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T F Parkerton

Publications and source records attributed to T F Parkerton.

10 recordsLinked to original sources
PubMed2006

Assessing the aquatic hazard of commercial hydrocarbon resins.

Hydrocarbon resins are used to modify polymer products to achieve desired functional properties for a diverse range of products. These complex hydrocarbon-based mixtures are typically poorly soluble in water. However, resins may leach lower-molecular-weight monomers or impurities upon contact with water, thus posing a potential hazard to the aquatic environment. The bioavailability and toxicity of leachable constituents of four solid and three liquid resins were evaluated by analyzing water-accommodated fractions prepared with each resin, using biomimetic solid phase microextraction (SPME) techniques. Liquid resins exhibited concentrations of bioavailable constituents that were sufficiently elevated to cause acute toxicity to the aquatic organism Daphnia magna. All solid resins exhibited lower bioavailable concentrations of leachable constituents that were unlikely to pose an aquatic toxicity concern. Since observed toxicity of both resin types was generally consistent with bioavailable concentrations determined using SPME fiber measurements, it is concluded that this approach provides a convenient in vitro screening tool that can help reduce the use of animal testing in environmental hazard assessment of complex hydrocarbon-based substances.

Animal Testing Alternatives↗
PubMed2005

Hazard evaluation of diisononyl phthalate and diisodecyl phthalate in a Japanese medaka multigenerational assay.

Reproductive and developmental effects of diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) were evaluated in a Japanese medaka (Oryzias latipes) multigeneration protocol. Each phthalate was administered via fish flake diets at a concentration of 20 microg/g (1 microg/g fish/day). Two controls were included, untreated and acetone carrier. The F(0) and F(1) generation adults were reared to sexual maturation and the test was ended prior to sexual maturation of the F(2) generation. Biochemical, individual, and population parameters were evaluated: testosterone metabolism, 7-ethoxyresorufin-o-deethylase (EROD) activity, survival, development, growth, gonadal-somatic index, histopathology, sex ratio, and fecundity. Male fish showed a two-fold induction of several testosterone metabolites in the DINP-treated group compared to the untreated control but not the acetone control. In a similar manner, in female fish only the DIDP-treated group expressed greater testosterone hydroxylase activity. There were neither sex- nor treatment-related differences in the results from the EROD assay. A statistically significant transient delay in red blood cell pigmentation was observed. The male-to-female ratio was consistent across treatments and the phenotypic and histological gender classifications were in agreement. Egg production was not significantly different among treatment groups. Neither phthalate elicited an effect on reproduction or development at various levels of biological organization.

Animals↗
PubMed2001

An assessment of the toxicity of phthalate esters to freshwater benthos. 1. Aqueous exposures.

Tests were performed with the freshwater invertebrates Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus to determine the acute toxicity of six phthalate esters, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), di-n-hexyl phthalate (DHP), and di-2-ethylhexyl phthalate (DEHP). It was possible to derive 10-d LC50 (lethal concentration for 50% of the population) values only for the four lower molecular weight esters (DMP, DEP, DBP, and BBP), for which toxicity increased with increasing octanol-water partition coefficient (Kow) and decreasing water solubility. The LC50 values for DMP, DEP, DBP, and BBP were 28.1, 4.21, 0.63, and 0.46 mg/L for H. azteca; 68.2, 31.0, 2.64, and > 1.76 mg/L for C. tentans; and 246, 102, 2.48, and 1.23 mg/L for L. variegatus, respectively. No significant survival reductions were observed when the three species were exposed to either DHP or DEHP at concentrations approximating their water solubilities.

Animals↗
PubMed2001

An assessment of the toxicity of phthalate esters to freshwater benthos. 2. Sediment exposures.

Seven phthalate esters were evaluated for their 10-d toxicity to the freshwater invertebrates Hyalella azteca and Chironomus tentans in sediment. The esters were diethyl phthalate (DEP), di-n-butyl phthalate (DBP), di-n-hexyl phthalate (DHP), di-(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and a commercial mixture of C7, C9, and C11 isophthalate esters (711P). All seven esters were tested in a sediment containing 4.80% total organic carbon (TOC), and DBP alone was tested in two additional sediments with 2.45 and 14.1% TOC. Sediment spiking concentrations for DEP and DBP were based on LC50 (lethal concentration for 50% of the population) values from water-only toxicity tests, sediment organic carbon concentration, and equilibrium partitioning (EqP) theory. The five higher molecular weight phthalate esters (DHP, DEHP, DINP, DIDP, 711P), two of which were tested and found to be nontoxic in water-only tests (i.e., DHP and DEHP), were tested at single concentrations between 2,100 and 3,200 mg/kg dry weight. Preliminary spiking studies were performed to assess phthalate ester stability under test conditions. The five higher molecular weight phthalate esters in sediment had no effect on survival or growth of either C. tentans or H. azteca, consistent with predictions based on water-only tests and EqP theory. The 10-d LC50 values for DBP and H. azteca were >17,400, >29,500, and >71,900 mg/kg dry weight for the low, medium, and high TOC sediments, respectively. These values are more than 30x greater than predicted by EqP theory and may reflect the fact that H. azteca is an epibenthic species and not an obligative burrower. The 10-d LC50 values for DBP and C. tentans were 826, 1,664, and 4.730 mg/kg dry weight for the low, medium, and high TOC sediments, respectively. These values are within a factor of two of the values predicted by EqP theory. Pore-water 10-d LC50 values for DBP (dissolved fraction) and C. tentans in the three sediments were 0.65, 0.89, and 0.66 of the water-only LC50 value of 2.64 mg/L, thereby agreeing with EqP theory predictions to within a factor of 1.5. The LC50 value for DEP and C. tentans was >3,100 mg/kg dry weight, which is approximately 10x that predicted by EqP theory. It is postulated that test chemical loss and reduced organism exposure to pore water may have accounted for the observed discrepancies with EqP calculations for DEP

Animals↗
PubMed2000

Assessing the aquatic toxicity of complex hydrocarbon mixtures using solid phase microextraction.

Assessing the ecotoxicity of hydrocarbon mixtures is complicated by the complex nature of these mixtures. Traditional analytical methods for characterizing hydrocarbon contamination are not good predictors of potential ecotoxicity because these methods fail to characterize the bioavailability of individual hydrocarbon components. Recent research indicates that hydrocarbons act by a common narcotic mode of action and that ecotoxicity occurs when the molar concentration in organism lipid exceeds a critical threshold. Since the ecotoxicity of narcotic mixtures appears to be additive, ecotoxicity thus depends upon the partitioning of individual hydrocarbons from the environment to lipids and the total molar sum of individual hydrocarbons in lipids. These insights have led previous investigators to advance the concept of 'biomimetic' extraction as a novel analytical tool for assessing narcosis-type or 'baseline'. Drawing from this earlier work, a simple method to quantify bioavailable petroleum hydrocarbons (BPHs) in hydrocarbon-contaminated aqueous and soil/sediment samples was developed. The proposed method combines the essential features of biomimetic extraction for simulating the bioconcentration process with the analytical advantages of solid phase microextraction (SPME). The procedure for determining BPH involves two steps. The sample is first equilibrated with a SPME fiber that serves as a surrogate for organism lipids. The total moles of hydrocarbons that partition to the SPME fiber is then quantified using GC/FID. The capability of this method to predict ecotoxicity was assessed by comparing BPH measurements for hydrocarbon contaminated aqueous samples to corresponding toxicity test results for rainbow trout. Results indicate that BPH analyses correlate to the observed acute toxicity. Consequently, BPH analyses offer a promising, cost-effective screening tool for predicting aquatic toxicity of complex hydrocarbon mixtures.

Animals↗
PubMed2000

Application of quantitative structure--activity relationships for assessing the aquatic toxicity of phthalate esters.

Phthalate esters (PEs) are an important class of industrial chemicals for which an extensive aquatic toxicity database is available. The objectives of this study were to use these data to develop quantitative structure-activity relationships (QSARs) that describe aquatic toxicity for different freshwater and marine species, gain insights into toxicity mechanisms, and calculate PE water quality criteria using statistical extrapolation procedures. Results for low-molecular-weight PEs with log Kow<6 indicate that toxicity data conform to a simple log Kow-dependent QSAR. Fish were found to be more sensitive than algae while invertebrates spanned a wide range in toxicological response. Freshwater and marine species demonstrated a similar distribution of sensitivities. Comparison of species-dependent QSARs supports the hypothesis that biotransformation plays an important role in explaining toxicity differences observed between species. Estimated critical body residues (CBRs) for parent PE in fish were in the range reported for other polar organic chemicals while CBRs for parent PE plus associated metabolites were in the range reported for nonpolar narcotics (i.e., baseline toxicity) suggesting a possible putative role of PE metabolites. Depending on extrapolation procedure and assumptions, predicted no-effect concentrations (PNECs) for dimethyl, diethyl, dibutyl, and butybenzyl phthalate ranged from 3109 to 4780, 865 to 1173, 43 to 62, and 38 to 60 microg l(-1), respectively. PNECs derived using this approach provide a transparent technical basis to support aquatic risk assessment for low-molecular-weight PEs. Results for high-molecular-weight PEs (log Kow>6) indicate that these chemicals are not acutely or chronically toxic to freshwater or marine organisms due to the combined role of low water solubility and limited bioconcentration potential which precludes attainment of internal concentrations that are required to elicit adverse effects. It is concluded that attempts to establish aquatic PNECs for high-molecular-weight PEs are not scientifically defensible.

Animals↗
PubMed2000

A risk assessment of selected phthalate esters in North American and Western European surface waters.

Potential risks to aquatic organisms by four commercial phthalate esters, dimethyl (DMP), diethyl (DEP), di-n-butyl (DBP), and butylbenzyl (BBP), were assessed using measured and calculated concentrations in North American and Western European surface waters. Predicted no effect concentrations (PNECs) were calculated using statistical extrapolation procedures and the large aquatic toxicity database. Surface water concentrations of DMP, DEP, DBP, and BBP were calculated using reported emissions to US surface waters from the toxics release inventory (TRI). Monitoring data obtained from the US EPA STORET database and literature surveys from North America and Western Europe show that DMP, DEP, DBP, and BBP are infrequently detected in surface water. Calculated and measured concentrations of DMP, DEP, DBP, and BBP are typically several orders of magnitude below their respective PNECs, indicating that these phthalate esters do not pose a ubiquitous threat to aquatic organisms in North American and Western European surface waters.

Animals↗
PubMed1999

A proposed multigeneration protocol for Japanese medaka (Oryzias latipes) to evaluate effects of endocrine disruptors.

Definitive data on reproductive impairment of chronically exposed populations may be required to assess the appropriateness of the existing test methods for hazard identification and prioritization of endocrine modulators. Multigeneration toxicity testing protocols for wildlife receptors are lacking. To help address this gap we describe a multigeneration fish assay using the freshwater fish, Japanese medake (Oryzias latipes). This test species has been used for the evaluation of carcinogenic, teratogenic and reproductive effects and is sensitive to estrogen exposure producing ovo-testis, altered biochemical parameters and phenotypic characteristics. Due to the short life cycle, a multigeneration test with medaka can be conducted in 1 year. Endpoints evaluated include: survival, growth, sex ratio, fecundity, embryonic lesion occurrence, embryonic stage development, gonadal and hepatic somatic indices, histopathology and biochemical parameters. As new endpoints are developed they can be incorporated into the protocol. Results of a positive control (17 beta-estradiol) study are presented to give an indication of the baseline associated with various test endpoints and to highlight the importance of nutrition in the experimental design. 17 beta-Estradiol treatment induced vitellogenin production in male and female medaka, feminized males, and disrupted egg production. The proposed protocol provides researchers with an effective multigeneration fish test that can be used to examine potential effects of stressors at the population, individual, cellular and subcellular level.

Animals↗
PubMed1989

Kinetics of chromium transformations in the environment.

Kinetics of chromium transformations under typical environmental conditions were systematically investigated using batch, microcosm and column experiments. Oxidation and reduction rates were evaluated in single phase water systems and in two phase water-solid systems. Natural and reference waters, sediments and soils representing a broad range of characteristics were used. Some of the investigated reactions, such as the reduction of Cr(VI) by S2- or Fe2+ ions under anaerobic conditions, were instantaneous and the experimental results exactly followed the stoichiometric and equilibrium calculations. Other reactions, such as the reduction of Cr(VI) by organics in sediments and soils, or the oxidation of Cr(III) by MnO2, were much slower and clearly exhibited kinetic controls. Reduction of Cr(VI) by organics was dependent on both the type and amount of organic material. Dissolved oxygen by itself did not induce measurable oxidation of Cr(III), spiked to the experimental waters, after 128 days. Slow Cr(III) oxidation to Cr(VI) was only noted in one of the natural waters and sediments with half-lives ranging from 2 to 9 years. In all cases the extent of Cr(III) oxidation did not exceed 15% of the initial Cr(III) present. The overall results indicate that the transport and transformation of chromium can be predicted using kinetics data derived from a simplified laboratory experiment, the Eh-pH data and the aquatic system characteristics. Results of the microcosm and laboratory experiments were in good agreement with the predicted concentrations.

Chemical Phenomena↗