Bioaccumulation In Food Chain Research Articles

Anaerobic semi-fixed bed biofilm reactor (An-SFB-BR) for treatment of high concentration p-nitrophenol wastewater under shock loading conditions.

P-nitrophenol (PNP or 4-NP) has been widely used as a biorefractory raw material in chemical industry, whereas been highly concerned for its characteristics of mutagenic/carcinogenic activity and food chain bioaccumulation. In this study, an anaerobic semi-fixed bed biofilm reactor (An-SFB-BR) was constructed and used to treat PNP wastewater which discharged from chemical industries. Experimental results revealed that the An-SFB-BR was successfully cultivated with the gradually increasing of influent PNP from 0 to 540mg/L (gradually increased 10mg/L every time in stage II and 30-50mg/L for stage III), with the observation of an average removal efficiency of 98% for PNP and 80% for chemical oxygen demand (COD), also a biogas production and biogas production rate of 2.1 L/(L·d) and 0.57 m3/kg-COD, respectively. Finally, the conversion rate of P-aminophenol (PAP), the primary intermediate of PNP reached 80% after An-SFB-BR biodegradation. A relatively stable pH was maintained throughout the entire process, and insignificant VFA accumulation. The reactor exhibited a strong toxic shock resistance, and 16S rRNA sequencing results demonstrated that the dominant microbial community changed slightly with the gradually increasing of PNP concentration, which guaranteed the PNP removal efficiency.

Contribution of Dietary Uptake to PAH Bioaccumulation in a Simplified Pelagic Food Chain: Modeling the Influences of Continuous vs Intermittent Feeding in Zooplankton and Fish.

Dietary uptake is important for trophic transfer of polycyclic aromatic hydrocarbons (PAHs) in the freshwater pelagic ecosystem. In this study, we hypothesized that both the dietary uptake rate and interval significantly influenced its relative contribution to bioaccumulation. We developed a toxicokinetic model framework for the bioaccumulation of deuterated PAHs (PAHs-d10) in aquatic organisms considering different feeding intervals ranging from none for phytoplankton to approximately continuous for zooplankton to discrete for fish and built a simple artificial freshwater pelagic food chain composed of algae Chlorella vulgaris, zooplankton Daphnia magna, and zebrafish. We conducted bioaccumulation experiments and simulations for Daphnia magna and zebrafish under different algal densities based on our model. The results showed that intermittent feeding led to a large fluctuation in the PAH-d10 concentrations in zebrafish compared to a leveled-off pattern in Daphnia magna because of approximately continuous feeding. Trophic dilution of PAHs-d10 occurred in the food chain when there was waterborne-only uptake, but dietary uptake largely mitigated its extent that depended on dietary uptake rates. The assimilation efficiency, dietary uptake rate, and its relative contribution to bioaccumulation of PAHs-d10 in zebrafish were all higher than those in Daphnia magna, suggesting that dietary uptake played a more important role in bioaccumulation of PAHs at higher trophic-level organisms.

Removal of phenolic contaminants from water by pervaporation

The removal of phenolic compounds from water streams is of great importance due to their high toxicity, carcinogenicity, and bioaccumulation in food chains. In this study, the separation of four representative phenolic compounds (including phenol (PhOH), p-cresol (MePhOH), p-chlorophenol (ClPhOH), and p-nitrophenol (O2NPhOH)) from aqueous solutions by pervaporation using poly(ether-b-amide) (PEBA) membrane was studied. The effects of feed concentration (up to 0.6 wt%) and operating temperature (30–70 °C) on the separation performance were investigated. While the permeation fluxes of phenolic compounds increased at higher feed concentrations, the increase in the flux was less than proportional, leading to a decrease in the enrichment factor. It was also shown that both the permeation flux and the enrichment factor increased with an increase in temperature. However, the permeabilities of the phenolic compounds in the membrane were impacted differently. Of particular interest were the coupling effects of co-existing phenolic compounds due to permeant-permeant interactions, which were found to be significant in permeation of multiple phenolic compounds that were relevant to practical applications. The permeation of PhOH, MePhOH and ClPhOH was all affected adversely by the presence of additional phenolic compounds in the feed solution, while the opposite was true for the permeation of slow-permeating O2NPhOH. Depending on the specific phenol solute, high-purity phenol crystals could be produced from the phenol-enriched permeate via de-sublimation in the cold trap, which was of particular interest for practical applications.

Mercury concentrations and associations with dissolved organic matter are modified by water residence time in eastern Canadian lakes along a 30° latitudinal gradient

AbstractSurface water mercury (Hg) and dissolved organic carbon (DOC) concentrations and their ratios, which play a critical role in food chain bioaccumulation of Hg, were examined in lakes from southern boreal, sub‐Arctic taiga, Arctic tundra and polar desert landscapes of eastern and northern Canada. The study sites investigated span a 30° latitudinal gradient representing differences in climate, ecosystem productivity, and atmospheric mercury deposition. Lakes were selected to obtain a range of simple morphometrics such as area, depth, volume and catchment area, with corresponding differences in water residence times (WRT), ranging from 0.1 to 7.5 years. Total mercury (THg) and mono‐methylmercury (MMHg) concentrations correlated positively but weakly with DOC in lake surface waters along the climate gradient, consistent with lower ecosystem and organic matter productivity at higher latitudes. Specific UV absorbance, an indicator of terrestrial organic matter sources, was found to explain some residual variability in THg not explained by DOC. Concentrations of THg and MMHg and their ratios with DOC, particularly the MMHg : DOC ratio as well as %MMHg, were best explained by inverse associations with WRT. These relationships were apparent both within and between regions along the latitudinal gradient, suggesting a net‐negative effect of in‐lake processing on THg and MMHg concentrations associated with longer WRTs. Since the water MMHg : DOC ratio was previously shown to explain foodweb MMHg in the same study lakes, our results suggest that smaller lakes with shorter residence times are more susceptible to MMHg exposure even at low levels of inorganic Hg loading or MMHg production.

Strategies for mitigation of polychlorinated biphenyls (PCBs): A review

Polychlorinated Biphenyls or PCBs belong to a broad family of chlorinated hydrocarbons and find use across industrial and commercial applications including hydraulic and electrical equipments, plastics, paints, rubber products, dyes, pigments and carbonless copy paper etc. PCB residues persist in the ecosystem and bioaccumulate in food chain due to their persistent nature and resistance against natural breakdown agents. Global case studies suggest widespread contamination of the toxicant. So it becomes the need of an hour to remove polychlorinated biphenyls entirely from the environment. Stepwise, physical, chemical and ecological remediation strategies have been applied but some lacuna in efficient mitigation was felt by various researchers in each of the methods. Therefore, combination of multiple technologies have been suggested. The current review provides the detailed descriptions on the different physical and chemical methods used for removal of PCBs including incineration, natural attenuation, supercritical water oxidation, ultrasonic radiation, bimetallic systems, nZVI, etc as well as the combination of multi techniques that have been used till date e.g. nZVI with metal combo and bimetallic metal combination etc. It also depicts the future prospects and acceptability of these methods for removal of the polychlorinated biphenyls from the ecosystem to help us achieve a green sustainable world.

Terrestrial methylmercury bioaccumulation in a pine forest food chain revealed by live nest videography observations and nitrogen isotopes

In comparison to the extensively documented mercury (Hg) biomagnification in food chains of aquatic/or aquatic-related systems, Hg biomagnification in food chains in strictly terrestrial systems is poorly explored. Here, we report Hg biomagnification through food webs in a monoculture subtropical pine forest in southwest China. A clear pine needle-caterpillar-tit nestling food chain was determined with the use of live nest videography observations combined with stable isotope analysis (SIA). Simultaneously, a potential pine needle-herbivorous/omnivorous insect-mantis/lacewing/spider food chain was identified by SIA. The results verify that dietary composition plays a pivotal role in terrestrial food chains. Distinct total Hg (THg) and methylmercury (MeHg) biomagnification through the determined and potential food chains was observed, with quite similar efficiency of Hg biomagnification based on the trophic magnification slope (TMS) (TMSTHg was 0.18 ± 0.03 and TMSMeHg was 0.36 ± 0.05 for the determined food chain; and TMSTHg was 0.18 ± 0.04 and TMSMeHg was 0.38 ± 0.07 for the potential food chain). The TMS values were significantly higher than those from freshwater studies in tropical regions (0.12 ± 0.12 for THg and 0.16 ± 0.07 for MeHg) and forest studies in temperate regions (0.20–0.28 for MeHg). We recommend live nest videography observations combined with nitrogen isotope analysis when specifically assessing the biomagnification of environmental pollutants through food webs involving nestlings of free-living birds.

ANALYSIS OF THE TRACE ELEMENT CONTENT OF GRAPE MOLASSES PRODUCED BY TRADITIONAL MEANS

Molasses, sugar and other food additives, such as without adding any substance, concentrated by boiling and shelf life is a long concentrated product. Molasses is an important food for humans in terms of mineral content and high energy content. Grape fruit is considered as a rich food source with strong health effects. Grape fruit generally contains 70-80% water, 15-25% carbohydrate and small amount of minerals, amino acids, phenolic compounds. Heavy metals are highly toxic elements, which can severely influence plants and animals and have been involved in causing a large number of afflictions. Heavy metals in the environment are non-biodegradable and ubiquitous, it can cause serious human health hazards and momentous ecological effects through food chain's bioaccumulation. Inorganic micro-pollutants are of important concern because they are non-biodegradable, highly toxic and have a probable carcinogenic influence. In this study, it was aimed to determine the heavy metal levels in grape molasses collected from the villages of Karaman and to emphasize the importance of nutrition in carob molasses. The samples were prepared to be 2 parallel for each sample and were solutioned by wet burning method. The concentrations of the determined elements were determined by Flame Atomic Absorption Spectrometry (FAAS). Traditional produced grape molasses are determined by comparing metal contents with each other and with standard values.

Selenium Bioaccumulation Across Trophic Levels and Along a Longitudinal Gradient in Headwater Streams.

Toxic effects of selenium (Se) contamination in freshwaters have been well documented. However, study of Se contamination has focused on lentic and larger order lotic systems, whereas headwater streams have received little scrutiny. In central Appalachia, surface coal mining is a common Se source to headwater streams, thus providing a useful system to investigate Se bioaccumulation in headwater food chains and possible longitudinal patterns in Se concentrations. Toward that end, we assessed Se bioaccumulation in 2 reference and 4 mining-influenced headwater streams. At each stream, we sampled ecosystem media, including streamwater, particulate matter (sediment, biofilm, leaf detritus), benthic macroinvertebrates, salamanders, and fish, every 400 m along 1.2- and 1.6-km reaches. We compared media Se concentrations within and among streams and evaluated longitudinal trends in media Se concentrations. Selenium concentrations in sampled media were higher in mining-influenced streams compared with reference streams. We found the highest Se concentrations in benthic macroinvertebrates; however, salamanders and fish bioaccumulated Se to potentially harmful levels in mining-influenced streams. Only one stream demonstrated dilution of streamwater Se with distance downstream, and few longitudinal patterns in Se bioaccumulation occurred along our study reaches. Collectively, our results provide a field-based assessment of Se bioaccumulation in headwater food chains, from streamwater to fish, and highlight the need for future assessments of Se effects in headwater streams and receiving downstream waters. Environ Toxicol Chem 2020;39:692-704. © 2020 SETAC.

Novel carbon-based sorbents for elemental mercury removal from gas streams: A review

• The prospect and limitation of low-dimensional carbon for Hg 0 removal are commented. • Bio-char, carbon nitride, and metal-organic framework are promising mercury sorbents. • The performances and mechanisms of diverse carbon-based sorbents are fully discussed. Mercury emission, derived from natural gas exploitation, metal sintering, coal gasification and combustion, gold mining, etc., has posed great threaten to the environment and human beings due to its volatility, mobility, toxicity, and bioaccumulation in ecosystem and food chains. Adsorption using carbon materials is regarded as one of the most promising techniques for mercury emission control due to its simple equipment, convenient operation, high removing efficacy, less secondary pollution, etc. This review comments the new research progress of elemental mercury capture by novel carbon-based sorbents in recent five years, particularly emerging carbon materials, such as bio-chars, graphene and graphene oxide, carbon nanotubes and nanofibers, carbon spheres, carbon aerogels, metal-organic frameworks, and graphitic carbon nitrides. The mercury removal performances and reaction mechanisms of diverse carbon-based sorbents along with their merits and drawbacks are fully discussed, which aims to strengthen the understanding of this emerging research topic and outline future research directions for the development of sustainable, recyclable, and cost-effective carbon-based mercury sorbents.

Heavy metal concentrations in commercially valuable fishes with health hazard inference from Karnaphuli river, Bangladesh

Heavy metals contamination is a serious threat for the toxicity and bioaccumulation in food chain. Aquatic environment contamination has become a global concern because they have toxic effects on fishes. The concentration of heavy metals like arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in commercially fishes (Tenualosa ilisha, Gudusia chapra, Otolithoides pama, Setipinna phasa, Harpadon nehereus, Polynemus paradiseus, Sillaginopsis panijus and Pampus chinensis) collected from Karnaphuli River in Bangladesh were (fish muscles) assessed with health risk during summer and winter season. These heavy metals are toxic in nature and can come to human food chain through fish consumption. The mean concentration of As, Cr, Cd and Pb was found 1.59, 0.73, 0.41 and 1.13 mg/kg in summer and 1.81, 0.92, 0.52 and 1.45 mg/kg in winter, respectively. Cr and Pb concentration of all fish species were found to be higher than Food and Agriculture Organization (FAO)/(WHO) tolerable concentration assuming these metal pose risk to human. The hazard quotients value of heavy metals in Harpadon nehereus was found higher than one resulting non-carcinogenic risk for consumption of this fishes. Carcinogenic risk value for As and Pb were remaining 10−6 to 10−4 indicating continuously consumption of studied fish samples may cause cancer risk.

Biogeochemistry of antimony in soil-plant system: Ecotoxicology and human health

Environmental contamination by antimony (Sb), a non-essential and non-beneficial metalloid, is a great threat to living organisms at a global scale. Owing to its various uses in numerous industrial processes, Sb is released into different environmental compartments every year. Environmental Sb contamination can result in food chain bioaccumulation, especially due to its uptake and accumulation in edible plant parts. Consumption of Sb-rich food (cereals, vegetables, pulses etc.) is the key source of Sb exposure to human. Since Sb does not possess any identified biological role and has genotoxic and carcinogenic potential, it is critical to monitor its biogeochemical behavior in the soil-plant system and its influence in term of possible food chain bioaccumulation up to human exposure. However, compared to other heavy metals, limited data is available regarding biogeochemical behavior of Sb in the soil-plant system and associated health risks.This review traces a plausible link among Sb exposure levels, its chemical speciation, and phytoavailability in the soil, uptake/accumulation/compartmentation by plants, phytotoxicity and detoxification inside the plant. The role of different enzymatic (peroxidase, catalase, ascorbate peroxidase, superoxide dismutase, glutathione peroxidase) and non-enzymatic (glutathione, phytochelatins, proline and ascorbic acid) antioxidants have also been elucidated with respect to enhanced generation of reactive radicles and oxidative stress. The review also outlines the role of different transporter proteins in Sb transport/compartmentation inside plants, build-up in edible plant tissues and associated health risks. The biogeochemical role of Sb in the soil and plant systems and associated health risks have been described in 11 tables and 4 figures.

Environmental factors controlling potentially toxic element behaviour in urban soils, El Tebbin, Egypt

This study focuses on the assessment of surface soils from industrially polluted region (El Tebbin) of southern Cairo, Egypt. The impact of agricultural, residential and industrial land use on soils developed from Nile river sediments has significantly compromised their function. Previous evidence has shown that the food chain is contaminated and enhances risk of contaminant exposure of the residential communities. This study investigates factors controlling potentially toxic element (PTE) distribution (Co, Ni, Pb, Cd, Zn, Cr and Cu) in El Tebbin soils and provide estimates of their mobility and bioavailability. The PTE concentrations are characterised by high variability as result of the variety of natural and anthropogenic influences. Highest spatial variability is found for Zn, Cd, Pb and Cu (C.V = 260.0%, 280.4%, 140.8% and 159.6% respectively) and enrichment factors indicate strong anthropogenic inputs. For Co and Ni, relatively low spatial variability (C.V = 65.8% and 45.0% respectively) with depletion in Ni suggests a relatively minor contribution from anthropogenic sources. For Cr, a more uniform distribution pattern showing depletion to minimal enrichment across the study area (C.V = 19.2%) reflects almost exclusive lithogenic control. Using principle component analysis (PCA) to explore concentration data reveals that the major inputs affecting PTE distribution are modified by primary soil properties (texture and pH). Their relative bioavailability (identified through sequential chemical extraction) relates strongly to local input sources. Those elements dominated by lithogenic input (Ni and Co) were found predominantly in soil residual fractions (95.6% and 90.5% respectively), while elements with stronger anthropogenic contributions (Cd, Zn, Pb and Cu) showed much higher portion in the more mobile and bioavailable fractions obtained from sequential chemical extraction, with average proportions of the totals being 62.6%, 57%, 40.7% and 39.2% respectively. Those PTEs with strong anthropogenic influence are potentially much more mobile for bioaccumulation in food chain with increased health risk for exposed residents and are confirmed by elevated concentrations of Cd, Zn, Pb and Cu recorded in local plant species. The main pollution sources were further highlighted by cluster analysis and showed vehicle traffic and specific industrial activities but which varied significantly from site to site. The identification of sources through the approach developed here allows prioritisation of monitoring and regulatory decisions by the local government to reduce further environmental exposure of the local population.

Context-specific behavioural changes induced by exposure to an androgenic endocrine disruptor

Pharmaceutical contaminants are being detected with increased frequency in organisms and ecosystems worldwide. This represents a major environmental concern given that various pharmaceuticals act on drug targets that are evolutionarily conserved across diverse taxa, are often persistent in the environment, and can bioconcentrate in organisms and bioaccumulate in food chains. Despite this, relatively little is known about the potential for pharmaceutical contaminants to affect animal behaviour, especially across multiple fitness-related contexts. Here, we investigated impacts of 21-day exposure of wild-caught male eastern mosquitofish (Gambusia holbrooki) to a field-realistic level of the veterinary pharmaceutical 17β-trenbolone—a growth-promoting steroid used extensively in beef production worldwide and a potent androgenic endocrine disruptor repeatedly detected in surface waters affected by livestock effluent run-off. First, we examined male boldness, activity, and exploratory behaviour in a novel environment (maze arena) and found no significant effect of 17β-trenbolone exposure. Second, the same males were tested in a reproductive assay for their tendency to associate with a stimulus (unexposed) female behind a partition. Exposed males exhibited reduced association behaviour, taking longer to first associate with, and spending less time within close proximity to, a female. Third, all males were assayed for sperm function (computer-assisted sperm analysis, sperm viability) or quantity (total sperm count) and, although no significant main effects of 17β-trenbolone were seen on sperm traits, exposure altered the relationship between male morphology and sperm function. Lastly, morphological traits were assessed and exposed males were found to have, on average, increased mass relative to length. In combination, these results demonstrate that exposure to a field-realistic level of 17β-trenbolone can produce subtle but important trait alterations in male fish—including context-specific behavioural changes, disruption of key sperm function trade-offs, and altered morphology—with potential impacts on exposed wildlife.

Removal of Cr, Cu and Zn from liquid effluents using the fine component of granitic residual soils

Abstract The practice of reuse of treated wastewater (TWW) is seen as a strategy for water conservation in regions where water scarcity is a natural reality and in those where population growth and/or climate change foresee this scarcity. In situations of lower water scarcity, reuse is practiced by imperatives of environmental protection of the receiving media, reducing the discharge of effiuents from wastewater treatment plants. The artificial recharge of aquifers (RAQ) with TWW is a very common practice at the international level, but little considered in Portugal. However, residual waste from TWW (e.g heavy metals), when deposited in soil or water, can cause significant environmental impacts on its uses, and cause serious health problems in several animal species due to their bioaccumulation in food chains. The present study intends to show that the granitic residual soils of the Quinta de Gonçalo Martins (Guarda), in the Beira Interior region of Portugal, present physical-chemical and mineralogical characteristics favorable to the infiltration of TWW into RAQ. The results of the batch sorption tests indicate that the soil has a reactive capacity to remove the Cu and Zn residual load at TWW at high efficiencies by adsorption and ion exchange mechanisms. The pseudo-first order model explained the reaction kinetics for the three heavy metals removal and when the sorption equilibrium state was reached, the removal of these metals was explained by the Freundlich isotherm.

The tendency of linuron in microcosmic system and its response to hydrodynamic conditions

The environmental fate and bioaccumulation of linuron in a laboratory microcosm were investigated at three flow velocity over a period of 10 days. Linuron concentrations were quantified in the environmental media water, sediment, algae and fish after 1, 2, 4, 7 and 10 days of exposure. The results showed that rapid decrease in water phase of the microcosm was occurred, linuron had decreased to 56.7%-67.9% of the initial concentrations on day 10, and reduction rates showed an obvious increase with increased flow velocity. The linuron concentrations in the sediment were 1.25-2.13 ng/g on day 10, which were much less than that in algae (387-477 ng/g). The linuron was widely detected in fish tissues, and the bioaccumulation concentrations were generally in the following order: liver > kidney > brain > skin > muscle > gill at an early stage of exposure. However, the ability of liver detoxification increased with the exposure time and exposure flow velocity, so that the bioaccumulation potential was highest in kidney at the end stage of exposure. This result indicates that a significant uptake potential of linuron in organisms, further studies are necessary to elucidate food chain bioaccumulation and toxicological effects of linuron.

Human exposure to trace elements in central Cambodia: Influence of seasonal hydrology and food-chain bioaccumulation behaviour

Exposure to mercury and other trace elements remains an important public health concern, worldwide. The present study involved a comprehensive field study to determine concentrations of fourteen trace elements (Al, As, Cr, Co, Cd, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in surface water and different fish species from Tonlé Sap Lake in central Cambodia, during both the dry and wet seasons. Total arsenic (tAs) and Mn in surface water during the dry season exceeded WHO drinking water guidelines. Total mercury (tHg) concentrations (µg/g wet wt.) in fish during the wet season (GM = 0.055; CI95 = 0.01–0.26) were approximately 15 times higher (P < 0.05) compared to those during the dry season (GM = 0.0035; CI95 = 0.0004–0.033). Mean target hazard quotients (THQs) for inorganic arsenic (iAs), methyl mercury (MeHg), Mn and Pb were > 1, with estimated maximum values greatly exceeding 1. Mean THQs of Zn, Cd, Ni and Se were very near 1, with estimated maximum values exceeding 1. The MeHg THQ (min-max range: 0.16–9.09) during the wet season was 7 times higher than in the dry season (min-max range: 0.05–1.35). Concentrations of Hg and other trace elements varied widely between fish species. The findings suggest that exposure of some trace elements via water and food is of concern in this region. High consumption rates of fish and rice key factors related to trace element exposure. Seasonal hydrology and species-specific bioaccumulation behaviour in the Tonlé Sap Lake watershed also play an important role. The generated information will be useful to better mitigate trace element exposure in this region.

Who in the world is most exposed to polychlorinated biphenyls? Using models to identify highly exposed populations

Human subpopulations experience different exposure to persistent organic pollutants (POPs) because of differences in the structure of their food webs and the extent of environmental contamination. Here we quantify the time-variant exposure of different human populations around the world to one representative POP, namely the polychlorinated biphenyl (PCB) congener 153, based on a dynamic simulation of both global environmental fate (using the model BETR-Global) and human food chain bioaccumulation (using the model ACC-HUMAN). The approach identifies subpopulations whose diets include a carnivorous mammal as experiencing the world’s highest PCB-153 exposure, i.e. the very large biomagnification potential of their food web more than makes up for the remoteness of their living environment. However, for subpopulations that do not eat warm-blooded carnivores, the proximity to sources of PCBs is more important than food web structure and environmental conditions for differentiating their exposure to PCBs.

Revisiting the Contributions of Far- and Near-Field Routes to Aggregate Human Exposure to Polychlorinated Biphenyls (PCBs).

The general population is exposed to polychlorinated biphenyls (PCBs) by consuming food from far-field contaminated agricultural and aquatic environments, and inhalation and nondietary ingestion in near-field indoor or residential environments. Here, we seek to evaluate the relative importance of far- and near-field routes by simulating the time-variant aggregate exposure of Swedish females to PCB congeners from 1930 to 2030. We rely on a mechanistic model, which integrates a food-chain bioaccumulation module and a human toxicokinetic module with dynamic substance flow analysis and nested indoor-urban-rural environmental fate modeling. Confidence in the model is established by successfully reproducing the observed PCB concentrations in Swedish human milk between 1972 and 2016. In general, far-field routes contribute most to total PCB uptake. However, near-field exposure is notable for (i) children and teenagers, who have frequent hand-to-mouth contact, (ii) cohorts born in earlier years, e.g., in 1956, when indoor environments were severely contaminated, and (iii) lighter chlorinated congeners. The relative importance of far- and near-field exposure in a cross-section of individuals of different age sampled at the same time is shown to depend on the time of sampling. The transition from the dominance of near- to far-field exposure that has happened for PCBs may also occur for other chemicals used indoors.

Proposal for a Monitoring Concept for Veterinary Medicinal Products with PBT Properties, Using Parasiticides as a Case Study.

The aim of this work is to prepare a proposal for the post-authorization monitoring (PAM) of veterinary medicinal products (VMP), in particular parasiticides. Such a monitoring might especially be useful for parasiticides identified as Persistence Bioaccumulation Toxicity (PBT) substances, i.e., chemicals that are toxic (T), persist in the environment (P) and bioaccumulate (B) in food chains and, thus, pose a hazard to ecosystems. Based on a literature search, issues to be considered when performing such a PAM are discussed (e.g., residue analysis, compartments to be included, selection of organisms and the duration of monitoring studies). The outcome of this discussion is that—and despite that there are huge challenges in detail (e.g., in terms of analytical chemistry or taxonomy)—the technical performance of such a PAM is not the main problem, since most of the chemical and biological methods to be used are well-known (partly even standardized) or could be adapted. However, it is very difficult to define in detail where and when a monitoring should be performed. The main problem is to link exposure to effects of a certain parasiticide in a way that any impact can directly be related to the use of this parasiticide. Therefore, a “Targeted Environmental Monitoring” (TEM) is proposed, which is essentially a combination between a field study and a PAM.

Pesticides and Related Toxicants in the Atmosphere.

Pesticides and other toxicants released into the environment can contaminate air, water, soil, and biota. This review focuses on sources, exposures, fate, analysis, and trends. The potential for exposures due to atmospheric transport and deposition of pesticides and related contaminants may pose risks to humans and wildlife. Emissions of chemicals to air are related to physicochemical properties (e.g., vapor pressure and chemical stability). Experimental design and computer-based modeling, as related to emissions and dispersion of pesticides along transects downwind from release sources, will be discussed using the example of pesticide volatilization and drift in California agriculture that results in the transport and deposition downwind to the Sierra Nevada mountains, where much work has been done to refine exposure data for use in risk assessment and management. Predictably, those chemicals found frequently in air are those used most extensively, have multiple emission sources, and resist degradation. Yet to be determined are definitive connections with adverse impacts to humans and wildlife, although the accumulating evidence suggests that endocrine disrupting chemicals, ChE inhibitors, and others warrant further attention. Steps that are being taken to limit emissions, such as in pest control and fuel combustion, offer promising opportunities for improving the quality of air and of the overall environment. Chemical degradation rates and products from trace organics in the air merit more attention, as do the potential for activation by photooxidation and bioaccumulation in food chains. The potential effect of climate change, on atmospheric processes affecting contaminant behavior, is an area ripe for further study.