How many of you have seen this?
An air sample is taken for a potentially hazardous environment. Five or ten or twenty toxins show up in the analysis, but each one of them is below the level you should be concerned with according to the MSDS. No problem, right?
Let's say it is the scene of a hazardous waste hauler where all sorts of chemicals were being transported, but each below the threshhold of concern. Is it safe.
Look, virtually no studies do in depth analysis of the health and safety exposure of mixtures of chemicals. Try looking up the MSDS sheet for a mixture of styrene, toluene, and benzene. Good luck finding one.
And according to Dennis Patrick, noted Industrial Hygienist and Safety Expert and founder of EPG Ltd., the real problem is the synergistic effects.
The problem to be addressed by the community of experts is how to rate cominbation of chemicals. I have my own way of doing this- I add up the totals of all the toxins, and if the aggregated number is higher than the lowest IDLH, then the whole mess is hazardous until proven otherwise. Not everyone likes this approach, but they aren't the ones who have to be around it, either.