Estimation of human body concentrations of DDT from indoor residual spraying for malaria control

Characteristics and Residual Health Risk of Organochlorine Pesticides in Fresh Vegetables in the Suburb of Changchun, Northeast China

In this study, eleven organochlorine pesticides (OCPs) in fresh vegetables in the Changchun suburb were investigated, and their potential health risks were evaluated. The average concentrations of OCPs in edible parts of vegetables were found in the following descending order: Σhexachlorocyclohexanes (ΣHCHs) (6.60 µg·kg^-1) > Σdichlorodiphenyltrichloroethanes (ΣDDTs) (5.82 µg·kg^-1) > ΣChlordanes (2.37 µg·kg^-1) > heptachlor (0.29 µg·kg^-1). Moreover, OCPs in different types of vegetables exceeded the maximum residue limits (MRLs), and the exceeding rates in various vegetables decreased in the following order: leafy vegetables (19.12%) > root vegetables (18.75%) > fruit vegetables (3.85%). The proportions of OCPs exceeding MRL in different vegetables were found in the following descending order: Welsh onion (22.50%) > radish (18.75%) > Chinese cabbage (14.29%) > pepper (6.90%) > cucumber (3.23%) > eggplant (2.94%) > tomato (2.78%). The sources' identification results showed that DDTs in vegetables came mainly from newly imported technical DDTs and dicofol, while HCHs originated mainly from lindane. For both adults and children, the average target hazard quotients (avg. THQ) were all less than 1, and the average hazard index (avg. HI) values were 0.043 and 0.036, respectively. There were no significant health risks associated with OCP exposure for the inhabitants of the study area.

A Systematic Review of Studies on Genotoxicity and Related Biomarkers in Populations Exposed to Pesticides in Mexico

In agricultural activities, pest control is essential, and the most effective method is the use of chemical agents that also represent an important source of exposure to potentially toxic compounds. Pesticides constitute a heterogeneous group of compounds designed specifically to control different pests. Besides measuring their levels or that of their metabolites in air, plasma, serum, blood, urine, etc., some studies reported increased DNA damage levels after occupational or environmental pesticides exposure, evidenced by several cytogenetic biomarkers such as chromosomal aberrations (CA), sister chromatid exchanges (SCE), micronuclei frequency (MN) together with other nuclear abnormalities (NA), alkaline comet assay, but also changes in oxidative stress parameters and miRNA levels. Single or combined, these techniques have also been used in genotoxic biomonitoring studies of workers occupationally exposed to pesticides in Mexico. Despite being a country with great agricultural activity and reported excessive pesticide use, genotoxic studies have been relatively few and, in some cases, contradictory. A review was made of the studies available (published until the end of 2020 on PubMed, Web of Science, Redalyc and Scielo, both in English and Spanish) in the scientific literature that evaluated occupational exposure of human samples to pesticides assessed with DNA damage and related biomarkers in Mexico.

Ten Bird Species, Six Guilds, Three Habitats, and 59 Chlorinated and Brominated POPs: What do 64 Eggs from the Largest Economic Hub of Southern Africa tell us?

There is little information on how POPs in eggs of different terrestrial, wetland, and aquatic birds share a large urban and rural landscape relate. We collected and analysed 64 eggs belonging to ten species of six feeding guilds, and compared organic chlorinated pesticide (OCP), polychlorinated biphenyl (PCB), and brominated flame retardants (BFR) residue concentrations and compositions. The eggs were collected in the Gauteng and the northern part of the Free Sate provinces of South Africa, one of the largest economic hubs in Africa. White-breasted Cormorant and African Darter eggs (at the highest trophic level as large aquatic predators) had the highest ΣOCP and ΣPCB concentrations, and Cape Sparrow and Southern Masked Weaver (granivores) eggs had the lowest concentrations, corresponding to the lowest trophic level in our collection. The highest percentage p,p'-DDT were in eggs of the terrestrial insectivore Crowned Lapwing (24%) and the scavenging African Sacred Ibis (17%), and the lowest in African Darter (1.0%) and White-breasted Cormorant (0.9%) eggs, suggesting that recency of DDT releases in a region cannot be gauged by this metric. African Sacred Ibis and Southern Masked Weaver eggs had the highest ΣBFR concentrations, with Crowned Lapwing, Cattle Egret, and White-breasted Cormorant eggs the least. Based on feeding guilds, the mean ΣPOP concentrations increased from granivore, aquatic omnivore, scavenger, terrestrial insectivore, small aquatic predator, to large aquatic predator. Mean ΣPOP concentrations in eggs increased from terrestrial, to wetland, to aquatic habitat birds. Interesting patterns were observed with multivariate analyses. There were no significant regressions between egg size and any summed POP classes. ΣBFR concentrations were not correlated with ΣOCPs or ΣPCBs. Eggshell thinning of African Darter eggs was associated with p,p'-DDE and ΣPCB suggesting risk. Other metrics also suggest risk. Therefore, different species of terrestrial and aquatic birds from the same area acquire and deposit POPs in different proportions and quantities in their eggs. Trophic levels and habitat explain the overall patterns, but detailed differences were found, some of which we are unable to explain. Based on POPs residues in terrestrial, wetland, and aquatic bird eggs, different POPs classes behave differently in a shared large inland industrial area, complicating deductions about POPs and associated risks based on one or few species.

Combined effect of microplastics and DDT on microbial growth: A bacteriological and metabolomics investigation in Escherichia coli

Microplastics (MPs) can adsorb toxic chemicals in biological or environmental matrixes and thus influence their behavior and availability. In order to investigate how the combined pollution of MPs and toxic organic chemical influence microbial growth and metabolism, Escherichia coli (E. coli) was grown in a complex, well-defined media and treated with polystyrene microplastics (PS MPs) and dichloro-diphenyl-tricgloroethane (DDT) at human relevant concentration levels. In vivo metabolites captured by a novel solid phase microextraction (SPME) probe, were used to reflect the metabolic dysregulation of E. coli under different pollution stresses. Results showed that the toxic effect of DDT displayed a distinct dose-dependent phenomenon while the existence of PS decreased the growth and metabolic interference effect of DDT on E. coli. Adsorption results revealed a mechanism that PS weakened the adverse impact of DDT by decreasing its free concentration in the treated culture media. Tricarboxylic acid (TCA) cycle related enzymes activities and antioxidant defense related substances of E. coli also proved the mechanism. The current study is believed to broaden our understanding of the ecotoxicity of MPs with toxic organic chemicals on microorganism.

Shorter interval and multiple flooding-drying cycling enhanced the mineralization of 14C-DDT in a paddy soil

DDT and its main metabolites (DDTs) are still the residual contaminants in soil. Sequential anaerobic-aerobic cycling has long been approved for enhancing the degradation of DDTs in soil. However, there is a lack of study investigating whether anaerobic-aerobic cycling would enhance the mineralization of DDT, and what a kind of anaerobic-aerobic management regimes would be optimal. To fill these gaps, the fate of ¹⁴C-DDT under different flooding-drying cycles was examined in a paddy soil by monitoring its mineralization and bioavailability. The results show the total mineralization of ¹⁴C-DDT in 314 days accounted for 1.01%, 1.30%, and 1.41%, individually for the treatments subjected to one, two, and three flooding-drying cycles. By comparison, the treatment subjected to the permanently aerobic phase had only 0.12% cumulative mineralization. Shorter intervals and multiple flooding-drying cycles enhanced the mineralization of ¹⁴C-DDT, however, reduced its bioavailability. Therefore, the enhanced mineralization was explained from an abiotic pathway as predicted by the one-electron reduction potential (E₁), the Fukui function for nucleophilic attack (f⁺) and the steps for anaerobic decarboxylation. From a practical view, it is important to investigate how the anaerobic-aerobic interval and frequency would affect the degradation and mineralization of DDT, which is very essential in developing remediation strategies.

Evidence of impacts from DDT in pelican, cormorant, stork, and egret eggs from KwaZulu-Natal, South Africa

DDT remains in use for malaria control in South Africa. We quantified DDTs in aquatic bird eggs from the highly biodiverse northern KwaZulu-Natal, a province of South Africa where DDT has been used for more than 80 years for malaria control. Pelican eggs had the highest ΣDDT concentration (7200 ng/g lipid mass; lm), Little Egret eggs had 6900 ΣDDT lm, African Openbill eggs had 3400 ng/g lm ΣDDT, and White-breasted Cormorant had 2400 ng/g lm. All species had non-significantly different mean concentrations of o,p'-DDT, p,p'-DDT, and ΣDDT, but with significant differences for p,p-DDE, o,p'-DDD, p,p'-DDD, %DDT, %DDD, and %lipid. The thinnest pelican eggshell (0.40 mm) had a ΣDDT concentration of 3300 ng/g lm.; the thickest shell (0.96 mm) had the lowest ΣDDT concentration at 29 ng/g lm; a 58% difference. Linear regressions of concentrations with shell thickness for the pelican eggs were significant for p,p'-DDE and p,p'-DDD, indicating risk of reproductive impairment. Compositional profiles indicate different food webs for the different species. DDT concentrations were lower than from another DDT-sprayed locality in South Africa, possible linked to differences in hydrology and rainfall. We conclude that significant ecotoxic threats associated with DDT remain in this area, and possibly threatens birds from less polluted areas. Our findings suggest continued negative human health and environmental impacts from DDT. There is an urgency to move away from DDT as quickly as possible; alternatively, to implement practices that prevent emissions of DDT to the environment while protecting human life.

Early-life exposure to p,p'-DDT and p,p'-DDE in South African children participating in the VHEMBE study: An assessment using repeated serum measurements and pharmacokinetic modeling

BACKGROUND

The World Health Organization recommends indoor residual spraying (IRS) of insecticides (including dichlorodiphenyltrichloroethane [DDT]) to fight malaria vectors in endemic countries. There is limited information on children's exposure to DDT in sprayed areas, and tools to estimate early-life exposure have not been thoroughly evaluated in this context.

OBJECTIVES

To document serum p,p'-DDT/E levels in 47 mothers and children participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE), a study conducted in an area where IRS insecticides are used annually, and to evaluate the precision and accuracy of a published pharmacokinetic model for the estimation of children's p,p'-DDT/E levels.

METHODS

p,p'-DDT/E levels were measured in maternal serum at delivery, and in children's serum at 12 and 24 months of age. A pharmacokinetic model of gestational and lactational exposure was used to estimate children's p,p'-DDT/E levels during pregnancy and the first two years of life, and estimated levels were compared to measured levels.

RESULTS

The geometric means of children's serum p,p'-DDT/E levels at 12 and 24 months were higher than those of maternal serum levels. Regression models of measured children's p,p'-DDT/E levels vs. levels estimated with the pharmacokinetic model (which only accounted for children's exposure through placental transfer and breastfeeding) had coefficients of determination (R2) ranging from 0.75 to 0.82. Estimated p,p'-DDE levels were not significantly different from measured levels, whereas p,p'-DDT levels were overestimated by 36% at 12 months, and 51% at 24 months.

CONCLUSION

Results indicate that children living in a sprayed area have serum p,p'-DDT/E levels exceeding their mothers' during the first two years of life. The pharmacokinetic model may be useful to estimate children's levels in the VHEMBE population.

Current implications of past DDT indoor spraying in Oman

In Oman, DDT was sprayed indoors during an intensive malaria eradication program between 1976 and 1992. DDT can remain for years after spraying and is associated with potential health risk. This raises the concern for human exposure in areas where DDT was used for indoor spraying. Twelve houses in three regions with a different history of DDT indoor spraying were chosen for a sampling campaign in 2005 to determine p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and p,p'-dichlorodiphenyldichloroethane (p,p'-DDD) levels in indoor air, dust, and outdoor soil. Although DDT was only sprayed indoor, p,p'-DDT, p,p'-DDE and p,p'-DDD were also found in outdoor soil. The results indicate that release and exposure continue for years after cessation of spraying. The predicted cancer risk based on concentrations determined in 2005, indicate that there was still a significant cancer risk up to 13 to 16years after indoor DDT spraying. A novel approach, based on region-specific half-lives, was used to predict concentrations in 2015 and showed that more than 21years after spraying, cancer risk for exposure to indoor air, dust, and outdoor soil are acceptable in Oman for adults and young children. The model can be used for other locations and countries to predict prospective exposure of contaminants based on indoor experimental measurements and knowledge about the spraying time-schedule to extrapolate region-specific half-lives and predict effects on the human population years after spraying.

Inverse correlation among organochlorine pesticide levels to total lipid serum contents: a preliminary study in Veracruz, México

Organochlorine pesticides, due to their hydrophobic nature and persistence, accumulate in tissues rich in lipids, which had been used as a biomarker for environmental pollution. In humans, organochlorine pesticides are continuously circulating and equilibrating among body compartments. The objective of the study was to evaluate the concentrations of organochlorine pesticides in blood serum and compare their levels to the total lipid contents in Veracruz, México inhabitants. Our hypothesis is that concentrations of organochlorine pesticides will increase just as lipid concentrations. Levels of organochlorine pesticides were divided in ascending tertils according to their total lipid content. The linear trend model applied surprisingly reveals that the average level of all organochlorine pesticides decreases as the lipid concentration increases. From one tertil to the next β-HCH, it shows a decrease of -3.19 mg kg(-1) on lipid basis, pp.'DDE levels decrease by -3.70 mg kg(-1) on lipid basis and pp.'DDT levels decrease -1.13 mg kg(-1) on lipid basis. We conclude that the levels and the orderly sequence of organochlorine pesticide distributions in the blood serum maintain an inverse relationship to total lipid blood serum concentrations.

Degradation of soil-adsorbed DDT and its residues by NZVI addition

Interaction of NZVI with DDTr in soil-slurry system.

Predictors of plasma DDT and DDE concentrations among women exposed to indoor residual spraying for malaria control in the South African Study of Women and Babies (SOWB)

BACKGROUND

Few studies have examined predictors of DDT (dichlorodiphenyltrichloroethane) and DDE (dichlorodiphenyldichloroethylene) levels among residents in homes sprayed with DDT for malaria control with the aim of identifying exposure-reduction strategies.

METHODS

The present analysis included 381 women enrolled in the Study of Women and Babies (SOWB) during 2010-2011, from eight South African villages in the Limpopo Province, South Africa. Indoor residual spraying (IRS) occurred in half of the villages. Questionnaires regarding various demographic and medical factors were administered and blood samples were obtained. We classified the women into three exposure groups by type of residence: unsprayed village (n = 175), IRS village in household with a low likelihood of DDT use (non-DDT IRS household, n = 106), IRS village in household with a high likelihood of DDT use (DDT IRS household, n = 100). We used multivariable models of natural log-transformed DDT plasma levels (in micrograms per liter) and DDE (in micrograms per liter) to identify predictors for each group.

RESULTS

Median levels of DDT and DDE among women in unsprayed villages were 0.3 [interquartile range (IQR): 0.1-0.9] and 1.7 (IQR: 0.7-5.5), respectively. Median levels of DDT and DDE among women in DDT IRS households were 2.6 (IQR: 1.1-6.6) and 8.5 (IQR: 4.7-18.0), respectively. In unsprayed villages, women with water piped to the yard, rather than a public tap, had 73% lower DDT (95% CI: -83, -57%) and 61% lower DDE (95% CI: -74, -40%) levels. In DDT IRS households, women who reported taking more than six actions to prepare their home before IRS (e.g., covering water and food) had 40% lower DDT levels (95% CI: -63, -0.3%) than women who took fewer than four actions.

CONCLUSION

The predictors of DDT and DDE plasma levels identified in the present study may inform interventions aimed at decreasing exposure. Among households where DDT is likely to be used for IRS, education regarding home preparations may provide an interventional target.

DDT residue contamination in sediments from Lake Sibaya in northern KwaZulu-Natal, South Africa: implications for conservation in a World Heritage Site

Maputaland in northern KwaZulu-Natal is a biodiversity hotspot and host to a number of ecologically important systems, including Lake Sibaya, southern Africa's largest natural freshwater lake. The region is malaria endemic and this study reports the presence of DDT and its metabolites in the sediments of Lake Sibaya that have resulted from the widespread and continued use of DDT in the region. DDT residues (p,p'-DDT, p,p'-DDD, and p,p'-DDE) were detected at all 11 sites sampled, with total concentrations ranging from 0.8 to 123 ng g(-1). Total DDT concentrations at Lake Sibaya represent some of the highest levels reported in South Africa, with most samples exceeding sediment quality guideline values. The findings from this study raise concerns and indicate that urgent further work is needed to investigate the potential for bioaccumulation, which could adversely affect breeding fish, bird, and crocodile populations in the region. While this study represents the first report on DDT contamination in Lake Sibaya, results have important implications for a number of other aquatic ecosystems within the Maputaland ecoregion, as well as the many local people who depend on them.

High levels of DDT in breast milk: intake, risk, lactation duration, and involvement of gender

We investigated presence and levels of DDT in 163 breast milk samples from four South African villages where, in three of them, malaria is controlled with DDT-sprayed indoors. Mean ΣDDT levels in breast milk were 18, 11, and 9.5 mg/kg mf (milk fat) from the three DDT-sprayed villages, respectively, including the highest ΣDDT level ever reported for breast milk from South Africa (140 mg/kg mf). Understanding the causes for these differences would be informative for exposure reduction intervention. The Provisional Tolerable Daily Intake (PTDI) for DDT by infants, and the Maximum Residue Limit (MRL) were significantly exceeded. DDT had no effect on duration of lactation. There were indications (not significant) from DDT-sprayed villages that first-born female infants drink milk with more ΣDDT than first-born male infants, and vice versa for multipara male and female infants, suggesting gender involvement on levels of DDT in breast milk - requiring further investigation.