Toxicity Identification Evaluation Methods Research Articles

APPLICATION OF TOXICITY-BASED FRACTIONATION TECHNIQUES AND STRUCTURE–ACTIVITY RELATIONSHIP MODELS FOR THE IDENTIFICATION OF PHOTOTOXIC POLYCYCLIC AROMATIC HYDROCARBONS IN SEDIMENT PORE WATER

Recent studies conducted at their laboratory have shown that sediments contaminated with complex mixtures of polycyclic aromatic hydrocarbons (PAHs) can exhibit enhanced toxicity (lethality) to a variety of aquatic species when the samples are tested under ultraviolet (UV) light designed to mimic the wavelengths present in sunlight. However, because these contaminated sediments can contain literally thousands of chemicals, it is difficult to use conventional analytical techniques to identify those compounds responsible for photo-induced toxicity. The purpose of this study was to adapt existing toxicity identification evaluation methods to attempt to identify those compounds contributing to the phototoxicity observed in their sediment samples. Pore water obtained from sediments collected near an oil refinery discharge was toxic to Lumbriculus variegatus following exposure to UV light, while organisms exposed to the same pore water, but without subsequent UV treatment, showed no toxic effect. Solid-phase extraction disks and high-performance liquid chromatography were used, in conjunction with toxicity tests with L. variegatus, to extract and fractionate phototoxic chemicals from the pore water. Phototoxic fractions analyzed by gas chromatography-mass spectrometry revealed the presence of a number of aliphatic hydrocarbons, substituted PAHs, and PAHs containing heteroatoms. Chemicals were screened for their phototoxic potential based on empirical datamore » and predictive models. A refined list of PAHs was then evaluated on the basis of their phototoxic potency as defined by a recently developed quantitative structure-activity relationship model and estimates of their bioaccumulation potential. Based on the model predictions of potency and bioaccumulation, nine likely phototoxic chemicals were identified.« less

Use of metal chelating agents to differentiate among sources of acute aquatic toxicity

AbstractMetals are common toxicants found in effluents and other environmental samples. Within Toxicity Identification Evaluation methods proposed by the U.S. Environmental Protection Agency and others, addition of ethylenediaminetetraacetic acid (EDTA) is used as an indicator of metal toxicity. Previous experiments showed that addition of sodium thiosulfate, originally included to detect toxicity due to oxidants, was also effective at reducing toxicity from some common metals. In the present study, we characterized the effectiveness of both EDTA and thiosulfate in removing the toxicity of 16 different metal ions to Ceriodaphnia dubia. Ethylenediaminetetraacetic acid addition removed toxicity associated with all cationic metals tested except for Cr3+, Fe2+, Al3+, and Ag+. Thiosulfate addition was less effective than EDTA for Zn2+, Mn2+, Pb2+, and Ni2+, but reduced toxicity of both Ag+ and selenite (Se[VI]), which EDTA did not. Results of this research can be used to categorize metal toxicity in unknown samples based on the response to additions of EDTA and thiosulfate.

An example of the identification of diazinon as a primary toxicant in an effluent

AbstractA toxicity identification evaluation (TIE) conducted on a municipal wastewater discharge from the southeast United States was part of a research project aimed at developing U.S. Environmental Protection Agency (EPA) TIE methods for acutely toxic effluents. The effluent consistently exhibited acute toxicity to Ceriodaphnia dubia but not to fathead minnows (Pimephales promelas). Toxicity characterization procedures revealed that the primary toxicant was a nonpolar organic. Toxicity was recovered through C18 solid‐phase extraction and concentration steps. Gas chromatography–mass spectroscopy of these concentrates revealed the presence of diazinon (O, O‐diethyl O‐[6‐methyl‐2‐(1‐methylethyl)‐4‐pyrimidinyl] phosphorothioate). Diazinon concentrations in whole effluent, determined by GC analyses, correlated well with the toxicity measurements of each sample. Relative species sensitivity also implicated diazinon as the primary toxicant. This study illustrates the successful application of EPA TIE methodologies for identifying a nonpolar organic toxicant in a complex effluent. The significance of detecting diazinon at acutely toxic concentrations in municipal wastewater may indicate a more widespread problem in this region of the United States. This toxicity problem may be attributed to the chemical characteristics of diazinon and its applications.

AN EXAMPLE OF THE IDENTIFICATION OF DIAZINON AS A PRIMARY TOXICANT IN AN EFFLUENT

A toxicity identification evaluation (TIE) conducted on a municipal wastewater discharge from the southeast United States was part of a research project aimed at developing U.S. Environmental Protection Agency (EPA) TIE methods for acutely toxic effluents. The effluent consistently exhibited acute toxicity to Ceriodaphnia dubia but not to fathead minnows (Pimephales promelas). Toxicity characterization procedures revealed that the primary toxicant was a nonpolar organic. Toxicity was recovered through C18 solid-phase extraction and concentration steps. Gas chromatography–mass spectroscopy of these concentrates revealed the presence of diazinon (O, O-diethyl O-[6-methyl-2-(1-methylethyl)-4-pyrimidinyl] phosphorothioate). Diazinon concentrations in whole effluent, determined by GC analyses, correlated well with the toxicity measurements of each sample. Relative species sensitivity also implicated diazinon as the primary toxicant. This study illustrates the successful application of EPA TIE methodologies for identifying a nonpolar organic toxicant in a complex effluent. The significance of detecting diazinon at acutely toxic concentrations in municipal wastewater may indicate a more widespread problem in this region of the United States. This toxicity problem may be attributed to the chemical characteristics of diazinon and its applications.