2
Interpreting Selenium
Concentrations
Introduction
The importance of selenium as an environmental contaminant has
gained widespread attention among field biologists, scientists, and natural resource managers during the past two decades. Although the basic
toxicological symptoms and the nutritional paradox of selenium (nutritionally required in small amounts but highly toxic in slightly
greater amounts) have been known for many years (Draize and Beath
1935; Ellis et al. 1937; Rosenfeld and Beath 1946; Hartley and Grant
1961), it was not until the late 1970s and early 1980s that the potential
for widespread contamination of aquatic ecosystems due to human
activities was recognized (Andren et al. 1975; Cherry and Guthrie 1977;
Evans et al. 1980; National Research Council 1980; Braunstein et al.
1981). As recently as 1970, selenium was being called the "unknown
pollutant" in the context of what was known about its cycling and
toxicity in the aquatic environment (Copeland 1970). Yet, within a
few years, several major cases of selenium contamination would take
place and reveal the need to interpret selenium concentrations in a
variety of aquatic habitats. Two examples were the pollution event at
Belews Lake, NC, in which an entire fish community (19 species) was
eliminated due to selenium in wastewater from a coal-fired power
plant (Cumbie and Van Horn 1978; Garrett and Inman 1984; Sorensen
et al. 1984; Lemly 1985a, 1993, 1997; Sorensen 1986), and the episode
at Kesterson National Wildlife Refuge, CA, in which thousands of fish
and waterbirds were poisoned by selenium in agricultural irrigation
drainage (Marshall 1985; Hoffman et al. 1986; Ohlendorf et al. 1986,
1988; Saiki 1986a, 1986b; Saiki and Lowe 1987).
The research studies that have resulted from these and other cases
of selenium contamination provide a foundation for interpreting selenium residues in the various environmental components that influence bioaccumulation and toxicity. This chapter reviews key literature
describing toxic effect levels, and gives guidelines for evaluating sele18
Interpreting Selenium
Concentrations
Introduction
The importance of selenium as an environmental contaminant has
gained widespread attention among field biologists, scientists, and natural resource managers during the past two decades. Although the basic
toxicological symptoms and the nutritional paradox of selenium (nutritionally required in small amounts but highly toxic in slightly
greater amounts) have been known for many years (Draize and Beath
1935; Ellis et al. 1937; Rosenfeld and Beath 1946; Hartley and Grant
1961), it was not until the late 1970s and early 1980s that the potential
for widespread contamination of aquatic ecosystems due to human
activities was recognized (Andren et al. 1975; Cherry and Guthrie 1977;
Evans et al. 1980; National Research Council 1980; Braunstein et al.
1981). As recently as 1970, selenium was being called the "unknown
pollutant" in the context of what was known about its cycling and
toxicity in the aquatic environment (Copeland 1970). Yet, within a
few years, several major cases of selenium contamination would take
place and reveal the need to interpret selenium concentrations in a
variety of aquatic habitats. Two examples were the pollution event at
Belews Lake, NC, in which an entire fish community (19 species) was
eliminated due to selenium in wastewater from a coal-fired power
plant (Cumbie and Van Horn 1978; Garrett and Inman 1984; Sorensen
et al. 1984; Lemly 1985a, 1993, 1997; Sorensen 1986), and the episode
at Kesterson National Wildlife Refuge, CA, in which thousands of fish
and waterbirds were poisoned by selenium in agricultural irrigation
drainage (Marshall 1985; Hoffman et al. 1986; Ohlendorf et al. 1986,
1988; Saiki 1986a, 1986b; Saiki and Lowe 1987).
The research studies that have resulted from these and other cases
of selenium contamination provide a foundation for interpreting selenium residues in the various environmental components that influence bioaccumulation and toxicity. This chapter reviews key literature
describing toxic effect levels, and gives guidelines for evaluating sele18