according to the iucn invasive alien species constitute the second most severe threat to freshwater fish species william et al changes in the natural morphology of water bodies eg channelized rivers dams canals can also affect the ability of ecosystems to process and retain pollutants wagenschein and rode high nitrate levels in drinking water can lead to infant methaemoglobinaemia bluebaby syndrome gastric cancer goiter metabolic disorder birth malformations hypertension and livestock poisoning khandare