This is totally correct. It is also not very applicable to drinking water & whole house systems that homeowners are interested in. There are carbon cartridges

This is totally correct. It is also not very applicable to drinking water & whole house systems that homeowners are interested in. There are carbon cartridges with ion-exchanges resins blended into the block that seem to be effective for lead removal at low flow rates. They tend to have lower flow-rates and capacity than is ideal.