Residues and chiral signatures of organochlorine pesticides in sediments from Xiangshan Bay, East China Sea

Residual levels and enantiomeric signatures of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in surface sediments from Xiangshan Bay, East China Sea were investigated. The concentrations of ∑HCHs (sums of α-, β-, γ-, and δ-HCH) and ∑DDTs (sums of p, p'-DDT, p, p'-DDD,p, p'-DDE, o, p'-DDT, and o, p'-DDD) ranged from 0.14 to 0.67 ng g?1 and 0.61 to 22.38 ng g?1, respectively. A slight potential health risk to the organism was then indicated for the residual levels of DDTs according to the ERL/ERM guidelines. Moreover, the predominant β-HCH implied that the technical HCH contamination was mainly due to the historical usage. But the high ratio of DDT/∑DDTs depicted a cocktail input pattern of fresh and weathered DDTs. The enantiomeric fractions (EFs) of α-HCH, o, p'-DDT, and o, p'-DDD were also determined. The degradation of α-HCH was enantioselective in all sediments samples, resulting in an enrichment of (-)-enantiomers. However, the racemic residues of o, p'-DDT and o, p'-DDD were observed in all sediments samples.     

Concentrations and compositions of organochlorine contaminants in sediments, soils, crustaceans, fishes and birds collected from Lake Tai, Hangzhou Bay and Shanghai city region, China

Contamination by persistent organochlorines (OCs), such as DDTs, hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) were examined in sediments, soils, fishes, crustaceans, birds, and aquaculture feed from Lake Tai, Hangzhou Bay, and in the vicinity of Shanghai city in China during 2000 and 2001. OCs were detected in all samples analyzed, and DDT and its metabolites were the predominant contaminants in most sediments, soils and biota. Concentrations of p,p'-DDT and ratio of p,p'-DDT to SigmaDDTs were significantly higher in marine fishes than those in freshwater fishes. While the use of DDTs has been officially banned in China since 1983, these results indicate a recent input of technical DDTs into the marine environment around Hangzhou Bay. Comparison of organochlorine concentrations in fishes collected from Lake Tai and Hangzhou Bay suggests the presence of local sources of HCHs, chlordanes and PCBs at Lake Tai. Higher proportions of penta- and hexa-PCB congeners in fishes at Lake Tai may suggest the use of highly chlorinated PCB product, such as PCB(5), around this lake. To our knowledge, this is a first comprehensive study to examine the present status of organochlorine contamination in various environmental media, such as sediments, soils and wildlife, in China.     

Persistent organochlorine residues in human breast milk from Hanoi and Hochiminh City, Vietnam: contamination, accumulation kinetics and risk assessment for infants

Despite the ban on persistent organochlorines (OCs) in most of the developed nations, their usage continued until recently in many Asian developing countries including Vietnam, for agricultural purposes and vector-borne disease eradication programs. In this study, we collected human breast milk samples from the two big cities in Vietnam: Hanoi (n=42) and Hochiminh (n=44) and determined the concentrations of persistent OCs such as PCBs, DDT and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), chlordane compounds (CHLs) and tris-4-chlorophenyl-methane (TCPMe). The contamination pattern of OCs was in the order of DDTs > PCBs > HCHs > CHLs approximately HCB approximately TCPMe. Compilation of available data indicated that DDT residue levels in human breast milk from Vietnam were among the highest values reported for Asian developing countries as well as developed nations. This result suggests recent usage of DDTs in both north and south Vietnam. Interestingly, in both cities, the p,p'-DDT portion was higher in multiparas than those in primiparas. Considering the fact that the interval between the first and the second child of a mother in Vietnam is usually short, this result probably indicates continuous intake of DDTs in the population. Analysis of infant exposure to DDTs via breast milk suggested that the daily intake rates for number of individuals are close to or above the threshold for adverse effects which may raise concern on children health.     

Vertical distributions of persistent organic pollutants (POPs) caused from organochlorine pesticides in a sediment core taken from Ariake bay, Japan

Persistent organic pollutants (POPs) of organochlorine pesticides such as dichlorodiphenyl trichloroethane (DDTs) and its metabolites, hexachlorobenzene (HCB), heptachlor, chlordane compounds (CHLs), aldrin, dieldrin, endrin, mirex and isomers of hexachlorocyclohexane (HCHs), were analyzed in sediment cores collected from Ariake Bay, Japan. Although Chikugo River has the largest flow in Ariake Bay, the total concentration of POPs in surface sediment was found in St.3, mouth of the Yabe River, where that level was two times higher than St.1, mouth of the Chikugo River. It could be assumed that the potential source of POPs contamination is relatively close to this study area. Relatively high residue levels of HCB, HCHs and DDTs in sediment core were found during the period from 1967 to 1970. In this layer, the HCB concentration investigated in sediment cores of Ariake Bay was maximum, 2.6 ng g(-1) dry weight and higher than that of Tokyo Bay and subsequently detected in deeper sediment cores. The ratio of (DDD+DDE)/SigmaDDTs was high in top sediments (0-2 cm). Although there was a concentration of DDTs in the top sediment, it was noticed that DDT emission did not cause direct input of DDT recently. The HCHs determined in upper sediment cores might be originated from long-range accumulation in environment after dispersing of technical-grade HCH. Moreover, the CHLs, dieldrin and heptachlor concentrations were detected and recently increased in sediment core. POPs in sediment cores of Ariake Bay based on the possibility of PCP contamination during the early 1960s were reflected.     

Organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers in Singapore's coastal marine sediments

Persistent organic pollutants (POPs) are ubiquitous pollutants in the marine environment, particular in coastal areas affected by industry and shipping traffic. POPs are known for their recalcitrance and toxicity in the environment, and there is increasing concern over their global distribution and impact upon wildlife. Marine surface sediment samples taken within 6 km of the coastline of Singapore were analyzed to determine prevailing concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyl (PCBs) and polybrominated diphenyl ethers (PBDEs). Total PCB concentrations varied widely from 1.4 to 329.6 ng/g (average 73.9 ng/g), where high concentrations were detected at sample locations closest to industrial areas with intensive shipping traffic. Total DDT concentrations ranged from 2.2 to 11.9 ng/g (average 6.7 ng/g) and were lower than the concentration range of 3.3-46.2 ng/g measured for total HCH (average 18.1 ng/g). Ratios of DDT/(DDE+DDD) in sediments do not indicate recent inputs of DDT into Singapore's marine environment, but high concentrations of alpha-HCH and gamma-HCH show evidence for the usage of HCHs in Southeast Asia. Peak concentrations of cis- and trans-Chlordane were 10 ng/g. Among the PBDE congeners BDE 47, 99, and 100 only BDE 47 could be detected at a range of 3.4-13.8 ng/g (average 6.2 ng/g). The levels of OCPs, PCBs and PBDEs were compared to available data for other countries in Asia, and indicated relatively moderate levels of contamination. Peak concentrations of PCBs, HCH isomers, Chlordane, Heptachlor, Heptachlor epoxide and Dieldrin have the potential to induce ecotoxicological impacts based on levels specified in the sediment quality standards of the USEPA and Canadian Council of Ministers of the Environment.     

Distribution and ecological risk of organochlorine pesticides and polychlorinated biphenyls in sediments from the Mediterranean coastal environment of Egypt

Organochlorine contamination in the Mediterranean coastal environment of Egypt was assessed based on 26 surface sediments samples collected from several locations on the Egyptian coast, including harbors, coastal lakes, bays, and estuaries. The distribution and potential ecological risk of contaminants is described. Organochlorine compounds (OCs) were widely distributed in the coastal environment of Egypt. Concentrations of PCBs, DDTs, and chloropyrifos ranged from 0.29 to 377 ng g⁻¹ dw, 0.07 to 81.5 ng g⁻¹ dw, and below the detection limit (DL) to 288 ng g⁻¹ dw, respectively. Other organochlorinated pesticides (OCP) studied were 1–2 orders of magnitude lower. OCP and PCBs had higher concentrations at Burullus Lake, Abu Qir Bay, Alexandria Eastern Harbor, and El Max Bay compared to other sites. OCP and PCB contamination is higher in the vicinity of possible input sources such as shipping, industrial activities and urban areas. PCB congener profiles indicated they were derived from more than one commercially available mixture. The ratios of commercial chlordane and heptachlor metabolites indicate historical usage; however, DDT and HCHs inputs at several locations appear to be from recent usage. The concentrations of PCBs and DDTs are similar to those observed in sediments from coastal areas of the Mediterranean Sea. Ecotoxicological risk from DDTs and PCBs is greatest in Abu Qir Bay, Alexandria Harbor, and El-Max Bay.     

Nationwide monitoring of polychlorinated biphenyls and organochlorine pesticides in sediments from coastal environment of Korea

To assess the organochlorine contamination in the Korean marine environment, a nationwide monitoring study was conducted. A total of 138 surface sediments, covering the whole Korean coast, were collected and analyzed. Organochlorine compounds (OCs) were widely distributed in the Korean coastal environment, with PCB and DDT contamination being particularly prevalent. The overall concentrations of PCBs, DDTs, HCHs, CHLs, and HCB in surface sediments were in the range of 0.088-199ngg(-1) (median value: 1.56ngg(-1)), 0.006-135ngg(-1) (0.68ngg(-1)), not detected (ND)-5.46ngg(-1) (0.32ngg(-1)), ND-3.26ngg(-1) (0.14ngg(-1)), and ND-2.59ngg(-1) (0.05ngg(-1)), respectively. The southeastern coast was found to be highly contaminated. Overall contamination status of Korean coastal sediments with regard to OCs is lower than that of USA. With the exception of highly industrialized sites, Korean coastal areas in general showed similar OC concentrations to those of other Asian countries. There was a significant correlation between distributions of most organochlorine contaminants with each other. OC contamination is closely related to shipping and industrial activities. Of the 7 sites categorized as highly polluted, 4 are in a harbor zone. Adverse effects to benthic communities are expected at the levels of OC contamination observed from harbor and industrial areas.     

The levels and distribution of organochlorine pesticides (OCPs) in sediments from the Haihe River, China

The levels and distribution patterns of the selected organochlorine pesticides (OCPs=p,p'-DDT, o,p'-DDT, p,p'-DDE, p,p'-DDD, alpha-, beta-, gamma- and delta-HCH) in surficial sediments from the Haihe River and Dagu Drainage River of Tianjin were investigated by means of gas chromatography coupled with micro-electronic capture detector (GC-microECD). Concentrations of OCPs in the sediments from the Haihe River ranged from 1.88 to 18.76ng g(-1) (mean 7.33ng g(-1)) for sum HCH, 0.32-80.18ng g(-1) (mean 15.94ng g(-1)) for sum DDT. Compared with the Haihe River, the Dagu Drainage River was much more contaminated by HCHs and DDTs, wherein sum HCH ranged from 33.24 to 141.03ng g(-1) (mean 87.74ng g(-1)) and sum DDT ranged from 3.60 to 83.49ng g(-1) with a mean value of 35.52ng g(-1). The concentration distribution of sum DDT and sum HCH was different indicated their different contamination sources. Composition analyses indicated that a recent usage or discharge of HCH and DDT into the Dagu Drainage River.     

Persistent organochlorine residues in soils from tropical and sub-tropical Asian countries

Soil samples from paddy fields, uplands, and urban areas (gardens and roadsides) collected from Vietnam, Thailand, and Taiwan were analysed to determine the residual levels of persistent organochlorine compounds such as DDTs, HCHs, and PCBs. DDT concentration in soil samples from Vietnam were found to be highest, with a mean value of 110 ng g(-1), and were followed by those in Taiwanese soils with a mean value of 20 ng g(-1). HCH concentrations were highest in soil samples from Vietnam (a mean value of 4.8 ng g(-1)) and were followed by those from Taiwan (a mean value of 1.4 ng g(-1)). Concentrations of PCBs were found to be highest in Taiwanese soil samples, with a mean of 95 ng g(-1). Interestingly, relatively high concentrations of PCBs in rural cultivated-soil samples from Vietnam were recorded with a mean value of 25 ng g(-1), probably suggesting PCB release from different kinds of weapons used during the Second Indochina war. The lowest concentrations of DDTs, HCHs, and PCBs were obtained in soil samples from Thailand, with mean values of 8.3 ng g(-1), 0.4 ng g(-1), and 2.7 ng g(-1), respectively.     

Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea

The residues of oragnochlorine pesticides (OCPs) in 62 sediments from Kyeonggi Bay and nearby areas in the west coast of Korea were determined. The concentrations of chlordanes (CHLs) and DDTs showed a distinctive gradient of contamination between inner and outer sites of Incheon North Harbor (INH), whereas hexachlorocyclohexanes (HCHs) were uniformly distributed at most sites studied. The distribution of CHLs and DDTs was strongly correlated with total organic carbon contents in sediments while HCH residue levels were independent. Relationship between contaminant's concentration and environmental factors was analyzed by principal component analysis. Distribution patterns of T-CHLs, T-DDTs, and TOC were similar while those of T-HCHs, mud content, and grain size were similar. The notable contamination by CHLs and DDTs was found in INH where these levels were one or two orders of magnitude higher than other sites. The dominant OCPs in sediments were beta-HCH among HCH compounds, trans-chlordane among CHL compounds, and p,p'-DDD among DDT compounds. The higher concentrations and compositional pattern of OCPs in INH sediments indicate that INH is in the vicinity of the source.     

Persistent organochlorines in human breast milk collected from primiparae in Dalian and Shenyang, China

The present study determined the concentrations of organochlorines (OCs) such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), hexachlorobenzene (HCB) and tris(4-chlorophenyl)methane (TCPMe) in human breast milk collected from primiparae in Dalian and Shenyang, northeastern China during 2002. In addition, dioxins and related compounds in pooled samples of human breast milk from Dalian and Shenyang were also analyzed. OCs were detected in all the human breast milk samples analyzed in this study. The predominant contaminants in human breast milk were HCHs, DDTs and HCB, and the levels were relatively higher than those in other countries. On the other hand, concentrations of dioxins and related compounds, PCBs, and CHLs were relatively low. Concentrations of OCs in human breast milk from Dalian, which is located along the coast of Bo Hai Strait, were significantly higher than those from Shenyang, implying that the residents in Dalian might be mainly exposed to these contaminants from seafood. When the relationship between concentrations of OCs in human breast milk and age of primiparae was examined, no significant correlation was observed. This might be caused by the limited sample numbers and narrow range of mother's age and/or recent ban of DDT and HCH production and use. Significant correlation between concentrations of TCPMe and DDTs in human breast milk suggested that technical DDT might be a source of TCPMe in the Chinese population. When daily intakes of DDTs and HCHs to infants through human breast milk were estimated, human breast milk from Dalian showed significantly higher contribution than Shenyang, implying that infants in Dalian might be at higher risk by these contaminants.     

Polychlorinated biphenyl congeners and organochlorine insecticides in the water column and sediments of Daya Bay, China.

Samples of sub-surface water, suspended particulate matter (SPM) and surface sediments collected from Daya Bay, China have been analysed for 12 polychlorinated biphenyl (PCB) congeners and 18 organochlorine insecticides, using gas chromatography electron capture detection. Total PCB levels varied from 91.1 to 1355.3 ng l-1 in water and from 0.85 to 27.37 ng g-1 dry weight in sediments. The levels of total organochlorine insecticides were in the range 143.3-5104.8 ng l-1 in water and 2.43-86.25 ng g-1 dry weight in sediment. None of the target compounds were detected in SPM. The levels of total hexachlorocyclohexanes in water varied from 35.5 to 1228.6 ng l-1, whilst in sediments they ranged from 0.32 to 4.16 ng g-1 dry weight. For the sum of dichlorodiphenyltrichloroethanes (DDTs), their levels were in the range 26.8-975.9 ng l-1 in water, and 0.14-20.27 ng g-1 dry weight in sediments. The distribution profiles of these contaminants in water and sediments suggest that there are a number of sources contributing to total contaminant burden in the bay, including soil runoffs, wastewater discharges, sewage outfalls and shipping activites. Ratios of DDT/(DDE + DDD) in the water and sediments indicate recent inputs of such chemicals into the day. The results, therefore, provide important information on the current contamination status of a key aquacultural area in China, and point to the need for urgent actions to stop the use of persistent agrochemicals such as DDT and lindane.     

Assessment of persistent organic pollutants in sediments from Lower Mekong River Basin

Organochlorine compounds (OCs) in sediments collected from various locations in Lower Mekong River Basin (MRB) in Laos and Thailand were examined to elucidate their occurrence, distribution and potential ecological risk. Concentration of PCBs and DDTs were higher than other OCs, ranging from 0.18 to 310 μg kg⁻¹ dry wt. and from 0.027 to 52 μg kg⁻¹ dry wt., respectively, whereas CHLs, HCHs and HCB were 1-3 orders of magnitude lower. Geographical distribution indicates that levels of PCBs, DDTs and CHLs in the Vientiane canal were significantly higher than those in mainstream of Mekong River, Phong River and its surrounding areas, indicating significant sources of these compounds in urbanized areas. Comparison with other parts of MRB indicates that PCBs were higher in Laos, whereas DDTs were more prevalent in Mekong Delta, indicating location specific contaminations of these compounds in MRB. The ratios of DDTs composition indicate possible difference in the historical input of DDT among locations in and around Mekong River. Hazard assessment of PCBs and DDTs indicate possible toxic potential particularly in areas close to point sources such as intensive human activities and agricultural areas which highlight the need for further study.     

Organochlorine residues in odontocete species from the southeast coast of India

Blubber from bottle-nose dolphins, spinner dolphins, humpback dolphin (Tursiops truncatus, Stenella longirostris and Sousa chinensis) were collected from the Bay of Bengal (southeast coast of India) and analyzed for the organochlorine pesticides hexachlorocyclohexane (HCHs), p,p'-dichlorodiphenyl trichloroethane (DDTs), and polychlorinated biphenyls (PCBs). All nine specimens analyzed contained considerable levels of all the three chemical classes where DDT was in the range of 3330-23330 ng/g; HCHs in the range of 95-765 ng/g; and PCBs in the range of 210-1220 ng/g (wet weight basis). The reasons for this and the variations in the isomer pattern of HCHs and DDT and its metabolites in marine mammal tissues are discussed.     

Pollution sources and occurrences of selected persistent organic pollutants (POPs) in sediments of the Mekong River delta, South Vietnam

The Mekong River delta is one of the largest agricultural land in the Southeast Asia. It plays a very important role for agriculture and fisheries in South Vietnam. However, comprehensive studies on the environmental pollution of persistent organic pollutants (POPs) in Mekong River delta have not been carried out in recent years. In this study, we collected sediment samples from the Mekong River to evaluate the contamination and ecological risks caused by several POPs. The contamination pattern of POPs was DDT>PCBs>CHLs>HCHs>HCB. DDTs are the most abundant pollutants, their concentration ranging from 0.01 to 110 ng/g dry wt, followed by PCBs (0.039-9.2 ng/g dry wt). DDTs and PCBs concentrations were higher in sediment from adjacent to urban areas than those from rural and agricultural sites, suggesting urban areas as important point sources of DDTs and PCBs to the river. Ratio of p,p'-DDT/p,p'-DDE was lower compared to those previously reported. However, some samples still had the ratio higher than 0.5, indicating recent input of DDT into the aquatic environments. This result shows that although the magnitude of contamination decreased over time, recent inputs of DDTs to the river still occur. Some sediment samples had concentrations of DDT compounds higher than the standards from the Canadian Environmental Quality Guideline, suggesting continuous monitoring for POPs contamination in the Mekong River is necessary.     

Chlorinated hydrocarbons in coastal bottom sediments of the Japan Sea

Data on distribution of chlorinated hydrocarbons in coastal bottom sediments of different areas of the Japan Sea are presented. Results obtained during the autumn 1994 expedition in Peter-the-Great Bay were compared with the data of previous surveys in the D.P.R. Korea coastal zone and Tatarsky Strait (Sakhalin Island). Concentrations of DDT metabolites and HCH isomers appear to be related mainly to pesticide usage in agriculture. Mean concentrations of total DDTs decreased from 12.5 ng g(-1) in the D.P.R.K. coastal zone to 2.2 ng g(-1) at Sakhalin Island shelf, whereas total HCH concentrations decreased from 3.4 to 0.4 ng g(-1). Differences in chemical composition of pesticides used in the D.P.R.K. and Russia were evident. The importance of further monitoring of persistent organochlorines in bottom sediments and the need for regulation of wastewater discharges is stressed.     

重庆典型岩溶区地下河表层沉积物OCPs初步研究

利用GC-ECD对重庆典型岩溶区地下河表层沉积物中19种有机氯农药进行分析，结果表明，研究区总有机氯农药浓度为4.73～286.03 ng/g，DDTs浓度为0.35～181.78 ng/g，HCHs浓度为nd～23.53 ng/g。与国内外其他河流表层沉积物有机氯农药相比为高，说明重庆典型岩溶区地下河已处于较高污染状态。统计DDE/DDD发现，除姜家溶洞外，其他取样点DDE/DDD均大于1，表明研究区DDT降解主要在好氧环境中进行。除靛水地下河，其他取样点表层沉积物(DDD+DDE)/DDT均大于0.5，表明这些地区近年来没有新的DDT类农药输入。     

Specific accumulation of organochlorines in human breast milk from Indonesia: levels, distribution, accumulation kinetics and infant health risk

This study determined concentrations of polychlorinated biphenyls (PCBs) and organochlorine compound (OC) pesticides in the milk samples of women from the general population in four locations of Indonesia. The most prevalent residues of OCs were DDTs, PCBs and hexachlorocyclohexane isomers (HCHs), whereas other OCs such as chlordane compounds (CHLs), tris(4-chlorophenyl)methane and hexachlorobenzene were lower. The levels of OCs varied between locations and individuals, with DDTs higher in suburban and rural areas than urban localities, may be due to the differences in food habits and sources between the individuals and locations. Data from Purwakarta site indicated continuing DDT exposure, which may confirm recent usage of DDT in Indonesia. A positive correlation was observed between concentration of OCs in human milk and age of mothers, primiparas women having higher OCs than multiparas, suggesting these parameters play an important role influencing the OC burdens in lactating women. Some individuals accumulated DDTs and HCHs in breast milk close to or even higher than the TDI (tolerable daily intake) guidelines proposed by Health Canada.     

Distribution and change of DDT and HCH levels in oysters (Crassostrea rivularis) from coast of Guangdong,China between 2003 and 2007

This investigation was undertaken to understand the temporal trend, the spatial distribution and the residue level of dichloro-diphenyl-trichloroethanes (DDTs) and hexachlorobenzenes(HCHs) in bivalves from the coast of the South China in recent years. Jinjiang oysters (Crassostrea rivularis) were sampled from 15 bays along the coast of Guangdong province, China between 2003 and 2007. Gas chromatography with electron capture detector was used to quantify the contents of HCH isomers (α-, β-, γ-, δ-HCH), DDT isomers (p,p′-, o,p′-DDT), p,p′-DDD and p,p′-DDE in the oyster tissues. The results demonstrate that annual level of DDTs in the tissue increase throughout the study, particularly between 2004 and 2006. The DDTs content in the tissue varied significantly among sampling regions and some sampling sites (p < 0.05). On the other hand, the HCHs content was significantly lower than DDTs content in the tissue (p < 0.01), and remain constant among sampling years, sampling regions and sampling sites (p > 0.10). Predominance of isomer form of DDTs and higher ratio of γ-HCH/HCHs at some sites indicated that recent input of DDT and lindane in the coastal waters of Guangdong, which might be caused by dicofol spraying in crop planting and lacquer painting on fisher boat. In the soft tissues of the oysters, the highest content of HCHs was 1.21 ng/g (wet weight), and DDTs levels ranged from 0.11 ng/g to 76.3 ng/g (wet weight), far below the Maximum Residual Limits in China and many developed nations.     

Organochlorine pesticide residuals in chickens and eggs at a poultry farm in Beijing, China

Chicken organs, animal feed, droppings, and ambient air were sampled at a farm in Beijing to determine the concentrations of hexachlorocyclohexane isomers (HCHs) and dichlorodiphenyltrichloroethane and metabolites (DDTs). Mean fresh weight concentrations of HCHs and DDTs were 0.122 ± 0.061 ng/g and 0.051 ± 0.038 ng/g in the muscles. These values are 1-2 orders of magnitude lower than those reported in China in 1980. Contaminated feed was the main source of HCHs and DDTs. Only 12.8% of HCH and 3.3% of DDT of the amount consumed were excreted. Accumulated quantities of HCHs and DDTs increased during growth. However, concentrations of HCHs and DDTs did not increase because of dilution from rapid growth. Based on the observed residual levels in mature chicken and the average diet of residents of China, the contributions from chicken and egg consumption to per capita daily intake of HCHs and DDTs were 487% and 88% of those of fish consumption.