Regulatory issues surrounding the management of selenium-introduction to a special series of papers.

Selenium (Se) is a naturally occurring metalloid in soils and rocks that is released by weathering processes; it is also enriched by some anthropogenic activities, including mining and agriculture. The mechanism of Se aquatic toxicity has been understood for several decades; at elevated concentrations, dietary Se can accumulate in maternal tissues of fish and birds, become deposited into their eggs, and can potentially result in impaired embryological development. North American environmental regulations have acknowledged differences in species sensitivity and variation among aquatic environments (i.e., lentic and lotic) that influence Se toxicity. The above subjects were thoroughly reviewed in a state-of-science SETAC Pellston workshop and book, entitled Ecological assessment of selenium in the aquatic environment, published in 2010. Since the publication of that book, regulatory guidance in North America has evolved further to enhance the protection of aquatic life exposed to Se. This IEAM special series entitled "Regulatory issues surrounding the management of selenium" is a compilation of recent research and reviews from North American experts addressing critical environmental, physiological, and operational factors warranting consideration in support of Se regulatory frameworks.