There are countless scientific studies on this topic, here are a few examples *https://www.csmonitor.com/1988/1216/z4chem5.html + https://www.wearethemighty.com/popular/world-war-i-battlefields-uninhabitable/ + https://pmc.ncbi.nlm.nih.gov/articles/PMC2376985/ + https://pubmed.ncbi.nlm.nih.gov/23077828/ + https://pubmed.ncbi.nlm.nih.gov/16607196/* + https://pmc.ncbi.nlm.nih.gov/articles/PMC7903104/ + https://pubmed.ncbi.nlm.nih.gov/23729095/