Toxicity of tetramethylammonium hydroxide to aquatic organisms and its synergistic action with potassium iodide

The aquatic ecotoxicity of chemicals involved in the manufacturing process of thin film transistor liquid crystal displays was assessed with a battery of four selected acute toxicity bioassays. We focused on tetramethylammonium hydroxide (TMAH, CAS No. 75-59-2), a widely utilized etchant. The toxicity of TMAH was low when tested in the 72 h-algal growth inhibition test (Pseudokirchneriellia subcapitata, EC50=360 mg L(-1)) and the Microtox® test (Vibrio fischeri, IC50=6.4 g L(-1)). In contrast, the 24h-microcrustacean immobilization and the 96 h-fish mortality tests showed relatively higher toxicity (Daphnia magna, EC50=32 mg L(-1) and Oryzias latipes, LC50=154 mg L(-1)). Isobologram and mixture toxicity index analyses revealed apparent synergism of the mixture of TMAH and potassium iodide when examined with the D. magna immobilization test. The synergistic action was unique to iodide over other halide salts i.e. fluoride, chloride and bromide. Quaternary ammonium ions with longer alkyl chains such as tetraethylammonium and tetrabutylammonium were more toxic than TMAH in the D. magna immobilization test.

Toxicity of Diuron and copper pyrithione on the brine shrimp, Artemia franciscana: the effects of temperature and salinity

Diuron and copper pyrithione (CuPT) are two substances that have been used worldwide as alternatives to tributyltin (TBT) in antifouling paints for the protection of ship hulls. In this study their toxicity against the brine shrimp Artemia franciscana is examined under several combinations of salinity and temperature using the LC(20), LC(50) and LC(80) values found for the 25 degrees C and 35 per thousand standard conditions. A significant interaction between temperature and salinity effects was observed for both chemicals. Decreasing temperature almost eliminated Diuron's toxicity, while a toxicity reduction was also observed for CuPT. Decreasing salinity decreased Diuron's toxicity, while for CuPT the effect of salinity was more complex. These two natural environmental parameters had a profound influence on the ecotoxicity of the two tested chemicals, and this highlights the importance of considering the implications of such factors when conducting ecological risk assessment.

Toxicity of four antifouling biocides and their mixtures on the brine shrimp Artemia salina

Zinc pyrithione (ZPT), Copper pyrihione (CPT), Chlorothalonil and Diuron are four of the most widely used as alternative to tributlytin (TBT) antifouling biocides in boat paints. As most previous laboratory bioassays for these biocides have been conducted solely based on acute tests with a single compound, information on the possible combined toxicity of these common biocides to marine organisms are limited. In this study, the toxicity of binary (in several proportions), ternary and quaternary mixtures were evaluated using the brine shrimp Artemia salina as test organism. Mixture toxicities were studied using the concentration addition model (isobolograms and toxic unit summation), and the mixture toxicity index (MTI). The ZPT-CPT combination had a strictly synergistic effect which requires attention because the coexistence of ZPT and CPT in the marine environment, due to transchelation of ZPT, may occur. The binary mixtures of Diuron with the metal pyrithiones exhibited various interactive effects (synergistic, antagonistic or additive) depending on concentration ratios, whereas all binary mixtures that contained Chlorothalonil exhibited antagonistic effects. The different types of combined effects subsequent to proportion variation of binary mixtures underline the importance of the combined toxicity characterization for various ratios of concentrations. The four ternary mixtures tested, also exhibited various interactive effects, and the quaternary mixture exhibited synergism. The models applied were in agreement in most cases. The observed synergistic interactions underline the requirement to review water quality guidelines, which are likely underestimating the adverse combined effects of these chemicals.

The interactive effects of binary mixtures of three antifouling biocides and three heavy metals against the marine algae Chaetoceros gracilis

Three of the most commonly used antifouling booster biocides that are usually combined with copper or copper compounds are Irgarol 1051, Diuron, and Zn pyrithione. This study represents an assessment of the interactive effects of the antifouling biocides combined with each other, and with three heavy metals (Cu, Cd, and Zn) in binary mixtures, on the marine algae Chaetoceros gracilis. Seventy-two hour growth inhibition tests were carried out, and the IC50 values of the chemicals were determined along with growth inhibition (%) for several concentrations. The joint effect of the binary mixtures of all the chemicals was assessed by using two models, concentration addition model and the model of probabilities. The following increasing order of toxicity was obtained: Cd < Zn < Cu < Diuron < Zn pyrithione < Irgarol 1051. The interactive effects of the organic chemicals combined with each other on the growth of Ch. gracilis were firmly synergistic. Irgarol 1051 combined with Cd performed synergistic effects, and Zn pyrithione with copper and cadmium action was strictly antagonistic, and the results of the two models were in agreement in almost all mixtures.