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4. Protocol for Aquatic Hazard Assessment
water quality criterion for the substance under evaluation, and it has
been widely applied for aquatic risk assessment in the United States
for many years. However, there are substantial differences between
the Protocol and HQ. The Protocol focuses on food-chain bioaccumulation and reproductive impairment in fish and aquatic birds
whereas HQ primarily uses information on waterborne selenium.
Comparison of the 2 methods gives additional insight into the validity
of the Protocol for hazard assessment.
The HQ for selenium is calculated by dividing the geometric mean
measured or expected environmental waterborne concentration by the
United States national water quality criterion for chronic exposure (5
Ilg SelL). The rationale of this technique is that, if waterborne concentrations of selenium exceed the criterion, substantial hazard exists. If
concentrations are below the criterion, then minimal hazard is expected. This method provides a quantitative estimate of the hazard
associated with single chemicals or elements, primarily from a waterborne route of exposure. However, the USEPA process for deriving national water quality criteria does allow for inclusion of data that would
account for bioaccumulation. In the case of selenium, field data on
food-chain transfer and reproductive toxicity to fish were included in
the derivation, and were largely responsible for the criterion being
lowered to its current value of 5 Ilg SelL (EPA 1987). Thus, even though
HQ uses only waterborne values, it reflects the extent to which the
United States national criterion is protective of dietary and reproductive hazards. Guidelines for interpreting HQ calculations are:
HQ < 0.1, No hazard exits
HQ =0.1-1.0, Hazard is low
HQ =1.1-10, Hazard is moderate
HQ> 10, Hazard is high
Field Sites and Hazard Ratings
Selenium data from three ecologically distinct systems were used in
the comparison: wetlands (Stephens et al. 1988, 1992; Hoffman et al.
1990; Pelz and Waddell 1991; Waddell and Stranger 1992), rivers (Finger 1995), and reservoirs (Lemly 1997b). Selenium concentrations in
whole-body fish samples and aquatic bird livers were converted to
equivalent egg concentrations for use in the Protocol method (Lemly
and Smith 1987: whole-body values x 3.3 for fish and liver values x
0.33 for birds).
Hazard ratings generated by the two methods are given in Table 4.1.
The Protocol indicated greater hazard than HQ for all locations except
Leota Bottom and High Rock Lake, which are considered to be uncon-
4. Protocol for Aquatic Hazard Assessment
water quality criterion for the substance under evaluation, and it has
been widely applied for aquatic risk assessment in the United States
for many years. However, there are substantial differences between
the Protocol and HQ. The Protocol focuses on food-chain bioaccumulation and reproductive impairment in fish and aquatic birds
whereas HQ primarily uses information on waterborne selenium.
Comparison of the 2 methods gives additional insight into the validity
of the Protocol for hazard assessment.
The HQ for selenium is calculated by dividing the geometric mean
measured or expected environmental waterborne concentration by the
United States national water quality criterion for chronic exposure (5
Ilg SelL). The rationale of this technique is that, if waterborne concentrations of selenium exceed the criterion, substantial hazard exists. If
concentrations are below the criterion, then minimal hazard is expected. This method provides a quantitative estimate of the hazard
associated with single chemicals or elements, primarily from a waterborne route of exposure. However, the USEPA process for deriving national water quality criteria does allow for inclusion of data that would
account for bioaccumulation. In the case of selenium, field data on
food-chain transfer and reproductive toxicity to fish were included in
the derivation, and were largely responsible for the criterion being
lowered to its current value of 5 Ilg SelL (EPA 1987). Thus, even though
HQ uses only waterborne values, it reflects the extent to which the
United States national criterion is protective of dietary and reproductive hazards. Guidelines for interpreting HQ calculations are:
HQ < 0.1, No hazard exits
HQ =0.1-1.0, Hazard is low
HQ =1.1-10, Hazard is moderate
HQ> 10, Hazard is high
Field Sites and Hazard Ratings
Selenium data from three ecologically distinct systems were used in
the comparison: wetlands (Stephens et al. 1988, 1992; Hoffman et al.
1990; Pelz and Waddell 1991; Waddell and Stranger 1992), rivers (Finger 1995), and reservoirs (Lemly 1997b). Selenium concentrations in
whole-body fish samples and aquatic bird livers were converted to
equivalent egg concentrations for use in the Protocol method (Lemly
and Smith 1987: whole-body values x 3.3 for fish and liver values x
0.33 for birds).
Hazard ratings generated by the two methods are given in Table 4.1.
The Protocol indicated greater hazard than HQ for all locations except
Leota Bottom and High Rock Lake, which are considered to be uncon-