Dick T.H.M. Sijm

Surfactant bioconcentration--a critical review.

Bioconcentration data for surfactants have been collected and critically reviewed. Twenty-two references report whole body bioconcentration data. Most of these data are inappropriate to quantitatively describe the bioconcentration of surfactants because the most frequently used analytical method, LSC without prior chromatographic separation of radiolabelled compounds, does not allow to distinguish between parent compound and metabolites. Hence, the measured concentrations very likely are overestimates of the concentration of the parent surfactant. In order to compare data we defined a comparability criterion. Data which fulfil this criterion consistently overestimate the true extent of bioconcentration. Fifty-four out of 100 whole body concentration ratios (CRs) were selected employing the above criterion, with 33, 11, and 10 Crs reported for anionic, cationic and nonionic surfactants, respectively. Further findings are: 1. Selected CRs range between 2.4 for octyltrimethylammonium chloride and 1960 for tallowtrimethylammonium chloride. In general, CRs increased with increasing alkyl chain length. 2. Surfactants of all classes are readily taken up across the gills. Hexadecylpyridinium and dialkyl dimethyl ammonium surfactants appear to be taken up rather slow. 3. Nonionic and anionic surfactants were demonstrated to be biotransformed. Tissue specific data demonstrated that elimination via the gall bladder is an important excretion route. 4. Environmental variables appeared to influence bioconcentration of ionic surfactants.

Intraspecies variation in lethal body burdens of narcotic compounds

Groups of fathead minnows were exposed to different concentrations of di- or trichlorobenzenes, tetrachloroethane or PCBs. Lethal body burdens (LBB, mmol compound/kg wet weight) were determined. The purpose of the study was to obtain information on the variability of the LBB within a population, and on the reasons for this variability. The variation in LBB within a population was 4- to 23-fold for the chemicals tested. Approximately 50% of this variation could be attributed to the lipid content of the individuals. The LBB did not depend on the weight of the fish. The exposure time until lethality did not influence the LBB for the di- and trichlorobenzenes and tetrachloroethane. In contrast, the LBB of the PCBs was influenced by this parameter, a shorter exposure time resulting in a lower LBB.

Estimating biotransformation rate constants of organic chemicals from modeled and measured elimination rates

In this study, biotransformation rate constants are estimated for a large set of organic compounds. Biotransformation (km) is considered part of the total elimination, further consisting of physico-chemical elimination to water (kw), depuration by feces (kf) and growth dilution (gamma). Existing models are used to estimate kw and kf, and gamma. The difference between measured elimination rate constants and the sum of predicted elimination rate constants for water, feces and growth indicates the ration of biotransformation in the total elimination. In all examined animal classes, polycyclic aromatic hydrocarbons seem to be metabolized at an intermediate rate. Because of the relative low hydrophobicity of some of the studied compounds, their physico-chemical elimination rate constant is relatively high, and the relative contribution of metabolism to total elimination of these compounds is therefore relatively low. Fish seem to be capable of metabolizing chlorodibenzo-p-dioxins and -furans, DDT, chloroanilines and phenol.

Dry deposition of atmospheric polycyclic aromatic hydrocarbons in three Plantago species

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the leaf wax of three Plantago species were determined weekly for 3 weeks. The almost glabrous, free-standing leaves of Plantago major and the sparsely hairy Plantago lanceolata leaves were more heavily contaminated with low molecular weight (MW) PAHs (MW < 228) than the densely hairy, partly overlapping Plantago media leaves. This may be caused by the lower canopy roughness (higher aerodynamic resistance), the higher amount of leaf hairs (higher boundary resistance), and/or the higher leaf overlap (smaller accessible leaf area) of P. media. On the other hand, PAHs with MW ≥ 252 tended to show higher concentrations in P. media than in the other two species. This is likely caused by the dense layer of hairs on P. media leaves, which can efficiently intercept the largely particle-bound high MW PAHs. When the PAH concentrations were normalized to projected leaf surface area, the differences between P. media and the other two species became significant (p < 0.05) for the high MW PAHs, while the differences for the low MW PAHs decreased. Although the differences in PAH concentrations between species are relatively small (factor 2-5), this study clearly shows that plant architecture and leaf hairs influence the dry deposition of PAHs.

Experimental octanol/water partition coefficients of chlorinated paraffins

Abstract Octanol/water partition coefficients (K OW ) of chlorinated paraffins (CPs) from a commercial mixture (‘Cereclor 60L’) were determined using a “slow-stirring” method. Log K OW values for the different congener groups ranged from 5.85 to 7.14. Equilibrium was reached within a few days, and K OW values were the same at two CP-concentrations. A clear relationship is found between the total number of chlorine and carbon atoms and log K OW for the CP-congener groups and a series of smaller chlorinated alkanes from the literature.

Biotransformation and tissue distribution of 1,2,3,7-tetrachlorodibenzo-p-dioxin, 1,2,3,4,7-pentachlorodibenzo-p-dioxin and 2,3,4,7,8-pentachlorodibenzofuran in rainbow trout

Abstract Two polychlorinated dibenzo-p-dioxins were eliminated more slowly in rainbow trout which were treated with an inhibitor of biotransformation. Fish were given a single oral dose of either 14 C-labeled 1,2,3,7-tetrachlorodibenzo-p-dioxin (T 4 CDD), 1,2,3,4,7-pentachlorodibenzo-p-dioxin (P 5 CDD) or 2,3,4,7,8-pentachlorodibenzofuran (P 5 CDF). Half of the fish were daily treated with piperonylbutoxide (PBO) which is a well known inhibitor of monooxygenase activity. The amounts of radioactivity were determined in liver, gall bladder, skin, muscle, spleen, heart, kidney, gills and intestine 2, 7, 14 and 21 days after administration. T 4 CDD and P 5 CDD were both eliminated more slowly in the PBO treated fish than in the fish which did not receive PBO. P 5 CDF showed no statistically different elimination rates in PBO treated and untreated fish. For all compounds the highest concentrations were found in liver and intestine. The highest absolute amounts of each compound was found in muscle. The slower elimination rates and the higher body burden of T 4 CDD and P 5 CDD in PBO treated trout indicate that biotransformation is very important for their elimination kinetics. Biotransformation may thus be responsible for the more rapid elimination and lower body burden of these compounds under normal conditions.

Leaf wax of Lactuca sativa and Plantago major

Abstract Wax layers of plants are able to accumulate semivolatile organic compounds (SOCs) from the atmosphere. In this study, the composition of the leaf cuticular waxes of lettuce ( Lactuca sativa ) and common plantain ( Plantago major ) was determined for future studies on the role of cuticular waxes in the uptake and bioaccumulation of SOCs. In addition, to find a suitable extraction solvent to be used in these studies, the extraction efficiency of several solvents for the cuticular wax of the plants was studied. Leaf wax of L. sativa consists mainly of long-chain linear alcohols and minor amounts of fatty acids, while the major components of leaf wax of P. major are the free polar triterpene acids, oleanolic and ursolic acid, and the linear alkanes C 27 H 56 C 33 H 58 . The wax composition of both species only slightly changes with leaf developmental stage. This property makes them highly suitable as test plants in studies on uptake of SOCs. The waxes of both plant species are readily extractable with chloroform, toluene and dichloromethane. A mixture of chloroform and methanol 2:1 additionally extracted internal lipids and chlorophyll and, therefore, is not suitable. The apolar solvent, n -hexane, did not extract the triterpene acids of P. major . However, this solvent readily extracted the relatively apolar leaf wax of L. sativa . Since the extraction of SOCs (also from deeper embedded wax layers) can only be efficient if all the components of the cuticular wax are removed, we recommend to test the extraction efficiency of the solvent for each plant species beforehand.

The influence of temperature on the uptake rate constants of hydrophobic compounds determined by the isolated perfused gills of rainbow trout (Oncorhynchus mykiss)

Abstract Uptake rate constants of four hydrophobic and one less hydrophobic compound were determined using the isolated perfused gills of rainbow trout. Uptake rate constants thus obtained were in accordance with in vivo literature data. The four hydrophobic compounds (log Kd,oct > 3) had similar uptake rate constants. The fifth, less hydrophobic compound, phenol in undissociated form (pH ≤ pKa) had a lower uptake rate constant. The uptake rate constants were reduced by lowering the temperature below the acclimation temperature of the fish. The temperature dependent decrease was most pronounced for hexabromobenzene, probably due to steric effects. The rate-limiting step in uptake seemed to be diffusion, either through the aqueous diffusion layer or through the lipid membrane, and not ventilation or blood flow-rate.

Uptake of hydrophobic halogenated aromatic hydrocarbons from food by earthworms (Eisenia andrei)

The intestinal uptake of hydrophobic halogenated aromatic hydrocarbons by the earthworm Eisenia andrei was studied. In one experiment, worms were fed a single dose of manure contaminated with three chlorobenzenes, one polychlorobiphenyl (PCB 153) and octachloronaphthalene (OCN). Body burdens were followed during the subsequent 6 days. In the second experiment, worms were fed penta- and hexachlorobenzene, using multiple oral doses during 70 days. Steady state was reached in this experiment. Uptake efficiencies (E) derived by three different methods varied between 2.5 and 6.5% for 1,2,3,4-tetrachlorobenzene and OCN, and between 8.5 and 22% for the other compounds. Biomagnification factors (BMF) calculated for penta- and hexachlorobenzene using the body burdens at steady state were 0.03 and 0.07, respectively.

Influence of soil organic matter content on elimination rates of hydrophobic compounds in the earthworm: Possible causes and consequences

Abstract In theory, elimination of organic hydrophobic compounds by terrestrial and aquatic organisms is a partitioning process determined by the elimination rate constant and the concentration of the compound in the organism, and usually results in a monophasic elimination curve. However, in the presence of sediment and soil, biphasic elimination is frequently observed. In this study, the underlying mechanism of this biphasic elimination is investigated with a terrestrial species. Elimination was studied in earthworms ( Eisenia andrei ), that were loaded with chlorobenzenes, in three types of clean OECD soil differing only in organic matter content (3%, 10% and 20%). It was observed that the first rapid elimination phase was influenced by the organic matter content in the soil: A larger part of the chlorobenzene body burden was eliminated in this first phase when earthworms were kept in soil with a higher organic matter content. In low organic matter soil, body burdens in earthworms remained higher during the whole elimination period. The rate of both the elimination phases was not influenced by the organic matter content in the soil. It is concluded that the organic matter content in soil is an influential factor in the elimination of hydrophobic compounds by earthworms, for which some explanations can be given.