A Morphometric Assessment of the Condition of White Croakers (Genyonemus Lineatus) and Queenfish (Seriphus Politus) with Access to a Wastewater Outfall and a DDT/Polychlorinated Biphenyl Superfund Site: A Los Angeles Outer Harbor Case Study.

Sediments and water columns in the Los Angeles Outer Harbor (CA, USA), a major port behind a breakwater, contain DDTs and polychlorinated biphenyls (PCBs) from a nearby Superfund site, and contaminants brought in by ships, boats, stormwater, a river, and a wastewater outfall. White croaker and queenfish, a bottom feeder and a water column feeder, respectively, are two bioindicators for this marine ecosystem. Their condition as populations of fish is assumed to be robust for this role at all times. The present study tests this benign assumption amid progressively increasing DDT/PCB levels in their tissues. The results, as shown by progressively shrinking gonads, show a less than robust white croaker population particularly. Although the males are generally larger than the females, the length (standard [SL] or total [TL]) and body mass (BM) of 80 white croakers collected over 8 years were found to be similar irrespective of gender (177 mm, 212 mm, and 114 g, respectively). Queenfish (67) did not show such similarity over the same period (female: 152 mm SL, 177 mm TL, 56 g BM; male: 145 mm SL, 172 mm TL, 50 g BM). The site-specific expressions/values capturing the current conditions of these fish populations are SL = 0.835[TL] - 1.68 (r2 = 0.914, n = 68) and SL = 0.891[TL] - 8.88 (r2 = 0.961, n = 50) for white croaker and queenfish, respectively. In the allometric growth equation BM = a[SL]b , a and b are 2.83 and 2.49 × 10-4 (r2 = 0.817) for white croakers, and 6.10 and 2.73 × 10-5 (r2 = 0.825) for queenfish, respectively. The relative coefficients of condition Kn are 0.97 ± 0.07 and 1.01 ± 0.12 for white croakers and queenfish, respectively. Molecular-level studies are needed to establish definitively the links between DDT/PCB bioaccumulation in fish tissues and the robustness of the fish populations. Environ Toxicol Chem 2022;41:410-425. © 2021 SETAC.

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.

Assessment of the effects of atrazine, dichlorodiphenyltrichloroethane, and dimethoate on freshwater fish (Oreochromis mossambicus): a case study of the A2 farmlands in Chiredzi, in the southeastern part of Zimbabwe.

A study was carried out to assess the levels and effects of atrazine, dimethoate, and dichlorodiphenyltrichloroethane on freshwater fish (Oreochromis mossambicus). Water and fish were sampled once from a dam within the Hippo Valley A2 farmlands in Chiredzi, in the southeastern part of Zimbabwe. The samples were screened for atrazine, dimethoate, and dichlorodiphenyltrichloroethane (DDT), the pesticides commonly used in the region. Atrazine and dimethoate are pesticides commonly used in the control of weeds and pests in the agricultural production of sugarcane in Hippo Valley, Chiredzi region. The effects of the pesticides on biochemical endpoints of the sampled fish were determined. The analyzed biochemical end parameters were superoxide dismutase, catalase, glutathione S-transferase, and glutathione peroxidase activities in liver and white muscle fish extracts. Dichlorodiphenyltrichloroethane was observed in water and fish muscle tissue at concentrations of 131.3 µg/l and 171.7 µg/kg, respectively, while atrazine was detected at concentrations of 6.15 µg/l and 142.0 µg/kg in water and fish muscle tissue, respectively. The observed concentrations of atrazine and DDT in water samples were above the limits permissible by the World Health Organization in drinking water. Dimethoate was found in concentrations of 4.21 µg/l and 1.30 µg/kg in water and fish muscle tissue respectively. The observed concentration of dimethoate in water was below the acceptable limit set by the Guidelines for Canadian Drinking Water. Antioxidant enzyme activities were increased significantly (p < 0.05) in fish exposed to water from Hippo Valley, Chiredzi, when compared with the controls. The enhanced activities of the studied antioxidant enzyme system were attributed to exposure to pollutants in the water body. Alterations of the biochemical integrity of fish indicate negative effects of the pesticides on the well-being of fish and undoubtedly other aquatic biota as well.

Full-Life Cycle Toxicity Assessment of Sediment-Bound DDT and Its Degradation Products on Chironomus dilutus.

Because of its hydrophobicity and persistence, dichlorodiphenyltrichloroethane (DDT) is ubiquitous in sediments and poses significant risk to benthic organisms. Therefore, it is imperative to evaluate the long-term toxicity of DDT. However, limited information is available on its chronic toxicity to benthic invertebrates. Full-life cycle toxicity of sediment-bound DDT to Chironomus dilutus was assessed. Median lethal concentrations (with 95% confidence limits) of DDT and its degradation products (DDX) to C. dilutus were 334 (165-568), 21.4 (11.2-34.3), and 7.50 (4.61-10.6) nmol/g organic carbon after 10-, 20-, and 63-d exposure, respectively. In addition, median effect concentrations of DDX were 20.0 (15.0-25.3), 7.13 (4.10-10.5), and 8.92 (3.32-15.1) nmol/g organic carbon for growth, emergence, and reproduction, respectively. A toxicity spectrum was established to visually summarize chronic effects of DDX to midges. In addition, DDT degraded to dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE) during sediment aging, and their toxicity differed from that of the parent compound. Predicted toxic units of DDX in porewater were utilized to distinguish between toxicity from DDT and that of DDD and DDE. The results showed that DDD was the main contributor to the toxicity in C. dilutus. To improve the accuracy of sediment risk assessment of DDT, the composition of DDX should be considered. Environ Toxicol Chem 2019;38:2698-2707. © 2019 SETAC.

Toxicity assessment of pollutants sorbed on environmental sample microplastics collected on beaches: Part I-adverse effects on fish cell line.

Microplastics (MPs), are tiny plastic fragments from 1 µm to 5 mm generally found in the aquatic environment which can be easily ingested by organisms and may cause chronic physical but also toxicological effects. Toxicological assays on fish cell lines are commonly used as an alternative tool to provide fast and reliable assessment of the toxic and ecotoxic properties of chemicals or mixtures. Rainbow trout liver cell line (RTLW-1) was used to evaluate the toxicity of pollutants sorbed to MPs sampled in sandy beaches from different islands around the world during the first Race for Water Odyssey in 2015. The collected MPs were analyzed for polymer composition and associated persistent organic pollutants: polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT). In addition, DMSO-extracts from virgin MPs, MPs artificially coated with B[a]P and environmental MPs were analyzed with different bioassays: MTT reduction assay (MTT), ethoxyresorufin-O-deethylase (EROD) assay and comet assay. Microplastics from sand beaches were dominated by polyethylene, followed by polypropylene fragments with variable proportions. Organic pollutants found on plastic from beach sampling was PAHs (2-71 ng g-1). Samples from Bermuda (Somerset Long Bay) and Hawaii (Makapu'u) showed the highest concentration of PAHs and DDT respectively. No toxicity was observed for virgin microplastics. No cytotoxicity was observed on cells exposed to MP extract. However, EROD activity was induced and differently modulated depending on the MPs locations suggesting presence of different pollutants or additives in extract. DNA damage was observed after exposure to four microplastics samples on the six tested. Modification of EROD activity level and DNA damage rate highlight MPs extract toxicity on fish cell line.

Cytokine expression and lymphocyte proliferative capacity in diseased harbor porpoises (Phocoena phocoena) - Biomarkers for health assessment in wildlife cetaceans.

Harbor porpoises (Phocoena phocoena) in the North and Baltic Seas are exposed to anthropogenic influences including acoustic stress and environmental contaminants. In order to evaluate immune responses in healthy and diseased harbor porpoise cells, cytokine expression analyses and lymphocyte proliferation assays, together with toxicological analyses were performed in stranded and bycaught animals as well as in animals kept in permanent human care. Severely diseased harbor porpoises showed a reduced proliferative capacity of peripheral blood lymphocytes together with diminished transcription of transforming growth factor-ß and tumor necrosis factor-α compared to healthy controls. Toxicological analyses revealed accumulation of polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (DDE), and dichlorodiphenyltrichloroethane (DDT) in harbor porpoise blood samples. Correlation analyses between blood organochlorine levels and immune parameters revealed no direct effects of xenobiotics upon lymphocyte proliferation or cytokine transcription, respectively. Results reveal an impaired function of peripheral blood leukocytes in severely diseased harbor porpoises, indicating immune exhaustion and increased disease susceptibility.

Assessment of tissue-specific accumulation, elimination and toxic effects of dichlorodiphenyltrichloroethanes (DDTs) in carp through aquatic food web.

Microcosms containing DDT spiked-sediment, Tubifex tubifex and carp (Cyprinus carpio) were constructed to simulate a freshwater system. The accumulation, elimination and toxic effects of DDT (p,p'-DDT, o,p'-DDT), and its metabolites DDD (p,p'-DDD, o,p'-DDD) and DDE (p,p'-DDE, o,p'-DDE) were studied in T. tubifex and carp. Tissue/organ distributions of DDTs were also investigated in carp. The bioaccumulation and elimination of DDT differed in T. tubifex, carp and its tissues/organs. Unimodal or bimodal distributions were observed, and the concentrations of DDT metabolites (DDD and p,p'-DDE) increased over time. The carp organ with the highest concentrations of DDTs (DDT, DDD and DDE) was the gill. The largest mass distribution of DDTs was also in gill, followed by muscle and gastrointestinal tract. Maximum levels of DDTs in whole carp and carp muscle were 161 and 87 ng/g, respectively; therefore, the levels of DDTs observed in carp in this study were insufficient to constitute a health concern if present in fish for human consumption. Significant changes were observed in some biomarkers, including superoxide dismutase, catalase, glutathione-S-transferase, glutathione, and carboxylesterase, in T. tubifex and carp tissues during DDT exposure. Tissue-specific accumulation of DDTs in carp can be a key indicator of exposure to environmentally relevant concentrations.

Toxicity risk assessment of mercury, DDT and arsenic legacy pollution in sediments: A triad approach under low concentration conditions.

The determination of sediment toxicity is challenging due to site-specific factors affecting pollutants distribution and bioavailability, especially when contamination levels are close to expected non-effect concentrations. Different lines of evidence and sensitive tools are necessary for a proper toxicity risk assessment. We examined the case study of the Toce River (Northern Italy), where past industrial activities determined Hg, DDT and As enrichment in sediments. A triad approach comprising chemical, ecotoxicological and ecological analyses (benthic invertebrates) was carried out for risk assessment of residual contamination in river sediments. A "blank" site upstream from the industrial site was selected to compare the other sites downstream. Sediment, water and benthic invertebrate samplings were carried out following standard protocols. Results emphasized that despite the emissions of the industrial site ceased about 20years ago, sediments in the downstream section of the river remain contaminated by Hg, DDT and As with concentrations exceeding Threshold Effect Concentrations. A chronic whole-sediment test with Chironomus riparius showed decreased development rate and a lower number of eggs per mass in the contaminated sediments. Benthic community was analyzed with the calculation of integrated (STAR_ICMi) and stressor-specific metrics (SPEARpesticide and mean sensitivity to Hg), but no significant differences were found between upstream and downstream sites. On the other hand, multivariate analysis (partial Redundancy Analysis and variation partitioning) emphasized a slight impact on invertebrate community, accounting for 5% variation in taxa composition. Results show that legacy contaminants in sediments, even at low concentrations, may be bioavailable and possibly toxic for benthic invertebrates. At low concentration levels, sensitive and site-specific tools need to be developed for a proper risk analysis.

Time matters: A stock-pollution approach to authorisation decision-making for PBT/vPvB chemicals under REACH.

A core aim of the European chemicals legislation REACH is to ensure that the risks caused by substances of very high concern (SVHC) are adequately controlled. Authorisation - i.e. the formal approval of certain uses of SVHC for a limited time - is a key regulatory instrument in order to achieve this goal. For SVHC which are, in addition to their toxicity, (very) persistent and/or (very) bioaccumulative (PBT/vPvB chemicals), decision-making on the authorisation is conditional on a socio-economic analysis (SEA). In a SEA companies must demonstrate that the gains from keeping a chemical in use outweigh expected damage costs for society. The current setup of the REACH authorisation process, including existing guidance on performing a SEA, ignores that PBT/vPvB chemicals are stock pollutants. This paper explores the implications of incorporating stock pollution effects of these chemicals into a SEA on authorisation decision-making. We develop a cost-benefit approach which includes stock dynamics of PBT/vPvB chemicals. This allows identifying the decision rules for granting or refusing an authorisation. Furthermore, we generalize the model to an entire set of damage functions. We show that ignoring stock pollution effects in a SEA may lead to erroneous decisions on the use of PBT/vPvB chemicals because long-term impacts are not adequately captured. Using a historic case of DDT soil contamination as an illustrative example we discuss information requirements and challenges for authorisation decisions on the use of PBT/vPvB chemicals under REACH.

Risk assessment for children exposed to DDT residues in various milk types from the Greek market.

The occurrence of residues of DDT and its metabolites was monitored in 196 cow milk samples of various pasteurized commercial types collected from the Greek market. Residue levels were determined by GC-MS analysis. In 97.4% of the samples at least one DDT isomer or one of the DDT metabolites was detected, in levels not exceeding the maximum permitted residue level by the EU. Hazard Index for both carcinogenic and non-carcinogenic effects was estimated under two assumptions: a) using DDT concentrations from positive samples and b) imputing LOD/2 as an arbitrary concentration for negative samples. No statistically significant differences in detected or summed residue (p > 0.05) concentrations between different milk types were observed, with the exception of specific metabolites of DDT in some milk types. Exposure assessment scenarios were developed for children aged 1, 3, 5, 7 and 12 years old based on estimated body weights and daily milk consumption. Hazard Indices for non-carcinogenic effects were below 0.109 covering also carcinogenic effects according to WHO approach. The cancer risk values for carcinogenic effects according to the US EPA Cancer Benchmark Concentration approach, ranged from 0.4 to 18. For both effects the highest values were calculated for the 1- to 3-year-old age groups.

DDT, epigenetic harm, and transgenerational environmental justice.

Although the environmentally harmful effects of widespread dichlorodiphenyltrichloroethane (DDT) use became well-known following Rachel Carson's Silent Spring (1962), its human health effects have more recently become clearer. A ban on the use of DDT has been in place for over 30 years, but recently DDT has been used for malaria control in areas such as Africa. Recent work shows that DDT has transgenerational effects in progeny and generations never directly exposed to DDT. These effects have health implications for individuals who are not able to have any voice in the decision to use the pesticide. The transgenerational effects of DDT are considered in light of some widely accepted ethical principles. We argue that this reframes the decision to use DDT, requiring us to incorporate new considerations, and new kinds of decision making, into the deliberative process that determines its ongoing use. Ethical considerations for intergenerational environmental justice are presented that include concern and respect for autonomy, nonmaleficence, and justice. Here, we offer a characterization of the kinds of ethical considerations that must be taken into account in any satisfactory decisions to use DDT.

Organochlorine pesticides in fish from Taihu Lake, China, and associated human health risk assessment.

Because contaminants and nutrients always coexist in fish, the risk from contaminants and the benefit from nutrients, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are also concomitant via fish consumption. To investigate the risk and benefit via fish consumption, concentrations of dichlorodiphenyltrichloroethane and its metabolites (DDTs), and hexachlorocyclohexanes (HCHs) in the whole- and portion-muscles of fish from Taihu Lake, China, were measured. Based on the contaminant data and nutrients from our previous study, and the associated risk and benefit via fish consumption were estimated. The concentrations of DDTs and HCHs in the whole-muscles ranged from 7.8 × 10² to 3.4×10³ pg g⁻¹ ww, and from 67.3 to 300 pg g⁻¹ ww, respectively. Of DDTs and HCHs measured, p,p'-DDE and ß-HCH were respectively the most abundant pesticides. The composition profiles of DDTs and HCHs suggested that the pesticides were mainly historical residues. The benefit-risk quotient (BRQ) of EPA+DHA vs. POPs (persistent organic pollutants including data of DDTs, HCHs, and those of polychlorinated biphenyls and polybrominated diphenyl ethers cited from our previous study) via consumption of fish from Taihu Lake was calculated. As a result, to achieve the recommended EPA+DHA intake of 250 mg d⁻¹ for a healthy adult, the consumption of most fish species from the lake can cause cancer and non-cancer risks. However, the fish consumption at the rates of 44.9 g d⁻¹ by Chinese would not lead to the risks for most of the species. The results also suggested that the risk of consuming silver carp was generally lower than other fish species, and those of dorsal muscles were lower than ventral and tail muscles.

The legacy of persistent organic pollutants in Azerbaijan: an assessment of past use and current contamination.

Azerbaijan has a history of production and heavy use of organochlorine pesticides (OCPs) with use focused in the main agricultural lowland region centred on the Kur River. Using a number of data sources, including archived reports from several government ministries, we attempt to construct production and use inventories for dichlorodiphenyltrichloroethane (DDT) and HCHs and compare these to scientific estimates of production and use of these chemicals in the 1960s to the 1980s. Notable discrepancies are evident particularly for DDT, with Azeri government records indicating much higher use (147-fold) than that estimated by the international scientific community. Soil and river sediment data from the 1980s and 2000s are also presented. While it is recognised that analytical uncertainties remain high for these older data (generated by GC-ECD), there is some evidence to show a decline in concentrations for some OCPs over this period. Extremely high concentrations of OCPs are evident for soils sampled in the vicinity of obsolete pesticide storage sites (found in numerous locations around the agricultural lowlands) and these levels may pose a health risk to wildlife and humans. River sediment data indicate high levels of both OCPs and polychlorinated biphenyls (PCBs), particularly downstream of the confluence of the two main rivers, the Kur and Araz. Particle-bound annual fluxes from the Kur River into the Caspian Sea are estimated for PCBs and OCPs and these are likely to influence levels observed in local coastal sediments, with agreement between river sediment data generated in the early 2000s and coastal marine sediment data generated from separate studies. We recommend that monitoring efforts should focus on soils in agricultural areas and around pesticide storage and production facilities as these soils will continue to provide a source of POPs to the regional environment.

Exposure and health risk assessment of applicators to DDT during indoor residual spraying in malaria vector control program.

We assessed exposure of applicators, health risk of DDT to the applicators and evaluated the applicability of existing pesticide exposure models for indoor residual spraying (IRS). Patch sampling for dermal and personal air sampler for inhalation exposure were used in monitoring 57 applicators on the exposure assessment to DDT. The exposure of the applicators was also estimated using three exposure models. The mean actual dermal exposure was 449 mg total DDT per applicator per one house treatment. The applicators were exposed to DDT much beyond the estimated AOEL (acceptable operator exposure level) of DDT. The exposure estimated with ConsExpo 5.0 b01 model is situated between the median and the 75th percentile of the experimental data. On the other hand, spraying model 1 and spraying model 10 overestimate the exposure. Thus, these three models cannot be directly used for the particular circumstances of IRS as a tool for risk assessment. In general, use of DDT in IRS as a control method for malaria mosquitoes holds a high health risk for the applicators. Strict implementation of spraying procedures stated in the IRS manual of World Health Organization (WHO) is necessary to reduce the exposure level and health risk of applicators to DDT.

Assessment of exposure to DDT and metabolites after indoor residual spraying through the analysis of thatch material from rural African dwellings.

INTRODUCTION: We report on the analysis of 4,4'-dichlorodiphenyltrichloroethane (4,4'-DDT) and its metabolites in thatch and branch samples constituting the wall materials of dwellings from South African subtropical areas. This approach was used to assess the exposure to DDT in the residents of the dwellings after indoor residual spraying (IRS) following recommended sanitation practices against malaria vectors. DISCUSSION: Examination of the distributions of DDT compounds (2,4'-DDT, 4,4'-DDT and its metabolites) in 43 dwellings from the area of Manhiça (Mozambique) has shown median concentrations of 19, 130, and 23 ng/g for 2,4'-DDT, 4,4'-DDT, and 4,4'-DDE, respectively, in 2007 when IRS implementation was extensive. The concentrations of these compounds at the onset of the IRS campaign (n = 48) were 5.5, 47, and 2.2 ng/g, respectively. The differences were statistically significant and showed an increase in the concentration of this insecticide and its metabolites. Calculation of 4,4'-DDT in the indoor air resulting from the observed concentrations in the wall materials led to the characteristic values of environments polluted with this insecticide.

DDTs in rice frogs (Rana limnocharis) from an agricultural site, South China: tissue distribution, biomagnification, and potential toxic effects assessment.

Contamination with agricultural pesticides such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD), is among several proposed stressors contributing to the global declines in amphibian populations and species biodiversity. These chemicals were examined in insects and in the muscle, liver, and eggs of rice frogs (Rana limnocharis) from the paddy fields of an agricultural site in South China. The ΣDDT (sum of DDT, DDE, and DDD) concentrations ranged from 154 to 915, 195 to 1,400, and 165 to 1,930 ng/g lipid weight in the muscle, liver, and eggs, respectively. All the DDTs (DDT, DDE, and DDD) showed higher affinity for the liver relative to muscle tissue and can be maternally transferred to eggs in female frogs. The average biomagnification factors for DDTs ranged from 1.6 to 1.9 and 1.5 to 2.9 in female and male frogs, respectively, providing clear evidence of their biomagnification from insects to frogs. Compared with the reported DDT levels demonstrated to have toxic effects on frogs, DDTs in the present frogs are unlikely to constitute an immediate health risk. However, the adverse impacts of high DDT residues in eggs on the hatching success and their potential toxicity to the newly metamorphosed larval frogs should be assessed further.

Health risk assessment of organochlorine pesticides with emphasis on DDTs and HCHs in abandoned agricultural soils.

The aim of this study was to evaluate the consequence of changing land use from agriculture land to other use purposes with respect to OCPs non-cancer and cancer risk on human health, based on concentrations of DDTs and HCHs in soils collected from 55 locations representing 12 different land use types. There were no non-cancer risks of DDTs and γ-HCHs on adults and children, and there were very low cancer risks of DDD, o,p'-DDE, DDT, α-HCH, ß-HCH, γ-HCH based on their total concentrations in all samples. Nonetheless, there were significant correlations of DDT to its metabolites (DDE and DDD) (r = 0.506 and r = 0.648) and DDE to DDD (r = 0.438) both at p < 0.01. OCP levels should be routinely monitored in different environmental media and food in order to verify whether there is fresh input. Their potential risks on human health should also be assessed.

Assessment of nonoccupational exposure to DDT in the tropics and the north: relevance of uptake via inhalation from indoor residual spraying.

BACKGROUND: People who live in dwellings treated with indoor residual spraying (IRS) of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] for disease-vector control in the tropics and indigenous populations in the Arctic who consume marine mammals experience high nonoccupational exposure to DDT. Although the use of DDT in IRS is rising, the resulting nonoccupational exposure is poorly characterized. OBJECTIVES: We have provided a comparative assessment of exposure to DDT and its metabolites in the general population of the tropical and northern regions and in highly exposed populations in these regions. METHODS: We compiled > 600 average or median DDT concentrations from the peer-reviewed literature, representing > 23,000 individual measurements in humans, food, air, soil, and dust. We use Monte Carlo sampling of distributions based on these data to estimate distributions of population- and route-specific uptake. We evaluate our exposure estimates by comparing them with biomonitoring data. RESULTS: DDT concentrations are highest in people living in IRS-treated houses and lowest in the northern general population, differing by a factor of about 60. Inuits and the general population in the tropics have similar concentrations. Inhalation exposure explains most of the difference in concentration between the highly exposed and the general population in the Tropics. Calculated exposure levels are consistent with human biomonitoring data. CONCLUSIONS: Nonoccupational inhalation exposure is a relevant exposure pathway for people living in homes treated by IRS of DDT. Continued monitoring of time trends and DDE to DDT ratios in the Tropics and in the North is needed to identify a possible slowdown in concentration decline and the influence of ongoing DDT use.

Probabilistic ecological risk assessment of DDTs in the Bohai Bay based on a food web bioaccumulation model.

The fugacity-based food web model was developed to simulate the bioaccumulation of dichloro-diphenyl-trichloroethanes (DDTs) in the aquatic ecosystem in the Bohai Bay. The internal exposure levels (IELs) of DDTs in various organism categories were calculated. Monte Carlo-based uncertainty analysis was performed to get the of IEL distributions of DDTs in organisms. Probabilistic ecological risk assessment (ERA) was performed based on IEL distributions and internal species sensitivity distributions (SSDs). The results show that fugacities and bioaccumulation factors (BAFs) generally increased with increasing trophic level in the food web. Octanol-water partition coefficient (K(ow)), DDT levels in water and the lipid contents had the greatest influences on IELs in the organism bodies. The ecological risks of DDTs were relatively high. The risk order was p,p'-DDT>p,p'-DDE>p,p'-DDD. At an internal hazard quotient (HQ(int)) criterion of 1/5, the risk probabilities were 0.10 (0.055-0.17), 0.079 (0.045-0.13) and 0.053 (0.028-0.092) for p,p'-DDT, p,p'-DDE and p,p'-DDD, respectively. The results from ERA based on the internal exposure approximated those based on external exposure. The food web model is a feasible method to predict the extent of bioaccumulation and IELs of hydrophobic organic pollutants in organisms as a step to evaluate their risk posed on aquatic ecosystems.