A chemical emergency has sparked road closures near a Boeing facility after a tanker truck spilled thousands of gallons of toxic nitric acid.
The incident in St Louis was triggered by a mechanical failure, releasing more than 4,500 gallons of the corrosive substance around 9am CT (10am ET).
Nitric acid is a strong oxidizing liquid commonly used in industrial and chemical processes. When inhaled, it can severely irritate or burn the lungs.
The chemical can cause a yellowish cloud to form if spilled, which locals reported seeing over the Boeing site on the 100 block of McDonnell Boulevard, near Lambert International Airport.
The Hazelwood Police Department warned locals that the road is closed between Lindbergh Boulevard and Byassee Drive, which is directly north of the airport that serves over 41,000 passengers daily.
Hazelwood Fire Chief Dan Luley said the cleanup would take several hours, with firefighters working in extreme heat and wearing heavy suits to protect them from the chemical. No injuries have been reported at this time.
A Boeing spokesperson said: 'The safety of our employees is our first priority.
'The Hazelwood Fire Department and Boeing responded to an incident outside one of our facilities and the situation was safely resolved.'
Authorities have yet to announce when the roads will reopen, but all eastbound lanes have been blocked off as crews work to contain the spill.
The incident happened as the truck was removing nitric acid at the facility.
The Metropolitan St Louis Sewer District's response involved the Missouri Department of Natural Resources, the Missouri Sewer District, Hazelwood Police, and several fire departments.
Crews were using dirt to contain the spill and prevent it from reaching nearby sewers and stormwater creeks, Luley said.
However, the fire chief added that there was potential contamination into a creek nearby, and that the St Louis County HAZMAT team is working to ensure a full cleanup.
Any chemicals that entered Coldwater Creek are expected to be cleaned up by the end of the day, local KSDK News reported.
Boeing purchased the facility in 2024, taking over the operations of GKN Aerospace St Louis, which manufactures parts for Boeing's F/A-18 and F-15 programs.
The purpose of the nitric acid is unknown, but Boeing utilizes the chemical in the passivation of stainless steel components, a process that removes 'free iron' from the surface of the metal.
This creates a thin, protective layer of chromium oxide that enhances the corrosion resistance of the material.
Nitric acid is also useful for cleaning and etching metal surfaces, removing contaminants and facilitating further processing steps.
