Lethal body burden

Illustrative Example 10.6 Evaluating Lethal Body Burdens of Chlorinated Benzenes in Fish... 

P 10.5 Estimating Lethal Body Burdens in Fish Using LCm values... 

P 10.6 Estimating the Lethal Body Burden (LBB,) for 4-Nonylphenol for the Marine Amphipod, Ampelisca abdita, and Setting a Corresponding Sediment Quality Criterion... 

Sijm, D. T. H. M., M. Schipper, and A. Opperhuizen, Toxicokinetics of halogenated benzenes in fish Lethal body burden as toxicological end point , Environ. Tox. Chem., 12,1117-1127 (1993). 

Deneer JW, Budde BJ, Weijers A. 1999. Variations in the lethal body burdens of organophos-phorus compounds in the guppy. Chemosphere 38 1671-1683. 

De Maagd PGJ, Van de Klundert ICM, Van Wezel AP, Opperhuizen A, Sijm DTHM. 1997. Lipid content and time-to-death-dependent lethal body burdens of naphthalene and 1,2,4-trichlorobenzene in fathead minnow (Pimephales promelas). Ecotoxicol Environ Safety 38 232-237. 

Van Wezel AP, De Vries DAM, Sijm DTHM, Opperhuizen A. 1996. Use of the lethal body burden in the evaluation of mixture toxicity. Ecotoxicol Environ Safety 35 236-241. 

Tas, J.W., Seinen, W., Opperhuizen, A. 1991. Lethal body burden of triphenyltin chloride in fish Preliminary results. Comp. Biochem. Physiol. 100C(l/2) 59-60... 

Molar concentrations or dosages provide a more accurate assessment of the toxicity of a particular compound. This relationship will be explored further in our discussion of quantitative structure-activity relationships. Another weakness of the LC50, EC50, and IC50 is that they reflect the environmental concentration of the toxicant over the specified time of the test. Compounds that move into tissues slowly may have a lower toxicity in a 96-h test simply because the concentrations in the tissue have not reached toxic levels within the specified testing time. L. McCarty has written extensively on this topic and suggests that a lethal body burden or some other measurement be used to reflect tissue concentrations. 

For a broad applicability applied to either lethal or sublethal effects, the internal effect concentration (expressed as mol kg or mol kgupy ) approach should meet a couple of conditions. The following examples refer to lethality. The first condition may be that an organism dies when a distinct internal effect concentration, the lethal body burden, of a specific chemical has been reached. The second condition is that any individual dies when it has attained this lethal body burden. The third condition is that the lethal body burden is independent of time of death or exposure concentration. In the latter case it may take longer to die at a lower exposure concentration and shorter to die at a higher concentration, but in either case, when the lethal body burden has been reached, it should be the same for both conditions. The fourth condition is that all chemicals which have the same mechanism of action have the same lethal body burden. The latter thus enables one to deal with additivity, since the individual chemicals of a mixture, all of which have the same mechanism of action, will contribute equally to the body burden on a molar basis. 

Fig. 1. The concept of attaining an internal effect concentration in time as the result of bioaccumulation. An organism is exposed to a contaminant from the ambient environment, which can be water (top) or soil (middle), or from food (bottom). The more it has taken up the higher its internal concentration will be until a critical internal concentration is reached, e.g. the lethal body burden, and the associated effect, e.g. death, is elicited...

In the following sections lethal body burden associated with some mechanisms of actions will be discussed first, which will then be followed by a critical discussion of the assumptions behind the internal effect concentration. 

While lethal body burdens of narcotic chemicals are in the range 2-8 mmol kg h LBBs of chemicals with other mechanisms of actions in fish are usually lower. McKim and Schmieder [107] and McCarty and Mackay [16] have collected toxi-... 

Table 2 and Fig. 3 show that each mechanism of action has one, but in some cases a rather broad range of, internal effect concentrations for aquatic organisms. Therefore there is not one distinct value of the lethal body burden associated with one mechanism of action, but rather a range of internal concentrations that is related to an ecotoxicological effect. Some other questions which can be asked to validate the use of the internal effect are how large is the interspecies variation in internal effect concentration (for two types of mechanisms of action), how large is the intraspecies variation in internal effect concentration (for one type of mechanism of action), and what is the time and concentration dependent influence on the internal effect concentration (for one type of mechanism of action). 

Table 2. Lethal body burdens (LBB) in fish associated to different mechanisms of action, according to McKim and Schmieder [107], and extended with data for polychlorinated dibenzo-p-dioxins (PCDDs) [86,108], and organotin compounds [109,110] ...

Table 3 shows that, for different aquatic, benthic and terrestrial organisms, the lethal body burdens vary approximately by two orders of magnitude, but most of the values are in the range as predicted by McCarty [15], i.e. 

One distinct lethal body burden caimot thus be used for either the polar or the nonpolar narcotic compounds, since there is again a significant variation in the data for the different organisms that have been studied. 

Table 4. Interspecies variation in experimentally determined lethal body burdens for polar narcotic chemicals (chlorinated phenols and anilines)...

A third condition in working with the internal concentration concept is the following. It may take a long time when exposed to a relatively low concentration or a small time when exposed to a relatively high concentration to reach the lethal body burden, but once the organism has reached this lethal body burden it will die (Fig. 4). 

Table 5. Intraspecies variation in wet weight lethal body burden (LBB) and the contribution of lipid content (lipid) to explain intraspecies variation in fish...

Fig. 4. Time and exposure concentration dependent concentrations in fish in addition to the lethal body burden (horizontal solid line) for 1,2,3-trichlorobenzene. The dotted lines are theoretical curves calculated with a bioaccumulation model. Exposure concentrations are 55.9 pmol 1 (I), 3.78 pmol (II), and 1.92 pmol (III). The symbols represent the mean of the internal effect concentrations of ten fish [9], reproduced with permission...

When the concentration in an aquatic organism which causes an ecotoxicological effect is replaced by the lethal body burden, when Eqs. (1), (2) and (18) are combined and resolved, and when a constant exposure concentration is assumed, then ecotoxicological effects can be related to aqueous exposure of chemicals ... 

Equations (20) - (23) include bio accumulation kinetics, and thus enable us to predict when organisms will attain lethal body burdens. The most important bioaccumulation parameters, and the relationships between the bioaccumulation parameters and physical-chemical and physiological factors, which are required can either be found in the literature or need to be studied. The equations can thus be used to predict if organisms are at risk and will experience adverse effect at a given external exposure concentration. Time will thus be a variable, whereas the external exposure concentration in either water or food will be the given input parameters in this exercise. The equations can also be used to estimate the external concentration which will lead to adverse effects at a given exposure time. Then, external exposure concentration will be a variable, whereas the time required for eliciting effects will be a constant. 

De Wolf, W., W. Seinen, A. Opperhuizen, and J.L.M. Hermens. 1992b. Bioconcentration and lethal body burden of 2,3,4,5-tetrachloroaniline in guppy, Poecilia reticulata. Chemosphere 25 853-863. 

Other procedures using, for example, exposure on filter paper impregnated with the toxicant for earthworms clearly presents an ideal situation that does not appear to be environmentally realistic. Comparison of different routes of exposure to the toxicant has, however, been made with Eisenia andrei (Belfroid et al. 1993), and the acute toxicity was given as lethal body burden (LBB) after exposure to 1,2,3-trichloro- and pentachlorobenzene. Exposure was carried out in water, in soil via food, and on filter paper, and when LBBs were normalized to lipid content the values for pentachlorobenzene were comparable, although the value for 1,2,3-trichlo-robenzene for exposure on filter paper was higher than for the other routes of exposure. 

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