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.

A bacterial biosensor for oxidative stress using the constitutively expressed redox-sensitive protein roGFP2.

A highly specific, high throughput-amenable bacterial biosensor for chemically induced cellular oxidation was developed using constitutively expressed redox-sensitive green fluorescent protein roGFP2 in E. coli (E. coli-roGFP2). Disulfide formation between two key cysteine residues of roGFP2 was assessed using a double-wavelength ratiometric approach. This study demonstrates that only a few minutes were required to detect oxidation using E. coli-roGFP2, in contrast to conventional bacterial oxidative stress sensors. Cellular oxidation induced by hydrogen peroxide, menadione, sodium selenite, zinc pyrithione, triphenyltin and naphthalene became detectable after 10 seconds and reached the maxima between 80 to 210 seconds, contrary to Cd(2+), Cu(2+), Pb(2+), Zn(2+) and sodium arsenite, which induced the oxidation maximum immediately. The lowest observable effect concentrations (in ppm) were determined as 1.0 × 10(-7) (arsenite), 1.0 × 10(-4) (naphthalene), 1.0 × 10(-4) (Cu(2+)), 3.8 × 10(-4) (H(2)O(2)), 1.0 × 10(-3) (Cd(2+)), 1.0 × 10(-3) (Zn(2+)), 1.0 × 10(-2) (menadione), 1.0 (triphenyltin), 1.56 (zinc pyrithione), 3.1 (selenite) and 6.3 (Pb(2+)), respectively. Heavy metal-induced oxidation showed unclear response patterns, whereas concentration-dependent sigmoid curves were observed for other compounds. In vivo GSH content and in vitro roGFP2 oxidation assays together with E. coli-roGFP2 results suggest that roGFP2 is sensitive to redox potential change and thiol modification induced by environmental stressors. Based on redox-sensitive technology, E. coli-roGFP2 provides a fast comprehensive detection system for toxicants that induce cellular oxidation.

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.

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.