Day 7: Selenium
Although selenium plays an important role in metabolic processes, large amounts of it consumed through drinking water can produce gastrointestinal disorders, hair loss, fatigue and neurological damage. Excessive exposure can damage the liver and eventually lead to death. In general, selenium contamination of water comes from improper disposal of waste from manufacturing and industrial activities, however it has also been shown that runoff produced by the agricultural development of dry areas can absorb water soluble selenium compounds, which then leaches into surface water and groundwater.
In 1873, Willoughby Smith discovered that the electrical resistance of selenium was dependent on levels of ambient light, a property that made it ideal for early photocells, light meters, numerous electrical components. It played a significant role in electronics until it was largely replaced by Silicon in the 1970’s. Today selenium demand continues to dwindle, however it still is used in photocopying, and photovoltaic applications.