Inquire about what the person values and provide information about the dangers of herbicides and their impact on the environment and human health.
What do you value?  There is no acceptable level of herbicides in living cells because the body will not flush it out of the system. It is in the  soil, watersheds, air, plants or other animals.  So if you can live without water, breathing, other life forms and the food you eat .  You need to take a look what has  determined an unsafe level of toxins being sprayed apparently everyone but the Forestry Department understands that once absorbed by the body you cannot get rid of it.  With Chidren it's evern more severe impacting their phsycial and emotional development.  There is no question about the damage these herbicides toxins do.  So get informed because you sound ignorant about the subject.