Aquatic Toxicity

FrogThe DEHP, DINP and DIDP risk assessments all show that these phthalates, at concentrations up to their solutbilities in water, produce no acute or chronic toxic effects in aquatic organisms.

However, in order to make the risk assessments as robust as possible, multigeneration fish studies are being carried out in which the fish will be exposed to phthalates via their food rather than in the usual way via water.

The lower molecular weight phthalates, DBP and BBP, have been classified as toxic to aquatic organisms but their EU risk assessments demonstrate that, at the levels at which they are present in the environment, there is no cause for concern.

It is well recognised that phthalates, due to their low water solubility, present special problems in aquatic toxicity testing. This is especially true in the case of tests on Daphnia where it is very easy to try to force too much of the phthalate into solution and the observed effects are due to entrapment of the Daphnia at the surface rather than the toxicity of the test compound.

Conflicting data

It is apparent that the conflicting data found in several chronic Daphnia studies are due to surface entrapment causing the Daphnia to become stressed and in many cases to die. This conclusion is supported by the studies carried out on a number of phthalate esters in the presence of a non-toxic dispersant. Under these conditions, at a concentration of 1 mg/litre, no surface entrapment occurs and the Daphnia are unaffected1.

Eighteen individual chronic fish toxicity tests from eight independent studies are available. These studies include data for phthalates ranging from dihexyl to diundecyl across nine fish species2. One early study by Mehrle & Mayer3, which appears to be an outlier, has been considered by US EPA scientists to be invalid due to unacceptable test conditions4. Discounting these results, the chronic fish NOEC for high molecular weight phthalates ranges from > 52 to 23,800 µg/l. The large variations in reported NOEC values between studies reflects the different experimental techniques that were used to obtain maximum exposure concentrations (i.e. emulsions). Collectively, these studies indicate that the phthalates are not chronically toxic to fish at the maximum concentrations that could be maintained as stable emulsions in the test systems employed.

References

  1. Brown D, Croudace, CP, Williams, N J, Shearing, J M and Johnson, P A (1998) The effect of phthalate ester plasticisers as surfactant stabilised dispersions on the reproduction of Daphnia magna. Chemosphere, 36 (6) 1367-1379.
  2. Staples, C A, Adams, W J, Parkerton, T F, Gorsuch, J W, Biddinger, G R and Reinert, K H (1997) Aquatic toxicity of eighteen phthalate esters. Env. Toxicol. and Chemistry, 16, 5, 875-891.
  3. Mehrle PM and Mayer FL, 1976, “Di-2-ethylhexyl phthalate: Residual Dynamics and Biological Effects in Rainbow Trout and Fathead Minnow”, University of Missouri’s Annual Conference of Trace Substances in Environmental Health, 10, 519 – 636
  4. US Environmental Protection Agency, 1994, “Ambient Aquatic Life Water Quality Criteria for DEHP”, Office of Water, Washington, DC