Bioaccumulation And Biodegradation

Environment - fishIt is now accepted that the commonly used phthalates are all readily biodegradable and do not biomagnify up the food chain. In fact it is more accurate to say that they biodilute.

Bioaccumulation

A large number of bioconcentration factors (BCF) computed from many early studies are fundamentally flawed because radio leabelled phthalates were used and the authors simply divided total radioactivity in the organism by that found in the water at the end of the experiment. They did not take into consideration the fact that the radioactivity in the water often declined several orders of magnitude during the course of the experiment. Moreover, results were often based on total radioactivity and do not distinguish between the phthalate and its metabolites which have been transformed by metabolic processes into fish tissue as all living creatures do with their food.  

Reliable bioconcentration studies that maintain constant exposure concentrations over the course of the exposure period indicate a much lower, more consistent range of BCFs for phthalates, eg around 120 for DEHP (level in fish is 120 times the level in water) in the carp and 9.4 for BBP in bluegill sunfish1. A comprehensive critical review of phthalate bioaccumulation literature is provided in the review paper of Staples et al2.

Biodegradation

The water solubility of the higher molecular weight phthalates is much lower than the levels used in many laboratory biodegradation studies. It follows that only a small part of the phthalate in the test system is available for biodegradation and consequently the test appears to indicate that these phthalates are not readily biodegradable. The more recent work on DBP, DEHP and DINP3 clearly demonstrates that these three phthalates are readily biodegradable. These studies were conducted using a modified Sturm test (OECD 1993, EEC 1992) which is specifically designed for testing substances of low water solubility.

The ready aerobic degradation of phthalates is also evidenced by the speed with which they break down in sewage sludge or in the soil 4, 5, 6, 7.

References

  1. Carr, KH, Coyle, GT and Kimerle, RA, Environmental Toxicology and Chemistry (1997), Vol 19, No 10, 2200-2203.
  2. Staples, CA., Peterson DR, Parkerton TF and Adams WJ, 1997, “The Environmental Fate of Phthalate Esters : A Literature Review”, Chemosphere 35, 667-749.
  3. Scholz, N. et al. (1997) Bull. Environ. Contam. Toxicol., 58, 527-534.
  4. Saeger, VW and Tucker, III, ES, 1976, "Biodegradation of phthalic acid esters in river water and activated sludge", Appl Environ. Microbiol, 31, 29-34.
  5. Shanker, R., Ramakrishna, C. and Seth, PK, 1985, "Degradation of some phthalic acid esters in soil", Environ. Poll., 39, 1-7.
  6. Fairbanks, B.C., O'Connor, GA and Smith, S.E., 1985, "Fate of di-2-(ethylhexyl)phthalate in three sludge-amended New Mexico soils", J; Environ. Qual, 14(4), 479-483.
  7. Schnitzer, JL, Schneunert, L., Korte F., 1988, "Fate of Bis(2-ethylhexyl) phthalate in laboratory and outdoor soil-plant-systems", J. Agr. Food Chem. 36, 210-215.