Don't worry too much! Obviously chemical fires are serious, and inexcusable, and it's unfortunately really easy to downplay their risks when doing back of the napkin math like I did in this thread, but your friend would have to be really unlucky in this scenario. Bear in mind the Chernobyl exclusion zone (the final one) was much larger than warranted at 30km (18.7miles) (to the point that it's probable many more years of life were lost by relocating people, in particular to relatively more polluted urban areas, who didn't need to be).

Fluid dynamics are weird though so it's entirely possible for pockets of these chemicals to get carried far away by the wind, but I think most of it should be heavier than air and stay mostly local. Long term the groundwater contamination is going to cause more lost years of life due to incidences of cancers.