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Mussels (Perna viridis) were collected from the northern coast of the South China Sea (NSCS) to investigate the geographical distribution and potential risk of dichlorodiphenyltrichloroethane and its metabolites (DDTs). DDTs had concentrations that ranged from 248 ng/g to 4650 ng/g lipid weight (lw), with an average of 807 ± 932 ng/ng lw. A comparison of the levels of DDTs in mussels indicated that the NSCS is still one of the most polluted areas in the world, although a decreasing trend was observed. DDT metabolites were predominant in all samples, suggesting that historical residue was the main source of DDT pollution. However, there were new inputs of DDTs which likely associated with antifouling paints. The human health risk assessment revealed that the current concentrations of DDTs in mussels might pose little health risk for the consumers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Sediments are reservoirs and sources of DDTs to the aquatic ecosystem. However, the role of sediment particulate matter and benthic organisms in transferring DDTs remains unclear. In this study, microcosms were built up with different groups to simulate a freshwater system with DDT-contaminated sediment and organisms. The impacts of different exposure routes (water and sediment) on the changes of DDT and its metabolites (DDD and DDE) in carp (Cyprinus carpio) were investigated. The bioturbation of Tubifex tubifex (Oligochaeta, Tubificidae) was investigated to understand the fate and transfer of DDTs in aquatic environment. For the sediment treatment, the concentrations of o,p'-DDT in carp were significantly higher than those of p,p'-DDT, and the metallothionein (MT) content decreased. The bioaccumulation of DDTs in carp via sediment particulate matter was significantly higher/faster than that via overlying water. T. tubifex and sediment particulate matter accelerate DDT bioaccumulation in carp. Selective enrichment of the (+)-o,p'-DDT and (+)-o,p'-DDD was found in carp. These results help to reduce uncertainty in ecological and health risk assessments and to better understand the risk of DDTs in the environment.

A high prevalence of infectious diseases (mostly lungworms) is found in finless porpoises (genus Neophocaena) in the coastal waters of China, which is one of the most dichlorodiphenyltrichloroethane (DDT)-polluted areas worldwide, while its association with contaminant exposure remains undetermined. To address this gap, we investigated blubber levels of polychlorinated diphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons in Indo-Pacific finless porpoises (Neophocaena phocaenoides) stranded in the Pearl River Estuary (PRE) of China. In the post-mortem examinations, lungworms (Halocercus species) were found to be the most common parasites, with a high density observed in lungs and bronchi. Severe infections by nematode parasites were also found in the uterus (Cystidicola species), intestine (Anisakis typica) and muscle (A. typica). For all the pollutant compounds analyzed, only the concentrations of p,p'-DDT, p,p'-dichlorodiphenyldichloroethane (DDD) and o,p'-DDD were significantly higher in porpoises died of infectious diseases than in the "healthy" individuals (died from physical trauma). Contrasted accumulation pattern of DDTs and their metabolites was found between animals with different health status. The proportion of p,p'-DDT in ΣDDTs was higher than that of p,p'-dichlorodiphenyldichloroethylene (DDE) in diseased animals, whereas an opposite pattern was shown for "healthy" ones. While this study is the first to describe a significant positive correlation between parasitic diseases and high levels of DDTs in cetaceans, the direction of causality cannot be determined in our data: either a parasitic infection affected the porpoises' ability to metabolize DDTs, resulting in high levels of p,p'-DDT in their blubber, or the pollutant burden rendered them more susceptible to parasitic infection., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Indo-Pacific humpback dolphins (Sousa chinensis) are apex predators in the Pearl River Estuary waters (PRE) of China. PCBs, DDTs and other organochlorine pesticides (OCPs) (e.g., HCHs, HCB, mirex and dieldrin) were analysed in blubber samples of 45 dolphins and 10 prey fishes of S. chinensis collected from 2004 to 2013 in the PRE region to investigate the bioaccumulation and potential biomagnification of persistent organic pollutants (POPs). DDTs were the most abundant residue in the dolphins, with an average of 6,2700 ng g(-1) wet weight (ww), followed by PCBs (average: 1,790 ng g(-1) ww) and other OCPs including ∑HCHs, mirex, endrin, ∑chlordanes, HCB, dieldrin, aldrin, heptachlor, and pentachlorobenzene. The concentrations of PCBs and DDTs in male dolphins significantly increased with age and length. In contrast, female dolphins did not show obvious bioaccumulation trends with age and body length, possibly due to the lactational and parturitional transfer of these compounds. Compared with the POP residues in the prey fishes, the concentrations of PCBs, DDTs, and HCHs in the dolphin blubber increased by factors of 99, 212, and 5, respectively, whereas the residue levels of the other OCPs increased 2-185 times, indicating a potentially significant biomagnification in the top predators. The potential biomagnification factors calculated for most POPs were significantly higher than those in the cetacean species from other regions., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Thirty-two light-vented bulbuls (Pycnonotus sinensis) were collected from six sampling sites in Guangdong Province, South China to investigate the geographical variation on the occurrence of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs). Concentrations of PCBs and DDTs in the pectoral muscle of light-vented bulbul ranged from 140 to 73,000 ng/g lipid weight (lw) and 12 to 4600 ng/g lw, respectively. PCB concentrations were significantly higher in birds from e-waste site compared to other sampling sites (mean, 18,000 vs 290 ng/g lw, p<0.0001), implying that PCBs mainly came from e-waste recycling activities. No significant differences for DDT levels were observed among the sampling sites (p=0.092). Differences in PCB homologue profiles among the sampling sites were found and can be probably ascribed to different local contamination sources. p,p'-DDE (>80%) was the most abundant component of DDTs in birds. Compositional pattern of DDTs suggested that historical residue was the main source of DDT. The toxic equivalent (TEQ) concentrations had significant positive correlations with PCB concentrations, indicating that elevated PCB levels may have adverse effects on light-vented bulbuls., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Four typical freshwater fish species in Lake Taihu (TH), China, were collected and analyzed for the residue levels of DDT and its metabolites DDD and DDE (sum of o,p'- and p,p'-DDT, DDD, and DDE is designated as DDTs). The DDTs concentrations ranged from 3.24 to 37.1 ng/g, and p,p'-DDE was the dominant isomer, followed by p,p'-DDD and o,p'-DDT. Source identification indicated that DDTs in TH was mostly stemmed from the historical usage of technical DDT mixture, but a new source of DDT, i.e., dicofol-type DDT, also occurred. The results from the present work, together with previously published data, clearly indicate that dicofol-type DDT was widespread and was an important continual source of DDTs in China., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Previously, we demonstrated that the concentrations of DDTs were greater in breast milk collected from Chinese mothers than from Japanese and Korean mothers. To investigate dicofol as a possible source of the DDTs in human breast milk, we collected breast milk samples from 2007 to 2009 in China (Beijing), Korea (Seoul, Busan) and Japan (Sendai, Takarazuka and Takayama). Using these breast milk samples, we quantified the concentrations of dichlorobenzophenone, a pyrolysis product of dicofol (simply referred to as dicofol hereafter), dichlorodiphenyltrichloroethane and its metabolites (DDTs) using GC-MS. Overall, 12 of 14 pooled breast milk samples from 210 mothers contained detectable levels of dicofol (>0.1 ng g⁻¹ lipid). The geometric mean concentration of dicofol in the Japanese breast milk samples was 0.3 ng g⁻¹ lipid and significantly lower than that in Chinese (9.6 ng g⁻¹ lipid) or Korean breast milk samples (1.9 ng g⁻¹ lipid) (p<0.05 for each). Furthermore, the ΣDDT levels in breast milk from China were 10-fold higher than those from Korea and Japan. The present results strongly suggest the presence of extensive emission sources of both dicofol and DDTs in China. However, exposure to dicofol cannot explain the large exposure of Chinese mothers to DDTs because of the trace levels of dicofol in the ΣDDTs. In the present study, dicofol was confirmed to be detectable in human breast milk. This is the first report to identify dicofol in human samples., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Six species of freshwater fish collected from 10 fishponds in Shunde and Zhongshan, China, four species of marine fishes collected from different mariculture farms [four in Hong Kong (Tung Lung Chau, Ma Wan, Cheung Chau and Kat O) and two in mainland China (Daya Bay and Shenzhen)] together with feed (both trash fish and commercial pellets) and sediment were analyzed for DDTs. Total DDTs in freshwater fish flesh decreased in the order of: carnivores [1742 microg/kg lipid weight (l.w.)] > herbivores (165 microg/kg, l.w.) > omnivores (42.5 microg/kg, l.w.), with the highest concentration detected in mandarin fish (Siniperca chuatsi) (2641 microg/kg, l.w.). For marine fish, snubnose pompano (Trachinotus blochii) and orange-spotted grouper (Epinephelus coioides) collected in Ma Wan contained elevated levels of total DDTs (2590 and 2034 microg/kg l.w., respectively). Trash fish used in both freshwater and marine fish farms contained significantly higher levels (86.5-641 microg/kg l.w.) (p < 0.05) of DDTs than in commercial pellets, but correlations between DDT levels in fish feed and muscle were not significant. The elevated biota-sediment accumulating factor for tilapia (Tilapia mossambicus) (24.1) indicated that accumulation of DDTs from sediment to the fish was evident. It can be concluded that trash fish should not be used for fish culture in order to lower the level of residual DDTs in fish muscle.

High levels of p,p'-DDT were detected in Hong Kong breast milk sampled in 1976 and 1985. Monitoring DDT levels in human breast milk in this region is important to identify trends in exposure. As part of the 2002-03 WHO/EURO coordinated exposure study, the concentrations of DDT and its metabolites were determined in 10 pooled milk samples classified by geographic origin and dietary history, comprising milk samples from 238 primiparous mothers giving birth in Hong Kong. Analysis was performed by Gas Chromatography (GC) with electron capture detector and confirmed by GC/Mass Spectrometry. The sum-DDT concentration (range: 0.92-2.05 mg/kg fat) was age-dependent and indicated a decreasing trend since the 1970s. Mothers who recently came from mainland China had higher p,p'-DDT to p,p'-DDE ratios, suggesting a more recent exposure compared to women mainly residing in Hong Kong. The average Hong Kong sum-DDT level (1.50 mg/kg fat) was among the highest of the contemporary levels (range: 0.12-1.97 mg/kg fat; median: 0.40 mg/kg fat) in the 16 countries/regions participating in the 2002-03 WHO/EURO exposure study. This is probably due to the previous extensive DDT exposure and continuing use of DDT in agriculture in mainland China. Despite the apparent decrease of DDT body load over 30 years, the environmental health hazard from DDT contamination in the Pearl River Delta region remains a concern. Measures to eradicate illegal use of DDT in mainland China and regular food monitoring programs are needed in the region. Despite the presence of DDT and other persistent organic pollutants in human breast milk, breastfeeding should continue to be strongly supported for its life-long benefits to infants.

Water, suspended solid (SS) and sediment samples were collected from nine water courses in Tianjin, China and analyzed for dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDXs, including o,p'-,p,p'-DDT, DDD and DDE). The average DDX concentrations in water, SS and sediment were 59+/-30 ng l(-1), 2690+/-1940 ng g(-1)dry wt. and 340+/-930 ng g(-1)dry wt., respectively. Due to the termination of the extensive agricultural application and industrial manufacture, DDXs in river sediment decreased by one order of magnitude since 1970's and low DDT fractions in these sediments were observed. Still, DDXs in the sediments near the outlets of the major manufacturers remained relatively high attributed to the historic input. DDXs in sediment were also positively correlated with organic matter content. Spatial distributions of DDXs in SS and water was different from that in sediment. For SS, a negative correlation between DDX concentration and SS content indicated a dilution effect in many rivers. Dissolved organic carbon content was the major factor affecting DDX concentrations in water phase. Wastewater discharged from dicofol manufacturers and likely illegal agricultural application were the primary reasons causing high DDT (DDE+DDD) ratios in SS and water.

One hundred and eighty eight surface soil samples were collected from the Tianjin area to study the contamination of DDT and its metabolites. Measurements were taken for p,p'-DDE, p,p'-DDD, p,p'-DDT, o,p'-DDE, o,p'-DDD and o,p'-DDT for all samples. The results indicated that p,p'-DDT and p,p'-DDE were the predominant contaminant compounds in the surface soil samples, with mean concentrations of 27.5 and 18.8 ng g(-1) respectively. No significant differences in DDT concentrations were found between the soils from wastewater treated irrigated areas and other areas, suggesting that wastewater irrigation is not an important source of DDT in the area. However, the spatial distribution of soil DDTs levels in the area did correlate well with early direct application rates of pesticides. In addition, both pH level and organic carbon content are also known factors affecting the level of DDT and its metabolites. Although it was assumed that the use of these chemicals was banned in the early 1980s, the current concentration levels appear to be too high to be mere residuals after 20 years degradation.