The man, who works for a transport company, was advised by his employer to seek medical attention after a colleague fell ill.
"The employee sought medical care at Sunderby Hospital and traces of various toxic gases were found in his blood," the company's CEO writes in a report to the Swedish Work Environment Authority, according to SVT.
The man left the hospital after about eight hours and the company has no further information about the case.
Around 20 people have fallen ill with various symptoms in connection with groundwork at SSAB's new steel mill in Luleå.
The cause of the illnesses is still unknown, but the County Administrative Board has stated that the construction is taking place in a heavily contaminated area.
