Using Isomeric and Metabolic Ratios of DDT To Identify the Sources and Fate of DDT in Chinese Agricultural Topsoil

Organochlorine pesticides: occurrence, spatial distribution of residues, toxicity, and toxic mechanisms

Organochlorine pesticides (OCPs) are a class of synthetic, broad-spectrum insecticides that have been widely used for plant pest control over the last century. OCPs are persistent organic pollutants (POPs) with mutagenic, teratogenic, and carcinogenic properties. Although most OCPs are banned to use now, they are ubiquitous in the environment and food, and identified in the serum and urine of humans. Exposure to OCPs could affect the human nervous system, auditory system, and endocrine system, leading to neurodegenerative diseases, hearing loss, cancer, and other diseases. Further, the toxic mechanisms of OCPs are explored from oxidative stress, DNA damage, and inflammatory response. Overall, this review offers a comprehensive insight into the occurrence, spatial distribution of residues, toxicity, and toxic mechanisms of OCPs.

Preparation of a national reference material organochlorine pesticide mixture for residue analysis

Feasibility studies were carried out for the preparation of a national reference pesticide mixture. Three mixtures containing 12 organochlorine pesticides were prepared. One was prepared volumetrically and two were prepared gravimetrically. α-HCH, γ-HCH, aldrin, dieldrin, endrin, 4,4'-DDD, 4,4'-DDT, 2,4'-DDT, α-endosulfan, β-endosulfan, heptachlor and heptachlor endo-epoxide were analysed in gravimetric mixtures, and except for heptachlor endo-epoxide, the same pesticides were analysed in volumetric mixtures. Short- and long-term stability tests of organochlorine pesticides were performed at 20 °C to determine transport behaviour and at +4 °C and -20 °C to determine behaviour under optimal storage conditions. The most stable temperature was considered -20 °C. There is no significant change in the concentration of the pesticides determined weekly and monthly in the mixtures over a period of 5 months. The uncertainty of these pesticides was calculated with respect to the uncertainty of homogeneity, short- and long-term stability, purity of standards, GC-MS calibration plot and uncertainty of characterization according to ISO Guide 17034. Consequently, the uncertainty results for α-HCH, γ-HCH, aldrin, dieldrin, endrin, 4,4'-DDD, 4,4'-DDT, 2,4'-DDT, α-endosulfan, β-endosulfan, heptachlor and heptachlor endo-epoxide were determined to be around 0.5, 0.5, 0.3, 0.2, 0.4, 0.6, 0.8, 0.7, 0.3, 0.3, 1.2 and 0.5 in gravimetric mixtures for 100 ppm. In volumetric mixtures, their uncertainties were determined to be 2.4, 3.1, 4.1, 2.7, 15, 2.8, 4.1, 3.9, 3.2, 3.6 and 12.6 for 80 ppm, respectively.

Legacy and currently-used pesticides in sedimentary archives: Anthropogenic footprint in the pearl river estuary

Pesticides are fundamental to modern agriculture but pose significant environmental risks due to their persistence, bioaccumulation potential, and toxicity. This study systematically investigates the pollution characteristics and historical trends of 28 legacy organochlorine pesticides (OCPs) and 17 currently-used pesticides (CUPs) in a sediment core from the Pearl River Estuary (PRE), assessing their potential as Anthropocene markers. The concentrations of Σ28OCPs ranged from 0.788 to 9.12 ng/g, dominated by dichlorodiphenyltrichloroethanes (DDTs, 49 ± 21 %) and chlordane (9 ± 6 %), while the Σ17CUP concentrations were an order of magnitude higher, ranging from 4.85 to 98.4 ng/g, with pyrethroids contributing 50-99 %. This shift in pesticide composition reflects the historical transition from OCPs to CUPs in China's pesticide usage. Temporal trends (1919-2019) showed that the concentrations of DDTs, chlordane, pyrethroids, and dicofol closely mirrored their usage history in China, demonstrating that sediment cores effectively record pesticide application history. Redundancy analysis identified total organic carbon, temperature, and precipitation as key environmental factors influencing the concentrations of DDTs, chlordane, pyrethroids, and dicofol. Correlation analysis further demonstrated that the concentrations of DDTs and phenothrin were linked to population, GDP, and agricultural activities, whereas dicofol, parathion-methyl, and bromophos-ethyl were primarily driven by agricultural activities. Moreover, DDT exhibited temporally abrupt trends, broad geographic signals, and permanent environmental records, suggesting its potential as a robust Anthropocene marker. This study provides critical insights into pesticide pollution dynamics and highlights the value of legacy and emerging pollutants in tracking human impacts on Earth's environmental systems.

Whale shark Rhyncodon typus exposure to organochlorine pesticides in the Southern Gulf of California, Mexico

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs), characterized by their high mobility and environmental persistence, bioaccumulation, and trophic transfer. Considering the highly migratory nature and longevity of the whale shark, this species can be considered as an early warning bioindicator of regional contamination from the marine environment. This work investigated the concentration of twenty OCPs in thirty whale shark skin biopsies, collected between 2014 and 2015 in Bahía La Paz (Gulf of California, Mexico). Mean detected OCP levels were 33.99 ± 105.23 ng/g dw (dry weight), and ΣChlordane, ΣDrin, and ΣHCH showed the highest concentrations. Statistically differences in mean OCP concentration were not found by sex and size. PC1 and PC2 accounted for 68.1 % and 16.1 % of the total variance, respectively. The presence of higher levels of some pesticides than their corresponding metabolites suggests recent applications related to agricultural activity in the surrounding areas of Baja California peninsula.

Isomer, enantiomer and compound-specific stable isotope evidences for the transformation of dichlorodiphenyltrichloroethanes (DDTs) in soils from three typical paddy fields in China

Chlorinated pollutants may follow distinct degradation pathways in anaerobic environments compared to aerobic settings. However, the understanding of the behaviors and fate of dichlorodiphenyltrichloroethanes (DDTs) under anaerobic conditions remains limited. To address this knowledge gap, we conducted a study on flooded soil samples collected from three typical paddy fields in China using an integrated approach of enantiomer-specific analysis and compound-specific stable carbon isotope analysis. It is unexpected that the dichlorodiphenyldichloroethane /dichlorodiphenyldichloroethylene ratios (DDD/DDE=(o,p'-DDD+p,p'-DDD)/(o,p'-DDE+p,p'-DDE)) were below 1 in over 90 % of the samples. This might be attributed to the higher recalcitrance of p,p'-DDE, which concentrations were found to be 36 times higher than p,p'-DDD on average. There were 71.7 % of the samples showing enantiomeric fractions (EFs) of o,p'-DDT below 0.5, indicating a preferential accumulation of the (-)-enantiomer. The δ13C values of the anaerobic metabolite o,p'-DDD (-24.76 ± 1.35 ‰ to -34.39 ± 0.20 ‰) all deviated negatively from the initial product, while those of the aerobic metabolite o,p'-DDE (-23.61 ± 0.48 ‰ to -38.95 ± 0.81 ‰) displayed either negative or positive deviations. This demonstrates that o,p'-DDD is the primary metabolite of o,p'-DDT under anaerobic conditions. However, no clear correlations were observed between the δ13C and EF of o,p'-DDT. This study underscores the importance of such an integrated methodology in unraveling the fate and behaviors of DDTs in complex environmental systems.

Deciphering the key factors affecting pesticide residue risk in vegetable ecosystem

Soil contamination, particularly from pesticide residues, presents a significant challenge to the sustainable development of agricultural ecosystems. Identifying the key factors influencing soil pesticide residue risk and implementing effective measures to mitigate their risks at the source are essential. Here, we collected soil samples and conducted a comprehensive survey among local farmers in the Three Gorges Reserve Area, a major agricultural production region in Southwest China. Subsequently, employing a dual analytical approach combining structural equation modeling (SEM) and random forest modeling (RFM), we examined the effects of various factors on pesticide residue accumulation in vegetable ecosystems. Our SEM analysis revealed that soil characteristics (path coefficient 0.85) and cultivation factor (path coefficient 0.84) had the most significant effect on pesticide residue risk, while the farmer factors indirectly influenced pesticide residues by impacting both cultivation factors and soil characteristics. Further exploration using RFM identified the three most influential factors contributing to pesticide residue risk as cation exchange capacity (CEC) (account for 18.84%), cultivation area (account for 14.12%), and clay content (account for 13.01%). Based on these findings, we carried out experimental trials utilizing Integrated Pest Management (IPM) technology, resulting in a significant reduction in soil pesticide residues and notable improvements in crop yields. Therefore, it is recommended that governmental efforts should prioritize enhanced training for vegetable farmers, promotion of eco-friendly plant protection methods, and regulation of agricultural environments to ensure sustainable development.

The effect of farming techniques on degradation of DDT in historical cotton farms

DDT was used in the mid 20th century for crop and livestock production. After use, DDT and its degradates DDE and DDD (collectively DDX) remain in the environment for decades. A few studies have reported that the rate of degradation of DDT into its metabolites is affected by various farming techniques like tillage, irrigation, and use of fertilizers. However, most of these studies did not evaluate active farms, and none of them focused on the Southeast US or historical cotton farms. Therefore, in this study, we aimed to determine if different farming techniques affect the decomposition of DDT in Walton County, Georgia, where farms historically grew cotton. Five Walton County farms were sampled for soil, and churches were sampled as control sites. The extensive land history of the farms was recorded, and the soil levels of p,p'-DDT, p,p'-DDE, p,p'-DDD, o,p'-DDT, and o,p'-DDE were measured using gas chromatography-tandem mass spectrometry. All farm sites had detectable levels of p,p'-DDT, p,p'-DDE, and p,p'-DDD, while few sites had detectable levels of o,p'-DDT and o,p'-DDE. Tillage was found to speed up p,p'-DDE degradation, but there was no effect on p,p'-DDT degradation. Plowing was associated with an increase in decomposition of p,p'-DDT, but p,p'-DDE and p,p'-DDD were not significantly increased. The largest difference in the degradation of DDT was based on the fertilizer type. Natural fertilizer sped up degradation of p,p'-DDT and p,p'-DDE; synthetic fertilizer increased p,p'-DDE degradation, but not p,p'-DDT degradation.

Systematic investigation of organochlorine pesticides and polychlorinated biphenyls blood levels in Greek children from the Rhea birth cohort suggests historical exposure to DDT and through diet to DDE

The blood levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) have been thoroughly investigated in Greek children from the Rhea birth cohort study. This investigation aimed to assess exposure levels, explore their possible relationship with children's age and sex, and indicate potential sources of exposure. Exposure patterns and common sources of PCBs and OCPs were analyzed using bivariate and multivariate statistics. A total of 947 blood samples from study participants were analyzed for OCP and PCB exposure, with 375 samples collected at 4 years old, 239 at 6.5 years old, and 333 at 11 years old. Elevated levels of DDE were observed in 6.5-year-old children compared to corresponding levels in other European countries. Higher levels of DDE were found in 4-year-old children, with the lowest concentrations in the 11-year-old group. The DDT/DDE ratio was consistently less than 1 among all the examined subjects. These results indicate exposure to DDT and DDE both in utero and through breastfeeding and dietary intake. For the entire cohort population, the highest concentration was determined for PCB 28, followed by PCBs 138, 153, and 180. The sum of the six indicator PCBs implied low exposure levels for the majority of the cohort population. Spearman correlations revealed strong associations between PCBs and OCPs, while principal component analysis identified two different groupings of exposure. DDE exhibited a correlation with a series of PCBs (153, 156, 163, 180), indicating a combined OCP-PCB source, and an anticorrelation with others (52, 28, 101), implying a separate and competing source.

Development and application of a new QuEChERS-molecularly imprinted solid phase extraction (QuEChERS-MISPE) technique for analysis of DDT and its derivatives in vegetables

The current study synthesized a molecularly imprinted polymer, combined it with the QuEChERS method to form a new hybrid technique, the QuEChERS-MISPE as an alternative to the QuEChERS-dSPE for analysis of DDTs as model pesticides. Batch studies confirmed that the binding of the DDTs to the MIP cavities formed a monolayer formation through chemisorption resulting in an adsorption capacity of 429 ng g-1. A study of matrix effects indicated signal suppression for both techniques. However, the new QuEChERS-MISPE technique is less affected by matrix effects, has better sensitivity and recoveries compared to the conventional QuEChERS-dSPE technique. Application of the new QuEChERS-MISPE technique detected trace levels of DDTs in vegetables in South Africa. However, a health risk assessment indicated that potential risks for consumers was minimal. Although the risk is minimal, the detection of DDTs in vegetables in South Africa should be a concern and more constant monitoring is required.

Distribution, sources and health risk assessment of DDT and its metabolites in agricultural soils in Zhejiang Province, China

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been officially banned as a pesticide around the world. However, DDT pollution still exists in natural environments in China because DDT degrade very slowly. In this study, 60 soil samples were collected from Cixi, Zhejiang Province, and the levels of DDTs and its metabolites in soil and health risks were investigated. The results showed that the detection rate of DDT in soil samples were 100%, and the total DDTs residue in soil ranged from 0.007 to 1.208 mg/kg, with an average of 0. 113±0. 035 mg/kg, which exceeded the second-level Chinese soil environmental quality standard for farmland soil. The average residuals of p,p'-DDT, p,p'-DDE (dichlorodiphenyldichloroethylene), p,p'-DDD (dichlorodiphenyldichloroethane) and o,p'-DDT accounted for 34.8%, 50.9%, 8.0% and 6.3% of the total DDTs, respectively. The DDD/DDE ratios indicated a dehydrochlorination of DDT to DDE under aerobic conditions at most sampling sites. The ratios of (p,p'-DDE+p,p'-DDD)/p,p'-DDT and o,p'-DDT/p,p'-DDT indicating the DDT in the field were mainly introduced via industrial DDT and dicofol, including historical residue and fresh input. The health risk assessment showed that DDT-contaminated sites do not pose a non-carcinogenic risk to humans, and pose a very low risk of cancer to children and a low risk of cancer to adults. Overall, this study helps to understand the distribution, sources and health risks of DDT in typical soils.

Contamination of Soil by Obsolete Pesticide Stockpiles: A Case Study of Derince Province, Turkey

The areal distributions of the soil organochlorine pesticide (OCP) levels were investigated at adjacent and surrounding sites of the obsolete pesticide stockpile warehouse in Kocaeli, Türkiye. OCP levels in soil at neighboring sampling locations (positioned at 0.4 to 3 km from the stockpile) varied from 0.4 to 9 µg/kg and 4.2 to 2226 µg/kg (dry weight) for ΣHCHs and ΣDDXs, respectively. Levels at adjacent locations (positioned within 20 m from the stockpile) were considerably higher, varying from 74 to 39,619 µg/kg and 1592 to 30,419 µg/kg for ΣHCHs and ΣDDXs, respectively. Levels of OCPs dropped abruptly with the horizontal distance from the stockpile and had different transect profiles. The enantiomer fractions (EFs) near the stockpile range from 0.494 to 0.521, 0.454 to 0.515, and 0.483 to 0.533 for α-HCH, o,p'-DDT, and o,p'-DDD, respectively. These near-racemic EFs suggested that observed soil OCP levels were mainly influenced by recent emissions from the stockpile. A comparison of OCP compositions observed in the soil at the present study with the technical HCHs and DDTs revealed that the material in the stockpile primarily contains byproducts that were discarded during DDT and Lindane production at the adjacent plant instead of their technical mixtures.

Persistent Organic Pollutants in Whale Shark (Rhincodon typus) Skin Biopsies from Bahía de Los Ángeles, Mexico

The whale shark (Rhincodon typus) is a filter-feeding organism that can be considered a sentinel species, and Bahía de los Ángeles (BLA) in the Gulf of California is an important sighting site for these elasmobranchs. This filter-feeding organism can be considered a pollutant sampler from the marine environment. Persistent organic pollutants are toxic compounds with high mobility and environmental persistence, bioaccumulation and trophic transfer. Among these are polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs). The present work aimed to determine concentrations of PAHs and OCPs in whale shark skin biopsies, collected in 2021 at BLA. Mean detected levels of PAHs and OCPs were 279.4 ng/g dw (dry weight) and 1478.1 ng/g dw, respectively. Analysis of similarities between the ordered sizes (4.2-7.6 m) and the concentrations of PAHs and OCPs indicated no significant differences. Individual PAHs detected indicate pyrogenic and petrogenic sources; the presence of pesticides at levels higher than those of hydrocarbons may be related to agricultural activity in the areas surrounding the Baja California peninsula. This study is the first report of PAH levels in R. typus for the Gulf of California and Mexico.

Cross-sectional and longitudinal associations of dichlorodiphenyltrichloroethane (DDT) metabolites exposure with lung function alternation in the Chinese general adults

Exposure of dichlorodiphenyltrichloroethane (DDT) pesticide was suggested to be associated with adverse effects on the respiratory system. However, the effects of DDT exposure on lung function remain unclear. Our objectives were to investigate the potential associations of internal levels of DDT and its metabolites including dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) with lung function. Serum DDT, DDE, and DDD concentrations and lung function were measured among 3968 general adults from the Wuhan-Zhuhai cohort. The cross-sectional and longitudinal associations of serum DDT and its metabolites with lung function were assessed using linear mixed models. The results showed negative dose-response relationships of serum DDT, DDE, and DDD levels with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). In the cross-sectional analyses, each 1-unit increase in natural log-transformed values of p,p'-DDE, o,p'-DDT, o,p'-DDE, or p,p'-DDD was significantly associated with a 25.77-, 44.84-, 51.13-, or 43.44-mL decrease in FVC, respectively. Each 1-unit increase in natural log-transformed values of o,p'-DDT, o,p'-DDE, o,p'-DDD, or p,p'-DDD was significantly associated with a 35.72-, 31.87-, 29.54-, or 36.80-mL decrease in FEV1, respectively. In the three-year longitudinal analyses, each 1-unit increase in natural log-transformed serum p,p'-DDT and p,p'-DDE was significantly associated with a 35.10 mL and 36.38 mL decrease in FVC, and a 26.32 mL and 32.37 mL decrease in FEV1, respectively. In conclusion, DDT and its metabolites exposure were associated with lung function decline in the general Chinese adult population.

Cross-regional scale studies of organochlorine pesticides in air in China: Pollution characteristic, seasonal variation, and gas/particle partitioning

Few simultaneous studies of organochlorine pesticides (OCPs) in the atmosphere have been conducted across Southeast and Northeast China, and no data on the gas/particle (G/P) partitioning behaviors of several current-use OCPs are available. In this study, a one-year synchronous monitoring program was conducted for OCPs in Chinese atmosphere spanning 30° latitude and 60 °C temperature. A total of 111 pairs of gas and particle samples were collected from Mohe and Harbin in Northeast China and from Shenzhen in Southeast China. The detection frequency for 66.7 % of the OCPs exceeded 80 %, indicating their prevalence in the atmosphere. The concentrations of individual OCPs spanned six orders of magnitude, indicating different pollution levels. Highest levels of hexachlorobenzene were observed at all sites. Banned OCPs were found predominantly in secondary distribution patterns, whereas current-use OCPs were dominated by primary distribution patterns. In Harbin and Mohe, the concentrations of OCPs were highest in summer, followed by autumn and winter. No obvious seasonal variation was observed in Shenzhen associated with different cultivation types. At all three sites, OCPs were predominantly found in the gas phase, and higher percentages of particle-phase OCPs were observed in Harbin and Mohe than in Shenzhen. In this study, G/P partitioning models were used to study the G/P partitioning mechanism of OCPs. The Li-Ma-Yang model provided the most accurate prediction of the G/P partitioning behavior of OCPs with high molecular weights and low vapor pressures, particularly at low temperatures. However, OCPs with lower molecular weights and higher vapor pressures were predominantly in the equilibrium state, for which the Junge-Pankow model was suitable. This systematic cross-scale study provides new insights into pollution, G/P partitioning, and the environmental behavior of OCPs in the atmosphere.

New and legacy pesticidal persistent organic pollutants in the agricultural region of the Sultanate of Oman

Comprehensive air and surface soil monitoring was conducted for new and legacy organochlorine pesticides (OCPs) to fill the knowledge and data gap on the sources and fate of pesticidal persistent organic pollutants (POPs) in the Sultanate of Oman. DDTs in agricultural soil samples ranged from 0.013 to 95.80 ng/g (mean: 8.4 ± 25.06 ng/g), with a median value of 0.07 ng/g. The highest concentration was observed at Shinas, where intensive agricultural practice is prevalent. The dominance of p,p'-DDT in soil and air reflected technical DDT formulation usage in Oman. Among newly enlisted POPs, pentachlorobenzene had the maximum detection frequency in air (47%) and soil (41%). Over 90% of sites reflected extensive past use of hexachlorobenzene. Major OCP isomers and metabolites showed net volatilisation from the agricultural soil, thereby indicating concurrent emission and re-emission processes from the soil of Oman. However, the cleansing effect of oceanic air mass is the possible reason for relatively lower atmospheric OCP levels from a previous study. Although DDT displayed maximum cancer risk, the level is below the permissible limit. DDT primarily stemmed from obsolete stock and inadequate management practices. Hence, we suggest there is a need for DDT regulation in Oman.

Primary emissions or environmental persistence contribute to the present DDTs: Evidence from sediment records in Tibetan lakes

Dichlorodiphenyltrichloroethane (DDT) compounds are still circulating the global environment even though the technical DDT has been restricted in agriculture since the last century. The persistent presence of DDTs worldwide remains uncertain, as it is unclear whether their existence is primarily due to ongoing use or the prolonged persistence in soils and sediments that result in continuous reemission into the atmosphere. The present study applied a sequential extraction procedure to determine the DDT concentrations in rapid desorption, slow desorption, and bound residue fractions in the dated sediment cores from distinct regions of Tibet. The temporal variation of total DDTs (sum of three fractions) in sediments from southern and eastern Tibet respectively revealed the different DDT usage histories in India and China mainland. Nevertheless, the current application volumes of DDT-containing products in these regions were found to decrease significantly. The reversible transformations among three fractions of DDTs with aging time was observed along sediment profile, including the back conversion from bound residue. This process may be the key driver to prolong the half-life of sediment p,p'-DDT, resulting in the persistence of secondary sources of this persistent organic pollutant in the global environment for a longer duration than previously expected.

Status, sources, and human health risk assessment of DDT pesticide residues in river sediments in a highly developed agricultural region in the upper Yangtze River in China

The concentrations of DDT and its metabolites in 19 sediment samples from a highly developed agricultural region in the upper reaches of the Yangtze River were measured. Non-carcinogenic hazard quotient for different age groups was evaluated using reference doses provided by the USEPA, and the excess lifetime cancer risk due to eating fish was assessed based on the local eating habits. The results showed that this region had a high level of residual DDT (12.84 ± 8.97 ng/g), which mainly came from the historically used technical DDT in agriculture. The non-carcinogenic risk was just acceptable in the region, but 11 of the 19 sites showed an unacceptable carcinogenic risk. Although DDT has been banned for decades, there were still notable health risks, especially for children. Special attention should be given to the potential health risks in historically developed agricultural regions.

A new insight into the emission source of DDT in indoor environment from rural area of South China and comprehensive human health exposure assessment

Human exposure to dichlorodiphenyltrichloroethanes (DDTs) and the subsequent risk to human health remain an important concern due to the "new" input of DDTs in the environment, especially since exposure to DDTs in indoor microenvironments is often ignored. In this study, we identified a new source of DDT emission in indoor environments and evaluated the health risk from the exposure to DDTs by investigating DDTs in indoor and outdoor dust, air, and coatings of household items in rural areas of Qingyuan, South China. The concentrations of DDTs in house dust and air were < MQL (method quantification limit)-3450 ng/g (median 42.4 ng/g) and 22.7-965 pg/m³ (median 49.5 pg/m³), respectively, which were significantly higher than the outdoor DDT values. Dichlorodiphenyldichloroethylene (DDE) was the main isomer in air samples, while DDT was the dominant isomer in indoor dust. Significant correlations between different DDT isomers were observed in indoor samples but not in outdoor samples. Furniture coating was identified as a source of DDTs in the indoor dust. The total daily exposure dose of DDTs (1.75 × 10^-2 ng/kg bw/day for adults and 1.28 × 10^-1 ng/kg bw/day for toddlers) through inhalation, dust ingestion, and dermal contact was found unlikely to pose a health risk. Our findings provide new insights into the emission sources and health risks caused by DDT indoors, highlighting the need to further investigate the toxicity mechanisms of parent DDT compound.

Development of structural equation models to unveil source-sink switches of mid-latitude soils for semi-volatile banned pesticides

A variety of semi-volatile banned pesticides (SVBPs) are ubiquitous in soils of mid-latitude regions. SVBPs undertake complicated soil-gas exchange processes in mid-latitude regions, challenging the understanding of source or sink roles of soils for the semi-volatile contaminants. Herein, we develop structural equation models (SEMs) to unveil source or sink roles of mid-latitude soils (Liaoning, China) in winter and summer for 12 SVBPs (7 organochlorine and 5 organophosphorus pesticides). The 12 SVBPs exhibit different distribution patterns in soils, dependent of sampling seasons, soil characteristics, topographic/climate conditions of soil sites and chemical properties of compounds. SEM Model I (winter) and Model II (summer) reveal the distribution patterns of SVBPs in soils over season changes, indicating sink-source switches of soils for SVBPS from winter to summer. In winter, soil is a sink of 12 SVBPs in the study area, associated with the inputs of SVBPs in soils by air-particulate partition and dry depositions. However, in summer, soil is mainly a source of the same contaminants, mainly through the volatilization and leaching of SVBPs in soils. The sink-source switches of soils for SVBPs are usually dependent of chemical properties of compounds to higher extents than soil characteristics and topographic/climate conditions of soil sites, though these parameters pose different influences in winter and summer. It has been revealed that soil acts as a sink of SVBPs in winter, associated with the inputs of SVBPs in soils by air-particulate partition and dry depositions, whereas soil acts as a source of SVBPs in summer, mainly through the volatilization and leaching of SVBPs in soils. This finding may provide new insights into the unique distribution patterns of SVBPs in soils in mid-latitude regions.

Exposure patterns, chemical structural signatures, and health risks of pesticides in breast milk: A multicenter study in China

China is the world's largest pesticide user. These chemicals are bioaccumulative in the human body, and eventually could be transferred from the mother to the fetus/infant via placental and breastfeeding transport, which might pose developmental deficiency risks. In this study, human biomonitoring of legacy pesticides was conducted in three Chinese cities using 60 breast milk samples. The patterns, chemical structural signatures, and the estimated daily intake of pesticides were assessed. The median concentration of HCB (57.8 ng g^-1 lw, Interquartile range: 28.5-76.9 ng g^-1 lw) was the highest among all pesticides, whereas the HCHs, DDXs, TCVP, and heptachlor were also detected. A significantly different pattern of pesticides was found among three sampling cities: the Mianyang cases were mostly DDXs oriented while the Wuhan and Hangzhou cases were under HCB, HCHs, TCVP, and heptachlor influences. Maternal age and pre-pregnancy BMI were found to be the influencing factors for the pesticides in the breast milk, and dietary preferences were an important factor in the exposure scenario. Chemical structural signatures indicated that for HCHs and DDXs the exposure was mostly historical, while the lindane and dicofol exposure may exist among the volunteering mothers. The EF for chiral pesticides did not deviate significantly from the racemic value. The risk from breastfeeding was negligible according to the Chinese and UN standard, while some cases from Hangzhou and Wuhan exceeded the Canadian restrictions. Thus, the adverse health effects of chemical exposure by dietary intake for infants need to be closely monitored in future studies.

Evaluation of residual level and distribution characteristics of organochlorine pesticides in agricultural soils in South Korea

In this study, we evaluated the residual levels and distribution characteristics of 10 organochlorine pesticides (OCPs) in the soil of agricultural lands (paddy field, vegetable field, and orchard, n = 150) nationwide. As a result of the investigation, 3-10 types of OCPs were detected in combination in 144 locations (96%) of the total 150 locations. Among those OCPs, dichlorodiphenyltrichloroethane (DDT) and endosulfan were detected in high amounts. The geometric mean concentrations of DDT and endosulfan were ∑DDT 0.31 ng g^-1 (ND-2187.18 ng g^-1) and ∑endosulfan 0.33 ng g^-1 (ND-312.68 ng g^-1), respectively. OCP concentrations were generally higher in orchards than in other agricultural fields due to a large amount of pesticides used. DDT in two orchards was detected at 2187.18 ng g^-1 and 1061.78 ng g^-1, exceeding the levels stated in the Canadian DDT Soil Quality Guidance (SQG, 700 ng g^-1). The result of applying the isomer ratio to evaluate the recent or past use of DDT, endosulfan, and hexachlorocyclohexane (HCH), which had a high detection rate, showed that it could be attributable to historical usage. DDT and HCH showed statistically similar residual distribution patterns; however, endosulfan did not show a clear correlation with DDT and HCH due to the effect of its recent use. Thus, the results of evaluation of OCP residual levels and distribution characteristics can be used for the soil management policy of OCPs in agricultural lands in Korea.

Organochlorine pesticides in riparian soils and sediments of the middle reach of the Huaihe River: A traditional agricultural area in China

Distributions, souces, ecological risks as well as environmental behaviors of 20 organochlorine pesticides (OCPs) in riparian soils and sediments of the middle reach of the Huaihe River, a traditional agricultural area of China, were investigated. ∑OCPs in riparian soils and sediments were 1.8-63 ng g^-1 (mean = 19 ± 12 ng g^-1) and 1.2-9.9 ng g^-1 (mean = 3.0 ± 1.8 ng g^-1), respectively. HCHs were the dominant OCPs in both soils and sediments, while high concentrations of ∑HEPTs and ∑DDTs were also detected in some soils and sediments. No correlations were found between concentrations of OCPs and organic matter contents in both soils and sediments. Based on the source analysis, most OCPs in the riparian soils were mainly from historical residues, such as historical usage of technical HCH, DDT, chlordane and endosulfan. OCPs in sediments were influenced not only by surface runoff by also by other factors, e.g. in-situ contamination (DDT-containing antifouling paints in ships) and/or hydraulic transport from some tributaries. Some never-used OCPs, such as heptachlor and aldrin, were widely detected in soils and sediments. This might be attributed to some unknown usages or long-range atmospheric transport of them from other source regions. Ecological risk analysis suggested that DDTs and HCHs in soils would not lead to an adverse effect on soil ecological environment as well as agricultural production, and OCP residues in sediments also would not pose a threat to the sediment-dwelling organisms.

Release of phthalate esters from a local landfill in the Tibetan Plateau: Importance of soil particle-size specific association

High loads of phthalate esters (PAEs) in background regions can be directly attributed to the local sources, and their association with soil particles may determine the environment behaviors. However, little is known about the particle-size specific distributions of PAEs in soils from point source to the surroundings. In this study, 12 PAE congeners were measured in clay (< 2 μm), silt (2-63 μm) and sand fractions (63-250 μm) from surficial soils and soil profiles (0-200 cm) around the Lhasa landfill. The total concentrations of PAEs in bulk soils varied from 0.44 to 22.3 μg/g, with a dominance of bis(2-ethylhexyl) phthalate (DEHP). The clay-sorbed PAEs exhibited a decreasing trend with the increasing distance from landfill. This distribution pattern was well described by the Gaussian air pollution model, suggesting the airborne particles/gaseous transport of clay-sorbed PAEs. The Boltzmann equation explained the spatial variation of silt-sorbed PAEs, reflecting the atmospheric dispersion of silt-sorbed PAEs. In comparison, the sand-sorbed PAEs in surrounding soils showed downslope accumulation possibly due to the aeolian transport of sand particles. Half-life of the most abundant PAE congener DEHP was assumed based on the soil inventories from observed concentration and the Level III fugacity model simulations, and the results indicated significant longer half-life of DEHP in deeper soils (~24,000 h) than in surficial soils (5500 h). This study elucidates that the distribution and fate of soil PAEs would depend on their association with particles in the source area, and the relative stability of DEHP in deeper soils would further increase PAE inventory in soil compartment.

DDT, Chlordane, and Hexachlorobenzene in the Air of the Pearl River Delta Revisited: A Tale of Source, History, and Monsoon

Although organochlorine pesticides (OCPs) have been banned for more than three decades, their concentrations have only decreased gradually. This may be largely attributable to their environmental persistence, illegal application, and exemption usage. This study assessed the historic and current regional context for dichlorodiphenyltrichloroethane (DDT), chlordane, and hexachlorobenzene (HCB), which were added to the Stockholm Convention in 2001. An air sampling campaign was carried out in 2018 in nine cities of the Pearl River Delta (PRD), where the historical OCP application was the most intensive in China. Different seasonalities were observed: DDT exhibited higher concentrations in summer than in winter; chlordane showed less seasonal variation, whereas HCB was higher in winter. The unique coupling of summer monsoon with DDT-infused paint usage, winter monsoon with HCB-combustion emission, and local chlordane emission jointly presents a dynamic picture of these OCPs in the PRD air. We used the BETR Global model to back-calculate annual local emissions, which accounted for insignificant contributions to the nationally documented production (<1‰). Local emissions were the main sources of p,p'-DDT and chlordane, while ocean sources were limited (<4%). This study shows that geographic-anthropogenic factors, including source, history, and air circulation pattern, combine to affect the regional fate of OCP compounds.

Rapid transport of organochlorine pesticides (OCPs) in multimedia environment from karst area

Karst groundwater is crucial, but particularly vulnerable to contaminants. Anthropologically derived pollutants on the surface-environment in karst areas could easily and rapidly enter groundwater through highly developed transmissible structures and threaten water safety. To investigate such transport, we analyzed 24 organochlorine pesticides (OCPs) in the multimedia environment from the Zigui karst area of China, where agriculture is the predominant human activity. OCPs were frequently detected with the total OCP concentrations ranged from 228 to 7970 pg/g, 300 to 32,200 pg/L, 318 to 2250 pg/L, 149 to 2760 pg/g, and 752 to 12,000 pg/g in the soil, spring water, river water, spring sediment, and river sediment, respectively. HCB and p,p'-DDT were the most dominant OCP species. Isomeric and metabolic ratios indicated fresh inputs of Lindane, technical DDT, and Aldrin, although they have been banned in China. The spatial distributions, correlation analysis, and regression analysis suggested rapid OCP transport from the soil to the spring water, and from the soil and spring water to river water. OCPs in the soil and springs explained 92.3% and 89.0% of those in the spring water and river water, respectively. The solid transport with the fast-moving water was predominant for OCPs in sediments. Highly dynamic water systems and rapid OCP transport in the intro- and inter-medium suggested by our results substantiate the groundwater's vulnerability in karst areas. More studies on levels and transport of organic contaminants in karst systems and policy for protecting the karst groundwater are urgently required to control contaminant sources and ensure groundwater sustainability, since the karst water resources may suffer a potentially bleak future consisted of the decreased groundwater quantity and low water quality.

Health risks of exposure to soil-borne dichlorodiphenyltrichloroethanes (DDTs): A preliminary probabilistic assessment and spatial visualization

Residues of dichlorodiphenyltrichloroethane and its metabolites (DDTs) in soils continue to severely threaten and endanger human health. This present study comprehensively interprets the health risks associated with exposure to soil-borne DDTs and also identifies the spatial visualization of risks at a large regional scale in Fujian, China. There was significant spatial variability of human risk across the region, while levels of health risk displayed a significant positive correlation with population density (p < 0.05). High risk levels occurred mostly in the coastal areas in northeastern Fujian, with additional hotspots in inland areas. The highest total incremental lifetime cancer risks (ILCRs) occurred in Sanming, reaching up to 9.52 × 10^-5, 3.27 × 10^-5, and 1.76 × 10^-4 for children, teens, and adults, respectively. Further, the highest hazard index (HI) value was observed in Fuzhou, reaching up to 6.09, 3.84, and 2.37, respectively. The 95% confidence interval of data regarding ILCRs exceeded the recognized safe threshold, whereas the HI has been deemed accepted. Adults were identified as the most susceptible population in terms of cancer risks, with o,p'-DDT being the primary contributor of ILCRs. Moreover, children were showed to be the most vulnerable in terms of non-cancer risks, with p,p'-DDD being the main contributor of HI. Food ingestion appeared to be the dominant exposure pathway, for both cancer and non-cancer risks. The concentration of DDTs (C_soil) and exposure duration (ED) also greatly influenced the risk, together contributing to over 99% of the ILCRs and HI.

Pesticides driven pollution in Kuwait: The first evidence of environmental exposure to pesticides in soils and human health risk assessment

Soil pollution from pesticide residues is a key concern due to the high soil accumulation of pesticides and their human toxicity. Pesticide concentration of surface soil samples from the Sulaibiya agricultural field located in Kuwait was assessed in the present study. The study also investigated health risk assessment for both children and adults based on the residual concentrations. The average concentration of ƩOCPs (sum of organochlorine pesticides) along the present study was 3062 pg/g. The residual concentration of ƩOCPs was comparatively lower as compared to other locations around the world. Out of the 11 observed locations, A, B, and D locations indicated higher concentrations of ƩOCPs. The results indicated that DDT showed higher concentrations 692.87 pg/g in soil samples as compared to the other pesticides. Cancer risks of OCP via ingestion, dermal contact and inhalation of soil particles suggested that all stations were in a safe zone. However, locations A, B and D were closer to the low-risk band. The distribution pattern for each form of organochlorine pesticides (OCP) was different in Sulaibiya, indicating the non-simultaneous use of different groups of OCPs in this region. Multivariate statistical analysis based on cluster analysis identified three classes, 1, 2 and 3 of pesticides, suggesting these are from the same sources. Principle component analysis (PCA) showed that soil physicochemical properties influence the pesticides in soil samples. The results provides the baseline data of pesticides in soils from Kuwait.

Multistage Defense System Activated by Tetrachlorobiphenyl and its Hydroxylated and Methoxylated Derivatives in Oryza sativa

Crops can initiate various defense responses to environmental stresses. The process is often accompanied by extensive transcriptional and metabolic changes to reallocate metabolites. However, it remains unclear how organic pollutants activate the defense systems to reallocate metabolites in crops. The current study demonstrates that three defense systems, including the cytochrome P450s (CYP450s), glutathione S-transferases (GSTs), and phenylpropanoid biosynthesis, were sequentially activated after Oryza sativa was exposed to 2,3,4,5-tetrachlorobipheny l (PCB 61) and its derivatives 4'-hydroxy-2,3,4,5-tetrachlorobiphenyl (OH-PCB 61) and 4'-methoxy-2,3,4,5-tetrachlorobiphenyl (MeO-PCB 61), respectively. Genes encoding CYP76Ms and CYP72As were significantly upregulated after 0.5 h of exposure, followed by the GST-coding gene GSTU48, suggesting that the biotransformation and detoxification of PCB 61, OH-PCB 61, and MeO-PCB 61 occurred. Subsequently, CCR1 and CCR10 involved in phenylpropanoid biosynthesis were activated after 12 h, potentially reducing the oxidative stress induced by PCB 61 and its derivatives. Furthermore, β-d-glucan exohydrolase involved in both phenylpropanoid biosynthesis and starch and sucrose metabolism was significantly downregulated by 7.04-fold in the OH-PCB 61-treated group, potentially contributing to the inhibition of sugar hydrolysis. These findings provide insights into increasing rice adaptability to organic pollutants by reinforcing the enzyme-mediated defense systems, characterizing a novel and critical strategy that enables augmented crop outputs and quality in environments stressed by organic contaminants.

Semi-centennial sediment records of HCHs and DDTs from the East China marginal seas: Role of lateral transport in catchment

We reconstructed the history of the inputs of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) into the marine environment to reveal the time-dependent influence of sources and associated anthropogenic activities in China, based on ²¹⁰Pb-dated cores from the East China marginal seas (ECMS). The temporal dynamics of pesticide contamination expresses as deposition fluxes, inventories, and half-life estimations varied among the cores, suggesting heterogeneity in transport pathways of pollutants. The depth profiles of pesticide inputs closely followed their historical production and application timelines in China, and were also affected by human activities in catchments, with general declines in HCH and DDT inputs to the coring sites after their peak deposition. Despite the prevalence of occurrence of weathered HCH/DDT in the cores, there were clear source-dependent differences in isomeric composition and accumulation between before and after these pesticides were banned. α-HCH and p,p'-DDT were relatively more enriched in sediments from the pre-ban period when heavy technical HCHs and DDTs use occurred, as indicated by the higher α-/β-HCH and lower (DDE + DDD)/DDTs ratios, and the larger fractions of α-HCH and p,p'-DDT influxes to the coring sites in the ΣHCH and ΣDDT fluxes, respectively, while this pattern shifted to be historical residue-based in the post-ban period. The difference in the recent influxes of pesticides to core sediments and their higher post-ban inventories highlight the increasing importance of historical sources over time and continuous input of weathered residues into marine environment via lateral transport.

Yellow-legged gull eggs (Larus michahellis) as persistent organic pollutants and trace metal bioindicator for two nearby areas with different human impact

The concentration of different persistent organic pollutants (POPs including chlorinated and brominated compounds) and trace metals and metalloids (As, Cd, Cu, Cr, Pb, Hg, Ni, and Zn) was examined in eggs from two colonies of yellow-legged gulls. The two colonies are established in Ría de Vigo, Northwest Spain, with a distance between them of only 10 km, one in Vigo town (industrial and harbour activities) and the other in the Cíes Islands in a Natural Park and Marine Protected Area -MPA- (with no known anthropogenic inputs). Statistically significant differences for the two colonies were observed for Hg, the sum of 7 CBs, the sum of DDTs y and the sum of 9 PBDEs, with values that could be causing some toxic effects in the area of the most anthropogenically influenced colony. The estimated isotopic niche was also calculated, based on δ¹⁵N and δ¹³C, for the two colonies, pointing to a wider diet in the Cíes colony when compared to the diet in the Vigo colony. The study supports the use of the yellow-legged seagull eggs as a bioindicator of pollution capable of differentiating pollution level even in geographically close areas.

How persistent are POPs in remote areas? A case study of DDT degradation in the Qinghai-Tibet Plateau, China

Persistent organic pollutants (POPs) can undergo long-range atmospheric transport (LRAT) and deposit in remote areas. How persistent are POPs in remote areas? To answer this question, we measured two parent-DDTs and eight metabolites in soil and air along a transect in the Qinghai-Tibet Plateau, China, to quantitatively evaluate the degree of degradation of DDTs. DDTs were ubiquitous in soil and air with the total DDT concentrations (Σ₁₀DDTs) ranging 37.7-70,100 pg g^-1 dw and 3.4-175 pg m^-3, respectively. The air-soil equilibrium status indicated that the forest/basin soil was a source for most DDTs, while the plateau soil was a sink receiving DDTs from the LRAT and photodegradation in the air (for metabolites). The metabolites accounted for avg. 64.1% of Σ₁₀DDTs in soil, with avg. 93.2% from local degradation, implying the overall high degradation of DDTs. With the significant degradation, the continuous input via LRAT was deemed to be the main reason for the stable level (persistence) of POPs in the Qinghai-Tibet Plateau. Therefore, we emphasize the importance of source control for the risk management of POPs. POPs in the environment might decline rapidly due to a reduction in source input and significant degradation as indicated by our study.

Geographical distribution and risk assessment of dichlorodiphenyltrichloroethane and its metabolites in Perna viridis mussels from the northern coast of the South China Sea

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.

Rapid changes in organochlorine pesticides in sediments from the East China sea and their response to human-induced catchment changes

Human-induced catchment changes have affected the sedimentary processes in marginal seas, which will impact the transport and burial processes of materials and inevitably impact marine biogeochemical cycles. Organochlorine pesticides (OCPs) and sediment characteristics in surface sediments from the East China Sea (ECS) at two time points (2006 and 2018) were compared to understand the response of OCPs to human-induced catchment changes. A significant coarsening trend occurred after the impoundment of the Three Gorges Dam (TGD), with the mean grain size increasing from 6.4 ± 1.2 Φ to 4.4 ± 2.1 Φ, suggesting that the sedimentary environment in the ECS changed drastically. OCP concentrations in the ECS evidently decreased after the impoundment of the TGD, with mean values decreasing from 2.55 ± 1.51 ng g^-1 to 1.08 ± 0.84 ng g^-1. The deposition flux of OCP also decreased from 2.65 ± 1.67 ng cm^-2 yr^-1 to 0.89 ± 0.60 ng cm^-2 yr^-1. The reduction in the riverine input might be the reason that caused variations in the OCP concentration and deposition flux. In addition, sediment coarsening is likely to be the another primary factor influencing the differences in the distribution and deposition flux of the OCPs in the ECS. Therefore, the distribution and burial of OCPs in the ECS have been changed drastically, which may broadly impact the marine environment and biogeochemical cycles.

Background levels of polycyclic aromatic hydrocarbons and legacy organochlorine pesticides in wheat sampled in 2017 and 2018 in Poland

Both polycyclic aromatic hydrocarbons (PAHs) and legacy organochlorine insecticides (OCPs), including DDT, are dangerous chemical contaminants. The aims of this study were to (i) determine background levels of PAHs and legacy OCPs for wheat samples collected in 2017 and 2018 in Poland, (ii) identify differences between levels in wheat harvested in various regions of Poland, (iii) evaluate differences in contamination sources manifested by the profiles of the identified chemicals, (iv) identify possible correlations between different classes of chemicals present in wheat, and (v) assess the health risks associated with the presence of PAHs and OCPs in Polish wheat. Average concentrations found in the samples were 0.09 ± 0.03 μg kg-1 for benzo[a]pyrene (BaP) (formerly used as a single PAH marker), 0.43 ± 0.16 for the more recently introduced collective PAH 4 marker (benzo[a]anthracene + benzo[a]pyrene + chrysene + benzo[b]fluoranthene), and 1.07 ± 0.68 μg kg-1 for DDT and its metabolites. The PAH profiles indicated contamination from combustion-related emission sources (liquid fossil fuels, coal, biomass). Health risks associated with the presence of PAHs and OCPs in cereals were assessed using the margin of exposure (MOE) approach. The MOE values calculated based on the highest concentrations found in this study exceeded 50,000 for both BaP and PAH 4. The calculated worst-case scenario value for DDT and metabolites was as low as 0.3% of the respective tolerable daily intake (TDI) value. Assessment of dietary risk has shown that the presence of the two contaminant classes in Polish wheat grains is of low concern.

Magnetic ferroferric oxide and polydopamine molecularly imprinted polymer nanocomposites based electrochemical impedance sensor for the selective separation and sensitive determination of dichlorodiphenyltrichloroethane (DDT)

Dichlorodiphenyltrichloroethane (DDT) is a kind of broad-spectrum insecticides, which is potentially toxic and persistently threatens the safety of environment and food, due to their stability in nature and difficulty to degrade. For the first time, a novel impedance chemical sensor based on magnetic Fe₃O₄ and polydopamine molecularly imprinted polymer magnetic nanoparticles (PDA@Fe₃O₄ MIP MNPs) was designed. Bisphenol A (BPA) and dopamine were used as virtual template molecules and functional monomer for MIP synthesis, respectively. Recognition cavities formed in PDA layers could specifically recognize and effectively adsorb DDT molecules, with the help of virtual templates that had similar molecular structure to DDTs. The as-prepared PDA@Fe₃O₄-MIP MNPs could be used for specific adsorption and efficient extraction of target molecules 4,4'-DDT from food samples. The electrochemical impedance of the PDA@Fe₃O₄-MIP MNPs increased sensitively with the adsorption of 4,4'-DDT, the correlationship between of the electrochemical impedance response and the concentration of 4,4'-DDT were applied in the construction of electrochemical impedance sensors for the determination of 4,4'-DDT. The sensor showed a good linear relationship between the charge transfer resistance (R_ct) and the 4,4'-DDT concentration over a range from 1 × 10^-11 to 1 × 10^-3 mol L^-1 with a detection limit of 6 × 10^-12 mol L^-1. The sensor also exhibited excellent sensitivity and selectivity as well as high stability for the detection of pesticide residues and other environmentally harmful chemicals in various food samples.

Degradation of DDTs in thermal desorption off-gas by pulsed corona discharge plasma

Thermal desorption has been widely employed to treat soils contaminated with chlorinated organics. The off-gas of thermal desorption must be treated to avoid secondary pollution. In this study, the treatment of DDTs in thermal desorption off-gas by pulsed corona discharge plasma was investigated. The effects of important operation parameters, including energy density, gas temperature, humidity, and O₂ content, on DDTs degradation were investigated. The main degradation products were also studied. The DDTs degradation efficiency increased with the increase in energy density, gas temperature, and O₂ content. The degradation efficiency of DDTs was achieved to 84.6% when the initial concentration, energy density, and gas flow rate were 2.0 mg/m³, 17.8 J/L, and 3.0 L/min, respectively. Maximum DDTs degradation efficiency was observed when the gas was at 5% relative humidity. The main degradation products identified were DM, phenol, benzene, acetic acid, and formic acid. It was calculated that 87% of chlorine in the degraded DDTs was converted into chloride ion.

Early-life exposure to endocrine disrupting chemicals associates with childhood obesity

Increasing prevalence of childhood obesity poses threats to the global health burden. Because this rising prevalence cannot be fully explained by traditional risk factors such as unhealthy diet and physical inactivity, early-life exposure to endocrine disrupting chemicals (EDCs) is recognized as emerging novel risk factors for childhood obesity. EDCs can disrupt the hormone-mediated metabolic pathways, affect children's growth and mediate the development of childhood obesity. Many organic pollutants are recently classified to be EDCs. In this review, we summarized the epidemiological and laboratory evidence related to EDCs and childhood obesity, and discussed the possible mechanisms underpinning childhood obesity and early-life exposure to non-persistent organic pollutants (phthalates, bisphenol A, triclosan) and persistent organic pollutants (dichlorodiphenyltrichloroethane, polychlorinated biphenyls, polybrominated diphenyl ethers, per- and polyfluoroalkyl substances). Understanding the relationship between EDCs and childhood obesity helps to raise public awareness and formulate public health policy to protect the youth from exposure to the harmful effects of EDCs.

Biodegradability and ecological safety assessment of Stenotrophomonas sp. DDT-1 in the DDT-contaminated soil

The biodegradability and ecological safety assessment of the previously isolated DDT-degrading bacterial strain Stenotrophomonas sp. DDT-1 were investigated in the DDT-contaminated soil under laboratory and field conditions. Under laboratory conditions, the degradation rates of fresh p,p'-DDT in soil were enhanced by 2.0-3.0-fold with the introduction of the strain DDT-1 compared to those of the control treatments. A similar enhancement in the dissipation of DDTs (p,p'-DDT, p,p'-DDE, p,p'-DDD, and o,p'-DDT) in the aged DDT-contaminated field plot soils resulted from the inoculation with this strain. Meanwhile, the degradation rates of DDTs increased by 2.9-5.5- and 2.8-7.6-fold in the inoculated greenhouse and open field soils, respectively, after field demonstration application of strain DDT-1 preparation. Moreover, no significant differences in the soil enzyme activity, microbial functional diversity, and bacterial community structure were observed between the inoculated and un-inoculated field soils, but several soil microbial genera exhibited some fluctuations in abundance. It is concluded that strain DDT-1 could accelerate the removal of DDTs residues in field soils, and furthermore, its inoculation was ecologically safe.