The internal investigation of what caused the chemical smell followed by evacuation of the Alfa building in Solna on May 12 has led to a theory about the sequence of events.
“We think it started with an accidental spill of xylene in a hood”, Said Fredrik Sterky, Site Manager of SciLifeLab in Stockholm. “When the xylene evaporated in the laboratory sewage system it spread throughout the building via dry sink traps. However, at this stage we cannot exclude alternative or additional sources.”
Xylene is a highly volatile substance, which might explain the dramatic effects although only a small amount was spilled in the hood. Humans also feel the smell of xylene already at very low air concentration (0.6 ppm). The symptoms of the affected people (nausea, dizziness etc.) also match the properties of xylene and when subjected to a smell test, the affected people also identified the leaked chemical as xylene.
“Now, there is a police investigation going on and hopefully it will give us some hard evidence of the cause and measured levels of xylene, but we think it is likely that it happened like this” Said Fredrik Sterky, Site Manager of SciLifeLab in Stockholm.
The police investigation is now continuing, as is an investigation by Arbetsmiljöverket and the landlord Akademiska hus. SciLifeLab will look over the safety routines to prevent similar incidents in the future.