Lead causes mental retardation of children. The use of lead free petrol is one measure to check this pollution, hut these heavy metals are also present in factory effluents, and need to be removed, before these effluents are discharged to natural land or waters.

The property of some species of bacteria and algae, to extract metals from their surroundings, has been utilized to purify industrial effluents.

Biotechnological approaches are recommended, where metal extracting forms (mainly algae) can be grown in ponds, where factory effluents(rich in heavy metals) are discharged. The microbes will extract the heavy metals and sequester them inside their cell membranes. The metal can be subsequently recovered from these microbes.