Chromium poisoning among leather tanners has long been known. The workers have been found to suffer from ulcers, allergic dermatitis, lung cancer, and liver necrosis due to prolonged contact with chromium salts. One of the highly catastrophic incidences of lung cancer as a result of inhaling dust containing Cr (VI) was reported in 1960 from the Kiryama factory of the Nippon-Denko concern on the island of Hokkaido, Japan.

Pollution of water resources, both surface and underground, by indiscriminate discharge of spent wastes of chromium-based industries has become a serious global concern, for it has created an acute scarcity of safe drinking water in many countries. In August 1975 it was observed that underground drinking water in Tokyo near the chromium (VI))–containing spoil heaps contained more than 2000 times the permissible limit of chromium. In Ludhiana and Chennai, India, chromium levels in underground water have been recorded at more than 12 mg/L and 550–1500 ppm/L, respectively.

A broad survey of available world literature showed that at least 98 wild Lactuca spp. (Asteraceae) have been described taxonomically. The distribution of the genus Lactuca worldwide includes 17 species in Europe, 51 in Asia, 43 in Africa, and 12 in the Americas (mostly the North American subcontinent). Species originating in Asia, Africa, and the Americas form ca. 83% of known Lactuca spp. richness; however, they are very poorly documented from the viewpoint of taxonomic relationships, ecogeography, and variability. The phytogeography of Lactuca spp. regarding their distribution on different continents and in relation to the structure of the lettuce gene pool is discussed. A more detailed analysis of geographical distribution and habitats is given for some species (L. serriola, L. saligna, L. virosa, L. perennis, L. quercina, L. tatarica), which represent the primary, secondary, and tertiary gene pools of cultivated lettuce (L. sativa). Original and synanthropic distributions of Lactuca spp. and their occurrence in natural and secondary habitats are discussed, along with the representation of wild Lactuca spp. in world gene-bank collections. Global biodiversity of Lactuca spp. and their representation in germplasm collections are poorly documented. Future studies of taxonomy, phytogeography, ecology, phylogenetic relationships, and genetic diversity are needed for a more complete understanding of this genus and taxonomically related genera.

Amazonian floodplain forests are characterized by an annual flood pulse with changes of the water table that exceed 10 meters. Seedlings and adult trees are waterlogged or submerged for continuous periods lasting up to seven months per year. The monomodal flood pulse of the rivers causes drastic changes in the bioavailability of nutrients, oxygen levels, and concentrations of phytotoxins. The aquatic phase occurs during a period in which temperature and light conditions are optimal for plant growth and development, implying the need for adaptations. Not only do trees persist in a dormant state, they grow vigorously during most of the year, including the aquatic period. The regularity of flooding may have enhanced the evolution of specific traits, which partially are well known from floodplain trees in other tropical and in temperate regions. Different kinds of adaptations are found at the level of structural, physiological, and phenological traits. Combinations of adaptations regarding seed germination, seedling development, and traits of roots, shoots, and leaves result in a variety of growth strategies among trees. These lead to specific species distributions and zonations along the flooding gradient and within Amazonian floodplain systems (nutrient-rich white-water várzea and nutrient-poor black-water igapó).