An investigation is underway into what caused a fatal leak of approximately 100,000 pounds (45,359kg) of a mixture of chemicals – including acetic acid, methyl iodide and hydrogen iodide – from a LyondellBasell plant in La Porte, Texas, US, on 27 July. The chemical release killed two contractors working on-site and sent another 30 people to the hospital, most with respiratory distress and at least one with burns.

‘We are not sure exactly what happened, there is decontamination that has to take place before we can actually enter that area, and the company is working on that now,’ said the county’s assistant chief fire marshall, Bob Royall, during a 28 July press conference .

The leak occurred at LyondellBasell’s acetyls business unit that manufactures acetic acid and vinylacetate, which is produced by combining acetic acid with ethylene and oxygen. The company describes this site as the world’s third largest producer of glacial acetic acid, a flavour enhancer and food preservative, and it includes two barge docks on the Houston Ship Channel.

LyondellBasell said its La Porte chemical complex gave the ‘all clear’ early in the morning on 28 July, after a response team acted quickly to isolate and contain the leak. Clean-up and decontamination efforts were continuing at that time, and monitoring activities did not indicate air quality or environmental impacts, the company stated .

Just a few days before the incident, employees at a separate Dow Chemical plant in La Porte were evacuated, as well as residents within a half mile radius of the facility, after it was discovered that an over-pressurised tanker truck was venting hydroxy ethyl acrylate. The evacuation was triggered by concerns about a potential explosion, which never occurred. Air monitoring has also indicated that there was no off-site impact from that chemical leak.

Back in late 2014, 10 tonnes of methyl mercaptan was released from an insecticide plant in La Porte that was owned by DuPont, leading to the deaths of four workers. DuPont permanently shut that facility down in April 2016, and the company agreed in August 2018 to pay a $3.1 million (£2.4 million) civil penalty to resolve chemical accident prevention violations. That incident took place at a separate facility than the one involved in the 27 July incident, which LyondellBasell told Chemistry World it has never owned.