The areas are saturated with unexploded shells (including many gas shells), grenades, and rusting ammunition. Soils were heavily polluted by lead, mercury, chlorine, arsenic, various dangerous gases, acids, and human and animal remains. The area was also littered with ammunition depots and chemical plants. The land of the Western Front is covered in old trenches and shell holes.
Each year, numerous unexploded shells are recovered from former WWI battlefields in what is known as the iron harvest. According to the Sécurité Civile, the French agency in charge of the land management of Zone Rouge, 300 to 700 more years at this current rate will be needed to clean the area completely.  Some experiments conducted in 2005–06 discovered up to 300 shells per hectare (120 per acre) in the top  of soil in the worst areas.
Areas where 99% of all plants still die remain off limits (for example, two small pieces of land close to Ypres and the Woëvre), as arsenic constitutes up to 175,907 mg (175.9 g) per kilogramme of soil samples because arsenical shells were destroyed in the 1920s.