Large stores use sweeping compounds and sweeping compounds are made from sawdust, sand, and oil. I am not sure... but it is possible that some type of sweeping compound was being used AND possibly this sweeping compound may have had Spanish Cedar sawdust in it? Spanish Cedar sawdust is highly irritating even in small amounts. It leaves a metallic taste in your mouth and will give you a sore throat and will make you feel like you can't breath and that your throat is closing up. It takes very little exposure to it and all the symptoms start right away when you are exposed to it even in very very small amounts. If I was on the HazMat team, this would be one item I would be looking for in the stores, to see if they had someone pushing sweeping compound around the store when the problems occurred. I would have it tested to see if it had Spanish Cedar sawdust in it. Some people are more sensitive to it than others, this would explain why some got sick and not others. Spanish Cedar sawdust is very small in particle size, it actually comes out like a powder when you cut it on a saw and it does not make large pieces of sawdust like Pine or other woods do. Spanish Cedar sawdust can become airborne easily. Is it possible that Spanish Cedar sawdust is being mixed or mistakenly mixed in when they made the sweeping compound? Do these stores use sweeping compound and if so, was it being used when the people became sick?
Sweeping Compound
Spanish Cedar has natural oils in it, so it may be used in sweeping compounds. Just some thoughts and maybe a possibility of what may have caused these instant illnesses... Sweepers move around stores pushing the sweeping compound with a dry flat mop and the human sweepers also tend to shake out the dry flat mops causing the dust to float into the air.