Actual Exposure Concentrations Research Articles

Degradation Kinetics of Antifouling Biocides in Sediment During the Spiking Equilibrium Phase

The new generation of antifouling biocides, as well as other emerging contaminants, has not yet been included in sediment quality guidelines or present standard protocols for sediment spiking. Most of these biocides have short half-lives in water, but little information is available regarding their degradation in sediments. Thus, there is a need to establish a reliable duration of the equilibrium phase for sediment spiking prior to sediment toxicity testing to determine the actual exposure concentrations during ecotoxicological tests. This study aimed to evaluate the degradation of DCOIT, Irgarol, Diuron, and Dichlofluanid during a spiking equilibrium phase of 24 h at three different time intervals (0, 6, and 24 h) and concentrations (10, 100, and 1000 ng g-1), by applying kinetic degradation models. The models presented a better fit for the 1000 ng g-1 treatments, in which the half-lives of DCOIT and Diuron were < 5 h, Dichlofluanid < 2 h, and Irgarol < 6h. Our results also indicate that, except for Dichlofluanid, the degradation rates of the other antifouling biocides were reduced dramatically after 6 h of equilibrium. Therefore, an equilibrium phase of 24 h (or greater than 6 h) was considered viable for sediment spiking. Our findings provide valuable information to guide future sediment toxicity tests using these compounds.

Benefits and costs: Understanding the influence of heavy metal pollution on environmental adaptability in Strauchbufo raddei tadpoles through an energy budget perspective

Understanding the impact of environmental pollution on organismal energy budgets is crucial for predicting adaptive responses and potential maladaptation to stressors. However, the regulatory mechanism governing the trade-off between energy intake and consumption remains largely unknown, particularly considering the diverse adaptations influenced by exposure history in realistic field conditions. In the present study, we conducted a simulated field reciprocal transplant experiment to compare the energy budget strategies of Strauchbufo raddei tadpoles exposed to heavy metal. The simulated heavy metal concentrations (0.29 mg/L Cu, 1.17 mg/L Zn, 0.47 mg/L Pb, 0.16 mg/L Cd) mirrored the actual environmental exposure concentrations observed in the field habitat. This allowed for a comparison between tadpoles with parental chronic exposure to heavy metal pollutants in their habitat and those without such exposure. Results revealed that under heavy metal exposure, tadpoles originating from unpolluted areas exhibited heightened vulnerability, characterized by reduced food intake, diminished nutrient absorption, increased metabolism cost, reduced energy reserves, and increased mortality rates. In contrast, tadpoles originating from areas with long-term heavy metal pollution demonstrated adaptive strategies, manifested through adjustments in liver and small intestine phenotypes, optimizing energy allocation, and reducing energy consumption to preserve energy, thus sustaining survival. However, tadpoles from polluted areas exhibited certain maladaptive such as growth inhibition, metabolic suppression, and immune compromise due to heavy metal exposure. In conclusion, while conserving energy consumption has proven to be an effective way to deal with long-term heavy metal stress, it poses a threat to individual survival and population development in the long run.

Reconciling the actual and nominal exposure concentrations of microplastics in aqueous phase: Implications for risk assessment and deviation control.

The deviation between actual and nominal concentrations of microplastics (MPs), as a long-standing issue, has been critically commented. However, there is still a lack of quantitative assessment and reconciling practice on the deviation. In this study, a total of 210 deviations were recompiled to thoroughly examine this issue. It was shown that up to 81 (39%) deviations exceeded the recommended ±20% variation specification, highlighting that the deviation of MPs should not be neglected. This study attempted to reconcile the deviation based on the most prominent driving factors. Specifically, the game theory-based SHapley Additive exPlanations (SHAP) algorithm identified that the particle size was the most important factor affecting the deviation. Subsequently, at each size magnitude, a significant linear correlation between the logarithmic actual and nominal concentrations was determined, which provided a sound basis for estimating the actual concentration from the nominal one. Furthermore, deviations of different size classes were simulated through 10, 000 points, suggesting that the ±20% deviation variation could be well maintained within a specific concentration range. Moreover, the potential interaction effects between factors were quantified by SHAP interaction values, with more detailed conversion bases proposed. Additionally, several control measures were recommended to reduce the deviation of MPs.

Similarity assessment of metallic nanoparticles within a risk assessment framework: A case study on metallic nanoparticles and lettuce

Similarity assessment is one of the means of optimally using scarcely available experimental data on the fate and hazards of nanoforms (NFs) for regulatory purposes. For a set of NFs that are shown to be similar it is allowed in a regulatory context to apply the information available on any of the NFs within the group to the whole set of NFs. Obviously, a proper justification for such a similarity assessment is to be provided. Within the context of exemplifying such a justification, a case study was performed aimed at assessing the similarity of a set of spherical metallic NFs that different with regard to chemical composition (three metals) and particle size (three different sizes). The endpoints of assessment were root elongation and biomass increase of lettuce (Lactuca sativa L.) seedlings and exposure assessment was performed in order to express the actual exposure concentration in terms of time-weighted average particle concentrations. The results of the study show that for the specific endpoints assessed, chemical composition is driving NF toxicity and this is mostly due to impacts on the fate of the NFs. On the other hand, particle size of Cu NFs had a negligible impact on the dose-response relationships for the specific endpoints assessed. It is thus concluded that hazard data available on spherical Cu NF tested in our case can be used to inform on the hazards of any spherical Cu NF within the size range of 25–100 nm, but only applies for the certain endpoints. Also, toxicity data for the Cu2+-ion are suited for such a similarity assessment.

Beebread consumption by honey bees is fast: results of a six-week field study

Due to their foraging behavior, honey bees interact with the landscape. As a result, honey bees and their brood will be exposed to pesticides through nectar and pollen entering the hive. Although these pathways seem rather straightforward, there are several steps between the entry of nectar and pollen and its consumption by the colony. One of the aspects involved here is the time between collection and consumption of pollen in the hive. This is of importance for the actual exposure of nurse bees and larvae to pesticides in pollen. Although lab and short-term field studies indicated that bees prefer to consume freshly stored pollen, this has to our knowledge not been verified in a long-term field study under realistic environmental and apiculturist conditions. To study pollen consumption dynamics, influx and consumption were recorded at 3 or 4 day intervals over a six-week period in two colonies. It was demonstrated that throughout the experimental period, beebread consumption was high in the first 3 to 5 days after collection, over which approximately 70% was consumed. The remaining 30% was consumed within a 2 to 3 week period. Pollen consumption is swift and indicates that only limited time is available for potential degradation processes. As actual data on degradation of pesticides in stored pollen are not available, a justified worse case assumption would be that the actual exposure concentrations consumed by the nurse bees and larvae are the same as the concentrations in collected pollen.

Experimental determination of indoor air concentration of 5-chloro-2-methylisothiazol-3(2H)-one/ 2-methylisothiazol-3(2H)-one (CMIT/MIT) emitted by the use of humidifier disinfectant.

A mixture of 5-chloro-2-methylisothiazol-3(2H)-one/2-methylisothiazol-3(2H)-one (CMIT/MIT) had been used as an active ingredient in humidifier disinfectants (HDs). Owing to its high reactivity, the atmospheric concentration of CMIT/MIT, following its use in HD, would be lower than expected assuming that it is removed by ventilation only. In order to evaluate the exposure concentration of CMIT/MIT used as an HD, room-scale chamber studies were conducted under plausible use of three different HD doses at air change rates (ACR) of 0.3, 0.5, and 1.0 h−1. Atmospheric CMIT/MIT was sampled using two serial impingers containing deionized water after the attainment of steady state. Water samples in which CMIT/MIT was dissolved were concentrated using a cosolvent evaporation method with efficiencies of 35.5 and 77.9% for CMIT and MIT, respectively. The estimated air concentration, assuming that all the CMIT/MIT is absorbed in deionized water, increased linearly with increasing emission rate, but was independent of the ACR. This indicates that the removal rate of CMIT/MIT via chemical reactions is more than the removal rate by ventilation. Further investigations on homogeneous and heterogeneous chemical reactions of CMIT/MIT under ambient conditions are necessary to understand the actual exposure concentration of the mixture in HD.

Personal black carbon exposure and its determinants among elderly adults in urban China

Personal exposure to air pollution is affected by its concentration in the microenvironment and individual time-activity patterns. To investigate personal black carbon (BC) exposure levels and identify their potential determinants, we conducted a panel study among 67 elderly residents aged 60–69 years in Jinan, China. Personal BC exposure was measured using portable real-time monitors, while corresponding ambient BC concentrations and meteorological conditions were also collected from the local central site. Time-activity and household characteristics were recorded. A linear mixed-effects model was used to identify potential determinants of personal BC exposure. The daily average personal BC exposure concentration was 4.1 ± 2.0 μg/m3 (±standard deviation, SD), which was significantly lower than the ambient concentration (4.6 ± 2.5 μg/m3) (p < 0.001). Strong correlation (Spearman’s r = 0.63, p < 0.001) was found between personal and ambient BC concentrations. The fixed-site monitoring ambient concentration cannot fully reflect the actual personal exposure concentration. Ambient BC concentration, ambient temperature, relative humidity, education level and air purifier use were significant determinants of personal BC exposure. Our findings highlight the need for detailed assessment of personal exposure on health risk assessment of BC and also help develop strategies for targeted risk reduction.

Four-week inhalation toxicity study of 1-propanol in F344 rats.

1-Propanol is used as a solvent for waxes, vegetable oils, resins, cellulose esters, and ethers, and is not considered harmful to humans by food and non-occupational exposures. However, workers are potentially exposed to 1-propanol by inhalation when it is used in the workplace. Thus, inhalation toxicity data are needed to assess the hazard of 1-propanol for workers safety. Five male and five female F344 rats were exposed to 1-propanol vapor for 4-weeks (6h/day, 5days/week) at concentrations of 0, 100, 400, and 1600ppm in a whole-body inhalation chamber system. The actual exposure concentrations were 100.11 ± 5.10, 403.19 ± 12.31, and 1598.08 ± 139.58ppm for the low, middle, and high dose groups, respectively. No clinical signs, significant mean body weight changes, significant changes of hematology or blood biochemistry results, or histopathological abnormalities were seen related to exposure to the test substance. Under the conditions of this study, the no-observed-adverse-effect level of 1-propanol was over 1600ppm.

Ecotoxicity of Nitrogen, Sulfur, or Oxygen Heterocycles and Short-Chained Alkyl Phenols Commonly Detected in Contaminated Groundwater.

Nitrogen, sulfur, or oxygen heterocyclic aromatic hydrocarbons (NSO-HETs) and short-chained alkyl phenols (SCAPs) are commonly detected in groundwater at contaminated sites and in the surrounding environment. It is now scientific consensus that these chemicals pose a risk to human and ecosystem health. However, toxicity data are comparably fragmentary, and only few studies have addressed the ecotoxicity of NSO-HETs and SCAPs in a systematic and comparative fashion. To overcome this shortcoming, we tested 18 SCAPs, 16 NSO-HETs, as well as the homocyclic hydrocarbons indane and indene in the Microtox® assay with Aliivibrio fischeri, the growth inhibition test with Desmodesmus subspicatus, the acute immobilization assay with Daphnia magna, as well as the fish embryo toxicity test with embryos of the zebrafish (Danio rerio). Because of the physicochemical properties of the tested chemicals (limited water solubility, volatility, and sorption to test vessels), actual exposure concentrations in test media and their dissipation over time were analytically quantified by means of gas chromatography with mass spectrometry. Analytically corrected effect levels (median effect and lethal concentrations) ranged from 0.017 to 180 mg L-1 , underlining the environmental relevance of some NSO-HETs and SCAPs. Para-substituted phenols showed the overall greatest toxicities in all 4 toxicity tests. We provide, for the first time, a complete high-quality data set in support of better environmental risk assessments of these chemicals. Environ Toxicol Chem 2019;38:1343-1355. © 2019 SETAC.

Method Suggestion of Predicting the Exposure to Residential Indoor Air Pollutants Using Time-Activity Patterns and Outdoor Air

Most people may be affected by indoor air quality at home since it is where they spend most of their time. Although air pollutants (APs) concentrations such as particulate matter, SO2, NO2, CO, and O3 is provided through ambient fixed monitoring system, it could be different from actual exposure concentrations because it has limitations such as distance and staying in indoor environments. The purposes of this study were to predict the concentrations of Indoor APs (IAPs) and to assess exposures at home considering indoor sources and house residential time of people by analyzing time-activity patterns including questionnaire.To estimate IAPs concentrations, we applied the concentration of outdoor air pollutants by measurements or atmospheric modelling, and indoor air quality model to PM, NO2, CO concentrations with indoor sources, and Indoor/Outdoor ratio acquired from previous studies, and to SO2 and O3 concentrations without indoor sources. The concentrations of APs were acquired from ambient fixed monitoring system. And the concentrations of IAPs were measured in houses with sensor instruments of particulate matter by adjusting gravimetric method, and exposure to IAPs were estimated.Residential time at home was more than about 90% their times. Results of measurements of sensor indicate increased concentrations of IAPs with indoor sources from cooking, cleaning and smoking than usual (no behavior) and concentrations of IAPs with indoor sources increase as number of the behavior increase.Sub-populations such as the old and housewives might be more likely to be affected by house indoor air because they spend most of their time at home. We predicted the concentrations of IAPs and assessed exposures at home to IAPs by modelling and analyzing time-activity patterns including questionnaire. These results will be expected to provide basis for preparing guidelines for prevention of diseases caused by house IAPs

In vitro genotoxicity of airborne Ni-NP in air-liquid interface.

Studies using advanced toxicological methods enabling in vitro conditions that are more realistic are currently needed for understanding the risks of pulmonary exposure to airborne nanoparticles. Owing to the carcinogenicity of certain nickel compounds, the increased production of nickel nanoparticles (Ni‐NPs) raises occupational safety concerns. The aim of this study was to investigate the genotoxicity of airborne Ni‐NPs using a recently developed air–liquid interface exposure system. The wild‐type Chinese hamster lung fibroblast cell line (V79) was used and cytotoxicity, DNA damage and mutagenicity were studied by testing colony forming efficiency, alkaline DNA unwinding and HPRT mutation assays, respectively. Additionally, co‐exposure to a PARP‐1 inhibitor was performed to test possible involvement of base excision repair (BER) in repair of Ni‐induced DNA damage. The results showed that cell viability was reduced significantly (to 45% and 46%) after 48 hours Ni‐NP exposure at concentrations of 0.15 and 0.32 μg cm−2. DNA damage was significantly increased after Ni‐NP exposure in the presence of the BER inhibitor indicating that Ni‐NP‐induced DNA damages are subsequently repaired by BER. Furthermore, there was no increased HPRT mutation frequency following Ni‐NP exposure. In conclusion, this study shows that Ni‐NP treatment of lung fibroblasts in an air–liquid interface system that mimics real‐life exposure, results in increased DNA strand breaks and reduced cellular viability. These DNA lesions were repaired with BER in an error‐free manner without resulting in mutations. This study also underlines the importance of appropriate quantification of the actual exposure concentrations during air–liquid interface exposure studies.

Exposure profile of volatile organic compounds receptor associated with paints consumption

Epidemiologic studies regarding solvent-based paints (SBPs) containing VOCs have demonstrated a strong correlation between chronic and acute adverse health effects and the SBPs. Therefore, new environmentally friendly paints as substitutes containing less or none VOCs have been rapidly developed in research for future sustainable use. However, a few studies focusing on penetration and exposure condition of the substitute have been reported duo to the complexity and inaccessibility of painting industry. Surveys specifically looking at the present status of exposure condition were conducted to ascertain the popularization of water-based paints (WBPs) which concluded that markers of SBPs were detected in all 134 samples indicating bad industrial penetration. VOCs exposure concentrations of painters ranged from 3.8 to 18.2mg/m3 for WBPs, 3.5×103 to 14.8×103mg/m3 for SBPs, respectively. The negative correlation between ambient concentration and breathing zone concentration suggested the former was incapable of representing the actual exposure concentration. The real-time concentration was proved to be closely associated with the activity patterns while the mean concentration level was found mostly dependent on the paint types. Authentic inhalation dose ranged from 7.68 to 15.84mg (WBPs) and 3.84 to 15.59g (SBPs), respectively, for occupational painters (work 8h per day) and the total inhalation dose was estimated through a new conception. The findings suggested that WBPs could significantly reduce VOCs emission and occupational exposure.

Vertical transport and plant uptake of nanoparticles in a soil mesocosm experiment.

BackgroundAgricultural soils represent a potential sink for increasing amounts of different nanomaterials that nowadays inevitably enter the environment. Knowledge on the relation between their actual exposure concentrations and biological effects on crops and symbiotic organisms is therefore of high importance. In this part of a joint companion study, we describe the vertical translocation as well as plant uptake of three different titanium dioxide (nano-)particles (TiO2 NPs) and multi-walled carbon nanotubes (MWCNTs) within a pot experiment with homogenously spiked natural agricultural soil and two plant species (red clover and wheat).ResultsTiO2 NPs exhibited limited mobility from soil to leachates and did not induce significant titanium uptake into both plant species, although average concentrations were doubled from 4 to 8 mg/kg Ti at the highest exposures. While the mobility of MWCNTs in soil was limited as well, microwave-induced heating suggested MWCNT-plant uptake independent of the exposure concentration.ConclusionsQuantification of actual exposure concentrations with a series of analytical methods confirmed nominal ones in soil mesocosms with red clover and wheat and pointed to low mobility and limited plant uptake of titanium dioxide nanoparticles and carbon nanotubes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0191-z) contains supplementary material, which is available to authorized users.

Chronic Toxicity of Unweathered and Weathered Macondo Oils to Mysid Shrimp (Americamysis bahia) and Inland Silversides (Menidia beryllina).

Chronic, 21-28-day toxicity tests of Macondo source (Massachusetts, or MASS) and weathered Slick A (CTC) and Slick B (Juniper) oils field collected during the 2010 Deepwater Horizon (DWH) Incident in the Gulf of Mexico (GOM) were conducted using standardized procedures. Standard species, Americamysis bahia and Menidia beryllina, were evaluated for changes in survival and growth during daily static-renewal tests. Both species demonstrated an increased sensitivity to low-energy water accommodated fractions (WAFs) of un-weathered MASS oil, with growth and survival decreasing as oil loading rate increased from 0.01 to 1.0g/L. Survival and growth of mysid shrimp exposed to weathered oil (Slick A and Slick B) did not differ from that of test controls. In contrast, survival and growth of inland silversides declined relative to that of test controls at loading rates of 1g/L for both weathered oils. Based on the concentration of total polycyclic aromatic hydrocarbons (TPAH42), no observed effect concentrations were lower for inland silverside survival (5.00-7.61µg/L) and growth (<2.02 to <7.61µg/L) in chronic exposures to Slick B and Slick A weathered oils compared with mysids (4.75-17.9µg/L). Average TPAH concentrations in full strength WAFs followed the weathering trend, with 165±17.2, 17.9±0.480, and 4.75±0.521µg/L for MASS, Slick A, and Slick B oils, respectively. The effect (LOEC, IC25) and no-effect exposure concentrations (in TPAHs) from the standardized laboratory toxicity studies with un-weathered and weathered oils are discussed relative to the actual exposure concentrations in the GOM in 2010. The exposures evaluated in the laboratory toxicity tests represent the highest concentrations of total PAHs that were rarely observed in water column samples collected in the GOM during the release and post release periods of the DWH incident.

Strong lethality and teratogenicity of strobilurins on Xenopus tropicalis embryos: Basing on ten agricultural fungicides

Agricultural chemical inputs have been considered as a risk factor for the global declines in amphibian populations, yet the application of agricultural fungicides has increased dramatically in recent years. Currently little is known about the potential toxicity of fungicides on the embryos of amphibians. We studied the effects of ten commonly used fungicides (four strobilurins, two SDHIs, two triazoles, fludioxonil and folpet) on Xenopus tropicalis embryos. Lethal and teratogenic effects were respectively examined after 48 h exposure. The median lethal concentrations (LC50s) and the median teratogenic concentrations (TC50s) were determined in line with actual exposure concentrations. These fungicides except two triazoles showed obvious lethal effects on embryos; however LC50s of four strobilurins were the lowest and in the range of 6.81–196.59 μg/L. Strobilurins, SDHIs and fludioxonil induced severe malformations in embryos. Among the ten fungicides, the lowest TC50s were observed for four strobilurins in the range of 0.61–84.13 μg/L. The teratogenicity shared similar dose–effect relationship and consistent phenotypes mainly including microcephaly, hypopigmentation, somite segmentation and narrow fins. The findings indicate that the developmental toxicity of currently-used fungicides involved with ecologic risks on amphibians. Especially strobilurins are highly toxic to amphibian embryos at μg/L level, which is close to environmentally relevant concentrations.

Energy-based modelling to assess effects of chemicals on Caenorhabditis elegans: A case study on uranium

The ubiquitous free-living nematode Caenorhabditis elegans is a powerful animal model for measuring the evolutionary effects of pollutants which is increasingly used in (eco) toxicological studies. Indeed, toxicity tests with this nematode can provide in a few days data on the whole life cycle. These data can be analysed with mathematical tools such as toxicokinetic-toxicodynamic modelling approaches. In this study, we assessed how a chronic exposure to a radioactive heavy metal (uranium) affects the life-cycle of C. elegans using a mechanistic model. In order to achieve this, we exposed individuals to a range of seven concentrations of uranium. Growth and reproduction were followed daily. These data were analysed with a model for nematodes based on the Dynamic Energy Budget theory, able to handle a wide range of plausible biological parameters values. Parameter estimations were performed using a Bayesian framework. Our results showed that uranium affects the assimilation of energy from food with a no-effect concentration (NEC) of 0.42mM U which would be the threshold for effects on both growth and reproduction. The sensitivity analysis showed that the main contributors to the model output were parameters linked to the feeding processes and the actual exposure concentration. This confirms that the real exposure concentration should be measured accurately and that the feeding parameters should not be fixed, but need to be reestimated during the parameter estimation process.

Toxicity of anthelmintic drugs (fenbendazole and flubendazole) to aquatic organisms.

Flubendazole (FLU) and fenbendazole (FEN) belong to benzimidazoles—pharmaceuticals widely used in veterinary and human medicine for the treatment of intestinal parasites as well as for the treatment of systemic worm infections. In recent years, usage of these drugs increased, which resulted in a larger contamination of the environment and possible negative effects on biota. Hence, in our research, we investigated an aquatic ecotoxicity of these pharmaceuticals towards: marine bacteria (Vibrio fischeri), green algae (Scenedesmus vacuolatus), duckweed (Lemna minor) and crustacean (Daphnia magna). Ecotoxicity tests were combined with chemical analysis in order to investigate the actual exposure concentration of the compounds used in the experiment as well as to stability and adsorption studies. As a result, study evaluating sensitivity of different aquatic organisms to these compounds and new ecotoxicological data is presented. The strongest negative impact of FLU and FEN was observed to D. magna.

Acute toxicity of the cationic surfactant C12‐benzalkonium in different bioassays: How test design affects bioavailability and effect concentrations

Using an ion-exchange-based solid-phase microextraction (SPME) method, the freely dissolved concentrations of C12-benzalkonium were measured in different toxicity assays, including 1) immobilization of Daphnia magna in the presence or absence of dissolved humic acid; 2) mortality of Lumbriculus variegatus in the presence or absence of a suspension of Organisation for Economic Co-Operation and Development (OECD) sediment; 3) photosystem II inhibition of green algae Chlorella vulgaris; and 4) viability of in vitro rainbow trout gill cell line (RTgill-W1) in the presence or absence of serum proteins. Furthermore, the loss from chemical adsorption to the different test vessels used in these tests was also determined. The C12-benzalkonium sorption isotherms to the different sorbent phases were established as well. Our results show that the freely dissolved concentration is a better indicator of the actual exposure concentration than the nominal or total concentration in most test assays. Daphnia was the most sensitive species to C12-benzalkonium. The acute Daphnia and Lumbriculus tests both showed no enhanced toxicity from possible ingestion of sorbed C12-benzalkonium in comparison with water-only exposure, which is in accordance with the equilibrium partitioning theory. Moreover, the present study demonstrates that commonly used sorbent phases can strongly affect bioavailability and observed effect concentrations for C12-benzalkonium. Even stronger effects of decreased actual exposure concentrations resulting from sorption to test vessels, cells, and sorbent phases can be expected for more hydrophobic cationic surfactants.

Toxicity testing of dispersed oil requires adherence to standardized protocols to assess potential real world effects

Recently, several researchers have attempted to address Deepwater Horizon incident environmental fate and effects issues using laboratory testing and extrapolation procedures that are not fully reliable measures for environmental assessments. The 2013 Rico-Martínez et al. publication utilized laboratory testing approaches that severely limit our ability to reliably extrapolate such results to meaningful real-world assessments.The authors did not adopt key methodological elements of oil and dispersed oil toxicity standards. Further, they drew real-world conclusions from static exposure tests without reporting actual exposure concentrations. Without this information, it is not possible to compare their results to other research or real spill events that measured and reported exposure concentrations.The 1990s' Chemical Response to Oil Spills: Ecological Effects Research Forum program was established to standardize and conduct exposure characterization in oil and dispersed oil aquatic toxicity testing (Aurand and Coelho, 2005). This commentary raises awareness regarding the necessity of standardized test protocols.

Toxicity of 15 veterinary pharmaceuticals in zebrafish (Danio rerio) embryos

Extensive use of veterinary pharmaceuticals may result in contamination of water bodies adjacent to pasture land or areas where animal manure has been applied. In order to evaluate the potential risk to fish embryos 15 veterinary pharmaceuticals were investigated by use of an extended zebrafish embryo toxicity test. Chemical analysis of the exposure medium was performed by solid phase extraction–liquid chromatography–tandem mass spectrometry (SPE–LC–MS/MS) for 11 of the compounds and potential metabolism by the embryos was studied for albendazole, febantel, fenbendazole and oxfendazole. Newly fertilized zebrafish eggs were exposed under static conditions in 96-well plates for 6 days to the pharmaceuticals: 5 antibacterials and 10 antiparasitics. Endpoints including mortality, malformations and other sublethal responses were recorded at 24, 48 and 144h post fertilization (hpf). The pharmaceuticals causing the highest toxicity were antiparasitics whereas the tested antibacterials, danofloxacin, enrofloxacin, tylosine, trimethoprim and oxytetracyclin had a much lower toxic potency in zebrafish embryos. Most toxic were fenbendazole, albendazole and flumethrin with no observed effect concentrations (NOECs) around 0.02mg/L. The overall NOEC was determined by lethality for the following pharmaceuticals: albendazole, fenbendazole and oxfendazole. Sublethal endpoints, including malformations, side-laying embryos, tremors, reduced movements and altered heart rate increased the sensitivity of the tests and determined the overall NOECs for febantel, doramectin, ivermectin, flumethrin and toltrazuril. Exposure to doramectin and ivermectin caused a decrease in movements at 24hpf and a decrease in heart rate at 48hpf. Flumethrin exposure resulted in decreased time to hatching, except at the highest concentrations, and caused an increase in heart rate at 48hpf. In contrast, toltrazuril caused an increased time to hatching and a decrease in heart rate. Chemical analysis of the exposure medium after the tests revealed great differences between nominal and measured concentrations, emphasizing the need of including analysis of the actual exposure concentrations. The results indicated that metabolism of albendazole into its sulfoxide protected the embryos from toxicity. Albendazole was metabolized efficiently into albendazole sulfoxide at lower exposure concentrations, resulting in reduced toxicity. At higher concentrations, an increasing proportion of albendazole remained unmetabolized and embryo mortality occurred. Metabolism by the embryos of febantel into fenbendazole and oxfendazole and of fenbendazole into oxfendazole was demonstrated. It is suggested that the toxic effect of febantel in zebrafish embryos is due to metabolism into fenbendazole.