PARENT SESSION

2A - Mixture toxicity
Poster Hall
8:30 AM - Monday, 28 April 2003
Chair: Hermens, J.¹, ¹
Co-chair: Toy, R.², Backhaus, T.³, ^{2 3}

(MOP/76) Rosin and Tall Oil Fatty Acids Do Not Exhibit Acute Toxicity To Aquatic Organisms Using OECD Methodology.

Kelly, Craig¹, Holm, Stewart², Golden, Robert³, Deardorff, Thomas⁴, ¹ Inveresk Research, Tranent, East Lothian, Scotland² Georgia-Pacific, Atlanta, GA, USA³ ToxLogic, Washington, MD, USA⁴ International Paper, Cincinnati, OH, USA

ABSTRACT- Test medium preparation methods in ecotoxicology for poorly soluble complex mixtures now have broad regulatory consensus (OECD 2000). Two such materials, Rosin and Tall Oil Fatty Acids (TOFA) have been tested in a number of standard ecotoxicology studies using widely different test medium preparation methods giving results on the same endpoint spanning more than three orders of magnitude. The present study investigated the toxicity of Rosin and TOFA by stirring known weights (loading rates) up to 1000 mg.l^-1 in test medium for 48 h following guidelines recommended in OECD (2000), on Aquatic Toxicity Testing of Difficult Substances and Mixtures. Fathead minnows, Daphnia magna, and algae were exposed to the resulting water accommodated fractions (WAF) following applicable OECD Guidelines. Rosin was not toxic to fish or algae at a loading rate of 1000 mg.l^-1 and gave a 48 h EL₅₀ of 911 mg.l^-1 for Daphnia. TOFA was not toxic to fish or Daphnia at 1000 mg. l^-1 and gave a 72 h EL₅₀ of 855 mg.l^-1 for algae. These data do not indicate acute toxicity. Importantly, the results of the present study can be directly linked to the solubility and exclude physical effects of insoluble fractions or changing the chemical nature of the test item. Our results reflect environmentally relevant ecotoxicology levels for these materials and demonstrate that extreme methods of sample preparation bring about uncertainty in assessing the true toxicological endpoint for complex mixtures. We conclude that data from ecotoxicology testing on complex mixtures that fail to follow the OECD guidelines should not be used in environmental risk assessment.

Key words: poorly soluble, complex mixtures, Rosin, Tall Oil Fatty Acids