a follow up report as authorized (by state law),” the company told regulators Wednesday.
The fire forced local and state officials to shut highways and send a few hundred people indoors with their air-conditioning off and windows shut for several hours on a steamy night and early morning in mid-July. No injuries have been reported, Dow says.
Ethylene oxide is a highly flammable, colorless gas. With long-term exposure, it is a potent human carcinogen, the U.S. Environmental Protection Agency says.
The chemical, which is used in the petrochemical industry but also as a critical element in medical sterilization, has gained new scrutiny over the past decade or so after the EPA concluded it was more carcinogenic than earlier believed.
Federal air pollution risk data show it has been a major driver of carcinogenic risk in portions of the Mississippi River corridor, triggering federal regulators to call on some plants to cut their emissions.
Dow officials estimated that 31,525 pounds of ethylene oxide were emitted. That’s equivalent to about two-thirds of all reported ethylene oxide air emissions in Louisiana in 2021, the latest federal toxics reporting data say.
The entire 1,500-acre Dow facility averaged about 3,461 pounds of ethylene oxide air emissions annually between 2013 and 2021, the self-reported federal data show.
Over that nine-year period combined, total ethylene oxide emissions at Dow hit 31,153 pounds, the federal data show.
In a statement Thursday, Dow officials added, however, that a majority of the reported release of ethylene oxide was combusted in the initial explosion and more was burned up in the remaining fire. All of the ethylene oxide release happened in the first 12 hours of the fire, Dow officials said.
During the chemical reactions caused by that combustion, the gas was converted into relatively less dangerous chemicals like methane, hydrogen, ethylene, carbon dioxide, carbon monoxide and water, Dow officials said, echoing the conclusion of some experts earlier this summer.
Dow, its contract air monitoring company, CTEH, and DEQ have all said their air monitoring did not pick up dangerous levels, if any levels at all, of ethylene oxide or other potentially dangerous chemicals outside the facility or in nearby communities.
These finding have drawn criticism and skepticism from local environmental groups, a view amplified again after the large Marathon Petroleum Co. oil refinery fire late last month in Garyville. The fire burned naphtha and sent a dark, towering plume high into the sky over St. John the Baptist, St. James and Ascension parishes.
“Anyone looking at the smoke can tell that this release is far from contained,” Anne Rolfes, executive director of the Louisiana Bucket Brigade, said in a statement on Aug. 25. “Nearby residents are reporting aggravated asthma and other respiratory symptoms.”
Dow officials said each step of the analytical process used to calculate the emissions releases from the July fire was evaluated by a third-party expert, Baker Engineering and Risk Consultants.
“Dow has taken extensive measures to ensure accuracy in calculating emissions from the July 14 incident at its Glycol 2 unit,” the company statement says.
Ethyl chloride constituted the largest single release from the Dow fire. Company officials estimated for DEQ that 59,609 pounds were released, more than twice the amount emitted statewide from all industrial facilities in the state in 2021, federal data show.
In 2021, Dow sent 154 pounds of ethyl chloride into the air.
Also known as chloroethane, ethyl chloride is another flammable colorless gas. It can cause dizziness, a drunken feeling and even unconsciousness in high, short-term doses.
Its long-term carcinogenic effects on humans are unknown, but one two-year study found it caused cancer in female mice that inhaled the gas, according to the U.S. Environmental Protection Agency.
Other sizeable releases from the fire were ethylene at 3,892 pounds and methane at 3,330 pounds, both flammable hydrocarbons.
Releases of a collection of several other chemicals were estimated at less than 30 pounds to as little as less than a pound: butane, isobutane, propane, cyclopropane, propylene, acetaldehyde and a collection of undetermined volatile organic compounds.
The company also reported less than a pound each of vinyl chloride, another known carcinogen, and methyl chloride.
Dow said that all of the compounds reported as being released, except ethylene, ethyl chloride and a portion of methane, came from one emissions point and were released within the first 12 hours of the incident, including ethylene oxide.
“All of these compounds were detectable through monitoring technology used during the incident,” the company said.
In the report to DEQ, the company noted that 485 pounds of ethylene oxide escaped into the plant’s water discharge system, which was handling water used to control and extinguish the fire that overflowed from containment systems.
Testing of water on July 15 near the glycol unit about three-quarters of the mile from the Mississippi River did detect some low concentrations of ethylene oxide. Under a state variance for the fire, that overflow water wound up in the river untreated.
But Dow said the chemical likely volatilized, or turned back from a liquid into a gas, which is ethylene oxide’s natural state at outside temperatures and pressures, and ended up in the air.
The EPA has noted this aspect of ethylene oxide’s characteristics, saying that though the chemical can dissolve in water, it can also evaporate from water back into the air.
The EPA says this is a reason a rainstorm is not likely to wash ethylene oxide from the air, though chemical’s high volatility means it doesn’t persist long in one spot in the air but will disperse quickly. The chemical has a natural, summertime half-life in the air of about 69 days.
The river is also a powerful force for dilution of chemical pollutants, state regulators say.