Assessing the impact of climatic factors on biosphere dose conversion factors in long-term safety assessment of radioactive waste disposal.

Climate factors from different regions were employed to assess the impact on Biosphere Dose Conversion Factors (BDCF) in the biosphere assessment of radioactive waste disposal. Climate characteristics of tropical and subtropical regions were considered alongside diverse climatic regions, observing the influence of different radionuclides. Data on annual rainfall, monthly rainfall distribution, temperature, and sunlight were collected for various regions. The relationship between rainfall and the processes of flooding, as well as erosion, was also established. Furthermore, the Water Budget Model (WBM) was used to calculate the required surface water flow parameters for the biosphere model. The results indicated limited effects from flooding and erosion, which could be evaluated using simplified methods. Under conditions of high evapotranspiration, low rainfall, or uneven rainfall distribution, specific radionuclides exhibited higher BDCF values. For regions currently and prospectively aligning with these climate characteristics, a comprehensive investigation into climate factors and their correlation with surface and near-surface hydrology is recommended to mitigate uncertainty.

The impact of different temporal resolution rainfall data on biosphere model of long-term safety assessment in groundwater release scenario for radioactive waste disposal in the tropical monsoon zone.

The impact of different temporal resolutions of rainfall data on the Biosphere assessment for radioactive waste disposal in the tropical monsoon region with concentrated rainfall is evaluated in this research. Two scenarios are considered to verify the effect of release location. A simplified surface water budget model is used to generate the surface water flow rates for the biosphere model, which is implemented using three different temporal averaging intervals to consider the uncertainty caused by short-term impact. Kaohsiung in Taiwan is chosen as an example because of its extreme rainfall distribution. The results show that it is improper to use the annual rainfall data for this case, and it is suggested to consider a 20% margin to cover the underestimation of dose if the monthly rainfall data are used. The results of the biosphere models built with different timesteps show that a non-negligible difference occurs for radionuclides with a low Kd value in the river water release scenario and no difference for the well water release scenario.

Factors associated with quality of life in patients with diabetic hypoglycaemia.

AIMS AND OBJECTIVES: To identify determinants of quality of life among patients who had experienced hypoglycaemia and who were undergoing insulin treatment. BACKGROUND: Patients with diabetes receiving insulin treatment are at high risk for hypoglycaemia, which tends to affect their quality of life. DESIGN: With a cross-sectional and observational study design (see the STROBE checklist and Appendix S1). METHODS: One hundred and fifty patients with type 2 diabetes who had received insulin treatment and had experienced hypoglycaemia (<70 mg/dl) in the last 6 months were recruited. Data were collected from May 2016-February 2018 using the Knowledge of Hypoglycaemia Scale, Fear of Hypoglycaemia Scale, Social Support Scale and the simplified Taiwanese version of the Quality of Life Scale developed by the World Health Organization. RESULTS: Factors found to be associated with quality of life in patients with hypoglycaemia included having an educational level of senior high school or above, being on an insulin regimen only, engaging in regular exercise, diabetes complications, fear of hypoglycaemia and greater social support, which accounted for 28.5% of the total variance. CONCLUSIONS: During the process of glycaemic control, patients inevitably experience hypoglycaemic episodes. Therefore, healthcare providers should assist patients with disease management to improve their quality of life. Future studies should also recruit patients who claim to have experienced hypoglycaemic symptoms, rather than considering only those with blood glucose levels below 70 mg/dl, to expand the generalisability of the findings. Future studies may also focus on the management of hypoglycaemia in patients on an insulin regimen, and on examining the effect of health education programmes on prevention of hypoglycaemia. RELEVANCE TO CLINICAL PRACTICE: The present findings could provide a reference for healthcare providers to consolidate nursing care guidelines and to improve such patients' quality of life.

Diabetes mellitus increases severity of thrombocytopenia in dengue-infected patients.

BACKGROUND: Diabetes mellitus is known to exacerbate bacterial infection, but its effect on the severity of viral infection has not been well studied. The severity of thrombocytopenia is an indicator of the severity of dengue virus infection. We investigated whether diabetes is associated with thrombocytopenia in dengue-infected patients. METHODS: We studied clinical characteristics of 644 patients with dengue infection at a university hospital during the epidemic on 1 June 2002 to 31 December 2002 in Taiwan. Platelet counts and biochemical data were compared between patients with and without diabetes. Potential risk factors associated with thrombocytopenia were explored using regression analyses. RESULTS: Dengue-infected patients with diabetes had lower platelet counts than patients without diabetes during the first three days (54.54±51.69 vs. 86.58±63.4 (p≤0.001), 43.98±44.09 vs. 64.52±45.06 (p=0.002), 43.86±35.75 vs. 62.72±51.2 (p=0.012)). Diabetes mellitus, death, dengue shock syndrome (DSS) and dengue hemorrhagic fever (DHF) and increased glutamic-pyruvate transaminase (GPT) levels were significantly associated with lower platelet counts during the first day of hospitalization for dengue fever with regression ß of -13.981 (95% confidence interval (CI) -27.587, -0.374), -26.847 (95% CI -37.562, -16.132), and 0.054 (95% CI 0.015, 0.094) respectively. Older age, hypoalbuminemia, and hypertriglyceridemia were independently correlated with thrombocytopenia in dengue patients with or without diabetes with regression ß of -2.947 (p=0.004), 2.801 (p=0.005), and -3.568 (p≤0.001), respectively. Diabetic patients with dengue had a higher rate of dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS) than non-diabetic patients. They also had lower blood albumin, were older, and higher triglyceride levels. Older age, hypoalbuminemia, and hypertriglyceridemia were independently correlated with thrombocytopenia in dengue patients. CONCLUSIONS: Dengue patients with diabetes tended to have more severe thrombocytopenia and were more likely to have DHF/DSS. Older age, hypoalbuminemia, and hypertriglyceridemia were independently associated with more severe thrombocytopenia in dengue patients.

Urea biosensor based on an extended-base bipolar junction transistor.

In this study, a urea biosensor was prepared by the immobilization of urease onto the sensitive membrane of an extended-base bipolar junction transistor. The pH variation was used to detect the concentration of urea. The SnO2/ITO glass, fabricated by sputtering SnO2 on the conductive ITO glass, was used as a pH-sensitive membrane, which was connected with a commercial bipolar junction transistor device. The gels, fabricated by the poly vinyl alcohol with pendent styrylpyridinium groups, were used to immobilize the urease. This readout circuit, fabricated in a 0.35-um CMOS 2P4M process, operated at 3.3V supply voltage. This circuit occupied an area of 1.0 mm × 0.9 mm. The dynamic range of the urea biosensor was from 1.4 to 64 mg/dl at the 10 mM phosphate buffer solution and the sensitivity of this range was about 65.8 mV/pUrea. The effect of urea biosensors with different pH values was considered, and the characteristics of urea biosensors based on EBBJT were described.

Toxicity of propargylic alcohols on green alga--Pseudokirchneriella subcapitata.

The present study evaluates the toxicity of 34 propargylic alcohols, including primary, primary homo-, secondary, and tertiary alcohols, based on their effects on phytoplankton. A closed-system algal toxicity test was applied because the closed-system technique presents more realistic concentration-response relationships for the above compounds than the conventional batch tests. The green alga, Pseudokirchneriella subcapitata, was the test organism and final yield and growth rate were chosen as the test endpoints. Among all the propargylic alcohols tested, 1-pentyn-3-ol is the most toxic compound with its EC50 equal to 0.50 mg L(-1), which can be classified as a "R50" compound (very toxic to aquatic organisms, EC50/LC50 < 1 mg L(-1)), following the current practice for classification of chemicals in the European Union (EU). There are several other compounds including 2-decyn-1-ol, 3-decyn-1-ol, 1-hexyn-3-ol, 3-butyn-2-ol, and 3-hexyne-2,5-diol, which deserve more attention for their possible adverse impact on the aquatic environment, because these alcohols can be classified as "R51" compounds (toxic to aquatic organisms, EC50/LC50 between 1 and 10 mg L(-1)). Compared to the base-line toxicity relationship (narcosis QSAR) derived previously, tertiary propargylic alcohols can be identified as nonpolar narcotic chemicals, while secondary alcohols and primary alcohols with low molecular weight generally exhibit obvious excess toxicity in relation to the base-line toxicity. Finally, quantitative structure-activity relationships were established for deriving a preliminary estimation of the toxicity of other propargylic alcohols.

Carbon nanotube composites for glucose biosensor incorporated with reverse iontophoresis function for noninvasive glucose monitoring.

This study aims to develop an amperometric glucose biosensor, based on carbon nanotubes material for reverse iontophoresis, fabricated by immobilizing a mixture of glucose oxidase (GOD) and multiwalled carbon nanotubes (MWCNT) epoxy-composite, on a planar screen-printed carbon electrode. MWCNT was employed to ensure proper incorporation into the epoxy mixture and faster electron transfer between the GOD and the transducer. Results showed this biosensor possesses a low detection potential (+500 mV), good sensitivity (4 microA/mM) and an excellent linear response range (r(2) = 0.999; 0-4 mM) of glucose detection at +500 mV (versus Ag/AgCl). The response time of the biosensor was about 25 s. In addition, the biosensor could be used in conjunction with reverse iontophoresis technique. In an actual evaluation model, an excellent linear relationship (r(2) = 0.986) was found between the glucose concentration of the actual model and the biosensor's current response. Thus, a glucose biosensor based on carbon nanotube composites and incorporated with reverse iontophoresis function was developed.

A preliminary study of the use of bioimpedance in the screening of squamous tongue cancer.

Oral cancers are the 11th most common malignancy reported worldwide, accounting for 3% of all newly diagnosed cancer cases, and one with high mortality ratios among all malignancies. The objective of this study was to study the electrical properties of cancerous tongue tissue (CTT) and normal tongue tissue (NTT). Five tongue cancer patients participated in this study. A disposable probe incorporating four silver electrodes was used to measure the electrical properties of CTT and the surrounding NTT of patients. Measurements were performed at six frequencies: 20 Hz; 50 kHz; 1.3 MHz; 2.5 MHz; 3.7 MHz; and 5 MHz, with the amplitude of the applied voltage limited to 200mV. Four measurement parameters of impedance (Z), phase angle (theta), real part of impedance (R), and imaginary part of impedance (X) of tongue tissue were assessed to see if there was any significant difference in the values obtained in CTT and surrounding NTT. The intraclass correlation coefficient showed that all measurements were reliable. A significant difference (P < 0.05 for the four measurement parameters) was found at 50kHz between CTT and surrounding NTT. It was also found that Z and R of CTT were generally smaller than that of surrounding NTT. In conclusion, bioimpedance at a particular frequency is a potentially promising technique for tongue cancer screening.

The use of bioimpedance in the detection/screening of tongue cancer.

Oral cancers are the 11th most common malignancy reported worldwide, accounting for 3% of all newly diagnosed cancer cases, and one with high mortality ratios among all malignancies. The objectives of this study were therefore to study the electrical properties of cancerous tongue tissue and normal tongue tissue, as well as to investigate a new approach for low-cost, noninvasive, and real-time screening of oral cancer. Twelve tongue cancer patients and twelve healthy subjects participated in this study. A disposable probe with four silver electrodes was used to measure the electrical properties of patient's and healthy subject's tongue tissues at six different frequencies, which were 20Hz, 50kHz, 1.3MHz, 2.5MHz, 3.7MHz and 5MHz. The amplitude of the applied voltage was limited to 200mV. Four measurement parameters of impedance, phase angle, real part of impedance, and imaginary part of impedance of tongue were assessed to see if significant difference in values obtained in patient's and healthy subject's tongue tissues existed. Intraclass correlation coefficient showed that all measurements had good reliability and validity (ICC>0.95 for all measurements). Significant differences were found at 20Hz (p<0.05-0.001 for the four measurement parameters) and 50kHz (p<0.001 for the four measurement parameters) between patient's and healthy subject's tongue tissues. In conclusion, bioimpedance at a particular frequency is a potentially promising technique for tongue cancer screening.

A mediated glucose biosensor incorporated with reverse iontophoresis function for noninvasive glucose monitoring.

The objective of this study was to develop a ferrocene mediated glucose biosensor for reverse iontophoresis. An amperometric ferrocene mediated glucose biosensor based on a three electrodes planar configuration was constructed using screen printing technique. Different combinations of glucose oxidase and ferrocene loading were drop coated onto the surface of the amperometric transducer. The amperometric transducer was characterized electrochemically using cyclic voltammetry and its electrochemical characteristics (DeltaE(p) = 70 mV, I(pa)/I(pc) = 0.89) were found close to an ideal amperometric transducer. The biosensor on the detection of glucose at 200 mV (vs. Ag/AgCl) showed a linear response range (0-4 mM). The response time of the biosensor was about 10 s. Finally, the biosensor was used together with reverse iontophoresis technique. By the use of an actual model for evaluation, an excellent linear relationship (r(2) = 0.99) was found between the glucose concentration of the actual model and the biosensor current response. In conclusion, a ferrocene mediated glucose biosensor incorporated with reverse iontophoresis function was developed.

Estimating low-toxic-effect concentrations in closed-system algal toxicity tests.

The no-observed-effect concentrations (NOEC) and EC(10) values for 108 organic compounds were estimated, using multiple endpoints (i.e., biopopulation, growth rate, and dissolved oxygen production), from previous data obtained by a closed-system algal toxicity test (test alga: Pseudokirchneriella subcapitata). These low-toxic-effect concentrations are valuable to risk assessment of chemicals and protection of the aquatic environment as such information is quite scarce in existing toxicological databases. Furthermore, based on limited amount of available data, we found that the risk of organic toxicants to phytoplankton may be severely underestimated by existing databases, which are primarily derived by the conventional batch technique. Good correlation relationships between NOEC (or EC(10)) and EC(50) values were established. For polar and nonpolar narcotics, quantitative structure-activity relationships (QSARs) based on hydrophobicity, and/or the lowest unoccupied molecular orbital energy (Elumo) were developed with satisfactory predictive powers. The above statistical relationships can be applied to derive a preliminary estimation for the low-toxic-effect levels for other (or new) organic compounds that has no toxicological data available.

Toxicity and quantitative structure-activity relationships of benzoic acids to Pseudokirchneriella subcapitata.

The present study presents the toxicity data of benzoic acid and its derivatives on Pseudokirchneriella subcapitata, in terms of EC50 and NOEC values. Median effective concentrations (EC50) range from 0.55 to 270.7 mg/L (based on final yield) and 1.93 to 726.3mg/L (based on algal growth rate). No-observed-effect concentration (NOEC) is within the range of <0.0057-179.9 mg/L. From both the NOEC and EC50 values, it was found that, 2,4,6-trihydroxybenzoic acid, 4-chlorobenzoic acid, 3-bromobenzoic acid, 4-bromobenzoic acid, 2,6-dihydroxybenzoic acid, and 2,3,4-trihydroxybenzoic acid possess much higher risks to the aquatic organisms as compared to the other benzoic acids. These data are useful for risk assessment and protection of the aquatic environments, because such information is not available in the existing toxicological databases. The toxicity of halogenated benzoic acids was found to be directly related to the compound's hydrophobicity (the logarithm of the 1-octanol/water partition coefficient, logKow). On the other hand, the number of hydroxyl groups (N(OH)) had a determinant influence to the toxicity of hydroxybenzoic acids. Quantitative structure-activity relationships were established to correlate the observed toxicity with logKow and N(OH) values. These statistical correlations are highly significant with the predictive power Q(2) ranging from 0.896 to 0.955. Furthermore, in terms of the species sensitivity, the luminescent bacteria (Microtox) and the alga P. subcapitata appeared to be more susceptible to benzoic acids than the water flea and ciliate.

Molecular cloning and tissue distribution of three estrogen receptors from the cyprinid fish Varicorhinus barbatulus.

We present molecular cloning and tissue expression analysis of three estrogen receptor (ER) subtypes, vbERalpha, vbERbeta1 and vbERbeta2, from liver of the cyprinid fish Varicorhinus barbatulus through reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The sequence alignment and phylogenetic analysis reconfirmed the evolutionary relationship of V. barbatulus within the family Cypriniformes. Directional constraints for subtype-specific substitution of critical amino acids were observed in the E2 binding region. For amino acid substitution, vbERbeta exhibited a M517L change in the ligand-dependent transactivation region. The tissue distributions were investigated using RT-PCR with subtype-distinguishable primers. Both vbERalpha and vbERbeta1 were most highly expressed in liver, while vbERbeta2 was higher in intestine. Here we demonstrate that the identification and cloning of ER subtypes using PCR is feasible in wildlife in that the temporal and spatial observations are consistent with those from phylogeny analysis and crystal structural investigation by others.

An algal toxicity database of organic toxicants derived by a closed-system technique.

The current study presents the toxicity data of 90 organic compounds with various modes of actions to Pseudokirchneriella subcapitata. The assessment was conducted using a closed-system technique, and a biomass-type end point based on the cell density was employed. The above toxicity data were compared with test results from ciliate (Tetrahymena pyriformis), water flea (Daphnia magna), fish (Pimephales promelas), and luminescent bacteria (Photobacterium phosphoreum). Satisfactory correlation relationships between toxicity data from algae and other aquatic organisms were found (r2 = 0.66-0.82). Pseudokirchneriella subcapitata revealed considerably higher sensitivity to organic toxicants compared with other organisms. Benzenes, aldehydes, and alkanes also were highly selective to the test alga. In addition, the results show that conventional algal batch tests tend to underestimate the toxicity of organic compounds, except in the case of 4-chlorophenol. Toxicity observed from the closed-system test is approximately 2- to 380-fold higher than that estimated by conventional batch tests. Such a phenomenon can be found in nearly all organic compounds, regardless of the chemical's Henry's law constant. In the risk assessment of chemicals, following the European Union's practice, approximately 30% (7 of 23) of the cases may result in a more strict classification when the batch test is replaced by the closed-system test. More effort therefore is needed to revise the algal toxicity database using the closed-system test method.

Toxicity of substituted anilines to Pseudokirchneriella subcapitata and quantitative structure-activity relationship analysis for polar narcotics.

This study evaluated the toxic effects of substituted anilines on Pseudokirchneriella subcapitata with the use of a closed algal toxicity testing technique with no headspace. Two response endpoints (i.e., dissolved oxygen production [DO] and algal growth rate) were used to evaluate the toxicity of anilines. Both DO and growth rate endpoints revealed similar sensitivity to the effects of anilines. However, trichloroanilines showed stronger inhibitory effects on microalgal photosynthetic reactions than that on algal growth. For various aquatic organisms, the relative sensitivity relationship for anilines is Daphnia magna > luminescent bacteria (Microtox) > or = Pocelia reticulata > or = Pseudokirchneriella subcapitata > or = fathead minnow > Tetrahymena pyriformis. The susceptibility of P. subcapitata to anilines is similar to fish, but P. subcapitata is apparently less sensitive than the water flea. The lack of correlation between the toxicity revealed by different aquatic organisms (microalgae, D. magna, luminescent bacteria, and P. reticulata) suggests that anilines might have different metabolic routes in these organisms. Both hydrogen bonding donor capacity (the lowest unoccupied molecular orbital energy, Elumo) and hydrophobicity (1-octanol:water partition coefficient, Kow) were found to provide satisfactory descriptions for the toxicity of polar narcotics (substituted anilines and chlorophenols). Quantitative structure-activity relationships (QSARs) based on Elumo, log Kow, or both values were established with r2 values varying from 0.75 to 0.92. The predictive power for the QSAR models were found to be satisfactory through leave-one-out cross-validation. Such relationships could provide useful information for the estimation of toxicity for other polar narcotic compounds.

Application of a yeast estrogen screen in non-biomarker species Varicorhinus barbatulus fish with two estrogen receptor subtypes to assess xenoestrogens.

Xenoestrogens can interfere with normal estrogen signaling by competitively binding to the estrogen receptor (ER) and activating transcription of target genes. In this study, we cloned the estrogen receptor alpha (vbERalpha) and beta 2 (vbERbeta2) genes from liver of the indigenous Taiwanese cyprinid fish Varicorhinus barbatulus and tested the direct impact of several xenoestrogens on these ERs. Transcriptional activity of xenoestrogens was measured by the enzymatic activity of estrogen responsive element (ERE)-containing beta-galactosidase in a yeast reporter system. The xenoestrogens tested were phenol derivatives, DDT-related substances, phthalic acid esters, and polychlorinated biphenyls, with 17beta-estradiol (E2) as a subjective standard. The phenol derivatives [4-nonylphenol (4-NP), 4-t-octylphenol (4-t-OP) and bisphenol A (BPA)] exhibited significant dose-dependent responses in both ligand potency and ligand efficiency. Consistent with yeast assays using human or rainbow trout ERs, we observed a general subtype preference in that vbERalpha displayed higher relative potencies and efficiencies than vbERbeta2, although our assays induced a stronger response for xenoestrogens than did human or trout ERs. Whereas 4-NP and 4-t-OP have similar EC50 values relative to E2 for both ER subtypes, the strong estrogenic response of BPA markedly differentiates vbERalpha from vbERbeta2, suggesting possible species-specific BPA sensitivity. We report that the ameliorative yeast tool is readily applicable for indigenous wildlife studies of the bio-toxic influence of xenoestrogens with wildlife-specific estrogen receptors.

Metal toxicity to Chlorella pyrenoidosa assessed by a short-term continuous test.

This study presents the metal toxicity as revealed by Chlorella pyrenoidosa using a short-term continuous test and the conventional batch test. Toxicity tests were conducted in a chemostat with a test duration of 1 day. Toxicity data of five different metals (Cd, Pb, Co, Ni, and Zn) derived from the continuous test were compared against results from the conventional batch tests. The batch test is characterized by its saturated nutrient status for algal growth and, on the other hand, the continuous test is conducted at a nutrient-limiting condition simulating more closely to the aquatic field environment. The continuous test consistently yielded smaller EC(50) values, which indicated that alga in the chemostat is approximately four to six times more sensitive than those from the batch culture. Similar phenomena between the two types of tests were observed based on the NOEC values. Compared to literature data (US EPA ECOTOX Database) from the same species of alga, differences in test sensitivity between the batch tests and chemostat technique varied from 9.25 to 160 times. Such distinct differences indicate that current toxicity database may not adequately reflect the impact of various metal toxicants on C. pyrenoidosa. The continuous test method presented herein is a sensitive and rapid assessment technique and, therefore, has a potential for more general applications such as routine checkup for regulatory purposes.

Toxicity and quantitative structure-activity relationships of nitriles based on Pseudokirchneriella subcapitata.

This study presents the toxicity data of various nitriles to Pseudokirchneriella subcapitata using a closed algal toxicity testing technique with no headspace. Two different response endpoints, i.e., dissolved oxygen (DO) production and algal growth rate, were used to evaluate the toxicity of nitriles. In general, the DO endpoint revealed higher inhibitory effects than that from algal growth rate. Furthermore, halogen-substituted nitriles were found to be extremely toxic to P. subcapitata. With increasing numbers of the halogen atoms, stronger toxicity was observed. The bromine substitutent also seems to be more toxic than chlorine substitutent. Quantitative structure-activity relationships (QSARs) were established based on the chemicals' Elumo values and hydrophobicity (logK(ow)). Such relationships may thus be useful in predicting the toxicity of other compounds of the same mode of toxic action. Furthermore, for various aquatic organisms, the relative sensitivity relationship is: Pimephales promelas > or = P. subcapitata> Tetrahymena Pyriformis>Daphnia magna>luminescent bacteria (Microtox). The alga, P. subcapitata, was found to be quite sensitive to nitriles compared to other organisms.

Quantitative structure-activity relationships for toxicity of nonpolar narcotic chemicals to Pseudokirchneriella subcapitata.

This study presents data for 27 nonpolar narcotic compounds regarding toxicity to Pseudokirchneriella subcapitata as evaluated using a closed-system algal toxicity test with an exposure time of 48 h. Two test endpoints, dissolved oxygen production and algal growth rate, were used to assess the toxicity of nonpolar narcotic chemicals on algae. Hydrophobicity (1-octanol-water partition coefficient [K(OW)]) provided satisfactory descriptions for the toxicity of nonpolar narcotic compounds, and quantitative structure-activity relationships based on log K(OW) were established. The relative sensitivity of various aquatic organisms to nonpolar chemicals was as follows: P. subcapitata > Vibriofischeri > or = Nitrosomonas sp. > fathead minnow > Daphnia magna > polytox > activated sludge. In addition, linear relationships were found between the toxicity observed in P. subcapitata and other aquatic organisms, except in the case of Nitrosomonas sp. Therefore, for nonpolar toxicants, the closed-system technique applied in the present study can be an ideal surrogate for other tests, such as fathead minnow and D. magna, that are either time-consuming or labor-intensive. However, because the current toxicity database is based primarily on the conventional batch tests, it cannot provide adequate assessment regarding the effects of various organic toxicants. Therefore, more extensive research is needed to revise the database for the toxicity of organic compounds on phytoplankton using the closed-system technique.

The combined toxic effects of nonpolar narcotic chemicals to Pseudokirchneriella subcapitata.

This paper presents the toxicity data of 10 nonpolar narcotic chemicals on Pseudokirchneriella subcapitata (green algae) assessed by a new algal toxicity testing technique conducted under air-tight environment. Based on DO production, median effective concentration (EC50) varies from 1.73 mg/L (1-octanol) to 8,040 mg/L (2-propanol). The endpoint of algal growth rate reveals similar sensitivity as that from DO production. Compared to literature data, Pseudokirchneriella subcapitata and Nitrosomonas are apparently more sensitive to nonpolar narcotics than other organisms such as minnow, daphnia, and Tetrahymena pyriformis. Furthermore, good correlations between toxic effects observed from Pseudokirchneriella subcapitata and other aquatic organisms were found. Hence, algal toxicity test can be considered as a surrogate test for estimating the toxicity of nonpolar chemicals to fathead minnow, Microtox, activated sludge, Daphina magna, and Tetrahymena pyriformis. The combined effects of 13 binary mixtures of nonpolar chemicals were investigated using both additive-index method and isobologram analysis. Overall speaking, the joint actions between these chemicals are strictly additive. Model analyses indicate that these compounds act on identical reaction sites or receptors, which verify that these chemicals are of the same toxicity mechanism (narcosis).