DDT Residues Research Articles

Environmental and Health Risks of Pesticide Use in Ethiopia.

Background.There are frequent reports of unsafe pesticide use in many parts of Africa. Ethiopia is the second most populous nation in Africa with around 80% of the population still depending on agriculture which intensively uses pesticides. A number of studies have examined pesticide-related health and environmental risks in Ethiopia. However, most of these studies have been small in scale and it is therefore challenging to get a general overview of the extent of health risks and level of environmental contamination in the country.Objectives.The aim of the present study was to synthesize and summarize contemporary knowledge on pesticide-related risks and relevant gaps in Ethiopia.Methods.An electronic database search and gathering of grey literature were done to collect information on the risks of pesticide use in Ethiopia. The electronic search was conducted using MEDLINE (via PubMed) without any publication date or language specifications. The Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) checklist was used as guide in the creation of this review.Discussion.A synthesis of the reviewed studies showed evidence of health risks due to occupational pesticide exposure, surface water pollution with pesticides that could cause chronic health risks to the public, evidence of pesticide contamination of the environment (e.g., soil organisms, fish, bee colonies and wildlife) and local as well as international consumer risks due to pesticide residues in food items. In addition, there have been frequent reports of health and environmental hazards in association with cut-flower farms. There is also evidence of direct use of DDT (dichlorodiphenyltrichloroethane) on food crops and detection of DDT residues in surface water, soil and human breast milk. Those reported risks might be due to lack of knowledge among farm workers, negligence of farm owners, absence of post-registration monitoring systems and poor implementation of both national and international regulations in Ethiopia due to poor institutional capacity.Conclusions.The health and environmental risks of inappropriate use of pesticides requires action by all concerned bodies. Improved institutional arrangements for enforcement of regulations, awareness and further intervention studies could lessen the high risks of pesticide misuse.Competing Interests.The authors declare no competing financial interests.

Sources of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) found in surface sediment from coastal areas of Beibu Gulf: A reflection on shipping activities and coastal industries

The presence of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) was determined in the sediments of Beibu Gulf, a newly developing industry and port in South China, to evaluate whether the rapid development of coastal cities has accelerated the organic pollution in the region. The levels of PCBs and DDTs ranged from 1.17 to 8.00 ng g−1 and ND (not detected) to 3.82 ng g−1, respectively. The levels were higher in the east of Beibu Gulf than in the west, which influenced by the industrialisation and urbanisation in the east. Additionally, penta-PCBs were the dominant PCB congeners, which are related to shipping activities, and DDTs may have originated from the historical use of technical DDT. The levels of pp′-DDD and PCBs did not have the potential to cause ecological risks in Beibu Gulf; however, residues of DDTs were at relatively higher ecotoxicological levels, thereby having the potential to cause adverse biological effects.

The level of selected organochlorine compounds residues in popular edible mushrooms from north-eastern Poland

Although DDT, γ-HCH and PCBs have been almost completely withdrawn from world production and use, they are still present in the environment. Mushrooms are eagerly collected and consumed local raw material in north-eastern part of Poland. The aim of the study was to determine the content of DDT, γ-HCH and PCB residues in popular species (Boletus badius, Boletus edulis, Cantharellus cibarius) and to estimate the human exposure of uptaking of these compounds with mushrooms. The content of γ-HCH, DDT and PCB was determined using gas chromatography. The presence of analyzed compounds was observed in all the species under study. The highest content of γ-HCH and ΣDDT was determined in C. cibarius − 7.19 and 180.37 µg/kg of lipids, respectively, whereas the highest amount of ΣPCB was observed in B. edulis − 20.89 µg/kg of lipids. The contents were low and did not pose a threat to human health.

Occurrence of agricultural pesticides in Mississippi Delta Bayou sediments and their effects on the amphipod: Hyalella azteca

ABSTRACT Agricultural activity enhances topsoil erosion and facilitates the transport of pesticides that alter watershed sediment quality. Agricultural stream (bayou) sediment quality in Mississippi, USA, was evaluated across three bayous, habitats (upstream, midstream, downstream), and seasonally from 2011 to 2014 for pesticide contamination, effects, and bioavailability to Hyalella azteca. Four-week (28-day) H. azteca sediment bioassays were conducted to assess survival and growth and tissue residues. Fourteen pesticides were detected in at least one sediment sample and nine pesticides were detected in H. azteca tissues. Sediment pesticides p,p’-DDT and p,p’-DDE were greatest in Cow Oak Bayou and heptachlor and bifenthrin were greatest in Howden Lake Bayou. Seasonally, λ-cyhalothrin and p,p’-DDT were greatest in winter while trifluralin, atrazine, and clomazone were greatest in the fall. H. azteca survival and growth ranged from 0 to 100% and 0.8–4.1 mg, respectively, with Cow Oak, downstream habitats, and spring samples having the greatest survival and growth. Greatest tissue pesticide residues were atrazine (1271 µg/kg), p,p’-DDT (1,093 µg/kg), and β-cyfluthrin (1003 µg/kg). Tissue pesticide residues were influenced primarily by p,p’-DDT with Cow Oak and fall tissue samples having the lowest residues. H. azteca tissue p,p’-DDT residues contributed to biological impairment. Although banned in the USA for 40 years, p,p’-DDT continues to impact sediment quality.

Pesticide residues in soil samples from vegetable growing area of Bihar

The surface soil samples (0-15 cm) were found contaminated with different pesticides in vegetable growing areas in Bihar. Total twenty samples were analysed in which HCH and endosulfan were found as the major contaminants of soil. Nine samples were found contaminated with HCH (ND-0.055mg kg-1) and ten with endosulfan (ND-0.078mg kg-1). DDT residues were detected only in three soil samples. Among the organophosphate pesticide, residues of quinalphos (ND-0.062mg kg-1) and chlorpyriphos (ND-0.037mg kg-1) were detected in five samples each while dimethoate present in only one sample. Residues of cypermethrin, fenvalerate and deltamethrin were also detected in four, three and one soil sample, respectively.

The Organochlorine Pesticide Residues of Mesona Chinensis Benth by Near Infrared (NIR) Spectroscopy and Chemometrics

Pesticide residue is a major problem in food safety. It is particularly important to detect pesticides in fruits and vegetables quickly and effectively The near infrared spectroscopy (NIR) technique was explored as a technique to predict organochlorine pesticides in Mesona chinensis Benth. Fourty-three samples were sacaned powder in a Antaris II FT-NIR. Samples were split into two sets, one set used as calibration (n=35) where the remaining samples (n=S) were used as validation set. The hexachlorocyclohexane (BHC). dichlorodiphenyltricliloroethane (DDT) and organochlorine residues were determined by gas chromatography as the reference ratio. The prediction model of total BHC. DDT and organochlorine of mesona chinensis benth was established by partial least square (PLS) method, which were optimized by the optimal spectral band range, spectral pretreatment and regression. Moreover, the prediction ability of the model was verified by validation set. The models gave the results that RMSEC. Rc. RMSEP and Rp of BHC. DDT and organochlorine residues respectively were 0.996. 0.9384, 0.151 and 0.9964; 1.21, 0.9889. 0.409. 0.9852: 2.21. 0.9423, 0.481, 0.9953. The relative errors of the predicted values are within 0.68% - 0.38% and - 0.34% - 6.88% and - 0.46% - 0.58% of the total validation set. It can be seen that the three models have good prediction effect, high precision and high stability, that is. NIR can be used as a simple, non-destructive, reliable and rapid method for the determination of organochlorine pesticide residues in mesona chinensis benth.

Assessment of organochlorine and organophosphorus pesticides in various meats samples of maharashtra-india using gas chromatography

Chronic pesticide toxicity, recognized as a major health hazard in human food chain, comprises of foods from animal source. Devising analytical methods for estimating pesticide residues will help to monitor the status of these contaminants in animal source foods. In this study, two pesticide groups viz., organochlorine (OC) and organophosphorus (OP) compounds were selected to detect pollutants in various meat samples. To detect these pesticides gas chromatography (GC) method was used, standardized and validated. Validation studies on meat samples included accuracy, precision, linearity, limit of detection and quantification. A total of 240 numbers of meat samples of chicken, buffalo, sheep/goat and pig were collected from three different regions of Maharashtra and used in validation studies. The mean concentration of DDT residues in the chicken, buffalo, sheep/goat and pig meat was found to be 27.34, 10.67, 76.33 and 44.12 pg/kg, respectively. Mean concentration of HCH residues in chicken and pig meat was found to be 7.50 and 112.20 pg/kg, and was not detected in buffalo and sheep/goat meat. Mean concentration of Endosulfan and Aldrin residues in chicken, buffalo and sheep/goat meat were found to be 51.09, 23.18, 211.37 pg/kg and 111.48, 81.85, 54.79 pg/kg, respectively. Chlorpyrifos was not detected in any of the meat samples collected. However, the values of pesticide residue concentration in all the 240 nos. of meat samples were found to be below the MRLs values set by Codex Alimentarius Commission and European Commission Regulation (EC) No. 149/2008. Therefore, it is concluded that the standardized GC method can be used for the detection of pesticides in different matrices.

Impact of DDT residues in feed on thyroid gland and liver secretory activity of Aberdeen-Angus cattle depending on cattle age and sex

Impact of DDT residues in feed on thyroid gland and liver secretory activity of Aberdeen-Angus cattle depending on cattle age and sex

Spatial distribution, source identification, and risk assessment of organochlorines in wild tilapia from Guangxi, South China

Seventy-five wild tilapia samples from six rivers (ten sites) in Guangxi province were collected and analyzed for 53 organochlorine compounds. DDTs, endosulfan, and PCBs were the most dominant compounds found in this study. Tiandong County (TD) and Guigang City (GG) sites were found to be heavily contaminated with high levels of endosulfan (385–925 ng/g lw) and/or DDTs (20.1–422 ng/g lw). The diagnostic ratios indicated that the residues of DDTs and endosulfan in wild tilapia are associated with historical applications as well as the recent introduction of technical DDTs and endosulfan at some sampling sites. The correlation between total length, body mass, and organochlorines (OCs) was higher than the correlation between age and lipid content. There was no significant correlation between organochlorine pesticides (OCPs) and lipid content. Therefore, for organisms, the feeding intensity (related to length and mass) of fish could better reflect degree of pollution than exposure time (age) of fish. The hazardous ratios for the 50th and 95th percentile data of OCPs and PCBs in fish were both below 1, suggesting that daily exposure to OCPs and PCBs yields a lifetime cancer risk lower than 1 in 10,000.

Monitoring of DDT in Agricultural Soils under Organic Farming in Poland and the Risk of Crop Contamination

The analysis of 142 agricultural soil samples collected in organic farms across Poland with the intent to evaluate the level of DDT contamination resulted in more than 80% of the soils containing DDT. The ΣDDT (sum of all metabolites and isomers) concentration ranged between 0.005 and 0.383 mg/kg ΣDDT, with an average value of 0.064 mg/kg ΣDDT. However, the majority of plant samples collected from the crops growing on the sampled soils did not contain detectable DDT residues. The high DDT pollution levels detected in samples from four voivodeships (regions) among those monitored have been hypothesised to be linked to horticultural productions occurring to the sampled fields and typical of those regions, particularly in big-sized farms, during the period of DDT application, as well as the number of pesticides landfills present in these voivodeships. The elaboration of the o,p′-DDT/p,p′-DDT and DDT/(DDE + DDD) ratios to appraise the source or the period of contamination suggested that the contamination originated from past use of DDT rather than from impurities of more recent applications of other formulated substances. Such outcome thus suggests that the risk of contamination of organic products is likely derived from general environmental pollution levels rather than from the use of unauthorised substances in organic farming productions. Data from a trial with artificial contamination of soils indicated that using the DDT/(DDE + DDD) ratio in the presence of a low level of contamination could be less reliable than in highly contaminated soils.

Sediment contamination of an urban canal\u2014a case study approach for an integrated assessment of organic sediment contamination

PurposeThe pesticide DDT and its metabolites represent a contamination risk for the aquatic environment, especially the polar metabolite DDA. The study provides a quantitative assessment of long-term pollution risks from sedimentary DDT residues with a special focus on DDA. It presents an overview of the contamination range of different DDX compounds in the sediments of a canal in Berlin (Germany), resulting from a former industrial point source that has implications for drinking water resources in the nearby area. The comprehensive analysis scheme provides information on free accessible and potentially metabolized precursors also in the non-extractable residues. This allows a quantitative assessment of the DDA pollution potential derived from the sedimentary DDT residues.Materials and methodsThe area was investigated for fine-grained sediment by means of a geo-electric mapping. Twelve sediment cores were taken in four areas (three in each section). A wider range of precursor metabolites has been included due to their transformation potential to the polar metabolite DDA. The sediments were analysed quantitatively for extractable and easily releasable fractions by application of a variety of degradation techniques as well as a dispersion extraction procedure on the sediment samples. These extracts were fractionated and subsequently analysed by GC-MS.Results and discussionConcentrations were obtained for extractable and bound metabolites. Different scenarios for the calculation of the amount of contaminated sediment are displayed as a tool for contamination assessment. The formation potential of DDA as the water-soluble metabolite is presented. Several precursor metabolites, e.g. DDD and DDMS, extractable from the sediment organic matter, revealed a high potential for a long-term formation of DDA, especially in the easily releasable fraction (via hydrolysis) with a mean concentration of up to 11,000 μg g−1 dry sediment. The resulting DDA contamination potential represents a significant pollution risk for the groundwater from a downstream waterworks area and by remobilisation into the whole ecosystem and adjacent rivers.ConclusionsThe application of the presented methods provides a tool for a quantitative assessment of the long-term release potential of DDA under different scenarios by a comprehensive analysis of contaminated sediments (and soils). This approach can be transferred to pollutants that are also characterized by a complex metabolism accompanied by bound residue formation.

Monitoring of adsorption and transfer of organochlorines in soybean seeds and sprouts with mass spectrometric imaging

Development of analytical techniques that can monitor the adsorption, transfer and in-situ distribution of environmental pollutants in agricultural products is essential to ensure the implementation of stringent food safety standards for consumer protection. A mass spectrometric imaging approach is described herein to investigate the dynamic changes and spatial distributions of 4, 4′-DDT (dichlorodiphenyltrichloroethane) in soybean seeds and sprouts during the growth. Soy beans seeds incubated in DDT containing water were sliced in every 20 μm and directly blotted on the surface of a compressed thin film of (Bi2O3)0.07(CoO)0.03(ZnO)0.9 nanoparticles. Endogenous molecules and exogenous DDT compounds in soy bean seeds were ionized and dissociated by photoelectrons that are generated on surfaces of semiconductor nanoparticles upon the irradiation of the 3rd harmonic (355 nm) of Nd3+:YAG laser. Structural identification is achieved by the interpretation of fragment ions resulting from electron-initiated specific bond cleavages or hole oxidization. Mass spectrometric images reveal increased quantities of DDT residues in soy bean seeds and sprouts during the growth. It provides an in situ way without extensive sample preparation to monitor the transfer and distribution of exogenous pollutants as well as the possible impacts on plant growth.

History traces of HCHs and DDTs by groundwater dating and their behaviours and ecological risk in northeast China

Organochlorine pesticides legacies, such as hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), remained in sediments or soils due to their difficulty in decomposition, especially in the agricultural areas where pesticides were widely used historically. Different from the little disturbed depositional environment of lake, it was difficult for rivers to explore the timing of DDT and HCH inputs through dating sediment cores as records. Based on groundwater dating, this study ascertained the historic pollution of DDT and HCH in Taizi River basin. HCH and DDT residues in groundwater were consistent with the historical production and usage, which increased from the 1950s to the 1980s and declined from the 1980s to the 1990s. Moreover, the partitioning behaviours of HCHs and DDTs in surface water and suspended particulate matter were discussed. It was revealed that β-HCH and o,p’-DDT were more likely to attach to suspended particulate matter than other isomers. Furthermore, species sensitivity distribution curves were generated using 54 toxicity data records to assess the risk of HCHs and DDTs in water and suspended particulate matter. These results indicated that p,p’-DDT in surface water posed a high risk to 95% of the aquatic life in the long run.

Occurrence of Carbaryl, DDT and Deltamethrin Residues in Bovine Milk in Chhattisgarh, India and Risk Assessment to Human Health

The aim of this study was to determine the occurrence of pesticide residues in bovine milk and associated health risks in human. To assess the pesticide residues, a total of 200 milk samples were analyzed using High Performance Liquid Chromatography (HPLC) with Photo Diode Array Detector (PDA).The residues of carbaryl, 4’4’ DDT and deltamethrin pesticides were found in the 27.5%, 11% and 5% milk samples, respectively. The spatial distribution of pesticide residues in milk samples indicated that carbaryl was wide spread over the entire study area. The non-significance differences in mean residual concentrations of all three pesticides in cow and buffalo milk samples were recorded. The human health risk assessment in terms of non-carcinogenic and carcinogenic health hazard was calculated based on both lower bound [LB (mean residue levels)] and upper bound [UB (95th percentile level)] limits at current levels of pesticides in bovine milk samples. The estimated average daily dietary intake (EADDI) of studied pesticides was found below the acceptable dietary intake (ADI) for both adult and children, at mean as well as 95th percentile upper bound (UB) levels. The values suggesting lower carcinogenic and non-carcinogenic health risk to adult however children are at greater health risk.

Organochlorine Pesticides in Sediment of Zhang River Estuary Mangrove National Natural Reserve: The Implication of Its Source Change in China’s Mangroves

Seventeen organochlorine pesticides (OCPs) were examined in surface sediments from Zhang River Estuary Mangrove National Natural Reserve, which is situated in the Fujian province in southeast China. The range of ∑OCPs concentration was 0.29–25.41 ng/g dry weight (average 4.53 ng/g), ∑HCHs was 0.008–0.906 ng/g dry weight (average 0.240 ng/g), and ∑DDTs was ND–4.743 (average 0.664 ng/g). The concentrations of the HCH isomers were observed in the following decreasing order: α-HCH > β-HCH > δ-HCH > γ-HCH, and that of the DDT isomers were as in the following order: p,p’-DDT > p,p’-DDE > p,p’-DDD. According to the analysis of the isomer ratios, γ-HCH (lindane) and endosulfan were rarely used recently around this mangrove forest. Instead, the ratios of (DDD+DDE)/DDT showed that DDTs were still illegally used. Compared with other mangroves in China, the residue level and ecological risk of the OCPs in surface sediment from ZREMNNR are both at a low level. Based on stepwise regression analysis, current fruit planting, as well as mariculture in developed areas and vegetable planting in developing areas, had a positive relation with DDT residues in mangrove sediment in China. Oppositely, HCH residues in mangrove sediment were derived from historical consumption, and generally the higher levels occurred in the developed areas. Through this study, we help to close the knowledge gap of OCPs in China’s mangroves and provide a possible management implication for sustainable development in the future.

Assessment of Organochlorine Pesticides Residues in Tilapia fish (Oreochromis niloticus)

The current study aimed to determine organochlorine pesticides (OCPs) residues in muscle tissues of Tilapia (Oreochromis niloticus) with different weights collected randomly from different localities at Cairo and Giza markets by Gas Chromatoghraphy. The total mean values of DDT, DDD, DDE, Endrin, Dieldrin, Endosulfan, γ-chlordane, δ-BHC, Hepatochlor epoxide, Methoxychlor and Hepatochlor residues in the examined samples of tilapia were 16.82 ± 4.7, 44.80 ± 4.65, 8.34 ± 1.42, 26.54 ± 3.13, 10.91 ± 2.72, 6.20 ± 1.17, 21.32 ± 3.44, 16.17 ± 3.07, 5.33 ± 10.67 , 1.24 ± 0.31 and 1.28 ± 0.31 ng/g, respectively. Accumulation of organochlorine pesticides in fish tissues was related to rate of pollution, lipid content, feeding behavior, rate, size and age. There were significant differences between organochlorine pesticides residues and different weights of tilapia. Most of the examined samples were within the maximum permissible limits of pesticides residues according to US-FDA (2008) and Codex Alimentarius Commission (1996) and should not pose a health risk to consumers. The public health hazards of organochlorine pesticides residues were discussed.

Detection of DDT and carbaryl pesticides in honey by means of immunosensors based on high fundamental frequency quartz crystal microbalance (HFF-QCM).

In recent years there has been a concern about the presence of pesticides in honey because residues of DDT and carbaryl were found in honey samples. Traditional techniques, such as chromatography, reach the required limits of detection (LOD) but are not suitable for in situ implementation in the honey-packaging industry due to their high cost and the need for highly qualified staff for routine operation. Biosensors offer simplicity, low cost, and easy handling for analytical purposes in food applications. Piezoelectric immunosensors based on high fundamental frequency quartz crystal microbalance (HFF-QCM) have been developed for the detection of carbaryl and DDT in honey. Biorecognition was based on competitive immunoassays in the conjugate-coated format, using monoclonal antibodies as specific immunoreagents. The assay LODs attained by the HFF-QCM immunosensors were 0.05 μg L-1 for carbaryl and 0.24 μg L-1 for DDT, reaching a similar level of detectability to that of the usual reference techniques. The practical LODs in honey samples were 8 μg kg-1 for carbaryl and 24 μg kg-1 for DDT. The immunosensors' analytical performance allow the detection of these pesticides in honey at EU regulatory levels with good accuracy (recovery percentages ranging from 94% to 130% within the working range of each pesticide standard curve) and precision (coefficients of variation in the 9-36% range). The proposed immunosensor is a promising analytical tool that could be implemented for quality control in the honey packaging industry, to simplify and to reduce the cost of the routine pesticide analysis in this appreciated natural food. © 2020 Society of Chemical Industry.

Concentration, characterization and risk assessment of polycyclic aromatic hydrocarbons and organochlorine pesticides in soils from the Corn Belt of northeast China

AbstractOrganic contaminants in agricultural soils are widely reported; however, their accumulation patterns are quite different among regions. This study reports the distribution, accumulation and risk assessment of polycyclic aromatic hydrocarbons (PAHs), dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) in soils from the Corn Belt of northeast China at a regional scale. Concentrations of PAHs, DDT and HCH were 306‐5300, 6.00–82.0 and 4.07–15.6 ng g−1, respectively. Source analysis suggests PAHs were derived from regional combustion of biomass and coal, except where sites are strongly affected by local sources. The DDT and HCH residues in soils are likely to be derived from previous agricultural applications that have persisted due to slow microbiological degradation under low mean temperatures. Precipitation was only significantly correlated with PAH concentrations, suggesting that precipitation affected PAH but not DDT and HCH distributions at a regional scale. Positive correlations between DDT concentrations and total organic carbon (TOC) contents of soils suggest hydrophobic organic contaminants were associated with organic matter. In contrast, TOC contents were correlated with PAHs in alfisols but not in pedocals. Pedocals contained mainly high molecular weight PAHs, indicating that eluviation affected the accumulation of less hydrophobic organic contaminants. Different correlations between low‐molecular‐weight PAH and HCH concentrations with TOC contents were found in alfisols, suggesting that contaminant structure may also affect the accumulation of less hydrophobic organic contaminants in these soils. Risk analysis suggested that potential ecological risks related to soils in the Corn Belt may lead to reduced maize production and the potential for human health risks in the future.Highlights Few studies focus on regional‐scale factors that affect organic contaminant accumulation in soils. Environmental process affects less hydrophobic organic contaminant distribution at regional scale. Precipitation and eluviation affected accumulation of less hydrophobic contaminants in soils. PAH and OCP residues in the soil of maize fields may pose ecological risks affecting future crop production and human health.

Residues and sources of HCHs and DDTs in the sediments of land-based sewage outlet to the Zhanjiang Bay, China

Due to the large usage of DDT-containing antifouling paints and lindane in China, heavy residuals of DDTs and HCHs have been found in many fishing harbors, but there is lack of studies on this issue for the Zhanjiang Bay which is an important fishing harbor and mariculture zone in South China. To evaluate the pollution status and sources of HCHs and DDTs in the Zhanjiang Bay, the concentrations, spatial distributions and sources in the sediments of 11 land-based sewage outlets to the Zhanjiang Bay were investigated. Since the 1980s, HCHs residuals had obviously decreased in studied areas, but DDTs had little change, even abnormally high levels were found in some sites. The content percentages and diagnostic ratios of HCHs isomers and DDTs showed that the source of HCHs was derived from soils around the bay and recent input of lindane, and DDTs were from historical residues of technical DDTs and fresh input of DDT-containing antifouling paints on fishing ships. Based on sediment quality guidelines, DDTs would be of more concern for the ecotoxicological risk on marine environment and adverse effects on benthonic organisms. This study indicated that lindane and DDT-containing products may be still used in some places of Zhanjiang City. It should be urgent to control their usage and clean the DDTscontaminated sites by the local government.

HCHs and DDTs in the Bohai Sea: Contamination, distribution and sources

Concentrations, distributions, and potential sources of DDTs and HCHs in seawater, sediments, soils, and atmosphere were collected to review their pollution statuses in the Bohai Sea and its coastal areas. In comparison to various sediment and seawater quality standards, DDTs and HCHs in sediments and seawater were at low levels in the entire Bohai Sea and might not cause adverse biological effects. However, DDTs and HCHs levels in various sea areas were closely associated with local pesticides production and application as well as hydrodynamic. DDTs and HCHs showed an obvious spatial distribution pattern. High levels were found in the Bohai Bay, Haihe River and Yellow River estuary. DDTs and HCHs concentrations in river and estuary sediments were higher than sea sediments and a seaward decreasing trend was observed. Although HCHs and DDTs residues in the Bohai Sea primarily originated from river runoffs (pesticide factory wastewater, historical applications and residues of technical HCH and DDT, etc.), additional sources of lindane and dicofol existed. Runoff from the demolished old pesticide factories might be another source. Further researches are highly recommended on pollution hotpots of DDTs and HCHs and investigate their migration and transformation at sediment-water interface and pollution history from sediment depth profiles.