Polychlorinated diphenyl ethers (PCDEs): environmental levels, toxicity and human exposure: a review of the published literature

This paper reviews the state of the science regarding polychlorinated diphenyl ethers (PCDEs), a group of halogenated aromatic compounds, which are structurally related to polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs). Special attention is paid to the environmental levels, toxicity, and human exposure. PCDEs have been detected in a number of environmental samples, and their widespread occurrence in the environment is mainly the result of their presence as impurities in chlorophenol preparations. In humans, PCDE congeners have been detected in adipose tissue. As for other persistent organic pollutants (POPs), dietary intake is very probably the main route of exposure to PCDEs for the general population. However, data concerning PCDE levels in foodstuffs are very limited. It is concluded that investigations on experimental toxicity, dietary intake, and potential human health effects of PCDEs are clearly necessary.     

Levels of PCDD/PCDFs and PCBs in edible marine species and human intake: a literature review

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) are lipophilic organic compounds whose origin comes from many different sources. PCDD/Fs and PCBs are ubiquitous and persistent environmental pollutants with a well known potential toxicity, which were included at the 1998 UN-EC POP protocol. Although human exposure to PCDD/Fs and PCBs can occur by various routes, food is the primary source. A number of studies have shown that the major food sources of these organic pollutants are fat-containing animal products, including fish and other seafood. Because of the frequent health recommendations concerning fish consumption, to determine the contribution to the dietary intake of chemical contaminants such as PCDD/Fs and PCBs through fish and other seafood consumption is an issue of special interest. This paper reviews the state of the science regarding recent literature on PCDD/F and PCB levels in marine species and human intake through fish and seafood consumption. The concentrations of these pollutants depend basically on the environment in which the respective species are caught. It is concluded that some groups of population frequently consuming high quantities of certain species could be significantly increasing health risks due to PCDD/F and PCB exposure.     

Brominated flame retardants and seafood safety: A review

Brominated flame retardants (BFRs), frequently applied to industrial and household products to make them less flammable, are highly persistent in the environment and cause multi-organ toxicity in human and wildlife. Based on the review of BFRs presence in seafood published from 2004 to 2014, it is clear that such pollutants are not ideally controlled as the surveys are too restricted, legislation inexistent for some classes, the analytical methodologies diversified, and several factors as food processing and eating habits are generally overlooked. Indeed, while a seafood rich diet presents plenty of nutritional benefits, it can also represent a potential source of these environmental contaminants. Since recent studies have shown that dietary intake constitutes a main route of human exposure to BFRs, it is of major importance to review and enhance these features, since seafood constitutes a chief pathway for human exposure and biomagnification of priority environmental contaminants. In particular, more objective studies focused on the variability factors behind contamination levels, and subsequent human exposure, are necessary to support the necessity for more restricted legislation worldwide.     

Worldwide occurrence and effects of antifouling paint booster biocides in the aquatic environment: a review

Organic booster biocides were recently introduced as alternatives to organotin compounds in antifouling products, after restrictions imposed on the use of tributyltin (TBT) in 1987. Replacement products are generally based on copper metal oxides and organic biocides. This ban has led to an increase in alternative coating products containing the above biocides. The most commonly used biocides in antifouling paints are: Irgarol 1051, diuron, Sea-nine 211, dichlofluanid, chlorothalonil, zinc pyrithione, TCMS (2,3,3,6-tetrachloro-4-methylsulfonyl) pyridine, TCMTB [2-(thiocyanomethylthio) benzothiazole], and zineb. Since 1993, several studies have demonstrated the presence of these biocides in European coastal environment as a result of their increased use. More recently, the presence of these biocides was also revealed in waters from Japan, United States, Singapore, Australia and Bermuda. This paper reviews the currently available data on the occurrence of these biocides in the aquatic environment. Some data dealing with the environmental fate, partitioning, behaviour and risk assessment of antifouling paint booster biocides are also reported in order to discuss the detected levels of contamination.     

Health risks of dietary exposure to perfluorinated compounds

Perfluorinated compounds (PFCs) form a diverse group of chemicals with surface-active properties manufactured for over 50 years. In recent years, a number of studies have reported the ubiquitous distribution of PFCs in human tissues and wildlife. Although the relative importance of the routes of human exposure to these compounds is not well established yet, it has been suggested that food intake and packaging, water, house dust, and airborne are all potentially significant sources. However, dietary intake is probably the main route of exposure to these compounds, including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), the most extensively investigated PFCs. This paper reviews the state of the science regarding the concentrations of PFCs in foodstuffs, human dietary exposure to these compounds and their health risks. The influence of processing, cooking and packaging on the PFCs levels in food is also discussed. Because of the rather limited information about human dietary exposure, studies to determine exposure to PFCs through the diet for the general population of a number of countries are clearly necessary. The correlation of PFCs body burdens and dietary intake of PFCs should be also established.     

Economic and Social Impact Assessment of the Alternatives to DDT Usage for Antifouling Paint Production in China

China is the only nation that uses DDT in antifouling pain at present, approximately 5% of DDT is applied as the additive of the antifouling paint production. Therefore, actions shall be taken urgently for banning the use of DDT and substituting with non-POPs alternatives in antifouling paints. The paper researches the social and economic backgrounds of DDT booster antifouling paint production and usage, analyzes the social and economic impact assessment of the alternatives to DDT usage for antifouling paint. The implementation of the project of alternatives will completely eliminate the adverse impact of DDT booster antifouling paint on terrestrial, marine ecosystem and human health. The broad use of alkali silicate and pepper alkali as substitutes will be feasible if appropriate measures will be taken to encourage their development, and the social and economic risk will be reduced to accepted levels.     

Butyltins in the sediments of Kochi and Mumbai harbours, west coast of India

Surface sediment samples were collected from various locations in the Mumbai and Kochi harbours, west coast of India, to assess the presence of butyltin compounds. Tributyltin (TBT) and dibutyltin (DBT) varied from 16 to 16,816 ng/g dry wt. and from undetected to 469 ng/g dry wt., respectively, of the sediment in Kochi harbour. In Mumbai harbour, the values of TBT and DBT ranged between 4.5 and 1193 ng/g dry wt. and from undetected to 131 ng/g dry wt. of the sediments, respectively. The concentrations of both TBT and DBT showed strong seasonal variation probably due to the effect of tides and currents. Nevertheless, the levels of butyltin compounds were generally higher at sites influenced by shipping activities such as navigation, dry dock and ship-building activities. The presence of DBT indicates the abiotic or microbiological degradation of TBT. Compared to TBT, DBT was relatively less abundant, suggesting either fresh inputs of TBT and/or less degradation of TBT. The concentrations of TBT showed significant positive relationships with organic carbon and lipid, implying that both lipophilic and ionic interactions were probably involved in controlling the abundance of TBT at these sediments. The observed levels of butyltin compounds are much higher than those required to induce toxic effects on marine organisms, suggesting that these sediments were contaminated with butyltin compounds.     

Assessment of persistent toxic substances in the environment of Egypt

The objective of this review is to provide a comprehensive assessment of the threats posed by persistent toxic substances (PTS) to the environment and human health in Egypt and to identify priorities, data gaps and recommendations for future intervention to control, reduce or eliminate releases of PTS. Data on available concentrations of persistent toxic substances in the different environmental compartments and their impacts on the ecosystem, and humans have been assembled and summarized. Despite extensive studies, most of the data available deal with limited studies or hot spot situations. Localized inputs of PTS have been identified from freshwater discharges in coastal areas (e.g., Nile estuaries and coastal lakes) and near sewage outfalls from highly industrialized and populated cities. Data are often missing for certain contaminants and in some compartments and geographical areas. The lack of standardized methodologies makes it difficult to compare and use existing data to provide exact conclusions on spatial and temporal trends. In spite of these restrictions, available data indicate that it is unlikely that present levels of cyclodiene pesticides would adversely affect marine organisms. Compounds which are proven to be of concern are DDT, PCBs, gamma-HCH, PAHs, HCB and organotin compounds. Other compounds are suspected to be ubiquitous but data are lacking. Based on few recent data, the reported levels of organochlorine pesticides in fish and human milk samples suggest a concentration decline during the 1990s consistent with the regulatory restrictions on the use of these compounds. It is essential to activate monitoring programs to fill data gaps in appropriate abiotic and biotic. Monitoring programs should be follow standard procedures and include improved QA/QC protocols.     

Predictors of PCP,OH-PCBs,PCBs and chlorinated pesticides in a general female Norwegian population

The aims of the current study were to assess plasma concentrations and predictors of halogenated phenolic compounds (HPCs), polychlorinated biphenyls (PCBs) and chlorinated pesticides in a representative group of postmenopausal Norwegian women (n = 311, mean age: 56 years). In addition to delivering a blood sample, the participants had also filled out a detailed questionnaire regarding their current health status, use of medication and dietary habits, etc. The association between a large number of dietary variables, lifestyle factors and plasma concentration of organic pollutants were investigated using multivariate statistics.Within the current study group, p,p′-DDE (median: 903 ng/L w.w.) and pentachlorophenol (PCP, median: 711 ng/L w.w.) were the dominating compounds on a wet weight basis and were present in considerable higher concentrations than the PCBs, the hydroxylated PCBs (OH-PCBs) and the remaining chlorinated pesticides. Of the PCBs, PCB 153 was detected in highest concentrations, whereas 4-OH-PCB187 was present in highest concentration of the selected OH-PCBs. The ratio of ΣOH-PCB to ΣPCB varied between 0.06 and 0.77 ng/L and were significantly lower in individuals with higher ΣPCB concentration. PCP did not co-vary with the other contaminants, indicating a different route of exposure. No clear food cluster was positively associated with PCP exposure; however intake of marine food was negatively linked to PCP concentration and age and being a non-smoker were positive predictors of PCP. The other investigated contaminants co-varied and were positively associated with age, plasma concentrations of marine derived omega-3 fatty acids and a traditional Norwegian fish and bread based diet. The difference in contaminant concentration between high, medium and low consumers of total marine food were however marginal for the dominating PCBs and chlorinated pesticides. The current results indicate however that marine food in itself could be a source of some of the OH-PCBs, regardless of their PCB precursors.As PCP is one of the dominating organic contaminants within the general female Norwegian population, future research on human concentrations, exposure routes and potential health effects of PCP is encouraged. Continued monitoring of human OH-PCB levels should also be performed as they could be present at levels almost as high as the PCBs and they are expected to be more toxic than their mother substances.     

Assessing noxious effects of dietary exposure to methylmercury,PCBs and Se coexisting in environmentally contaminated rice in male mice

Polychlorinated biphenyls and methylmercury are two of the most ubiquitous environmental contaminants in Guizhou province. Rice is eaten with almost every meal and provides more calories than any single food in Guizhou province. The estimated tolerable daily intake of total mercury, MeHg, Se and PCBs from Guizhou contaminated rice by Chinese people showed that MeHg and/or PCBs exceeded the corresponding limits. The aim of this study was to characterize the effects of exposure to environmental contaminated rice on neurobehavioral development and neurobiological disruptions in mice. Animals were treated from postnatal day (PND) 22 to 91. At PND 26–91 days of age, mice were tested for neurobehavioural development and neurochemical level changes. We showed that dietary exposure to environmentally contaminated rice gave rise to different changes in antioxidants. Reduced superoxide dismutase (SOD) activity and excess increased nitric oxide (NO) indicated aggravation of oxidative status after long-term dietary intake of Hg and PCBs. Neurobehavioral derangement in the central nervous system and significant delay in the Morris water maze test response on PND 91 are correlated with the increased of c-fos/c-jun expression levels in the cerebral cortex. These results suggest that MeHg neurotoxicity might be a greater hazard than that associated with PCB, but PCB may augment the neurobehavioral deficits caused by increased levels of mercury exposure. The simultaneous intake of selenium might have a protective effect on Hg accumulation in the body, and vitamin C might protect mice against the toxic effects of PCBs. However, the protective role of Se and vitamin C is very limited for multiple-agent pollution. Immediately early genes in the brain response to contaminated rice might be dependent on interaction among NO, NO synthase (NOS), SOD and reduced glutathione (GSH). We should be alert to mental health problems in human beings when any kind of Hg- and PCB-polluted food is consumed.     

Imposex as a biomonitoring tool for marine pollution by tributyltin: some further observations

Imposex, i.e., the imposition of male sexual characteristics on female neograstropods, has been used worldwide as a bioindicator of pollution by the antifouling agent TBT as well as to assess the related ecological impact. The recent total ban on the use of TBT in the maritime industry has been partly based on the use of such a biomarker. This is mainly based on the assumption that no other pollutant, or environmental stress, is able to induce such a biological response. Nonetheless, several authors had challenged this idea. The present paper will present further field observations on imposex in Hexaplex trunculus from Malta (Central Mediterranean) which may help clarify this issue. Furthermore, the incidence of imposex in this species will be related to body burdens and to the environmental levels of organotins as measured analytically. First histological observations will also be presented which may help clarify the ecological significance of this response in this species. Finally a number of alternative scenarios regarding the relationship between imposex and TBT will be discussed.     

PestScreen: a screening approach for scoring and ranking pesticides by their environmental and toxicological concern

A chemical ranking and scoring method entitled PestScreen has been developed as a screening tool to provide a relative assessment of pesticide hazards to human health and the environment. The method was developed to serve as an analytical tool in screening and identification of pesticides of environmental concern used in agriculture. PestScreen incorporates both the toxic effects of pesticides and their fate and exposure characteristics in different compartments of the environment. This is done by combining measures of chemical toxicity pertaining to both human health and the environment with chemical release amounts and information on overall environmental persistence, long-range transport potential and human population intake fractions. Each hazard measure is scored and weighted and finally combined with the pesticide application dose to provide a single final indicator of relative concern (PestScore). Results for 217 pesticides are presented and the practical implementation is illustrated on behalf of three practical case studies.     

Dietary exposure to dioxins and PCBs in a large cohort of pregnant women: Results from the Norwegian Mother and Child Cohort Study (MoBa)

Exposure to dioxins and polychlorinated biphenyls (PCBs) during pregnancy and breastfeeding may result in adverse health effects in children. Prenatal exposure is determined by the concentrations of dioxins and PCBs in maternal blood, which reflect the body burden obtained by long term dietary exposure. The aims of this study were (1) to describe dietary exposure and important dietary sources to dioxins and PCBs in a large group of pregnant women and (2) to identify maternal characteristics associated with high dietary exposure to dioxins and PCBs. Dietary exposure to dioxins (sum of toxic equivalents (TEQs) from dioxin-like (dl) compounds) and PCB-153 in 83,524 pregnant women (gestational weeks 17–22) who participated in the Norwegian Mother and Child Cohort Study (MoBa) during the years 2002–2009 was calculated based on a food frequency questionnaire (FFQ) and a database of dioxin and PCB concentrations in Norwegian food. The median (interquartile range, IQR) intake of PCB-153 (marker of ndl-PCBs) was 0.81 (0.77) ng/kg bw/day. For dioxins and dioxin-like PCBs, the median (IQR) intake was 0.56 (0.37) pg TEQ/kg bw/day. Moreover, 2.3% of the participants had intakes exceeding the tolerable weekly intake (TWI) of 14 pg TEQ/kg bw/week. Multiple regression analysis showed that dietary exposure was positively associated with maternal age, maternal education, weight gain during pregnancy, being a student, and alcohol consumption during pregnancy and negatively associated with pre-pregnancy BMI and smoking. A high dietary exposure to PCB-153 or dl-compounds (TEQ) was mainly explained by the consumption of seagull eggs and/or pate with fish liver and roe. Women who according to Norwegian recommendations avoid these food items generally do not have dietary exposure above the tolerable intake of dioxins and dl-PCBs.     

Genotoxic effects of binary mixtures of xenoandrogens (tributyltin, triphenyltin) and a xenoestrogen (ethinylestradiol) in a partial life-cycle test with Zebrafish (Danio rerio)

A partial life-cycle test with the model fish Danio rerio was performed in order to evaluate the genotoxic potential of binary mixtures of xenoandrogenic (tributyltin--TBT; triphenyltin--TPT) and an estrogenic compound (ethinylestradiol--EE2). Five days post-fertilisation larvae were diet-exposed to environmental relevant concentrations of TBT and TPT (25 ng/g-100 ng/g), and water-exposed to ethinylestradiol (3.5 ng/L) for a four-month period; binary mixtures of TBT plus EE2 and TPT plus EE2 were run in parallel. The erythrocytic nuclear abnormalities (ENA) assay in circulating erythrocytes was used to evaluate genotoxicity in the end of the four-month exposure period. A significant increase (p<0.05, Kruskall-Wallis non-parametric ANOVA) in ENA frequency, in comparison with control animals, was observed in those animals exposed to TBT and TPT (the highest doses only), and to EE2 and the binary mixtures, although neither synergistic nor additive effects of the tested compounds were evident. Overall, the results clearly indicate that chronic exposure to low levels of TBT, TPT, EE2 and binary mixtures of TBT plus EE2 and TPT plus EE2 are genotoxic to zebrafish, which may suggest that wild fish populations may be under increased DNA damage in areas contaminated by these endocrine disrupting chemicals.     

Environmental release and behavior of brominated flame retardants

Recently, environmental problems relating to brominated flame retardants (BFRs) have become a matter of greater concern than ever before, because of the recent marked increase in levels of polybrominated diphenyl ethers (PBDEs) found in human milk in Sweden and North America. The question that arises is whether environmental levels of PBDEs and other BFRs will continue to increase, causing toxic effects to humans. In an attempt to elucidate the current state of the science of BFRs, we review the consumer demand for BFRs (mainly in Japan), the characteristics of waste flame-retarded products, sources of emission, environmental behavior, routes of exposure of humans, temporal trends, and thermal-breakdown products of BFRs. At present, flame-retarded consumer products manufactured 10-20 years ago, when PBDEs were frequently used, are being dumped. The possible major sources of emission of BFRs into the environment are effluent and flue gases from BFR factories and other facilities processing BFRs. With respect to the environmental behavior of BFRs, the lower brominated compounds are, on the whole, predicted to be more volatile, more water soluble, and more bioaccumulative than the higher brominated compounds. The most probable route for exposure of the general human population to PBDEs, especially the lower brominated congeners, is through the diet. The release of BFRs from consumer products treated with these compounds could also lead to human exposure. Temporal trends in PBDE levels in the environment and in humans worldwide seem to vary considerably, depending on the regions or country, with possible reflections of the historic and current use of PBDEs. The environment and the general human population are also exposed to the thermal-breakdown products of PBDEs, such as polybrominated and mixed brominated/chlorinated dibenzo-p-dioxins and dibenzofurans (PBDDs/DFs and mixed PXDDs/DFs).     

Occurrence,fate and ecological risk of chlorinated paraffins in Asia: A review

Chlorinated paraffins (CPs), complex mixtures of polychlorinated alkanes, are widely used in various industries and are thus ubiquitous in the receiving environment. The present study comprehensively reviewed the occurrence, fate and ecological risk of CPs in various environmental matrices in Asia. Releases from the production and consumption of CPs or CP-containing materials, wastewater discharge and irrigation, sewage sludge application, long-range atmospheric transport and aerial deposition have been found to be most likely sources and transport mechanisms for the dispersion of CPs in various environmental matrices, such as air, water, sediment, soil and biota. CPs can be bioaccumulated in biota and biomagnified through food webs, likely causing toxic ecological effects in organisms and posing health risks to humans. Inhalation, dust ingestion and dietary intake are strongly suggested as the major routes of human exposure. Research gaps are discussed to highlight the perspectives of future research to improve future efforts regarding the analysis of CPs, the environmental occurrence and elimination of CPs, the total environmental pressure, and the risks to organisms and populations.     

Occurrence,fate and effects of azoxystrobin in aquatic ecosystems: A review

The use of pesticides for crop protection may result in the presence of toxic residues in environmental matrices. In the aquatic environment, pesticides might freely dissolve in the water or bind to suspended matter and to the sediments, and might be transferred to the organisms' tissues during bioaccumulation processes, resulting in adverse consequences to non-target species. One such group of synthetic organic pesticides widely used worldwide to combat pathogenic fungi affecting plants is the strobilurin chemical group. Whereas they are designed to control fungal pathogens, their general modes of action are not specific to fungi. Consequently, they can be potentially toxic to a wide range of non-target organisms. The present work had the intent to conduct an extensive literature review to find relevant research on the occurrence, fate and effects of azoxystrobin, the first patent of the strobilurin compounds, in aquatic ecosystems in order to identify strengths and gaps in the scientific database. Analytical procedures and existing legislation and regulations were also assessed. Data gathered in the present review revealed that analytical reference standards for the most relevant environmental metabolites of azoxystrobin are needed. Validated confirmatory methods for complex matrices, like sediment and aquatic organisms' tissues, are very limited. Important knowledge of base-line values of azoxystrobin and its metabolites in natural tropical and estuarine/marine ecosystems is lacking. Moreover, some environmental concentrations of azoxystrobin found in the present review are above the Regulatory Acceptable Concentration (RAC) in what concerns risk to aquatic invertebrates and the No Observed Ecologically Adverse Effect Concentration (NOEAEC) reported for freshwater communities. The present review also showed that there are very few data on azoxystrobin toxicity to different aquatic organisms, especially in what concerns estuarine/marine organisms. Besides, toxicity studies mostly address azoxystrobin and usually neglect the more relevant environmental metabolites. Further work is also required in what concerns effects of exposure to multi-stressors, e.g. pesticide mixtures. Even though Log K_ow for azoxystrobin and R234886, the main metabolite of azoxystrobin in water, are below 3, the bio-concentration factor and the bioaccumulation potential for azoxystrobin are absent in the literature. Moreover, no single study on bioaccumulation and biomagnification processes was found in the present review.     

Occurrence and degradation of butyltins and wastewater marker compounds in sediments from Barcelona harbor, Spain

Contamination of Barcelona harbor sediments was assessed by the quantitative determination of butyltins (TBT, DBT and MBT) and surfactant intermediates, namely linear alkylbenzenes (LABs) and nonylphenols (NPs), as markers of urban and industrial wastewater contamination, respectively. Degradation indexes of TBT and LABs were calculated. Tributyltin predominated in the whole area over its degradation products, ranging from 98 to 4702 ng Sn/g. These elevated concentrations reveal a persistent historical contamination and a moderate degradation (BT(deg)). Moreover, the high LAB concentrations (1.2-53.1 microg/g) compared to the relatively low NP levels (3.8-72.0 ng/g) suggest a predominance of urban over industrial wastewater inputs, although a significant correlation (r(2) = 0.82, N = 12, P = 0.001) between LABs and NPs was found. Stormwater runoff and combined sewer overflows (CSO) were likely the most possible sources for both surfactant intermediates. The high degradation index values obtained for LABs could indicate an improvement in the wastewater management reducing its recent discharge into the Barcelona harbor area.     

Disruption of retinoid transport, metabolism and signaling by environmental pollutants

Although the assessment of circulatory levels of retinoids has become a widely used biomarker of exposure to environmental pollutants, the adverse effects caused by imbalance of the retinoid metabolism and signaling in wildlife are not known in detail. Retinoids play an important role in controlling such vital processes as morphogenesis, development, reproduction or apoptosis. Unlike other signaling molecules, retinoids are not strictly endogenous but they are derived from dietary sources of vitamin A or its precursors and thus they are sometimes referred to as 'dietary' hormones. Some environmental pollutants that affect embryogenesis, immunity or epithelial functions were also shown to interfere with retinoid metabolism and signaling in animals. This suggests that at least some of their toxic effects may be related to interaction with the retinoid metabolism, transport or signal transduction. This review summarizes in vivo and in vitro studies on interaction of environmental complex samples, pesticides, polychlorinated dioxins, polychlorinated biphenyls, polycyclic aromatic compounds and other organic pollutants with physiology of retinoids. It sums up contemporary knowledge about levels of interaction and mechanisms of action of the environmental contaminants.