Polychlorinated dibenzo-p-dioxins and dibenzofurans in eggs of eight avian species from Dongting Lake, China

Legacy persistent organic pollutants (POPs) in eggs of night herons and poultries from the upper Yangtze Basin, Southwest China

Black-crowned night heron (Nycticorax nycticorax) eggs have been identified as useful indicators for biomonitoring the environmental pollution in China. In this study, we investigated thirty eggs of black-crowned night heron collected from the upper Yangtze River (Changjiang) Basin, Southwest China, for the occurrence of legacy persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Our results showed a general presence of POPs in night heron eggs with OCPs being the dominant contaminants, having a geometric mean concentration of 22.2 ng g-1 wet weight (ww), followed by PCBs (1.36 ng g-1 ww), PBDEs (0.215 ng g-1 ww), and PCDD/Fs (23.0 pg g-1 ww). The concentration levels were found to be significantly higher in night heron eggs than in poultry eggs by one or two magnitude orders. Among OCP congeners, p,p'-DDE was found to be predominant in night heron eggs, with a geometric mean concentration of 15.1 ng g-1 ww. Furthermore, species-specific congener patterns in eggs suggested similar or different sources for different POPs, possibly associated with contaminated soil and parental dietary sources. Additionally, estimated daily intakes (EDIs) were used to evaluate non-carcinogenic and carcinogenic risk associated with consumption of bird eggs. Our results revealed non-negligible non-cancer and cancer risk for humans who consume wild bird eggs as a regular diet instead of poultry eggs.

Persistent organic pollutants in typical lake ecosystems

Persistent organic pollutants (POPs) are highly toxic organic chemicals. Lakes are one of the main sinks of POPs. POPs can be accumulated in multiple matrices in lake ecosystems and biomagnified through the food web, and thus pose a potential threat not only to lake ecosystems, but also to human health. Given their potential persistent risks, they have received much attention over the past decades. This review comprehensively summarizes the data on the levels and distributions of POPs in selected typical lake ecosystems in China and worldwide, involving water, sediments, organisms, and surrounding soils and atmosphere. It was found that current publications on POPs in Chinese lakes are mainly related to lakes in the developed eastern plain area, with only a few studies concerning the less-developed Qinghai-Tibet Plateau area. Similarly, around the world, there are more research on POPs in developed countries and less in relatively less-developed areas. Moreover, there are significant differences in the levels of POPs in different matrices in different lake ecosystems. Legacy POPs, such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs), were commonly detected and reported in different lakes, while emerging POPs like perfluorinated compounds (PFCs), polychlorinated naphthalenes (PCNs), Tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HCBD) were relatively less detected or reported. A comprehensive summarization on the levels and distributions of traditional and emerging POPs in lake ecosystems could be significant for further understanding the behaviors and risks of POPs in lake ecosystems.

Seasonal variations of PCDD/Fs in fishes: inferring a hidden exposure route from Na-PCP application for schistosomiasis control

Japanese schistosomiasis was endemic in Dongting Lake, the second largest freshwater lake in China. The technical sodium pentachlorophenate (Na-PCP) was widely used during the period between the early 1960s and early 1990s to kill oncomelania, the intermediate host of Schistosomes. However, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) also contaminated the environment of Dongting Lake due to trace impurities of Na-PCP. In this study, 13 species of freshwater fish were collected from Dongting Lake and analyzed in wet and dry seasons. Temporal (wet and dry season) variations in PCDD/Fs in fishes from Dongting Lake were observed. The concentration of PCDD/Fs was considerably higher in the wet season than in the dry season and in areas in China where Na-PCP was not applied. The higher level of PCDD/Fs in the wet season may be attributed to the use of Na-PCP in the past and to the increase in the migration of PCDD/Fs from sediments to water in the wet season. The results indicate that the risk of PCDD/Fs contamination is connected with prior consumption of fishes that live in the Na-PCP application area. However, there was no difference in the concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) between the wet and dry seasons.

Tissue distribution and maternal transfer of persistent organic pollutants in Kentish Plovers (Charadrius alexandrines) from Cangzhou Wetland, Bohai Bay, China

Several persistent organic pollutants, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs), were comprehensively investigated in the egg, muscle and liver samples of Kentish Plover (Charadrius alexandrines) collected from Cangzhou Wetland in western Bohai Bay, China. DDTs were the most abundant contaminants (35.4-9853ngg^-1 lipid weight, lw), followed by HCHs, PCBs, PBDEs and HCB. PCDD/Fs exhibited the lowest concentrations in all tissues (8.74-4763pgg^-1 lw). PCBs and PCDD/Fs were dominated by penta- and hexa-homologs, and PBDEs mostly consisted of the signature congeners of BDE formulations, such as BDE-209, -47, -153 and -99. Significant correlations were found between the lipid-normalized concentrations in muscle and liver (r: 0.37-0.90, p<0.05) and no significant differences (p<0.05), indicating the homogenous distribution of POPs in tissue lipids at steady state. The ratios of concentrations in muscle and liver (M/L) ranged from 0.20 to 1.51, and higher ratios of M/L were found for those compounds with log K_ow in the range of 6.5-7.0, suggesting the preferential accumulation of mid-halogenated compounds in muscle. Significant correlations were generally observed between the concentrations in egg and the maternal tissue (p<0.05). The concentration ratios of egg to liver (E/L) were in the range of 0.10-1.24 except for p,p'-DDT (12.7), and compounds with log K_ow of 6.5-7.0 exhibited higher E/L ratios, suggesting the selective maternal transfer of mid-halogenated compounds.

Human exposure to PCDDs and their precursors from heron and tern eggs in the Yangtze River Delta indicate PCP origin

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are highly toxic to humans and wildlife. In the present study, PCDD/Fs were analyzed in the eggs of whiskered terns (Chlidonias hybrida), and genetically identified eggs from black-crowned night herons (Nycticorax nycticorax) sampled from two lakes in the Yangtze River Delta area, China. The median toxic equivalent (TEQ) of PCDD/Fs were 280 (range: 95-1500) and 400 (range: 220-1100) pg TEQ g^-1 lw (WHO, 1998 for birds) in the eggs of black-crowned night heron and whiskered tern, respectively. Compared to known sources, concentrations of PCDDs relative to the sum of PCDD/Fs in bird eggs, demonstrated high abundance of octachlorodibenzo-p-dioxin (OCDD), 1,2,3,4,6,7,8-heptaCDD and 1,2,3,6,7,8-hexaCDD indicating pentachlorophenol (PCP), and/or sodium pentachlorophenolate (Na-PCP) as significant sources of the PCDD/Fs. The presence of polychlorinated diphenyl ethers (PCDEs), hydroxylated and methoxylated polychlorinated diphenyl ethers (OH- and MeO-PCDEs, known impurities in PCP products), corroborates this hypothesis. Further, significant correlations were found between the predominant congener CDE-206, 3'-OH-CDE-207, 2'-MeO-CDE-206 and OCDD, indicating a common origin. Eggs from the two lakes are sometimes used for human consumption. The WHO health-based tolerable intake of PCDD/Fs is exceeded if eggs from the two lakes are consumed regularly on a weekly basis, particularly for children. The TEQs extensively exceed maximum levels for PCDD/Fs in hen eggs and egg products according to EU legislation (2.5 pg TEQ g^-1lw). The results suggest immediate action should be taken to manage the contamination, and further studies evaluating the impacts of egg consumption from wild birds in China. Likewise, studies on dioxins and other POPs in common eggs need to be initiated around China.

Unexpected promotion of PCDD/F formation by enzyme-aided Cl2 bleaching in non-wood pulp and paper mill

Enzyme-aided Cl₂ bleaching is widely considered as promising replacements for conventional Cl₂ bleaching in wood pulp and paper mills. However, the effects of using enzyme-aided bleaching on the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the non-wood pulp and paper mills are unclear. A field study was performed to investigate PCDD/F formation when enzyme-aided Cl₂ bleaching was used to replace conventional Cl₂ bleaching in non-wood pulp and paper mills. Unexpectedly, the PCDD/F toxic equivalents (TEQs) in solid samples were higher when using enzyme-aided bleaching (0.49-5.4 pg TEQ/g) than that using conventional Cl₂ bleaching (0.15-2.44 pg TEQ/g). Large amounts of octachlorodibenzo-p-dioxin were formed during the enzyme-aided bleaching process. This could have been because enzyme strongly promoted the release of organic molecules bound to lignin and thus accelerated the formation of octachlorodibenzo-p-dioxin through organic molecular precursors. Although enzyme-aided Cl₂ bleaching was previously considered to be efficient for reducing PCDD/F releases and to be the best available technologies and best environmental practices for wood pulp and paper mills, the results obtained in this study suggested the necessity and urgency to evaluate the suitability of enzyme-aided Cl₂ bleaching for non-wood pulp and paper mills that intensively practiced in developing countries.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in the sediment core from a schistosomiasis area with Na-PCP application in China

Spatial and temporal distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was explored in the Dongting Lake area. The concentrations of total PCDD/Fs ranged from 15.4 to 38.9 pg I-TEQ g(-1) in surface sediments and 0.55 to 38.9 pg I-TEQ g(-1) for sediment core. The vertical distributions of PCDD/Fs in the sediment core reflected the past history of using Na-PCP and the impact of the massive flood events on the distribution of PCDD/Fs to some extent. The sediment still acts as significant PCDD/F sources and they would pose a risk to sensitive species, resulting in the risk for human exposure to PCDD/F.

Standardization of egg collection from aquatic birds for biomonitoring--a critical review

Collecting bird eggs is an established method of biomonitoring for specific pollution hazards. One of the most critical problems with this method is the extreme biological variability in bird eggs, but standardizing the collection and preservation of eggs can reduce these problems. Furthermore, standard practices are required so that the results can be compared among studies because mistakes cannot be corrected by laboratory analysis. Therefore, a standard procedure for collecting and preserving bird eggs may be necessary. The objective of this review is to investigate the current standard of quality assurance in the field by analyzing 86 peer-reviewed papers describing egg collection and use for aquatic birds. We show that little attention has been paid to standardizing how eggs are collected and stored in the field. Important information is often absent, including crucial aspects of sample collection and preservation, such as the freshness of the eggs, the position of the eggs in the laying sequence, the selection criteria, random sampling, and the duration and temperature of transport. Potential standards are suggested and discussed as a foundation for the development of quality assurance standards in the field.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in different tissues of the cormorants (Phalacrocorax carbo) from Dongting Lake, China

Tissue distribution provides important information regarding the pharmacokinetic behavior of pollutants and is invaluable when analyzing the risk posed to avian species by the exposure to such kind of pollutants. In this study, concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in muscle, liver, spleen, kidney, stomach, gall bladder, skin, heart, pancreas, intestine and lung tissue extracts of cormorants collected from Dongting Lake, China. Tissue distribution results showed preferential accumulation of PCDD/Fs in both liver and skin. The total concentration of PCDD/Fs ranged from 421 to 5696 pg/g lipid weight. Octachlorinated dibenzo-p-dioxin (OCDD) was the predominant congener in all tissues and contributed between 31% and 82% to all 17 PCDD/Fs in different tissues. The liver/muscle ratios progressively increased with the degree of chlorination of PCDDs, except for OCDD. The relative toxic potential of PCDDs and PCDFs in tissues were calculated using the World Health Organization (WHO) Toxic Equivalency Factors (TEFs) for birds. The concentrations of WHO-toxic equivalent in different tissues ranged between 14.8 and 2021 pg/g lipid weight. These results indicated PCDD/Fs may have been bio-accumulated in cormorant via food-web. Furthermore, when compared with studies reported in the literatures, the PCDD/Fs levels in the cormorant collected from Dongting Lake were still relatively high.

PCBs and organochlorine pesticides in ducks of Fereydoon-kenar wildlife refuge in Iran

Levels of organochlorine pesticides (OCPs) and PCB were determined in three duck species: Pintail (Anas acuta), Common Teal (Anas creaca), and Mallard (Anas platyhynchos). Both persistent organochlorines were more abundant in muscle than in the liver; Mallard had the highest levels of PCBs [84.0 +/- 39.0 ng/g wet weight (ww)], and Common Teal showed the highest levels of DDTs (561.0 +/- 220.0 ng/g ww). This exposure level is more than two orders of magnitude below provisional tolerable daily intake (PTDI) (0.01 mg/kg bw for DDT and its associated compounds) of The Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).

Avian liver organochlorine and PCB from South coast of the Caspian Sea, Iran

Liver samples (n = 43) of 9 avian species representing the families Phalacrocoracidae, Podicipedidae, Laridae, and Anatidae, were collected from the Iranian coast of the Caspian Sea. Samples were analyzed for organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, hexachlorobenzene (HCB), hexachlorocyclohexane isomers (HCHs), and seven PCB congeners. p,p'-DDE was predominantly found in all species, at concentrations ranging from the limit of quantification (LOQ) to 340 ng/g ww. Most frequently encountered PCB congeners, in all samples, were 118, 153 and 138; and birds in Phalacrocoracidae had the highest liver PCB (mean 90 +/- 32; ranging from <LOQ to 106 ng/g ww) whereas Podicipedidae had the highest OCP (mean 147 +/- 49; ranging from <LOQ to 340 ng/g ww) (P < 0.05). Differences in the diet, and migratory routes, were important species-specific factors that affected hepatic concentration of OCP and PCB in the species we studied. Range of OCP and PCB concentrations in the present study was lower than those reported for birds in other regions of the world. Hepatic PCB concentration found in our avian species was below toxic effect levels that have been previously reported in birds. To our knowledge this is the first report of persistent organochlorine pollutants in liver of birds from Iran.