Could have been too far away. Plus which, an ill wind would probably blow the bad stuff toward our guys if the barrel got ruptured. Finally, who says they didn't get taken out?
To far away for an airstrike???.
The Marine would have MOP gear. And knowing Marines, even of he didn't, he'd go for it.
If we took 'em out it would be a MAJOR event. We'd be rubbing CNN/al Jazeera/BBC's noses in it. Without masks...