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At least 613 records · Page 34Linked to original sources
PubMed2004

Uptake and elimination routes of inorganic mercury and methylmercury in Daphnia magna.

Mercury (Hg) is an important environmental pollutant due to its highly toxic nature and widespread occurrence in aquatic systems. The biokinetics of Hg in zooplankton have been largely ignored in previous studies. This study examines the assimilation, dissolved uptake, and efflux of inorganic mercury [Hg(II)] and methylmercury (MeHg) in a freshwater cladoceran, Daphnia magna, and models the exposure pathways of Hg(II) and MeHg in the daphnids. The assimilation efficiencies (AEs) of both Hg species decreased significantly with increasing algal carbon concentrations. The dissolved uptake of Hg(II) and MeHg was proportional to the ambient concentration (ranging from environmentally realistic to high concentration over a 3-4 orders of magnitude variation), whereas MeHg had a slightly higher uptake rate constant (0.46 L g(-1) h(-1)) than Hg(II) (0.35 L g(-1) h(-1)). Surprisingly, the efflux rate constants of Hg(ll) and MeHg were rather comparable (0.041 -0.063 day(-1)). The release of both Hg(II) and MeHg via different routes (excretion, egestion, molting, and neonate production) was further examined at different food concentrations. It was found that regeneration into the dissolved phase was important for D. magna to eliminate both Hg species, but maternal transfer of Hg(II) (11-15%) and MeHg (32-41%) to neonates represented another important pathway for the elimination of Hg(II) and MeHg from the mothers. Modeling results suggest that food is an important source for MeHg exposure (47-98%), but water exposure represents 31-96% of Hg(II) accumulation in D. magna, depending on the variation of Hg bioconcentration factor in ingested food. Furthermore, MeHg predominates the bioaccumulation of Hg in D. magna even though MeHg constitutes only a small percentage of the total Hg in the water. The results strongly indicate that maternal transfer of Hg(II) and MeHg in freshwater zooplankton should be considered in manytoxicity testings and risk assessment in aquatic food chains.

Animals↗
PubMed2006

Influence of biotransformation on trophic transfer of the PAH, fluoranthene.

The persistence of polycyclic aromatic hydrocarbons (PAHs) in marine sediments may be influenced by benthic invertebrate bioturbation. Through processes such as deposit-feeding and enhancement of microbial metabolic activity PAHs may be remobilized from the sediment compartment, and either transferred to organisms at higher trophic levels or to the overlying water column, both processes inevitably changing the bioavailability of the PAH. Accumulation of contaminants from one level in the food chain to the next depends on feeding rate and assimilation efficiency, two factors that basically vary with food quality and contaminant type. Though it is generally believed that pre-consumptive biotransformation will reduce bioavailability due to the more polar nature of the metabolites compared to the unchanged parent compound, theoretically the decrease in lipophilicity will increase the sediment/food desorption rate in the intestine, and some metabolites will still be lipophilic enough to be absorbed by passive diffusion. We examined the trophic transfer of the PAH, fluoranthene from two closely related polychaete species (i.e., Capitella sp. I and Capitella sp. S), differing in their biotransformation ability, to the predatory polychaete, Nereis virens. We found that N. virens fed the biotransforming species, Capitella sp. I, accumulated significantly more Flu equivalents compared to worms fed Capitella sp. S, which have a very limited biotransformation ability. The dose-specific increase in N. virens intestinal Flu concentration was approximately twice as high in worms fed Capitella sp. I (equation: gut content=7.3 x dose-3.9) compared to worms fed Capitella sp. S (equation: gut content=3.2 x dose+0.6). In addition, we measured DNA damage, using the comet assay, in N. virens intestinal cells after feeding with the two prey species. We did not detect DNA damage above 'background' levels for worms fed either of the two Capitella species, possibly due to relatively low intestinal Flu concentrations in N. virens. Our results indicate that accumulation of PAHs by infaunal organisms may play an important role in the transfer of this type of contaminant to higher trophic levels. Moreover, we observed differences in transfer potential between parent compounds and their respective metabolites, which may influence the fate of these compounds in marine ecosystems. However, from the present study it cannot be concluded whether differences in biotransformation ability among prey species can lead to different effects in their predators.

Animal Feed↗
PubMed1998

Twenty years of trace metal analyses of marine mammals in Alaska: evaluation and summation.

The compilation of existing data on contaminants in the marine food chain is essential in addressing concerns regarding the magnitude of potential human exposures and in the evaluation of subsistence food safety. This paper presents a summary of studies on trace metals in tissues of Alaska marine mammals from the 1970s to the present, along with derived mean tissue trace metal concentrations. The derived mean can serve as a norm against which future monitoring results may be compared, and may be used to estimate human exposure to trace metals through the consumption of marine mammals. Additionally, the variation among studies in the reported mean tissue concentrations has been described through a derived standard deviation. Sufficient analytical and methodological details were available to derive means and standard deviations for tissues in bearded seal, bowhead whale, beluga whale, fur seal, harbor seal, Pacific walrus, and ringed seal. A high concordance between trace metal values reported in tissues (i.e., liver, kidney, muscle) was observed despite significant differences in reported sampling and analytical methodologies. Consistent with other reviews of trace metal concentrations in marine species, the standard deviation of tissue metal concentrations was generally < or = 100% of the reported mean. Significant gaps in available information remain, particularly for muscle tissues and for methylmercury, despite the considerable efforts to monitor marine mammal species in Alaska.

Alaska↗
PubMed2004

Uptake, retention and organ/tissue distribution of 137Cs by Japanese catfish (Silurus asotus Linnaeus).

The work describes the uptake, retention/biological elimination and organ/tissue distribution of 137Cs by freshwater Japanese catfish (Silurus asotus Linnaeus) under laboratory conditions. The fish were divided into three groups based on their size and age and reared in 137Cs-spiked water. The concentration of 137Cs in the whole body of the live fish was measured at regular intervals up to 60 days. A significant accumulation of 137Cs was found, but a steady state condition was not achieved by the end of the experiment. The bioaccumulation factors at steady state and the required time to reach steady state were estimated to be 1.55 and 255 days, 1.76 and 180 days and 1.99 and 160 days for large, medium and small size fish, respectively. To determine the effective half-life of 137Cs, the fish were transferred and reared in the non-contaminated host water. The concentration of the remaining 137Cs in the whole body of the live fish was measured up to 66 days. The average effective half-life of 137Cs in the fish species was found to be approximately 142 days for fish of all sizes. The distribution of 137Cs in different organs/tissues of the fish was determined. Accumulation of 137Cs in muscle/flesh of the fish was found to be approximately 75% of whole body accumulation. The uptake rate and the retention capability of juvenile fish were found to be higher and therefore, these were more susceptible to 137Cs than adult and old fish, and could be an important source of 137Cs in the human food chain.

Age Factors↗
PubMed2006

Parasites entangled in food webs.

Food webs are a fundamental concept in ecology in which parasites have been virtually ignored. In a recent article, Lafferty et al. address this imbalance, finding that the inclusion of parasites in food webs could be of greater importance to ecosystem stability than was previously thought. Furthermore, the bottom of the food chain is perhaps no longer the most dangerous place to be.

Animals↗
PubMed2005

Laboratory and field assessment of uranium trophic transfer efficiency in the crayfish Orconectes limosus fed the bivalve C. fluminea.

At present, ecotoxicological information regarding the impact of natural uranium (U) on freshwater ecosystems via the trophic contamination route is scarce. We generated an experimental trophic food chain involving the prey species, Corbicula fluminea, and a predator, Orconectes limosus, for a 10-day and a 30-day feeding periods (food ration: one whole soft body/day/crayfish). We studied the efficiency of U trophic transfer and the distribution of U in the predator. During the test, we varied the quantity of dietary U (from beforehand contaminated bivalves at concentrations ranging from 0.9+/-0.1 to 20.2+/-9 microg/g fw provided to each crayfish over the 10 days) applying a daily feeding rate equal to 3.9+/-0.8% fw. The efficiency of U trophic transfer from clams to crayfish varied between 1 and 13% depending on the prey exposure modalities. Accumulation of U was observed in the digestive gland but also in gills, in the muscle, and in the molt of the crayfish after trophic exposure treatments. Under high-level exposure conditions, the digestive gland was the main target-organ, however a significant accumulation was also observed in the stomach. With regard to low levels of trophic exposure, accumulation of U in gills, in the stomach, and in the digestive gland was of the same order of magnitude. Longer exposure period which incorporated a crayfish molt, resulted in a decrease of trophic transfer ratio and a modified U tissue distribution.

Animals↗
PubMed1977

[Oxidation of a naphthenic hydrocarbon, dodecylcyclohexane, in the rat].

Naphthenic hydrocarbons, mainly of fossil origin, are widespread in our environment, and contaminate the food chains; they are also used as food additives. Their fate in mammals is unknown, except for the fact that they are absorbed and accumulate in tissues. Only a few microorganisms have been shown capable or oxidising n-alkyl substituted cycloparaffins. In this study, dodecylcylohexane has been chosen as a typical monocycloparaffin, and has been administered orally to rats. The GLC and GLC-MS analysis of the methylesters of body and hepatic fatty acids led to the identification of cyclohexyldodecanoic and its decanoïc and octanoïc homologs. The alkyl chain undergoes a terminal oxidation followed by the classical beta-oxidation process. After administration of one 200 mg dose, or incorporation of 0.1% of the cycloparaffin in the diet for 2 months, these acids were found at low levels in neutral lipids and phospholipids. Their subsequent metabolic pathway and their possible interaction with the biochemical mechanisms involving phospholipids are under investigation.

Adipose Tissue↗
PubMed2006

Parasites dominate food web links.

Parasitism is the most common animal lifestyle, yet food webs rarely include parasites. The few earlier studies have indicated that including parasites leads to obvious increases in species richness, number of links, and food chain length. A less obvious result was that adding parasites slightly reduced connectance, a key metric considered to affect food web stability. However, reported reductions in connectance after the addition of parasites resulted from an inappropriate calculation. Two alternative corrective approaches applied to four published studies yield an opposite result: parasites increase connectance, sometimes dramatically. In addition, we find that parasites can greatly affect other food web statistics, such as nestedness (asymmetry of interactions), chain length, and linkage density. Furthermore, whereas most food webs find that top trophic levels are least vulnerable to natural enemies, the inclusion of parasites revealed that mid-trophic levels, not low trophic levels, suffered the highest vulnerability to natural enemies. These results show that food webs are very incomplete without parasites. Most notably, recognition of parasite links may have important consequences for ecosystem stability because they can increase connectance and nestedness.

Animals↗
PubMed1999

Distribution and sequestration of palytoxin in coral reef animals.

In the reefs off the Colombian coast (Caribbean Sea) and around Lizard Island, Australia (Pacific), palytoxin (PTX), which has been detected in zoanthid species of the genus Palythoa, also occurred in various other marine organisms living in close association with zoanthid colonies, e.g. sponges (Porifera), soft corals (Alcyonaria), gorgonians (Gorgonaria), mussels, and crustaceans. Predators, e.g. polychaete worms (Hermodice carunculata), a starfish (Acanthaster planci) and fish (Chaetodon species) feeding on Palythoa colonies, accumulate high toxin concentrations in their organs, where PTX is stored in its active form. The high level of toxin tolerance observed in marine animals may enable the wide distribution of PTX in marine biota and its transport and sequestration in food chains.

Acrylamides↗
PubMedDate not supplied

Determinants of p,p-dichlorodiphenyldichloroethane (DDE) concentration in adipose tissue in women from five European cities.

To identify the determinants of p,p'-dichlorodiphenyldichloroethane (p,p'-DDE) in adipose tissue in subjects who participated in a cross-sectional study, we analyzed fatty acids, antioxidants, and p,p'-DDE in aspirates of adipose tissue of 328 postmenopausal women from 5 European countries. The overall mean of p,p'-DDE concentration was 1.66 microg/g of fatty acids (95% confidence interval = 1.46, 1.88). In a multiple-regression analysis, the main predictors of log10(p,p'DDE) were center of recruitment (p < .0001), adipose arachidic acid (p = .001), and adipose retinol (p = .04). These factors explained 14.9% of the overall variability of log10(p,p'-DDE). In our subjects, adipose tissue p,p'DDE concentrations were only weakly related with biomarkers reflecting intake of fish and other foods. This result is consistent with the notion that p,p'-DDE exists in different foods and, given the widespread contamination of the food chain, is relatively evenly distributed among foods.

Adipose Tissue↗
PubMed1990

Fungi: a major source of radiocesium contamination of grazing ruminants in Norway.

Transfer of radiocesium from vegetation to milk was studied in dairy goats grazing heavily contaminated mountain pasture in southern Norway in the years following the Chernobyl accident. Radiocesium activity in milk and green vegetation remained stable throughout 1986 and 1987. In 1988, a sudden three- to fivefold increase in milk radioactivity occurred during the second half of the summer. Whole-body content of radioactivity in sheep and reindeer also increased rapidly. This coincided with an abundant growth of fungal fruit bodies with radiocesium levels up to 100 times higher than green vegetation. Fungal radiocesium was found to be highly available in a digestibility study with goats. Milk radioactivity levels in the field could be accounted for by consumption of as little as 20-100 g d-1 of fungal dry matter (DM). The importance of fungal fruit bodies in transferring radiocesium to ruminants was further substantiated by comparing meat activities in grazing ruminants in 1988 and 1989. Fungal fruit bodies were present in minor quantities in 1989, and radioactivity levels in sheep and reindeer in August-September were only 28-35% of those in 1988. This ability of fungi to mobilize radiocesium from natural soils and transfer the isotopes into the human food chain greatly enhances the vulnerability of food production in natural ecosystems to radiocesium pollution.

Accidents↗
PubMed1977

Haloethylene-related compounds of industrial, environmental, and medical significance.

A broad-based literature survey was made for chemicals that contain either a haloethylene or a related substructure. Two hundred and sixty-two compounds, including synthetic intermediates, pesticides, solvents, drugs, food components, natural products, and metabolites, are grouped by their structures. Some are in current use or are bioavailable while little exposure is expected from others. As more biologic-response information is reported for small compounds of these types, it should become possible to select others for research on additional questions of structure-activity relationships. Some of the compounds are widespread while others are not. Some are used or found in large amounts while others may be trace contaminants, minor or more major by-products of synthesis or isolation. The pesticides and solvents, for example, are knowingly and often deliberately released to the environment, sometimes in very large quantities. Inadvertent release also occurs, sometimes referred to as fugitive emission. Food contaminants and drugs are directly accessible to humans. Sparsely distributed natural products could be accessible to humans, for example, via the food chain. Some of the compounds in food may be formed during preparation, storage or metabolically. Last, the haloethylene function has often been synthesized into compounds in order to achieve desired biologic activities. There are many types and degrees of relatedness of structure, depending upon atomic dimensions and stereochemical, polar, resonance, and other factors. Furthermore, for some chemical series, biologic responses are continuously variable while, in other cases, it is not uncommon that qualitatively different types of response occur with apparently very close homologs. Genetic, metabolic, and behavioral factors affecting response must also be considered. Thus, safety or hazard cannot yet be predicted conclusively by apparent relatedness of structure alone. Also, since the tables are noncomprehensive, some relevant compounds have likely been omitted. The haloalkanes, for example, are not here because of their large number, despite the knowledge that some are either metabolized or nonbiologically converted to haloalkenes.

Alcohols↗
PubMed1997

Establishment of microbiological safety criteria for foods in international trade. International Commission on Microbiological Specifications for Foods.

Microbiological safety is achieved by applying good hygienic practices throughout the food chain, "from farm to fork". Governmental food control is traditionally based on inspection of the facilities where foods are handled, and on testing food samples. Testing is usually applied to imported foods, when no information concerning the safety of a consignment is available. The microbiological safety is judged by means of microbiological criteria. Such criteria should, in the context of the WTO/SPS measures, be scientifically justified, and established according to the principles described by the Codex Alimentarius. However, microbiological testing is not a very reliable tool for consumer protection; the emphasis is currently shifting to the application of food safety management tools such as the Hazard Analysis Critical Control Point system (HACCP).

Food Contamination↗
PubMed1997

A regulatory perspective on the potential uses of microbial risk assessment in international trade.

The recent ratification of the World Trade Organisation Agreement will arguably be the most important factor in developing new sanitary measures for the international trade in food over the next decade. There is a markedly increased desire for quantitative data on the microbial risks associated with different classes of foods, and traditional good manufacturing practice (GMP)-based food hygiene requirements are coming under increasing challenge. As the risk assessment paradigm is increasing applied and as decision-making criteria for risk management become established, more emphasis will be placed on predictive microbiology as a means of generating exposure data and establishing critical limits for Hazard Analysis Critical Control Point (HACCP) plans. In this respect, developing international guidelines for risk management arguably presents the greatest challenge in establishing and maintaining quantitative Sanitary and Phytosanitary (SP) measures for food in international trade, and for judging their equivalence. Where specific industry sectors and regulators do not have jurisdiction over the entire food chain, from production of raw materials through to consumption, it will be difficult to apply the risk assessment paradigm in the design of HACCP plans. Thus, it appears that default to food safety objectives for many segments of food production chains subject to application of HACCP plans is inevitable in the medium term.

Food Microbiology↗
PubMed2003

Changes in dietary bioaccumulation of tributyltin chloride (TBTCl) in red sea bream (Pagrus major) with the concentration in feed.

The effect of the concentration of tributyltin (TBT) in feed on the dietary bioaccumulation of tributyltin chloride (TBTCl) was studied in an 8-week uptake experiment and a 4-week elimination experiment using red sea bream (Pagrus major). The biomagnification factor (BMF) and the assimilation efficiency (AE) decreased from 0.30 to 0.15 and from 13% to 5.9%, respectively, as the TBT concentration in feed increased from 1.3 to 20 microg/g. The elimination rate constant (k(2)) was independent of the TBT concentration in the fish. Laboratory measurements of the BMF and AE of TBTCl underestimate actual field values if highly contaminated feed is used. Judging from the BMF and AE, the risk of the bioaccumulation of TBTCl through the food chain might be smaller than that of polychlorinated biphenyls.

Animals↗
PubMed2002

A logical starting point for developing priorities for lizard and snake ecotoxicology: a review of available data.

Reptiles, specifically lizards and snakes, usually are excluded from environmental contamination studies and ecological risk assessments. This brief summary of available lizard and snake environmental contaminant data is presented to assist in the development of priorities for lizard and snake ecotoxicology. Most contaminant studies were not conducted recently, list animals found dead or dying after pesticide application, report residue concentrations after pesticide exposure, compare contaminant concentrations in animals from different areas, compare residue concentrations found in different tissues and organs, or compare changes in concentrations over time. The biological significance of the contaminant concentrations is rarely studied. A few recent studies, especially those conducted on modern pesticides, link the contaminant effects with exposure concentrations. Nondestructive sampling techniques for determining organic and inorganic contaminant concentrations in lizards and snakes recently have been developed. Studies that relate exposure, concentration, and effects of all types of environmental contaminants on lizards and snakes are needed. Because most lizards eat insects, studies on the exposure, effects, and accumulation of insecticides in lizards, and their predators, should be a top priority. Because all snakes are upper-trophic-level carnivores, studies on the accumulation and effects of contaminants that are known to bioaccumulate or biomagnify up the food chain should be the top priority.

Animals↗
PubMed2004

Congener-specific intake fractions for PCDDs/DFs and Co-PCBs: modeling and validation.

Intake fractions (iFs) for emissions to air, water, and soil for 17 PCDDs/DFs and 12 Co-PCBs were calculated with a level III multimedia model and a food-chain exposure model in succession. The two integrated models were tested by comparing the predicted and measured concentrations in the environment and by comparing intakes through food. Measurement-based iFs were also calculated and compared with the model-based iFs. The air concentrations predicted by the fate model were close to the median of the observed concentrations, whereas the predicted soil and water concentrations were one-third to one-tenth the observed concentrations. This difference was large in case of PCDDs and Co-PCBs, which was explained by the past pollution such as commercial PCB products and PCDD impurities in chloronitrofen (CNP) and pentachlorophenol (PCP). For fish, the predicted and observed exposures agreed well each other. For meat and milk, the predicted exposures were about 10 times the observed exposures for PCDDs/DFs, whereas the predicted and observed values agreed well for Co-PCBs. When the model was modified to consider feeding of fish meal to livestock and geographic bias in feed-grass production, the predicted congener profile was comparable to the measured profile. The comparison also suggested that chickens should be modeled separately from other terrestrial livestock. The model-based iFs for air emission of OCDD and 2378-TCDD were 0.001% and 0.1%, respectively. The iFs of most Co-PCBs were higher than those of PCDDs/DFs. These iF differences suggest the importance of the fate factor in assessing emissions of the 29 congeners.

Animal Feed↗