The inorganic pigments which are used in plastics, paints, enamels, inks, rubbers, and ceramics are manufactured using cadmium sulfoselenide (Waitkins et al. 1942).
Figure 3.1 Global refinery production for 2018 and 2019 (USGS 2020).
To increase the resilience of rubber and to promote heat, oxidation, and abrasion resistance, Se compounds are used as accelerators and vulcanizing agents in rubber manufacturing (Dudley 1938). Se is added to the stainless steel during manufacturing, which will improve its characteristic properties such as forging, casting, and machining without sacrificing corrosion resistance. Se compounds such Se dioxides catalyze many organic reactions such as hydrogenation, oxidation, isomerization, and polymerization. Se is extensively utilized to help control micro cracking in electroplated chromium as reducing or oxidizing agent (Rashkov et al. 1983). Due to the antioxidant and antigalling properties of Se it is utilized in insecticides, parasiticides, bactericides and herbicides, mercury vapor detectors, insect repellents, etc. (Mechora 2019). Since 1974 the Food and Drug Administration has removed the ban on Se and established it as an essential micronutrient. Therefore, Se in small amounts is used as a food additive for livestock. Utilization of Se in industrial applications has been proven for a long time and the wastes generated from these industrial applications are polluting the environment day by day.
Se is also used as catalyst in some chemical reactions. In X‐ray crystallography, incorporation of one or more Se atoms in place of sulfur helps with multiple or single wavelength anomalous dispersion. Se is widely used for toning of photographic prints and it intensifies tonal range of black and white photographic images, resulting in improved permanence of prints (Wall 1924). The worldwide consumption of Se in different applications is presented in Figure 3.2.
Figure 3.2 Global consumption of Se (USGS 2020).
3.6 Conclusions
This chapter summarized the occurrence, sources, and importance of Se in environment. The major source of Se is from natural activities and nowadays anthropogenic sources are also releasing a huge amount of Se into the environment. The Se from the soil and water enters into the food chain where it is bioaccumulated and transferred into humans and animals through diet.
Earlier, the deficiency of Se was of major concern as it could be one of the important factors in various diseases such as Keshan and Kashin–Beck diseases, infertility in female, etc. However, augmented consumption can also lead to the adverse health impacts.
Demand for Se has increased due to the growth of industrialization and the use of Se in different manufacturing processes. Major Se production is from refineries and copper smelting processes. In the United States fish and wildlife poisoning occurred due to elevated concentration of Se in water. Such episodes have grabbed the attention of researchers for data generation and possible implications of excessive Se and its hazards to human health. Se is an important trace element due to its Janus nature. It is an essential nutrient to human and animal while it can also act as potent toxin if consumed beyond certain limits. Timely dealing with this issue in connection with an environmental Se database can be useful to avoid any adverse impact on humans and the environment.
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