New Delhi, July 10 -- Increased river and coastal flooding could expose people to legacy toxic pollutants that were long buried in water and sediments, the United Nations Environment Programme warned in its report Frontiers 2025: The Weight of Time.

These legacy chemicals include heavy metals (like lead, cadmium, which are toxic at even low concentrations), certain persistent organic chemicals (like pesticides, synthetic chemicals, by-products of industrial processes and waste incineration). Both these categories do not breakdown easily and are prone to accumulate in sediments of polluted rivers, lakes and estuaries.

International and national regulations have banned some of them, but the older chemicals continue to stay even decades af...