Donald J. Versteeg

Consideration of exposure and species sensitivity of triclosan in the freshwater environment

ABSTRACT Triclosan (TCS) is a broad-spectrum antimicrobial used in consumer products including toothpaste and hand soap. After being used, TCS is washed or rinsed off and residuals that are not biodegraded or otherwise removed during wastewater treatment can enter the aquatic environment in wastewater effluents and sludges. The environmental exposure and toxicity of TCS has been the subject of various scientific and regulatory discussions in recent years. There have been a number of publications in the past 5 y reporting toxicity, fate and transport, and in-stream monitoring data as well as predictions from aquatic risk assessments. State-of-the-science probabilistic exposure models, including Geography-referenced Regional Exposure Assessment Tool for European Rivers (GREAT-ER) for European surface waters and Pharmaceutical Assessment and Transport Evalutation (PhATE™) for US surface waters, have been used to predict in-stream concentrations (PECs). These models take into account spatial and temporal variability in river flows and wastewater emissions based on empirically derived estimates of chemical removal in wastewater treatment and in receiving waters. These model simulations (based on realistic use levels of TCS) have been validated with river monitoring data in areas known to be receiving high wastewater loads. The results suggest that 90th percentile (low flow) TCS concentrations are less than 200 ng/L for the Aire–Calder catchment in the United Kingdom and between 250 ng/L (with in-stream removal) and 850 ng/L (without in-stream removal) for a range of US surface waters. To better identify the aquatic risk of TCS, a species sensitivity distribution (SSD) was constructed based on chronic toxicity values, either no observed effect concentrations (NOECs) or various percentile adverse effect concentrations (EC10–25 values) for 14 aquatic species including fish, invertebrates, macrophytes, and algae. The SSD approach is believed to represent a more realistic threshold of effect than a predicted no effect concentration (PNEC) based on the data from the single most sensitive species tested. The log-logistic SSD was used to estimate a PNEC, based on an HC5,50 (the concentration estimated to affect the survival, reproduction and/or growth of 5% of species with a 50% confidence interval). The PNEC for TCS was 1,550 ng/L. Comparing the SSD-based PNEC with the PECs derived from GREAT-ER and PhATE modeling to simulate in-river conditions in Europe and the United States, the PEC to PNEC ratios are less than unity suggesting risks to pelagic species are low even under the highest likely exposures which would occur immediately downstream of wastewater treatment plant (WWTP) discharge points. In-stream sorption, biodegradation, and photodegradation will further reduce pelagic exposures of TCS. Monitoring data in Europe and the United States corroborate the modeled PEC estimates and reductions in TCS concentrations with distance downstream of WWTP discharges. Environmental metabolites, bioaccumulation, biochemical responses including endocrine-related effects, and community level effects are far less well studied for this chemical but are addressed in the discussion. The aquatic risk assessment for TCS should be refined as additional information becomes available.

Ceriodaphnia and Daphnia : A comparison of their sensitivity to xenobiotics and utility as a test species

A comparison between Ceriodaphnia sp. and other Cladoceran species including Daphnia magna and D. pulex was made in terms of their life history, geographical distribution, available acute and chronic toxicity test methods and their sensitivity to compounds. Standardized methods currently exist to conduct acute and chronic toxicity tests with C. dubia and this species has received considerable attention in North America. Reasons for this attention include the taxonomic closeness to D. magna, distribution throughout North America, relatively short duration of chronic reproductive toxicity tests (seven days), and Ceriodaphnias sensitivity. Our review of the literature demonstrates the pandemic distribution of Ceriodaphnia (Europe, Asia, and North America included), the ecological importance of Ceriodaphnia species in freshwater plankton communities, and comparative acute and chronic sensitivity to a broad array of compounds and effluents. These attributes suggest that data from acute and chronic Ceriodaphnia toxicity tests can be considered equivalent to data from D. magna in environmental risk assessments and regulatory filings.

Hepatic gene expression profiling using GeneChips in zebrafish exposed to 17α-methyldihydrotestosterone

Concentration and time-dependent changes in hepatic gene expression were examined in adult, female zebrafish (Danio rerio) exposed to 0, 0.1, 0.7, 4.9 microg/L of a model androgen, 17alpha-methyldihydrotestosterone (MDHT). At 24 and 168 h, fish were sacrificed and liver was extracted for gene expression analysis using custom Affymetrix GeneChip Zebrafish Genome Microarrays. In an effort to link gene expression changes to higher levels of biological organization, blood was collected for measurement of plasma steroid hormones (17beta-estradiol (E2), testosterone (T)) and vitellogenin (VTG) using ELISA. Body and ovary weight were also measured. A significant reduction in E2 occurred at 24h (0.7 and 4.9 microg/L) and 168 h (4.9 microg/L) following MDHT exposure. In contrast, T was significantly increased at 24h (4.9 microg/L) and 168 h (0.1, 0.7, 4.9 microg/L). 171 and 575 genes were significantly affected in a concentration-dependent manner at either 24 or 168 h by MDHT exposure at p<or=0.001 and p<or=0.01, respectively. Genes involved in retinoic acid metabolism (e.g. aldehyde dehydrogenase 8, member A1; retinol dehydrogenase 12), steroid biosynthesis and metabolism (e.g. hydroxysteroid (11beta) dehydrogenase 2; hydroxy-delta-5-steroid dehydrogenase, 3 beta-), hormone transport (e.g. sex hormone binding globulin), and regulation of cell growth and proliferation (e.g. N-myc downstream regulated gene 1; spermidinespermine N(1)-acetyltransferase) were affected by MDHT exposure. In this study, we identified genes involved in a variety of biological processes that have the potential to be used as markers of exposure to androgenic substances. Genes identified in this study provide information on the potential mode of action of strong androgens in female fish. In addition, when used for screening of EDCs, these genes may also serve as sensitive markers of exposure to androgenic compounds.

Environmental Safety of the Use of Major Surfactant Classes in North America

This paper brings together over 250 published and unpublished studies on the environmental properties, fate, and toxicity of the four major, high-volume surfactant classes and relevant feedstocks. The surfactants and feedstocks covered include alcohol sulfate or alcohol sulfate (AS), alcohol ethoxysulfate (AES), linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and long-chain alcohol (LCOH). These chemicals are used in a wide range of personal care and cleaning products. To date, this is the most comprehensive report on these substances chemical structures, use, and volume information, physical/chemical properties, environmental fate properties such as biodegradation and sorption, monitoring studies through sewers, wastewater treatment plants and eventual release to the environment, aquatic and sediment toxicity, and bioaccumulation information. These data are used to illustrate the process for conducting both prospective and retrospective risk assessments for large-volume chemicals and categories of chemicals with wide dispersive use. Prospective risk assessments of AS, AES, AE, LAS, and LCOH demonstrate that these substances, although used in very high volume and widely released to the aquatic environment, have no adverse impact on the aquatic or sediment environments at current levels of use. The retrospective risk assessments of these same substances have clearly demonstrated that the conclusions of the prospective risk assessments are valid and confirm that these substances do not pose a risk to the aquatic or sediment environments. This paper also highlights the many years of research that the surfactant and cleaning products industry has supported, as part of their environmental sustainability commitment, to improve environmental tools, approaches, and develop innovative methods appropriate to address environmental properties of personal care and cleaning product chemicals, many of which have become approved international standard methods.

Interspecies Comparisons of A/D Ratios: A/D Ratios Are Not Constant across Species

The hypothesis that the ratio of the adult (A) and developmental (D) toxicity of a chemical is constant across animal species has been proposed as the basis for identifying developmental hazards, both from traditional developmental toxicity screens using laboratory mammals and from alternative systems such as the coelenterate Hydra attenuata. The purpose of this study was to determine whether A/D ratios are constant across species. The developmental and adult toxicity of 14 chemicals was assessed in four phylogenetically different species. The chemicals tested were aminopterin, bromodeoxyuridine, cadmium chloride, caffeine, congo red, dinocap, dinoseb, diphenylhydantoin, epinephrine, ethylenethiourea, 2-methoxyethanol, mirex, all-trans-retinoic acid, and trypan blue. These chemicals are representative of a variety of toxic mechanisms and a range of potencies. Species used were the CD-1 mouse (Mus musculus), South African clawed frog (Xenopus laevis), fathead minnow (Pimephales promelas), and fruit fly (Drosophila melanogaster). The mouse is a commonly used model for developmental toxicity. The other species are known to be sensitive to mammalian toxicants and have well-studied embryologies. Mice were exposed to chemicals either po or by sc injection using a standard Segment II protocol in which pregnant mice are administered the test agent on a daily basis from Gestation Days 6 to 15, adult toxicity is evaluated during and after treatment, and developmental toxicity is evaluated in fetuses at term. The exposure duration spans the period of organ formation in the embryo. The other species were exposed to test agents for a developmentally comparable period. This was from blastulation (shortly after fertilization) to the free-swimming tadpole stage in Xenopus (4 days); from blastulation to the free-swimming fry stage in Pimephales (7 days); and for the entire larval period, the period of development of the imaginal discs, in Drosophila (6 days). Adults of each species were exposed to test agents for 4, 7, and 6 days, respectively. The route of exposure was via the water column in the two aquatic species and via the diet in Drosophila. Statistical lowest observed effect level (LOEL) and no observed effect level (NOEL) values were generated for adult and developmental toxicity in each species. A/D ratios were calculated using both LOEL and NOEL values.(ABSTRACT TRUNCATED AT 400 WORDS)

Marine risk assessment: linear alkylbenzenesulponates (LAS) in the North Sea.

The fate of linear alkylbenzenesulponates (LAS) in estuaries and coastal areas of the North Sea has been characterized with simple environmental models. The predicted concentration range in the estuaries around the North Sea (0.9-9 microg LAS l(-1)) was validated by monitoring data (1-9 microg LAS l(-1)). In offshore sites of the North Sea, it is estimated--and experimentally verified for a few sites--that the LAS concentration is below analytical detection limit (i.e., 0.5 microg LAS l(-1)). The effects of LAS on marine organisms have been reviewed. For short-term acute tests, there was no significant difference (p = 0.83) between the mean LC50 values of freshwater and marine organisms (mainly pelagic species tested, 4.1 and 4.3 mg LAS l(-1), respectively). For longer-term chronic tests, it appeared that the sensitivity (mean no-observed effect concentration (NOEC) value) of marine and freshwater organisms (0.3 and 2.3 mg LAS l(-1), respectively) was significantly different pt-test = 0.007). The predicted no-effect-concentrations (PNEC) were 360 and 31 microg LAS l(-1), for freshwater and marine pelagic communities, respectively. Given that the maximum expected estuarine and marine concentrations are 3 to > 30 times lower than the PNEC, the risk of LAS to pelagic organisms in these environments is judged to be low.

An environmental risk assessment for DTDMAC in the Netherlands

The environmental safety of the cationic surfactant, ditallow dimethyl ammonium chloride (DTDMAC), has been determined from usage rates and fate data from The Netherlands and standard, well accepted assessment techniques. An environmental concentration model was developed using DTDMAC tonnages for 1990, actual per capita waste flow, and measured removal rates in wastewater treatment plants. This model incorporated a state of the art dilution model, instream removal and background DTDMAC concentrations. Based on this model, the 90th percentile river concentration of DTDMAC below wastewater treatment plant outfalls was estimated as 0.021 mg/L (i.e., 90% of Dutch surface waters receiving wastewater effluents have environmental concentrations less than 0.021 mg/L). This estimated concentration agrees well with the maximum measured DTDMAC concentrations in Dutch surface waters. Toxicity values for the risk assessment were derived from a study which used an environmentally relevant dosing system (i.e., effluent from an activated sludge treatment system) to measure commercial DTDMAC toxicity. Based on chronic toxicity data for Ceriodaphniadubia and Selenastrumcapricornutum from this study, a no effect level of 4.53 mg/L was determined for use in the risk assessment. Thus, the DTDMAC safety factor for aquatic organisms is 215 (4.53/0.021). It is concluded that DTDMAC poses a low risk to aquatic life based on testing of sensitive species and environmental concentrations predicted by state-of-the-art assessment methods.

A laboratory-scale model for evaluating effluent toxicity in activated sludge wastewater treatment plants

Abstract Laboratory-scale wastewater treatment systems were used to assess the potential contribution of a specific waste source, a detergent manufacturing plant, to wastewater treatment plant (WWTP) effluent toxicity. Laboratory-scale, continuously-fed activated sludge treatment systems (CAS units) were established and seeded with sludge from one of two activated sludge WWTPs. The CAS units were fed influent from these WWTPs supplemented with detergent manufacturing plant waste (plant waste). CAS unit effluent toxicity was measured with the 7 day Ceriodaphnia dubia survival and reproduction test and the 4 day Selenastrum capricornutum population growth test. Control (ambient WWTP influent) CAS unit and actual WWTP effluents had similar toxicity, indicating the CAS units generated effluent toxicologically similar to actual effluent for the two species tested. Untreated WWTP influent was supplemented with atypically high concentrations of plant waste in an attempt to establish a dose-response relationship between influent plant waste levels and effluent toxicity. However, there was no trend toward increasing effluent toxicity to Ceriodaphnia or algae with increasing influent plant waste concentrations. Thus, the detergent manufacturing plant waste is not contributing to the toxicity of the municipal WWTP effluent. This case study demonstrated the utility of CAS units for assessing the impact of WWTP influent sources on final effluent toxicity.

Plant growth response to olestra as related to beneficial use of municipal sludge

Consumer food ingredients may enter the terrestrial environment as constituents of municipal sludge which is used as a beneficial fertilizer source in land application. Evaluation of the plant/soil response to specific organic constituents, in the presence and absence of municipal sludge, is thus an important scientific component. Olestra is a consumer ingredient used in savory snacks to eliminate fat content and reduce calories in these foods. The fat substitute olestra is a mixture of hexa, hepta, and octaesters of sucrose with medium and long-chain fatty acids.Experiments were conducted of plant response in olestra mixtures with soil or municipal sludge/soil over a range from 0–1,000 mg olestra/kg dry soil. The plants grown from seed were corn, fescue, wheat, and soybean, with the latter two continued to seed production maturity. The comparison of effects rationale used in this study requires some consistent response to be measured and removes emphasis from singular, statistically significant response. The investment in multiple measures of plant response, separate periods of time, and appropriate multiple controls are necessary to place emphasis on consistent trends for a comparison rationale. For olestra, the notion of consistent effects permits the conclusion that more highly saturated solid olestra did not impact plant growth at concentrations of 0–1,000 mg olestra/kg dry soil in soil alone or in sludge/soil mixtures. The absence of effects occurred with germination, height, and biomass parameters.

Environmental toxicology of succinate tartrates

Abstract Succinate tartrates (ST) are a mixture of organic builders (water softening agents) developed for use in commercial cleaning products. Extensive toxicological studies were conducted on the mixture and its two principal components (85% sodium tartrate monosuccinate (CAS No. 111451-13-9); 15% sodium tartrate disuccinate (CAS No. 111451-16-2)) to evaluate its environmental safety. Median effect concentrations of ST to 11 species of freshwater and marine fishes and invertebrates ranged from 110 to > 1000mg/l. No observed effect concentrations in chronic studies with 7 species of fishes, invertebrates and algae ranged from 16 to 560 mg/l. An inverse relationship between water hardness and toxicily was observed in tests with fish, invertebrates and algae. Low bioconceniration factors (