4
Protocol for Aquatic
Hazard Assessment
Introduction
Agencies that manage natural resources and regulate water quality
are becoming aware of the toxic threat posed by selenium, and much
time and effort is being expended to monitor selenium concentrations
in aquatic habitats. Once these data are collected, it is essential to
conduct an overall evaluation and determine the degree of hazard
present in order to identify appropriate management actions and develop local water quality criteria to protect aquatic life. However, few
comprehensive hazard assessments have been completed. There are
two likely reasons for this. First, it has been difficult for those conducting the monitoring programs to determine the toxicological significance of selenium residues in aquatic organisms. Locating, obtaining,
and interpreting the results of selenium toxicity tests for a variety of
aquatic species is a difficult task because of the time required. Fortunately, this type of information synthesis has been done. Guidelines
are now available for evaluating selenium in food-chain organisms
and fish and aquatic bird tissues based on an extensive amount of
toxicological information (see Chapter 2). Interpreting selenium residues is no longer a problem.
The second reason is the lack of a broadly applicable procedure for
conducting an aquatic hazard assessment of selenium. This has left investigators on their own, struggling with selenium monitoring data and trying to come up with a reasonable approach for characterizing hazard.
Several approaches have been tried. Early attempts relied on comparisons between waterborne concentrations measured in the field and concentrations that were toxic to aquatic organisms in the laboratory (Cumbie
and Van Horn 1978; Adams and Johnson 1981; Lemly 1982). However,
the laboratory data did not adequately explain the greater toxic effects
observed for fish in the field. Subsequent research on selenium indicated
that food-chain bioaccumulation, dietary intake, and reproductive effects
61
Protocol for Aquatic
Hazard Assessment
Introduction
Agencies that manage natural resources and regulate water quality
are becoming aware of the toxic threat posed by selenium, and much
time and effort is being expended to monitor selenium concentrations
in aquatic habitats. Once these data are collected, it is essential to
conduct an overall evaluation and determine the degree of hazard
present in order to identify appropriate management actions and develop local water quality criteria to protect aquatic life. However, few
comprehensive hazard assessments have been completed. There are
two likely reasons for this. First, it has been difficult for those conducting the monitoring programs to determine the toxicological significance of selenium residues in aquatic organisms. Locating, obtaining,
and interpreting the results of selenium toxicity tests for a variety of
aquatic species is a difficult task because of the time required. Fortunately, this type of information synthesis has been done. Guidelines
are now available for evaluating selenium in food-chain organisms
and fish and aquatic bird tissues based on an extensive amount of
toxicological information (see Chapter 2). Interpreting selenium residues is no longer a problem.
The second reason is the lack of a broadly applicable procedure for
conducting an aquatic hazard assessment of selenium. This has left investigators on their own, struggling with selenium monitoring data and trying to come up with a reasonable approach for characterizing hazard.
Several approaches have been tried. Early attempts relied on comparisons between waterborne concentrations measured in the field and concentrations that were toxic to aquatic organisms in the laboratory (Cumbie
and Van Horn 1978; Adams and Johnson 1981; Lemly 1982). However,
the laboratory data did not adequately explain the greater toxic effects
observed for fish in the field. Subsequent research on selenium indicated
that food-chain bioaccumulation, dietary intake, and reproductive effects
61