Gau mutra and Gobar are in the base of all purification methods prescribed in Ayurveda. In fact, Bangladesh or Greater Bengal used to use to reduce ground water arsenic toxicity.
Gau mutra and Gobar = अपान
अपान = महाप्राण (Universal sum total of all our Prana) ‘s feature to purge toxins for current organism. So that they can maintain immunity i.e. ability to recognize self from non-self and so that they can perform their dharma peacefully.
So when metals are purified in Gau mutra and Gobar, अपान filters out toxins from metals, toxins for parent organism i.e. Cow (and all mammalian animals). They may not be toxins as such but for parent organism class, they are difficult to digest. So called toxins.
Same concept applies to Agriculture.
Lack of गोबर & मूत्र in forest/farm = Lack of अपान प्राण in प्राणमयकोश of the local body (forest/farm) = Compromised intuitive intelligence for plant’s प्राणमयकोश for elimination process = Accumulation of toxins (आम) = Diseases and death
Ayurveda prefers no boundary of safe plant vs poisonous plant or safe animal vs venomous animal. Safe metal vs Toxic metal.
What a bold and fearless science!
There is always a meticulous purification method employed before administering plants based drugs.
What is used for purification?
None other than Gau mutra of desi breed cow.
There is only one effective and sustainable detoxification and de-pollution method that I know: Take help of mother Gau. Be it farming or food or medicine.