FISHERY BULLETIN: VOL. 74, NO. 3 



BENZENE , INTEGUMENT 



GALL BLADDER 



(BILE) 



-r- STOMACH INTESTINES 



METABOLITES 



OUT WITH FECES 



Figure 3.- Hypothetical pathway and distribution of benzene in 



fish. 



Figure 3 shows a hypothetical distribution and 

 pathway of benzene in fish which is substantiated 

 by our results. Benzene is absorbed across the gills 

 into the blood where, being lipid soluble, it at- 

 taches to the erythrocytes and lipoproteins (Ger- 

 arde 1960). It is then translocated via the blood to 

 the tissues where it either accumulates or is 

 metabolized. Parke (1968), Meyers (1970), and Lee, 

 Sauerheber, and Dobbs (1972) described me- 

 tabolism of benzene to phenol in the liver of fish 

 and mammals. The metabolites are excreted from 

 the liver with the bile and stored in the gallblad- 

 der. From the gallbladder the bile is excreted into 

 the intestine and finally eliminated through the 

 colon with the feces. Our results show high ac- 

 cumulation in the liver and gallbladder. Lee, 

 Sauerheber, and Dobbs (1972) also found the 

 gallbladder of fish to be a storage site for poly- 

 cyclic aromatic compounds. Our results indicate 

 that the pathway through the liver, gallbladder, 

 intestine, and colon is a major depuration route. 

 These tissues take the longest to accumulate and 

 depurate. This is probably due to the time needed 

 for metabolism of benzene. The gill also was one of 

 the tissues which depurated later. Some un- 

 changed benzene metabolites are probably ex- 

 creted across the gills. 



The secondary increase in ^^C radioactivity 

 (days 4-7) observed after initial depuration (days 

 2-4) in several striped bass tissues (Figure 3) is 

 difficult to interpret. One explanation may be that 

 the metabolism of benzene is limited to a certain 

 rate and that until the initial metabolism is 

 complete, some benzene accumulates in non- 

 metabolic tissues and is not totally metabolized 

 until later. The secondary increase in residues in 

 fat and brain tissues, however, suggests that 

 perhaps metabolites such as phenol are ac- 

 cumulating in the tissues for a period before they 

 too are depurated. Additional work with uptake 



and depuration in herring tissues shows a similar 

 pattern. Further research must be done to clarify 

 this point. 



The low accumulation tissues such as heart, 

 muscle, and stomach are also low in lipid content 

 and apparently do not directly contribute to the 

 metabolism of benzene. Lee, Sauerheber, and 

 Dobbs (1972) found similar results with naph- 

 thalene and benzopyrene in fish. Later work at 

 Tiburon has demonstrated that little benzene 

 and/or metabolites accumulate in the kidney 

 tissue of herring. Because of this and the fact that 

 fish in salt water excrete little urine, we feel the 

 kidneys are not a major depuration pathway in 

 fish from saline waters. Further study of urinary 

 depuration is needed. 



Northern anchovies are schooling fish, and they 

 swam constantly during the tests-striped bass 

 were more sedentary. This difference in activity 

 might explain the higher accumulation in 

 anchovies. 



The short duration of low-level water column 

 exposures of benzene in these experiments did not 

 reveal obvious detrimental effects on behavior or 

 physiology of fish. However, equilibrium ac- 

 cumulation levels have not been obtained because 

 of the static exposure with decreasing benzene- 

 water concentration. During chronic exposures, 

 higher accumulations of benzene and toxic me- 

 tabolites (such as phenol) with deleterious effects 

 are possible. Further, because of the rapid uptake 

 rate over a wide range of concentrations, it is 

 conceivable that both species could accumulate 

 significant benzene levels after brief exposure 

 during an oil spill. The severity of effects at 

 chronic and acute levels will depend greatly on the 

 energy requirements of the fish and the degree of 

 stress to which they are already subjected. Fish in 

 spawning condition are particularly susceptible to 

 additional stress from pollutants (e.g., spawning 

 Pacific herring [Struhsaker^]). Further study of 

 uptake in the lipid-rich mature ovaries of fish 

 should be done. 



The rapid depuration of benzene the first day 

 after exposure ended appears to be due to me- 

 tabolism and excretion via the liver-intestine 

 route. Because of this rapid depuration, the pos- 

 sibility of bio-amplification in fish does not appear 



^Struhsaker, J. W. Effects of benzene (a toxic component of 

 petroleum) on spawning Pacific herring. Manuscr. in prep. 

 Southwest Fish. Cent. Tiburon Lab., Natl. Mar. Fish. Serv., 

 NOAA, Tiburon, CA 94920. 



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