Application Of DDT Research Articles

Multiple-point ignition as a driver of flame acceleration at the early stage of burning in channels

In the present study, flame acceleration driven by an array of multiple ignition kernels, equally spaced in the axial direction of a channel closed at one end, is studied numerically. In order to demonstrate the effects of the proposed ignition configuration on the flow dynamics, free-slip wall boundary condition is adopted. It is demonstrated that the burning of multiple flame kernels generates a powerful upstream flow, propelling the flame kernels, with the leading kernel’s tip undergoing a strong exponential acceleration. In a channel with smooth walls, such a powerful acceleration process is limited in time. The present study is mainly focused on the dynamics of the flame during the exponential stage of acceleration. The dependence of the acceleration rate, total acceleration time, and the maximum flame velocity on the initial distance between the kernels, the number of ignition kernels, and the thermal gas expansion coefficient, is quantified. Remarkably, the initial distance between the kernels has a weak influence on the above mentioned characteristics of flame dynamics as long as it is sufficiently large. It is observed that the acceleration rate increases with the kernel number. Notably, a significantly large maximum flame tip velocity can be achieved using the multi-kernel configuration as compared to the single-point ignition scenario. The acceleration rate demonstrates a nearly linear dependence on the thermal expansion coefficient, thus, the increase in thermal expansion results in a considerably stronger flame acceleration process.Novelty and Significance StatementFor the first time, the flame acceleration process upon simultaneous ignition of a multi-point array of hot kernels equally spaced at the centerline of a channel was systematically studied. The work emphasizes the potential for achieving an extremely high flame speed within a very short time as compared to the single-ignition method. The acceleration rate, total acceleration time, and maximum achievable flame velocity were quantified. In a multi-point ignition scenario, we demonstrate that the burning of the fresh mixture between the kernels increases an overall cumulative gas expansion, propelling the leading tip. This result suggests a method for creating a powerful flame acceleration, which is an essential step in deflagration-to-detonation transition. Notably, the powerful acceleration is achieved in channels with smooth walls, which is important for DDT applications, in which using obstructed channels may be associated with a range of operational problems. The simplicity of the setup is also emphasized.

Evaluation of the degree of contamination of breast milk by organochlorine pesticides in the Lower Amazon region: a preliminary study

The main source of human exposure to organochlorines is through food, especially food with a high fat content, such as breast milk, which is critical for child hood development. Therefore, it is important to analyze milk and other biological matrices for organochlorine pesticides (OCPs), and then determine the source of the OCP contamination. The objective of this study was to evaluate the degree of contamination by OCP residues and their metabolites in breast milk samples from the municipalities of Mojuí dos Campos and Belterra-Pará, Brazil. The OCPs analyzed were dichlorodiphenyltrichloroethane (DDT) and its metabolites (o,p'-DDT, p,p'-DDT, o,p'-DDE, p,p'-DDE, o,p'-DDD, and p,p'-DDD), aldrin, endrin, dieldrin, hexachlorocyclohexanes (α-HCH, β-HCH, lindane (γ-HCH), and δ-HCH­­), endosulfan α and β, endosulfan sulfate, heptachlor, and heptachlor epoxide. These substances were analyzed in 22 breast milk samples using gas chromatography with an electron capture detector (GC-ECD). Seven were contaminated with p,p'-DDT and/or p,p'-DDE. The mean p,p'-DDT and p,p’-DDE content in the contaminated samples was 0.0022 and 0.0152 mg·kg-1 of milk, respectively. This contamination may have been due to the inadequate application of DDT until the end of the 1990s for the control of tropical diseases, including malaria. Despite being a preliminary study, the number of contaminated samples was significant, which suggests the need to expand this study to other environmental and biological matrices.

Interventions in scholarly communication: Design lessons from public health

Many argue that swift and fundamental interventions in the system of scholarly communication are needed. However, there are substantial disagreements over the short- and long-term benefits of most proposed approaches to changing the practice of science communication, and the lack of systematic, empirically based research in this area makes these controversies difficult to resolve. We argue that experience within public health can be usefully applied to scholarly communication. 
 Starting with the history of DDT (Dichlorodiphenyltrichloroethane) application, we illustrate four ways complex human systems threaten reliable predictions and blunt ad-hoc interventions. We then show how these apply to interventions in scholarly publication – open access based on the article processing charge (APC), and preprints – to yield surprising results. Finally, we offer approaches to help guide the design of future interventions: identifying measures and outcomes, developing infrastructure, incorporating assessment, and contributing to theories of systemic change.

Elucidating the status of malaria in Andaman and Nicobar Islands post-millennium 2000.

Malaria is a major vector-borne disease in the Indian sub-continent and has been pestering Andaman and Nicobar islands (ANI's) as well since British colonial times. A retrospective data mining technique has been adhered to assess the status of malaria for nineteen years from 2000 to 2019 in ANI's. The altered environment due to 2004 tsunami had increased malaria incidence significantly during (2005-2010). The Nicobar district recorded high incidence of malaria while the least in the north and middle Andaman district. Comparative high incidence of malaria was documented due to Plasmodium falciparum than Plasmodium vivax in the Nicobar district between 2005 and 2009. The declining trend of malaria-positive cases in ANI's was observed post 2010, articulating various initiatives taken by the local Andaman and Nicobar administration to curb this vector-borne disease. The initiatives were like (1) large-scale release of larvivorous fish, Gambusia affinis in the transient water pools, (2) outdoor application of DDT, (3) indoor application of Pyrethrum, (4) malaria awareness drive that led to the curbing of the proliferation not only the malaria vector but also other potential mosquito vector species as well, and (5) implementation of revised drug policy.

Experimental, DFT study, and in silico molecular docking investigations of dichlorodiphenyltrichloroethane against human estrogen receptor alpha

Advanced computational tools allowed to study a pure commercial sample of dichlorodiphenyltrichloroethane (DDT) prepared in liquid phase in KBr pellets and characterized using FT-IR and GC-MS followed by the application of DDT for molecular docking against human estrogen receptor alpha. The compound was modelled using GaussView software. Using Veda 04 program, the theoretical vibrational energy distributions and experimental vibrational frequencies were compared. Interestingly, C1 and C2�possess the highest atomic charge density distribution (ACDD)�of -0.284e and -0.283e while C21 and C11 have lowest ACDD of -0.064e and -0.063e in a relative manner, since the deactivating power of chlorine atoms decreases charge densities of the bonded carbon. The highest intramolecular interacting perturbation energy is 1121.92 kJ mol�1 occurs between ?*C19�C21 donor orbital and ?*C14�C16 acceptor orbital while the least intramolecular interaction occurs in the lone pair of LPC26 and the�sigma nonbonding (??C1�Cl24) NBO orbitals with E(2) of 32.21�kJ mol�1. Steric interaction was the only interaction found within the complex after the docking.

Experimental, DFT study, and in silico molecular docking investigations of dichlorodiphenyltrichloroethane against human estrogen receptor alpha

Advanced computational tools allowed to study a pure commercial sample of dichlorodiphenyltrichloroethane (DDT) prepared in liquid phase in KBr pellets and characterized using FT-IR and GC-MS followed by the application of DDT for molecular docking against human estrogen receptor alpha. The compound was modelled using GaussView software. Using Veda 04 program, the theoretical vibrational energy distributions and experimental vibrational frequencies were compared. Interestingly, C1 and C2�possess the highest atomic charge density distribution (ACDD)�of -0.284e and -0.283e while C21 and C11 have lowest ACDD of -0.064e and -0.063e in a relative manner, since the deactivating power of chlorine atoms decreases charge densities of the bonded carbon. The highest intramolecular interacting perturbation energy is 1121.92 kJ mol�1 occurs between ?*C19�C21 donor orbital and ?*C14�C16 acceptor orbital while the least intramolecular interaction occurs in the lone pair of LPC26 and the�sigma nonbonding (??C1�Cl24) NBO orbitals with E(2) of 32.21�kJ mol�1. Steric interaction was the only interaction found within the complex after the docking.

Organochlorine pesticides in marine sediments and seawater from Cirebon coastal water, West Java, Indonesia: Concentration, spatial distribution, potential sources, and ecological risk assessment

Organochlorine pesticides (OCPs) were investigated in surface sediments and seawater from three major estuaries at Cirebon coastal water, West Java Province, Indonesia. Total concentrations of OCPs in seawater and sediment varied from 10 to 120 ng/L (32 ± 36 ng/L) and 1.5 to 17 ng/g dw (mean of 7.4 ± 4.0 ng/g dw), respectively. OCPs concentrations in Sukalila estuary were higher than those detected in Bondet and Kejawan estuaries. The drins group was the predominant OCPs contaminant in seawater and sediment samples. Historical application of DDT, recent use of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), and application of technical hexachlorocyclohexanes (HCHs) are significant sources of DDTs and HCHs, respectively. The concentrations of γ-HCH and heptachlor epoxide in marine sediment elevated the value of Threshold Effect Limit (TEL) in 48% of the total study stations but lowered the value of Probable Effect Limit (PEL), suggesting that they ocassionally trigger adverse effects on benthic organisms.

Levels and Trophic Transfer of Selected Pesticides in the Lake Ziway Ecosystem.

The levels of 30 selected pesticides and trophic biomagnification of DDT were investigated in biota samples of the Lake Ziway in the Rift valley region, Ethiopia. Carbon source and trophic position were calculated by using 13C and 15N stable isotopes, individually, and trophic magnification factors (TMFs) were inferred. Only DDT and its metabolites were quantified in all samples analyzed. The most prominent metabolite was p,p'-DDE with mean concentration ranging from the 0.82-33.69ngg-1 lipid weight. Moreover, the ratio of DDT/DDD + DDE in all the biota samples was less than 1 signifying historical DDT application. Regression of log [ΣDDT] vs TL (trophic level) among all biota species showed a significant correlation, indicating that DDTs are biomagnifying along with the food web of Lake Ziway with an estimated TMF of 2.75. The concentrations of DDTs and other organochlorine pesticides found in biota from Lake Ziway were, in general, lower than studies found in previous studies carried out in the same lake.

Selective Sweeps in a Nutshell: The Genomic Footprint of Rapid Insecticide Resistance Evolution in the Almond Agroecosystem.

Among the most familiar forms of human-driven evolution on ecological time scales is the rapid acquisition of resistance to pesticides by insects. Since the widespread adoption of synthetic organic insecticides in the mid-twentieth century, over 500 arthropod species have evolved resistance to at least one insecticide. Efforts to determine the genetic bases of insecticide resistance have historically focused on individual loci, but the availability of genomic tools has facilitated the screening of genome-wide characteristics. We resequenced three contemporary populations of the navel orangeworm (Amyelois transitella), the principal pest of almond orchards in California, differing in bifenthrin resistance status to examine insecticide-induced changes in the population genomic landscape of this species. We detected an exceptionally large region with virtually no polymorphisms, extending to up to 1.3 Mb in the resistant population. This selective sweep includes genes associated with pyrethroid and DDT resistance, including a cytochrome P450 gene cluster and the gene encoding the voltage-gated sodium channel para. Moreover, the sequence along the sweep is nearly identical in the genome assembled from a population founded in 1966, suggesting that the foundation for insecticide resistance may date back a half-century, when California’s Central Valley experienced massive area-wide applications of DDT for pest control.

Monitoring personal exposure to semi-volatile organic chemicals in Uruguayan school children using silicone wristbands

Children are vulnerable to the harmful effects of chemicals and are exposed to many potentially toxic compounds in their daily lives. Due to their ease of implementation and non-invasive, silicone wristbands have emerged as passive samplers to study personal environmental exposures. The Scola-Exposome study in Montevideo, Uruguay investigated the extent of exposure to several classes of chemicals among school children (n=23) aged 6-7 years old, who wore a silicone wristband for 7 days. All wristbands were quantitatively analyzed using gas chromatography tandem mass spectrometry (GC-MS/MS) at the University at Buffalo for 46 chemicals, including polychlorinated biphenyls (PCBs), pesticides, polybrominated diphenyl ethers (PBDEs), organophosphorus flame retardants (OFPRs), and novel halogenated flame retardants (NHFRs). An average of 13 analytes were detected in each wristband. OPFR concentrations ranged from <LOD to 8920 ng/g band. The sum of PBDE (ΣPBDE) concentrations ranged from <LOD to 433 ng/g band, DDT and its derivatives (DDx) range from 0.2 to 23.5 ng/g band, and ΣPCBs range from <LOD to 8.4 ng/g band. Urban children in Uruguay are exposed to a wide range of chemicals, with nearly half of them to a recent application of DDT. Silicone wristbands show promise for passive, non-invasive exposure assessment to environmental chemicals in children, detecting both legacy and emerging pollutants.

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.

Polychlorinated biphenyls and organochlorines pesticides in indoor dust: An exploration of sources and health exposure risk in a rural area (Kopawa) of Nepal.

While contamination of indoor environment with organochlorine compounds (OCs) is well documented worldwide, only a few studies highlighted the problem of indoor pollution in Indian sub-continent, including Nepal. This study insight the contamination level, distribution pattern, and sources of OCs in indoor dust from a rural area of Nepal. Additionally, daily exposure risk through different intake pathways was estimated in order to mark the potential risk of OCs to local residents. Results indicated the predominance of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in dust. Ʃ26OCPs (median 87ng/g) in dust was about 7-8 times greater than Ʃ30PCBs (median 10.5ng/g). DDT was the most abundant chemical among Ʃ26OCPs, followed by HCHs and endosulfan, and accounted for 73%, 7%, and 4% of Ʃ26OCPs, respectively. A relatively high level of ƩDDT than other OCPs suggests the existence of DDT source in the Nepalese environment. Among PCB, tetra-CBs were most prevalent, trailed by penta-CBs, hexa-CBs, and hepta-CBs, and comprised 28%, 21%, 17% and 17% of Ʃ30PCBs, respectively. Dioxin like-PCBs (median 3.48ng/g) was about two times higher than the total indicator-PCB (median 1.63ng/g). High p,p-DDT/p,p-DDE ratio (median 2.89) suggested fresh application and minimal degradation of DDT in the local environment of Kopawa. While lower α-/γ-HCH ratio (median 0.75) indicated lindane contamination as the primary sources of HCH. Moreover, the low α-/β-endosulfan ratio (median 0.86) specified the fresh use of commercial endosulfan. Among OCPs, only DDT positively related to total organic carbon (TOC) (Rho=0.55, p<0.05) but not black carbon (BC), proposing minimal or zero impact of TOC and BC. For PCBs, PCB-126 was moderately and negatively correlated with TOC (Rho=-0.49, p<0.05), but not BC. The daily risk exposure (DRE) assessment showed that children are more vulnerable to OCs than the adult. The DRE of OCs in this study were 2-4 order of magnitude lower than their corresponding reference dose (RfD), proposing insignificant risk.

Levels and enantiomeric signatures of organochlorine pesticides in Chinese forest soils: Implications for sources and environmental behavior

We investigated the levels and distributions of organochlorine pesticides (OCPs) in 159 background soil samples collected from 30 forested mountain sites across China. The sum of DDT was the most abundant OCP, with the concentrations of 0.197–207 ng/g and 0.033–122 ng/g in the O-horizon and A-horizon, respectively. High concentrations of OCPs usually occur near agricultural regions or high consumption areas. The spatial distribution was mainly influenced by the emission sources and soil total organic contents (TOC). The chiral compounds were generally nonracemic in the soils and showed preferential degradation of (−) o,p′- dichlorodiphenyltrichloroethane, (+) trans-chlordane, and (−) cis-chlordane in both the O- and A-horizons. The enantiomeric fraction (EF) distributions of chiral OCPs displayed no differences across the forest sites in the O-horizon or the A-horizon. Comparing the deviation of EFs from racemic (DEVrac = absolute value of 0.500 - EF) with environmental parameters, we found that DEVrac of cis-chlordane demonstrated a strong positive correlation with TOC (p < 0.05) and the C/N ratio (p < 0.01). This relationship suggests that these factors could affect the microbial activity and significantly impact the extent of enantioselective degradation of chiral compounds in the soils. Fresh and historical applications of DDT and historical chlordane and endosulfan uses may be prominent sources of OCP accumulation in Chinese forest soils.

Ecological Legacy of DDT Archived in Lake Sediments from Eastern Canada.

Historic forest management practices led to widespread aerial application of insecticides, such as dichlorodiphenyltrichloroethane (DDT), to North American conifer forests during ∼1950-1970. Lake basins thus may provide an important archive of inputs and aquatic responses to these organochlorines. We use dated sediment cores from five study lakes in multiple watersheds in New Brunswick (NB), Canada, to provide a regional paleo-ecotoxicological perspective on this potential legacy stressor in remote lake ecosystems. Peak sedimentary levels of p, p'- and o, p'-DDT (ΣDDT) and breakdown products ΣDDE (dichlorodiphenyldichloroethylene) and ΣDDD (dichlorodiphenyldichloroethane) generally occurred during the 1970s to 1980s. Sediments exceeded probable effect levels (PELs) by ∼450 times at the most impacted lake. Modern sediments in all study lakes still contained levels of DDT-related compounds that exceed PELs. For the first time, we show that aerial applications of DDT to eastern Canadian forests likely resulted in large shifts to primary consumers within several lake food webs, principally through lake-specific impacts on zooplankton community composition. Modern pelagic zooplankton communities are now much different compared to communities present before DDT use, suggesting that a regional organochlorine legacy may exist in the modern food webs of many remote NB lakes.

Organochlorine pesticides in ambient air from the littoral cities of northern China: Spatial distribution, seasonal variation, source apportionment and cancer risk assessment

Concentrations, composition and seasonal variations of organochlorine pesticides (OCPs) in the atmosphere (particulate phase and gaseous phase) at coastal cities in northern China were determined. OCP transport from emission source areas and lifetime excess cancer risks by inhalation exposure to specific OCPs were also investigated. The annual average concentration of total OCPs in gaseous phase ranged from 1.0ng/m3 to 6.3ng/m3, with the peak observed in summer at most sites. Particulate phase concentrations ranged from 29.9pg/m3 to 103.3pg/m3, with the maximum found in the local heating period at most locations. The detection rates of gaseous samples were considerably higher than those of particulate ones. The dominant components included endosulfan (I and II), (α- and γ-) chlordane, pentachlorobiphenyl (PeCB), hexachlorobenzene (HCB), heptachlor, (α-, β- and γ-) hexachlorocyclohexane (HCH), dichloro-diphenyl-trichloroethane (DDT) and their metabolic products. The specific ratios indicated different applications of DDT, technical HCH and endosulfan at most sites. Large differences in compositional profiles occurred in January (typical heating period) and July (representative non-heating period), and diurnal changes in component concentrations may have been influenced by local emission pattern. The potential source contribution function (PSCF) manifested seasonal concentrations of airborne OCPs affected by the input of potential sources in different regions. The emission sources with higher contribution probabilities to the sites were primarily distributed in the surrounding areas. The lifetime excess cancer risks for the local residents by inhalation exposure to specific components were not high, though the potential threat of α-HCH and HCB should be concerned. CapsuleGaseous OCPs reached peak values in summer and dominated relative to particulate (PM10) values; meanwhile, surrounding sources affected air OCP concentrations, and cancer risks of OCPs by inhalation exposure were not high.

Bone density and asymmetry are not related to DDT in House Sparrows: Insights from micro-focus X-ray computed tomography

In organisms, DDT (Dichlorodiphenyltrichloroethane) and its metabolites, DDE (Dichlorodiphenyldichloroethylene) and DDD (Dichlorobischlorophenylethane) are endocrine mimics. They can influence bone density and other bone structural features. This study was conducted on House Sparrows (Passer domesticus) caught from the Free State - and the Limpopo Provinces of South Africa (SA). The sites were chosen based on spraying patterns of DDT for malaria control or non-spraying. The bone mineral densities of the femurs as well as the lengths of the left- and right leg bones were determined using micro-focus X-ray computed tomography (μ-XCT). The concentrations of DDT and its metabolites in the liver were determined with gas-chromatography mass-spectrometry to provide baseline concentrations of DDT in the body, allowing comparison of the various groups of birds. There was no asymmetry between the lengths of the bones of the left- and the right legs. DDT concentrations in the liver did not correlate with bone lengths. In addition, there were no significant differences between the relative densities of the left- and right leg bones with increase of concentrations of DDT. The concentrations of DDT and its metabolites did not have a significant effect on the measured bone parameters of House Sparrows. It is possible that the concentrations of DDT and its metabolites in the environments were too low to be injurious to the birds and/or tolerance to the insecticide has developed in the birds over more than six decades of almost continuous application of DDT.

Degree of phenyl chlorination of DDT-related compounds as potential molecular indicator for industrial DDT emissions

The pesticide DDT (1-chloro-4-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene) and its degradates are among the most persistent and abundant organochlorine contaminates in the environment, and DDT is still being produced in several Asian countries. In this study, we report for the first time on the detection of DDT-related compounds with one additional or missing chlorine atom at the phenyl group (DDX±Cl) in sediment and soil samples taken in the vicinity of former and current DDT production sites. These congeneric compounds most likely originate from production residues disposed of into the environment. In order to ensure an adequate identification and quantification of this novel organic pollutant group, individual DDX±Cl were synthesized as reference compounds by simulating an impure production of DDT in the laboratory. In contrast to DDX±Cl with (chloro)alkyl moieties, DDX±Cl with (chloro)alkenyl moieties cannot be unambiguous assigned by gas-chromatographic/mass spectrometric (GC/MS) fragmentation and elution orders. The occurrence of DDX±Cl in environmental samples allows to draw conclusions about the purity of the production process in the associated production sites. Moreover, they potentially can serve as molecular indicators to differentiate between industrial DDT emissions and insecticidal applications of DDT. This hypothesis has yet to be confirmed by further research.

Body Burden of Dichlorodiphenyl Dichloroethene (DDE) and Childhood Pulmonary Function.

Longitudinal studies have shown that early life exposure to dichlorodiphenyl dichloroethene (DDE) can lead to growth reduction during childhood and adolescence. In addition, DDE exposure has been linked to respiratory tract infections and an increased risk of asthma in children. Our aim was to understand the relationships between DDE exposure and pulmonary function in children, and, particularly, whether associations are mediated by the height of the children. We used data from an environmental epidemiologic study conducted in central Germany in children aged 8-10 years. The pulmonary function (forced vital capacity, FVC, and forced expiratory volume in one second, FEV1) were measured in three consecutive years. Blood DDE levels were measured at 8 and 10 years. We used linear mixed models for repeated measurements and path analyses to assess the association between blood levels of DDE and pulmonary function measurements. All models were adjusted for confounders. Linear mixed approaches and modelling concurrent effects showed no significant associations. The path analytical models demonstrated that DDE measured at eight years had significant, inverse, indirect, and total effects on FVC at ten years (n = 328; −0.18 L per μg/L of DDE) and FEV1 (n = 328; −0.17 L per μg/L of DDE), mediated through effects of DDE on height and weight. The DDE burden reduces pulmonary function through its diminishing effects on height and weight in children. Further studies are required to test these associations in other samples, preferably from a region with ongoing, high DDT application.

The distribution of organochlorine pesticides in sediments from iSimangaliso Wetland Park: Ecological risks and implications for conservation in a biodiversity hotspot

The iSimangaliso Wetland Park World Heritage site, located on the east coast of South Africa, spans ∼3300 km2 and constitutes the largest protected estuarine environment for hippopotami, crocodiles and aquatic birds in Africa. Given the ecological importance of this site and continued use of organochlorine pesticides (OCPs) in the region, this study focused on the nature, distribution and potential sources of organochlorine contamination within iSimangaliso Wetland Park. OCPs were widely distributed in surface sediment samples obtained from the four main Ramsar wetland systems within the park (Lake St Lucia, Mkhuze, Lake Sibaya and Kosi Bay). ∑HCH and ∑DDT were the dominant contaminants detected with concentrations in the range of 26.29–282.5 ng/g and 34.49–262.4 ng/g, respectively. ∑DDT concentrations revealed a distinctive gradient, with significantly higher concentrations at Kosi Bay and Lake Sibaya attributed to the application of DDT for malaria control. p,p'-DDE and p,p'-DDD were the dominant isomers detected, but the detection of p,p'-DDT in a number of samples reflects recent inputs of technical DDT. Highest concentrations of HCH, endosulfan and heptachlor were detected in sediments from Mkhuze and reflect the substantial residue load these wetlands receive from agricultural activities within the catchment area. Isomeric compositions indicate that endosulfan and heptachlor residues are derived mainly from historical application, while inputs of HCH, aldrin and endrin could be attributed to more recent usage at several sites. OCP sediment concentrations from iSimangaliso represent the highest yet recorded in South Africa and some of the highest reported globally this century. Sediments found within the lakes and wetlands of iSimangaliso represent large reservoirs of contaminants that pose ecotoxicological threats to this globally important biodiversity hotspot. Detailed investigation into the bioaccumulation and toxicological risks of OCPs within the wetland park is urgently required.

Exposure to Dichlorodiphenyl Dichloroethene (DDE) and Childhood Pulmonary Function

Background: Longitudinal studies have shown that both prenatal and postnatal exposure to DDE leads to reduction in growth of height and increase in BMI during childhood. DDE is also known to interfere with normal pubertal growth and alter cellular and humoral immunity. In addition, prenatal DDE exposure has been linked with respiratory tract infections and increased risk of asthma in early childhood. Our aim was to investigate the effects of DDE exposure on childhood pulmonary function. Methods: We used data from an environmental epidemiologic study conducted in central Germany in children of ages 8-10 years during 1995-97. Pulmonary function were measured in three consecutive years while blood DDE levels were measured in 1995 and 1997. We used correlations, linear mixed models, and path analysis to assess the association between blood levels of DDE and repeated pulmonary function measurements. All models were adjusted for age, sex, birth weight, breast feeding duration, height, weight, smoking during pregnancy, parental history of asthma and environmental tobacco exposure. Results: We observed weak negative correlations between DDE levels and height, weight, FEV1 and FVC. Linear mixed models showed no significant associations between the burden of DDE and pulmonary function. Path-analytical models demonstrated that DDE measured at baseline (1995) had significant inverse indirect and total effects on FVC (total in 1995: -0.17 L per g/L of DDE; 1997: -0.18 L per g/L of DDE) and FEV1 (total in 1995: -0.15 L per g/L of DDE; 1997: -0.17 L per g/L of DDE) mediated through effects of DDE on height and weight after controlling for age, sex, breast feeding, and maternal smoking during pregnancy. Conclusions: Post-natal DDE exposure has adverse effects on pulmonary function mediated through its effects on height and weight in children. Further studies are needed to test these associations in other samples, preferable from a region with continuous high DDT application.