Estimated Bioconcentration Factors Research Articles

First insights into the bioaccumulation, biotransformation and trophic transfer of typical tetrabromobisphenol A (TBBPA) analogues along a simulated aquatic food chain

Tetrabromobisphenol A (TBBPA) analogues have been investigated for their prevalent occurrence in environments and potential hazardous effects to humans and wildlife; however, there is still limited knowledge regarding their toxicokinetics and trophic transfer in aquatic food chains. Using a developed toxicokinetic model framework, we quantified the bioaccumulation, biotransformation and trophic transfer of tetrabromobisphenol S (TBBPS) and tetrabromobisphenol A di(allyl ether) (TBBPA-DAE) during trophic transfer from brine shrimp (Artemia salina) to zebrafish (Danio rerio). The results showed that the two TBBPA analogues could be readily accumulated by brine shrimp, and the estimated bioconcentration factor (BCF) value of TBBPS (5.68 L kg-1 ww) was higher than that of TBBPA-DAE (1.04 L kg-1 ww). The assimilation efficiency (AE) of TBBPA-DAE in zebrafish fed brine shrimp was calculated to be 16.3%, resulting in a low whole-body biomagnification factor (BMF) in fish (0.684 g g-1 ww). Based on the transformation products screened using ultra-high-performance liquid chromatograph-high resolution mass spectrometry (UPLC-HRMS), oxidative debromination and hydrolysis were identified as the major transformation pathways of TBBPS, while the biotransformation of TBBPA-DAE mainly took place through ether bond breaking and phase-II metabolism. Lower accumulation of TBBPA as a metabolite than its parent chemical was observed in both brine shrimp and zebrafish, with metabolite parent concentration factors (MPCFs) < 1. The investigated BCFs for shrimp of the two TBBPA analogues were only 3.77 × 10-10 - 5.59 × 10-3 times of the theoretical Kshrimp-water based on the polyparameter linear free energy relationships (pp-LFERs) model, and the BMF of TBBPA-DAE for fish was 0.299 times of the predicted Kshrimp-fish. Overall, these results indicated the potential of the trophic transfer in bioaccumulation of specific TBBPA analogues in higher trophic-level aquatic organisms and pointed out biotransformation as an important mechanism in regulating their bioaccumulation processes. Environmental ImplicationThe internal concentration of a pollutant in the body determines its toxicity to organisms, while bioaccumulation and trophic transfer play important roles in elucidating its risks to ecosystems. Tetrabromobisphenol A (TBBPA) analogues have been extensively investigated for their adverse effects on humans and wildlife; however, there is still limited knowledge regarding their toxicokinetics and trophic transfer in aquatic food chains. This study investigated the bioaccumulation, biotransformation and trophic transfer of TBBPS and TBBPA-DAE in a simulated di-trophic food chain. This state-of-art study will provide a reference for further research on this kind of emerging pollutant in aquatic environments.

Bioconcentration of carbamazepine, enalapril, and sildenafil in neotropical fish species.

Sewage effluents are the main source of entry of Human Pharmaceutical Active Ingredients (HPAIs) to surface water bodies. Carbamazepine (CBZ), psychiatric drug, enalapril (ENA) antihypertensive, and sildenafil (SIL), to treat erectile dysfunction, have been frequently detected in receiving wastewater and in wild fish species from Argentina. This study aimed to assess the bioconcentration of selected HPAIs in native fish species of the Del Plata Basin. In a first trial, the bioconcentration factors of CBZ, ENA, and SIL were obtained by exposing Cnesterodon decemmaculatus, respectively, to 135, 309, and 70μg/L during 96h. Then the bioconcentration kinetic of SIL was comparatively assessed in C. decemmaculatus and Piaractus mesopotamicus exposed, respectively, to 44.1 and 16.2μg/L during a one-week, followed by a four-day depuration phase. HPAIs concentrations in water and tissue were measured by HPLC-MS after 0.22μm filtration and direct injection or solid-liquid extraction, respectively. Bioconcentration factors obtained empirically (BCFe) for C. decemmaculatus were CBZ = 1.5, SIL = 1.4, and ENA = 0.007. Parameters estimated by the SIL bioconcentration kinetic model for C. decemmaculatus were: uptake rate constant (k1) = 5.5L/kg d, elimination rate constant during uptake phase (k2u) = 0.00175 d-1, maximum predicted tissue concentration (Ct(max)) = 138588μg/kg, estimated bioconcentration factor (BCFm) = 3143, lag time between the exposure and the first detection in tissue (tlag) = 0 d, elimination rate constant in the depuration phase (k2d) = 0.49 d-1 and half-life in the tissue (t1/2) = 1.4 d. The model parameters for P. mesopotamicus were k1: 7.3L/kg d, k2u: 0.0836 d-1, Ct(max): 1423μg/kg, BCFm: 88, tlag: 3.8 d in the uptake phase and k2d: 0.31 d-1 and t1/2: 2.3 d in the depuration phase. The reached conclusions were: 1) the bioconcentration capacity of CBZ and SIL are similar but around 200 times higher than ENA, 2) the time to reach the bioconcentration equilibrium for SIL is longer than 1week, then estimated BCFm are between 1 and 3 orders of magnitude higher than BCFe obtained after 96h exposure, but actual values need to be verified, 3) substantial differences (≈30 fold) were observed in the estimated BCF of SIL among species, indicating the need for further studies toward understanding such diversity to improve HPAIs ecological risk assessment worldwide.

Uptake and depuration of three common antibiotics in benthic organisms: Sea cucumber (Holothuria tubulosa), snakelocks anemone (Anemonia sulcata) and beadlet anemone (Actinia equina)

Antibiotics are widely used drugs in human and veterinary medicine, which has attracted great attention in relation to the development of bacterial resistance, currently a problem of great concern for governments and states, as it is related to the resurgence of infectious diseases already eradicated. Understanding the bioaccumulation of antibiotics in aquatic organisms is an important key to understanding their risk assessment. The present study was designed to study the bioaccumulation of target antibiotics in relevant organisms inhabiting benthic marine environments. The uptake and elimination of ciprofloxacin (CIP), sulfamethoxazole (SMX) and trimethoprim (TMP) were investigated in sea cucumbers (Holothuria tubulosa), snakelock anemone (Anemonia sulcata) and beadlet anemone (Actinia equina) under controlled laboratory conditions. The results show that antibiotics have a particular trend over time during all periods of absorption and depuration. The tissue distribution of antibiotics in sea cucumber is strongly influenced by the structure of the compounds, while CIP is concentrated in the body wall; TMP is concentrated in the digestive tract. Two different approaches were used to estimate bioconcentration factors (BCFs) in different animal models, based on toxicokinetic data and measured steady-state concentrations. The BCF ranges were 456–2731 L/kg, 6–511 L/kg and 9–100 L/kg for TMP, CIP and SMX, respectively. The estimated BCF values obtained classify TMP as cumulative in A. equina and H. tubulosa, underlining the potential bioconcentration in these marine organisms. A correlation was observed between the BCFs of the target antibiotics and the octanol-water distribution coefficient (Dow) (r2 > 0.7). The animal-specific BCF followed the order of beadlet anemone > sea cucumber > snakelock anemone.

Improved plant bioconcentration modeling of pesticides: The role of periderm dynamics.

BACKGROUNDThere is a continuous need to advance pesticide plant uptake models in support of improving pest control and reducing human exposure to pesticide residues. The periderm of harvested root and tuber crops may affect pesticide uptake, but is usually not considered in plant uptake models. To quantify the influence of the periderm on pesticide uptake from soil into potatoes, we propose a model that includes an explicit periderm compartment in the soil–plant mass balance for pesticides.RESULTSOur model shows that the potato periderm acts as an active barrier to the uptake of lipophilic pesticides with high K OW, while it lets more lipophobic pesticides accumulate in the medulla (pulp). We estimated bioconcentration factors (BCFs) for over 700 pesticides and proposed parameterizations for including the effects of the periderm into a full plant uptake modeling framework. A sensitivity analysis shows that both the degradation half‐life inside the tuber and the lipophilicity drive the contributions of other aspects to the variability of BCFs, while highlighting distinct dynamics in the periderm and medulla compartments. Finally, we compare model estimates with measured data, showing that predictions agree with field observations for current‐use pesticides and some legacy pesticides frequently found in potatoes.CONCLUSIONConsidering the periderm improves the accuracy of quantifying pesticide uptake and bioconcentration in potatoes as input for optimizing pest control and minimizing human exposure to pesticide residues in edible crops.

Tradeoff between risks through ingestion of nanoparticle contaminated water or fish: Human health perspective

This study proposed a framework (termed as “nanoHealthRisk” hereafter) for incorporating i) interaction of nanoparticles (NPs) with fishes, ii) availability of NPs to the human digestive system, and iii) estimation of health risk due to fish consumption and inadvertent ingestion of NP-contaminated surface water, for the first time as per the literature review. The framework was applied for estimating health risks due to hypothetical exposures of pristine ZnO, CuO, and TiO2 NPs (without any surface functionalization) from fish tissues. Values of bio- concentration factors (BCF) of ZnO, CuO, and TiO2 NPs in fish and model distributions of bio-assimilation factor of ZnO, CuO and TiO2 NPs in the human digestive system were incorporated explicitly in the risk assessment of NPs for the first time. ZnO NP was observed to be transferred more to the human digestive system from aqueous matrix than the other two NPs. Maximum allowable values of NP posing no risk were found to be 0.115 mg/L, 0.152 mg/L, and 1.77 × 107 mg/L for pristine ZnO, CuO and TiO2 NP, respectively. At the environmental concentration range, exposures of studied NPs from aquatic environment under the assumptions used did not pose any health risk under the conditions studied in this study. More work is required to (1) Estimate bio-concentration factors of a mixture of NPs with other constituents in fish tissues, (2) Estimate dissolution of NP from fish tissue in human digestive media, (3) Generate new data to develop reference dose of NP for human health risk assessment, and (4) Study effect of NP fate in the water on health risk through fish consumption pathway. Until all above-mentioned aspects are not explicitly incorporated in the risk assessment framework, risk estimates do not represent the risk from environment completely. Thus, continuous monitoring of these NPs in the environment is required to protect health due to chronic exposure of small concentrations of NPs from an aqueous matrix.

Copper and arsenic accumulation of Pityrogramma calomelanos, Nephrolepis biserrata, and Cynodon dactylon in Cu- and Au- mine tailings

Metallophytes are group of plants that can thrive on metal-rich substrate. These plants have potential in various green technologies. However, it is a must to first identify plants that can absorb heavy metals and tolerate the high concentration in their tissues. This study assessed the ability of plants thriving in a Cu-Au mined areas to uptake copper (Cu), and arsenic (As). The Cu and As content of the dried leaves, root tissues and soils were quantified using Atomic Absorption Spectrophotometer (AAS), and their bioaccumulation coefficient (BAC) were computed. Three species, Pityrogramma calomelanos, Cynodon dactylon and Nephrolepis biserrata , showed metal accumulation in the plant tissues. The three species have accumulation of Cu in the root and the estimated bioconcentration factor (BCF) is more than 1.0 which indicates the ability of these species to tolerate for said the metal hence is a good candidate for phytostabilization of polluted soils. Noteworthy was the accumulation of As in the shoot of the three species despite of the low soil As (<0.01 µg/g). Nephrolepis biserrata had the highest arsenic bioaccumulation factor of 30.91 followed by Cynodon dactylon (11.01) then Pityrogramma calomelanos (8.78) which make them potential species for clean-up of As through phytoextraction. Moreover, this study added C. dactylon as tolerant of arsenic in mined-out area in the Philippines.

In vitro and in vivo metabolic stability of various fragrance materials and insect repellent in rainbow trout (Oncorhynchus mykiss).

Commercial fragrances consist of several thousand natural and synthetic substances formulated in complex combinations. These ingredients are frequently blended at very low concentrations but they are typically lipophilic and a few of them (e.g., synthetic musks) have been detected in aquatic systems, albeit at low concentrations. Few fragrances have guideline in vivo data on bioaccumulation, so in silico modeling has been widely used to estimate bioconcentration factors (BCFs). This study used in vitro metabolism assays with trout S9 cell fractions and cryopreserved hepatocytes to improve estimates of fish BCFs and to test published methods for extrapolating in vitro metabolic rate data to whole fish and corresponding BCFs. These estimates for several chemicals were compared with new in vivo bioconcentration measurements and previously published data on fragrances and the insect repellent, DEET. In total, 17 (20 including isomers) fragrance chemicals (abalyn, amberwood, amboryl acetate, bisabolene, cedroxide, coniferan, elemol, givescone, maritima, precyclemone B, polysantol, sandela, sanjinol, santalex, timberol and vernaldehyde) and DEET were metabolized at various rates. Only three materials tested did not appear to undergo enzymatic degradation (caryophyllene oxide, galaxolide and ketone patchouli). Even relatively slow rates of metabolism had a large influence on bioconcentration estimates. This work adds valuable information to the evolving body of work supporting the use of in vitro determinations of hepatic clearance to improve modeled predictions of bioaccumulation. It can also be used directly to help prioritize testing of potential bioaccumulative chemicals or serve as a more economical method for screening these chemicals.

Uptake, depuration, bioaccumulation, and selective enrichment of dechlorane plus in common carp (Cyprinus carpio).

Dechlorane plus (DP) is a chlorinated flame retardant with high production volume (HPV) and is widely used in our daily necessities. In the present study, a laboratory-scale microcosm was built up to simulate the uptake, depuration, bioaccumulation, and stereoselective enrichment of DP in a lower concentration and equilibration condition. Common carp (Cyprinus carpio) were used for 32days exposure and 32days depuration. The concentration ratios of syn-DP to total DP (fsyn values) in fish examined were lower than that in commercial products. Rate constants of uptake (kS) and elimination (ke) for the syn- and anti-DP were calculated using a first-order kinetic model. The uptake rate constants of syn- and anti-DP were 0.63 and 0.89day-1, respectively. The depuration rate constants of syn-DP (0.11day-1) were similar to anti-DP (0.096day-1), suggesting that anti-DP is absorbed faster than syn-DP by common carp. The estimated bioconcentration factors for both syn-DP (5700L/kg) and anti-DP (9300L/kg) were higher than the bioconcentration hazard criteria outlined in the Stockholm Convention, suggesting the bioconcentration potential to aquatic organisms for DP.

Acute exposure to an environmentally relevant concentration of diclofenac elicits oxidative stress in the culturally important galaxiid fish Galaxias maculatus.

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) of growing concern in aquatic environments worldwide; nevertheless, knowledge of its effects on aquatic biota is restricted to a few model species with limited information regarding its mechanisms of impact. In the present study, diclofenac accumulation, its effects on metabolic rate, ionoregulation, and oxidative stress were examined at environmentally relevant (0.17 µg L-1 ) and elevated (763 µg L-1 ) concentrations in a culturally and economically important galaxiid fish, inanga (Galaxias maculatus), from the Southern Hemisphere. This species is among the most widespread freshwater fish in the world but its sensitivity to emerging contaminants is unknown. Following an acute 96-h exposure, bioconcentration of diclofenac was measured in the inanga whole-body, resulting in an estimated bioconcentration factor of 87 for the 0.17-µg L-1 exposure concentration, approaching values where transfer through the food chain should be considered. Lipid peroxidation in the liver was significantly elevated at both 0.17- and 763-µg L-1 exposure concentrations but lipid peroxidation in the kidney and gill decreased after diclofenac exposure. Catalase activity was also elevated in the liver of inanga but activity decreased in the gill. There were no effects of diclofenac on metabolic rate or ion (sodium and calcium) influx rates. These data indicate that toxicologically relevant adverse outcomes and bioconcentration of diclofenac at environmentally relevant levels warrant additional study in this important fish. Environ Toxicol Chem 2018;37:224-235. © 2017 SETAC.

Uptake and effects of 2, 4, 6 - trinitrotoluene (TNT) in juvenile Atlantic salmon (Salmo salar)

Organ specific uptake and depuration, and biological effects in Atlantic salmon (Salmo salar) exposed to 2, 4, 6-trinitrotoluene (TNT) were studied. Two experiments were conducted, the first using radiolabeled TNT (14C-TNT, 0.16mg/L) to study uptake (48h) and depuration (48h), while the second experiment focused on physiological effects in fish exposed to increasing concentrations of unlabeled TNT (1μg–1mg/L) for 48h. The uptake of 14C-TNT in the gills and most of the organs increased rapidly during the first 6h of exposure (12h in the brain) followed by a rapid decrease even though the fish were still exposed to TNT in the water. The radioactivity in the gall bladder reached a maximum after 55h, 7h after the transfer to the clean water. A high concentration of 14C-TNT in the gall bladder indicates that TNT is excreted through the gall bladder. Mortality (2 out of 14) was observed at a concentration of 1mg/L, and the surviving fish had hemorrhages in the dorsal muscle tissue near the spine. Analysis of the physiological parameters in blood from the high exposure group revealed severe effects, with an increase in the levels of glucose, urea and HCO3, and a decrease in hematocrit and the levels of Cl and hemoglobin. No effects on blood physiology were observed in fish exposed to the lower concentrations of TNT (1–100μg/L). TNT and the metabolites 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT) were found in the muscle tissue, whereas only 2-ADNT and 4-ADNT were found in the bile. The rapid excretion and estimated bioconcentration factors (range of 2–18 after 48h in gills, blood, liver, kidney, muscle and brain) indicated a low potential for bioaccumulation of TNT.

Bioaccumulation of pharmaceuticals and personal care products in the unionid mussel Lasmigona costata in a river receiving wastewater effluent.

Freshwater mussels are frequently found in rivers receiving effluent from wastewater treatment plants (WWTP), and there is strong evidence that poor water quality is deleterious to freshwater mussel populations. WWTPs are among the main sources of pharmaceuticals and personal care products (PPCPs) in surface waters. We monitored 145 PPCPs in wild and caged mussels both upstream and downstream of the Kitchener WWTP in the Grand River, Ontario, as well as 118 PPCPs in water samples. Our objectives were to characterize the seasonal changes in PPCP concentrations in water, to calculate bioaccumulation factors (BAFs) of PPCPs in mussels, and to determine the chemical and physical properties of PPCPs driving the bioaccumulation. Seventy PPCPs were detected in water, and concentrations were highest in the summer or early fall, which corresponded to low river flow. Forty-three PPCPs from many pharmaceutical classes were detected in mussel tissues, including stimulants, a contrasting agent, anti-inflammatory drugs, anti-bacterial agents, antibiotics, antidepressants, antihistamines, progestins, and illicit drugs such as cocaine and amphetamines. The BAFs ranged from 0.66 for metformin to 32,022 for sertraline. Using partial least squares to predict BAFs based upon chemical properties, log KOC, Log KOW, and fugacity ratio (sediment) all had similar and positive loadings with BAFs (R(2)X = 0.70; caged mussels). BAFs of PPCPs in mussels were predictable from fugacity models that estimate bioconcentration factors using log KOW. Our study demonstrated that mussels readily bioaccumulate PPCPs, in a manner consistent with expectations based upon BCF models and the chemical characteristics of each compound.

Occurrence and bioaccumulation of pharmaceuticals in a fish species inhabiting the Suquía River basin (Córdoba, Argentina)

In South America, there is a lack of data concerning the occurrence and levels of pharmaceuticals in main rivers as well as their negative effects on the biota. Here we report the occurrence as well as the spatial and temporal variations of some common prescribed pharmaceuticals in the Suquía River basin (Córdoba, Argentina). We also report the bioconcentration of two of them in Gambusia affinis, a widely distributed fish species inhabiting the river basin. The influence of the wastewater treatment plant of Córdoba City was critical (up to 70km downstream). Among 15 compounds analyzed, atenolol, carbamazepine and diclofenac were the most frequently detected (reaching sub μgL−1 levels), showing different distribution patterns. Bioconcentration of atenolol and carbamazepine was studied under laboratory controlled conditions. Estimated bioconcentration factors (BCFs) were: 0.13 and 0.08Lkg−1 upon exposure to 100 and 1000μgL−1 atenolol in water, respectively; while BCFs were 0.7 and 0.9Lkg−1 when exposed to 10 and 100μgL−1 carbamazepine, respectively. To the extent of our knowledge, this is the first report on pharmaceuticals in superficial waters of Argentina as well as the first report on the bioaccumulation of atenolol in whole body fish.

Assessment of heavy metal contamination and bioaccumulation in soybean plants from mining and smelting areas of southern Hunan Province, China

Soybean is one of most important dicotyledonous food crops and is widely planted in Hunan Province, China. However, mining activity causes contamination of the soil in which soybean grows. To assess the impact of mining-induced soil contamination on soybean plants, a geoaccumulation index (I(geo)) was used to evaluate 20 soil samples from the mining and smelting areas of southern Hunan Province. The results indicated that Zn ranged from uncontaminated to a moderately contaminated level (I(geo)<1), Pb was at a strongly contaminated level (I(geo)>3), and Cd was at an extremely contaminated level (I(geo)>5) across the whole study area. All of the studied soybean plants were affected by heavy metal Pb and Cd contamination, and the mean concentrations in seeds were 13.9 mg/kg and 2.95 mg/kg, respectively. The estimated bioconcentration factor and translocation factor showed that the soybean roots had a strong Cd bioconcentration capability and the stems had a strong translocation capability in terms of Pb, Cd, and Zn, with preferential transference of metals to the soybean leaves. The bioavailable fraction in the soil was characterized by the exchangeable fraction of heavy metals. In the present study, the bioavailable fractions of Pb, Cd, and Zn were significantly positively correlated with the concentration of these metals in soybean tissues (roots, stems, leaves, husks, and seeds).

Rapid determination of polycyclic aromatic hydrocarbons (PAHs) in zebrafish eleutheroembryos as a model for the evaluation of PAH bioconcentration

A simple and fast approach for a novel bioaccumulation test by exposing zebrafish eleutheroembryos to fluorene and anthracene (PAHs) at two concentration levels below 1% of their LC50 is presented. This alternative protocol sets an uptake period of 48h at 26°C for bioconcentration of the compounds tested and an additional 24h for depuration. Two different methods to estimate bioconcentration factors (BCFs) of PAHs were used. The first consists in the ratio between concentrations of the tested compounds in the zebrafish eleutheroembryos and the exposure media when a steady state during exposure is reached (BCFss). The second employs the concentration–time profile with the use of a least-square fit to a non-linear model (BCFk). A steady state (ss) was reached after 12h and 22h for fluorene and anthracene exposure, respectively. Uptake and depuration rate constants obtained were similar for the two exposure levels tested, hence toxicokinetic rate constants appeared to be independent of the exposure level. Bioconcentration factors of 1164 and 817 for fluorene exposure at 0.99ngmL−1 and 7.9ngmL−1 and of 2089 and 2344 for anthracene at 0.63ngmL−1 and 6.1ngmL−1 were assessed. The good agreement of the obtained results with those reported in the literature proves the feasibility of the proposed method for estimation of both toxicokinetic parameters and bioconcentration factors. Furthermore, this protocol, has potential to be an alternative to the Organisation for Economic Cooperation and Development (OECD) 305 method, considerably reducing time and associated costs of the test suggested by European legislation.

Using Quantitative Structure–Activity Relationships to Support the Assessment of the Environmental Fate and Aquatic Toxicity of a Series of Methacrylic Acid Esters

ABSTRACT Methacrylic acid esters or methacrylates (with C1 to 8 alkyl side-chains) are a group of compounds used in the manufacture of resins and plastics. Releases to the atmosphere, surface waters, or soil can come about during manufacturing, use, transport, and storage activities. Given the potential for environmental exposures, an examination into factors that control the distribution, fate, and toxicity of methacrylates is warranted. Methacrylates are relatively volatile compounds that are easily and rapidly degraded in the atmosphere and in oxic surface waters and sediments, and so are not considered persistent. Aquatic organisms are also able to metabolize methacrylates as demonstrated by estimated bioconcentration factors of < 45 for the acid and the C1-4 esters, and a measured bioconcentration factor (BCF) for 2-EHMA. Thus, the methacrylates are not considered bioaccumulative. Acute and chronic aquatic toxicity data for the methacrylates were assembled. Quantitative structure–activity relationships (QSARs) were developed with the acute and chronic fish, invertebrate, and algal datasets to support the toxicity assessment of the methacrylates (with log octanol-water partition coefficients used as surrogates for structures). The data show the methacrylates to be of low to moderate toxicity with all acute LC/EC50 values and chronic no observed effect concentrations ranging from about 2 to 170 mg/l for the acid and C1-4 esters, and 0.1 mg/l up to the aqueous solubility limit (about 2 mg/l) for the C8 ester. The measured toxicity data and the data estimated from the QSARs were used to develop predicted no effect concentrations in water and sediment for methacrylic acid and the C1-C8 esters.

Estimated bioconcentration factors (BCFs) for the C4 through C8 perfluorinated alkylsulfonic acid (PFSA) and alkylcarboxylic acid (PFCA) congeners

Bioconcentration factors (BCFs) were estimated for all congeners in each of the C4 through C8 homologue groups for perfluorinated alkylsulfonic acids (PFSAs) and alkylcarboxylic acids (PFCAs). Predictive equations were developed between molecular areas and volumes using optimized gas-phase geometries from the AM1 and PM3 semiempirical computational basis sets and previously determined BCFs for representative straight-chain members of each contaminant class. Molecular area approaches for estimating PFSA and PFCA BCFs resulted in more variability both between and within homologue groups than the use of molecular volumes as proxies for hydrophobicity of the perfluoroalkyl chain. An increasing degree of perfluoroalkyl chain branching within each homologue group reduces the estimated BCF, suggesting that the more linear PFSA and PFCA congeners will display the highest BCFs in aquatic organisms.

Animal use replacement, reduction, and refinement: Development of an integrated testing strategy for bioconcentration of chemicals in fish

AbstractWhen addressing the use of fish for the environmental safety of chemicals and effluents, there are many opportunities for applying the principles of the 3Rs: Reduce, Refine, and Replace. The current environmental regulatory testing strategy for bioconcentration and secondary poisoning has been reviewed, and alternative approaches that provide useful information are described. Several approaches can be used to reduce the number of fish used in the Organization for Economic Cooperation and Development (OECD) Test Guideline 305, including alternative in vivo test methods such as the dietary accumulation test and the static exposure approach. The best replacement approach would seem to use read‐across, chemical grouping, and quantitative structure‐activity relationships with an assessment of the key processes in bioconcentration: Adsorption, distribution, metabolism, and excretion. Biomimetic extraction has particular usefulness in addressing bioavailable chemicals and is in some circumstances capable of predicting uptake. Use of alternative organisms such as invertebrates should also be considered. A single cut‐off value for molecular weight and size beyond which no absorption will take place cannot be identified. Recommendations for their use in bioaccumulative (B) categorization schemes are provided. Assessment of biotransformation with in vitro assays and in silico approaches holds significant promise. Further research is needed to identify their variability and confidence limits and the ways to use this as a basis to estimate bioconcentration factors. A tiered bioconcentration testing strategy has been developed taking account of the alternatives discussed.

Animal Use Replacement, Reduction, and Refinement: Development of an Integrated Testing Strategy for Bioconcentration of Chemicals in Fish

When addressing the use of fish for the environmental safety of chemicals and effluents, there are many opportunities for applying the principles of the 3Rs: Reduce, Refine, and Replace. The current environmental regulatory testing strategy for bioconcentration and secondary poisoning has been reviewed, and alternative approaches that provide useful information are described. Several approaches can be used to reduce the number of fish used in the Organization for Economic Cooperation and Development (OECD) Test Guideline 305, including alternative in vivo test methods such as the dietary accumulation test and the static exposure approach. The best replacement approach would seem to use read-across, chemical grouping, and quantitative structure-activity relationships with an assessment of the key processes in bioconcentration: Adsorption, distribution, metabolism, and excretion. Biomimetic extraction has particular usefulness in addressing bioavailable chemicals and is in some circumstances capable of predicting uptake. Use of alternative organisms such as invertebrates should also be considered. A single cut-off value for molecular weight and size beyond which no absorption will take place cannot be identified. Recommendations for their use in bioaccumulative (B) categorization schemes are provided. Assessment of biotransformation with in vitro assays and in silico approaches holds significant promise. Further research is needed to identify their variability and confidence limits and the ways to use this as a basis to estimate bioconcentration factors. A tiered bioconcentration testing strategy has been developed taking account of the alternatives discussed.

Brachidontes variabilis and Patella sp. as quantitative biological indicators for cadmium, lead and mercury in the Lebanese coastal waters

The mussel, Brachidontes variabilis, and the limpet, Patella sp., were used as indicators to monitor cadmium, lead and mercury concentrations along the Lebanese coast. Studies were carried out in order to define the best strategy for assessing and minimizing the effects of size and physiological condition on the metal contents of the molluscs, and corrective models were constructed. Metal concentrations in surface water were measured to estimate bioconcentration factors (BCFs). The BCFs varied from 8.3 × 10 3 to 3.4 × 10 4, from 7.5 × 10 3 to 8.0 × 10 3 and from 3.0 × 10 4 to 3.2 × 10 4, for Cd, Pb and Hg, respectively. For limpets, BCFs varied from 1.7 × 10 4 to 7.4 × 10 4 for Cd, from 2.5 × 10 3 to 6 × 10 3 for Pb and remained fairly constant at around 10 4 for Hg. The highest BCFs were associated with lowest contamination levels. The results of the geographical survey exhibited a similar large-scale spatial pattern for the two species and followed the metal concentration distributions measured in the waters.

Comparative Toxicokinetics of Explosive Compounds in Sheepshead Minnows

Juvenile sheepshead minnows Cyprinodon variegatus were exposed to the explosive compounds 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and to the TNT transformation products 2-aminodinitrotoluene (2-ADNT) and 2,4-diaminonitrotoluene (2,4-DANT) in five separate water-only experiments. A one-compartment model was used to characterize uptake (k(u)) and elimination (k(e)) rate constants and to estimate bioconcentration factors (BCFs). The compounds investigated in this study are weakly hydrophobic. Kinetically derived BCFs (9.6, 13.1, 0.5, 1.7, and 0.5 ml g(-1) for TNT, 2-ADNT, 2,4-DANT, RDX, and HMX, respectively) confirmed the expected low bioaccumulative potential of those compounds and the positive relationship between log BCF and log K(ow) (1.6, 2.0, 0.8, 0.9, and 0.2 for TNT, 2-ADNT, 2,4-DANT, RDX, and HMX, respectively). The uptake clearance (k(u)) was relatively slow for all compounds (7.3, 12.6, 1.3, 0.15, and 0.06 ml g(-1)h(-1) for TNT, 2-ADNT, 2,4-DANT, RDX, and HMX, respectively), and overall, it decreased with decreasing compound hydrophobicity. Elimination was extremely fast for the nitroaromatic compounds (0.77, 0.96, and 2.74 h(-1) for TNT, 2-ADNT, and 2,4-DANT, respectively), thus resulting in very short biological half-lives (<1 hour), but it was much slower for the cyclonitramines (0.09 h(-1) for RDX and 0.12 h(-1) for HMX). Although ADNTs were present in fish exposed to TNT, the parent compound was the dominant compound in tissues during the uptake and elimination exposures. The rates of metabolite formation (0.06 h(-1)) and elimination (0.16 h(-1)) were much slower than the rate of elimination of the parent compound (0.80 h(-1)). Because of the fast elimination rate of TNT and its transformation products and the exceedingly low bioaccumulative potential of RDX and HMX, exposure conditions likely associated with the presence of explosives in aquatic systems are unlikely to pose unacceptable risks to fish.