In brief, More than 530 hyper accumulators of heavy metals have been identified worldwide and the list is growing. Among those majority are Ni hyper accumulators (75%), only 5 species are Cd hyper accumulators and 12-14 species are Zn hyper accumulators. Approximately, 25% of discovered hyper accumulator plant belong to the family of Brassicaceae (genera Thlaspi and Alyssum).
After brassicaceae, most of the hyper accumulators belong to the families; Crassulaceae, Solanaceae, Fabaceae, Asteraceae, Rubiaceae, Scrophulariaceae and Chenopodiaceae, brake ferns of genus Pteris are known to hyperaccumulate As.