I have only been in one plume grounding incident. It happened in Bratton in Wiltshire downwind from a factory chimney that puts thousand of tonnes of poisons into the atmosphere every year
At the time I was visiting an elderly friend when suddenly on the pavement I was enveloped in a blanket of foul smelling tyre fumes. It was smothering and highly unpleasant. The experience lasted for about a minute before the air cleared and I was once again breathing air that you would expect in a rural village.