There's a difference between vinyl chloride and PVC. In organic chemistry the halogen (chlorine) in vinyl chloride is very reactive. That's why it is carcinogenic. However PVC is just a bunch of carbons and is not very reactive at all.
You said your brother got brain cancer in a PVC plant. PVC comes from crude oil and is distillated into aromatic carbons which is very posioness and gets into the air easily if not contained. Thats why many perfumes are aromatic. Not sure the plant your bro dealt with solvents. But if it did, tjey should have been working under hoods or fume extracors or using respirators.
What is the jet stream path? How long until the cloud hits each state in it in path? It supposed to rain later tonight. It will rain HCL acid.
Got to love how this happens in the path of all the largest metro areas NYC, Philly, Boston