Encl. (1) TO COMDTINST 16478.12
The ER-L level represents the lower 10-percentile concentration level of the sorted data
set. In other words, it is the level measured in the sediment below which adverse
biological effects were measured in the aquatic environment 10% of the time (Long and
Morgan, 1991). It may be thought of an approximation of the concentrations at which
adverse ecological effects were first detected. The calculation of percentiles of the data
help eliminate the undue influence of a single (possibly outlier) data point upon the
establishment of the ER-L and ER-M ranges. For the contaminants of concern, the ER-L for
mercury is 0.15 ppm, while the ER-L forlead is 35 ppm.
ER-M - Effects Range Median
The ER-M level is similar to the ER-L level, except that it corresponds to the mercury
level measured in the sediment below which adverse biological effects were measured 50% of
the time (Long and Morgan, 1991). Both the ER-L and ER-M values have been determined
objectively because they simply represent percentile points where sediment levels can be
attributed to ecological health effects. The ER-M levels for mercury and lead are 1.3 ppm
and 110 ppm, respectively.
Evaluation of the NS&T Program Sediment Data Relative to the Effects Ranges
The third step in the National Status and Trends Approach compared the ambient sediment
chemistry data from the NS&T Program with the respective ranges in chemical concentrations
apparently associated with observations and effects. Contaminant field measurements
conducted for the AtoN battery project can be compared with background levels and with the
ER-L and ER-M levels in order to make conclusions about the possibility of environmental
harm due to battery disposal. However, it should be noted that NOAA clearly states that
the ER-L and ER-M concentrations may be used by others as guidance in evaluating sediment
contamination data, but there is no expressed or implied intent of establishing these
values as official NOAA standards.
Strengths of the National Status and Trends Program Approach
These are several advantages to the methodology used in the NSTPA. One of the most
important benefits is that it provides a weight of evidence approach to the assessment of
sediment quality. Numerous biological effects-based approaches were employed for
determining associations between chemical quality and biological effects. This adds to the
credibility of the resulting guidelines.
For both mercury and lead, the degree of confidence in the ER-L estimate is considered by
NOAA to be moderate, while the degree of confidence in the ER-M estimate is considered by
NOAA to be high. With respect to mercury, there are clusters around the 0.15 and 1.3 ppm
values, suggesting that these values are supported by a preponderance of evidence. A
relatively large amount of data exist for lead to relate sediment concentrations with
measures of effects (Long and Morgan, 1991).
Another main advantage of the NS&T approach is that it can be conducted with existing data,
and no additional field work or laboratory investigations are required. But at the same
time, the database is expandable to encompass data collected from additional studies. In
addition, the method facilities the identification of ranges of contaminant concentrations
which provide a means of determining the probability of observing adverse biological
effects at a given contaminant concentration.
The NSTPA has been extensively reviewed by experts from across North America. It has been
peer reviewed and been selected from incorporation into an EPA sediment classification
document. Also, it has been adopted and/or modified for implementation by a variety of
states (MacDonald, 1993).
Weaknesses of the National Status and Trends Program Approach
The main limitation of this approach is associated with the quality and compatibility of
the available data. The data were often generated using different analytical procedures in
numerous laboratories and considered many species and locations across the United States.
Therefore, information on a wide variety of sediment types (i.e., with different particle
sizes and concentrations of substances that influence bioavailability) were combined, and
may have resulted in unknown biases. This amalgamation of the data may have resulted in
the interpretation of responses as being attributable to a single contaminant when, in
fact, synergistic and/or additive effects were actually driving the response. The
shortcomings may be compounded by locations where only a moderate amount of data exists, or
only acute toxicity data are represented, and could result in inappropriate guidelines.
Florida Sediment Quality Assessment Guidelines (SQAG)
Overall Approach
Several modifications were made to the NSTPA by the Florida Department of Environmental
Regulation in order to increase its applicability to Florida. These modifications are
designed to increase the quality and suitability of data used to evaluate
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