10.4 tonnes of methyl mercaptan were released in La Porte, US

DuPont has quantified the amount of methyl mercaptan that leaked from its plant in La Porte, US, last month, killing four workers. After examining its process records from before the leak, and levels in tanks and pipework afterwards, the company estimates around 23,000 pounds (10.4 tonnes) of the chemical escaped.

Federal and state rules require the company report leaks of over 100lb, which Dupont did at the time of the accident. The refined figure has emerged as part of the company’s ongoing investigation.

‘The release occurred inside a process building at the site’s Crop Protection unit and dissipated from openings in that structure over time,’ the company said in a statement. Local authorities monitoring air quality following the release in nearby communities concluded that the release posed no health hazards to the public, noting that methyl mercaptan oxidises and rapidly degrades once released to air.