Environmental Engineering Reference
In-Depth Information
Only a few of the guidelines give specific data quality parameters for some kinds
of physical-chemical data. The Dutch methodology (RIVM 2001) requires that
solid-water partition coefficients ( K p ) be determined in batch experiments as
described in Bockting et al. (1993). Tests conducted according to the OECD guide-
lines are also acceptable. The Netherlands guidance also points out that water solubility
should be determined at an appropriate temperature, usually at 25°C, which
matches standard laboratory toxicity test temperatures. Because other physical-
chemical parameters such as vapor pressure, Henry's constant ( K H ), octanol-water
partition coefficient ( K ow ), and solid-water partition coefficient ( K p ) are also
temperature-dependent, the temperature at which they were measured should also
be noted and values should be adjusted, if necessary (Schwarzenbach et al. 1993).
The OECD guidelines (1995) specify that K ow values may be calculated using the
ClogP3 algorithm of Hansch and Leo (1979), or may be taken from the THOR/
Starlist database. Both the ClogP3 algorithm and the THOR/Starlist database are
now accessible through the Bio-Loom program (Biobyte at www.biobtye.com).
For highly hydrophobic compounds (log K ow > 5), the OECD methodology (1995)
requires that the K ow be determined by either the slow stirring or generator column
method. The guidelines recommend expert evaluation of K ow values, because there
are many compounds for which reliable values cannot be determined. If measured
data are not available, OECD (1995) allows that water solubility may be determined
by appropriate QSARs that relate K ow to solubility.
The USEPA (1985) has specific criteria for acceptance of bioconcentration
factors (BCFs). To be used in determination of final residue values (FRVs), BCFs
must be from flow-through tests, must be based on measured concentrations of test
substance in both tissue and test solution, and must be from tests that were long
enough for the system to reach steady state. For lipophilic materials, the percent
lipid in the tissue must be reported. If a BCF was determined at an exposure that
caused adverse effects in the test organism, it should not be used. If reported on a
dry weight basis, BCF values must be converted to a wet weight basis. Finally, if
more than one acceptable BCF is available, the geometric mean of available values
is used, provided they are from exposures of the same length.
Any physical-chemical data used in derivation of water quality criteria should
be evaluated to ensure that they were determined by appropriate methods. Generally,
data from current, standard methods (e.g., ASTM, OECD), applied and performed
correctly for the chemical of interest, will be acceptable. Nonstandard methods may
also be appropriate, but only if valid reasons are given for deviation from standard
methods. In regard to pesticides, which vary widely in characteristics such as
hydrophobicity, water solubility, and ionizability, it is particularly important to
verify that reported partition coefficients were determined correctly.
For ecotoxicity data, the EU TGD (ECB 2003) defines data quality in terms of
reliability and relevance. “Reliability” is the inherent quality of a test, relates to test
methodology, and the way that the performance and the results of the test are
described. “Relevance” refers to the extent to which a test is appropriate for a particular
hazard or risk assessment. “Reliable data” are from studies for which test reports
describe the test in detail and indicate that tests were conducted according to gener-
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