A short-term study on the interaction of bacteria,fungi and endosulfan in soil microcosm

Endosulfan is one of the few organic chlorine insecticides still in use today in many developing countries. It has medium toxicity for fish and aquatic invertebrates. In this study, we added different concentrations of endosulfan to a series of soil samples collected from Baihua Park in Jinan, Shandong Province, China. Interactions of exogenous endosulfan, bacteria and fungi were analyzed by monitoring the changes in microbe-specific phospholipid fatty acids (PLFA), residual endosulfan and its metabolites which include; endosulfan sulfate, endosulfan lactone and endosulfan diol during a 9 days incubation period. Our results showed that endosulfan reduced fungi biomass by 47% on average after 9 days, while bacteria biomass increased 76% on average. In addition, we found that endosulfan degraded 8.62% in natural soil (NE), 5.51% in strepolin soil (SSE) and 2.47% in sterile soil (SE). Further analysis of the endosulfan metabolites in NE and SSE, revealed that the amount of endosulfan sulfate (ES) significantly increased and that of endosulfan lactone (EL) slightly decreased in both samples after 9 days. However, that of endosulfan diol (ED) increased in NE and decreased in SSE. After collective analysis our data demonstrated that fungi and bacteria responded differently to exogeous endosulfan, in a way that could promote the formation of endosulfan diol during endosulfan degradation.     

Isolation of an endosulfan-degrading bacterium from a coffee farm soil: Persistence and inhibitory effect on its biological functions

Endosulfan is a lypophilic persistent organic pollutant (POP) that has caused widespread concern due to its persistence in the environment, toxicity and bioaccumulation in living organisms. The aim of this study is to isolate endosulfan-degrading bacteria taken from five coffee farms historically exposed to this insecticide which could be used in future remediation strategies. The biodegradation capability of the isolated strain as well as endosulfan's impact on some of the strain's biological functions was studied. Endosulfan and its metabolites were analyzed using TLC and GC-MS. The isolated strain, capable of growing in a liquid culture treated with this insecticide as the sole sulfur source rather than a carbon source, was selected for further study. The isolated bacterium is Gram-negative, having the morphological and biochemical characteristics of Azotobacter sp. The remaining concentrations after 6 days, using 2 and 10 mg l^? 1 of endosulfan, were 57.6 and 72.3% respectively, and the degradation constants were 0.12 d^? 1 and 0.26 d^? 1. Four metabolites were detected, one of which was identified as endosulfan ether. Endosulfan reduced nitrogenase activity but had no impact on indole 3-acetic acid production. Thus, these results suggest that this strain has the potential to act as a biocatalyst in endosulfan degradation.     

Dechlorination of endocrine disrupting chemicals using Mg 0/ZnCl 2 bimetallic system

In the present study, Mg⁰/ZnCl₂ bimetallic system was evaluated for its efficiency to dechlorinate endosulfan and lindane in aqueous phase. Presence of acetone in the reaction mixture played an important role by increasing the solubilities of both pesticides and thereby accelerating its mass transfer. Water acetone ratio of 2:1 and 1:1 (v/v) was found optimum for the dechlorination of endosulfan and lindane respectively. Presence of H⁺ ions in the reaction mixture (50 μl ml⁻¹ of glacial acetic acid) accelerated the degradation efficiency of 30 ppm initial concentration of endosulfan (96% removal) and lindane (98% removal) at Mg⁰/ZnCl₂ dose of 5/1 mg ml⁻¹ within 30 min of reaction. Dechlorination kinetics for endosulfan and lindane (10, 30 and 50 ppm initial concentration of each pesticide) with varying Mg⁰/ZnCl₂ doses and the time course profiles of each pesticide were well fitted into the first order dechlorination reaction. The optimum observed rate constant (k_obs’) values for endosulfan (0.2168, 0.1209 and 0.1614 min⁻¹ for 10, 30 and 50 ppm initial concentration respectively) and lindane (0.1746, 0.1968 and 0.2253 min⁻¹ for 10, 30 and 50 ppm initial concentration respectively) dechlorination were obtained when the reactions were conducted with doses of 7.5/1 mg ml⁻¹ and 5/1 mg ml⁻¹ Mg⁰/ZnCl₂ respectively. Endosulfan and lindane were completely dechlorinated into their hydrocarbon skeletons namely, Bicyclo [2,2,1] hepta 2-5 diene and Benzene respectively as revealed by GCMS analysis.     

Dietary high protein and vitamin C mitigates endosulfan toxicity in the spotted murrel, Channa punctatus (Bloch, 1793)

The amelioration effect of dietary high protein and vitamin C against stress was evaluated in spotted murrel, Channa punctatus, exposed to endosulfan. Two hundred and forty fish (average weight: 27.01 g/fish), distributed equally into 4 different groups (control, T₁, T₂, and T₃), each with 6 replicates were fed with control (40% crude protein, CP and 0.1% vitamin C), T₁ (40% CP and 0.1% vitamin C), T₂ (50% CP and 0.1% vitamin C), and T₃ (50% CP and 0.2% vitamin C) diets for 90 days. Groups fed T₁, T₂, and T₃ diets were exposed to sublethal endosulfan concentration, whereas the control was maintained without endosulfan exposure. Results indicated significant reduction in the growth performance, survival, and activities of lactate dehydrogenase (liver and muscle), malate dehydrogenase (liver and muscle), enzymes of protein metabolism (aspartate amino transferase in liver and alanine amino transferase in liver and muscle), acetyl choline esterase (brain), alkaline phosphatase activity (liver), and ATPase (gill) enzymes of group fed control diet and exposed to endosulfan. However, endosulfan exposed fish fed high CP and vitamin C diet exhibited significant (P < 0.05) improvement in their growth performance and metabolic enzyme activities. Further, high CP and vitamin C diet reduced endosulfan accumulation in the muscle. Overall results indicate that vitamin C (0.2%) supplementation in high CP (50%) diet improves growth, metabolism, and reduce endosulfan bioaccumulation in C. punctatus.     

Monitoring of estrogen mimics by a recombinant yeast assay: synergy between natural and synthetic compounds?

Properties of mixtures of compounds exhibiting estrogenic potential have been questioned in the past. Synergistic effects of endocrine disrupters have been proposed, but could never be confirmed. In this study, the transactivational potential of xenoestrogens and phytoestrogens has been evaluated in a yeast test system. Pesticides such as endosulfan, dieldrin, atrazine, and the main metabolites, desethylatrazine and desisopropylatrazine, have been tested and their behavior as mixtures is compared to the behavior of the single compounds. Our results are in contrast to a report (Tran et al., 1996) on the inhibitive effects of xenoestrogens on 17 beta-estradiol-dependent transactivation. Phytoestrogens have been investigated in a similar manner. A synergistic effect could not be confirmed for both, xenoestrogens and phytoestrogens. These compounds are either weak estrogens or completely lack estrogenic potential. Their endocrine disrupting potential in more complex systems must be therefore attributed to other molecular mechanisms such as to metabolic modification or interference with steroidogenesis. This study shows that yeast systems are useful tools for monitoring pure estrogenic properties.     

Removal of endosulfan in a sequencing batch reactor: addition of granular activated carbon as improvement strategy

A granular activated carbon‐sequencing batch reactor (GAC‐SBR) was used to assess the removal of organochlorine endosulfan pesticide. The reactor operated in three stages: (I) starter and stabilization; (II) addition of 4 mg/L of endosulfan in feed; and (III) a single addition of 1 g/L of GAC to mixed liquor. During the 249 days of operation, the removal efficiency of COD was 96 ± 2%; for ‐N 72 ± 1%; and for PO₄^?3‐P 48 ± 13%. Was eliminated the 79% of endosulfan in stage II and 99% in stage III, not found its metabolite (endosulfan sulphate) in the reactor effluent. A consortium of eight bacterial strains was identified in the reactor stages, assessing five of them in the presence of 4 mg endosulfan/L by growth kinetics. According to the results, the joint action of the consortium and GAC addition is the responsible of eliminating the pesticide.     

An Overview Of Exposure And Management Of Persistent Organic Pesticides In Swaziland

Available information in Swaziland indicates that there are stocks of persistent organic pesticides that have been discontinued elsewhere because of their carcinogenic, mutagenic and teratogenic properties. Some of these pesticides, such as DDT and endosulfan, are still used in agriculture to protect crops and livestock from pests and diseases, and in vector control especially mosquitoes. There has been an increase in the use of these pesticides over the years. It is estimated that about 30-40% of the population may have already been exposed to these pesticides. The cultural and lifestyle determinants of pesticide exposure are highlighted.     

Organochlorine pesticides in serum and adipose tissue of pregnant women in Southern Spain giving birth by cesarean section

Since the appearance of DDT, increasingly potent insecticides have been developed to overcome the resistance developed by insects to successive products. Pesticides are also used in public health programs to control disease vectors. Despite legislation to control the use of certain products, they repeatedly appear in the adipose tissue, milk and serum of human populations. The present study determined the presence of organochlorine molecules in the adipose tissue, serum, and umblical cord of women giving birth by cesarean section in order to establish a possible correlation in organochlorine molecule content between these biological compartments and to examine fetal exposure to molecules with hormonal effects. Presence of nine organochlorines was detected by GC/ECD and confirmed by GC/MS. Highly significant differences (p<0.000) were observed between adipose tissue and maternal serum in concentrations of lindane, HCB, DDE, DDD, and endosulfan but not (p>0.5) in concentrations of endosulfan II or endosulfan sulfate. Only DDE concentrations differed (p<0.001) between maternal serum and umbilical cord serum. An association between pp'DDE and op'DDT was observed in maternal serum (p<0.094). An association in pp'DDE and pp'DDD content was found between adipose tissue and umbilical cord serum, and in pp'DDT content between adipose tissue and maternal serum. Results obtained indicate that exposure can be measured solely in serum when relatively high concentrations of pesticides are present.     

Exposure limits for occupational and environmental chemical pollutants in various media

Exposure limits for occupational and environmental chemical contaminants are based on animal experimentation and observation in humans. Usually, the final recommendations are "predictions" which can hardly guarantee the absolute safety for all. Late effects were discovered to lately in the past. The impact of the biotransformation of pollutants on their biological activity is demonstrated with trichloroethylene, styrene and N,N-dimethylformamide, which are suspected of having carcinogenic potential. In addition, trichloroethylene and N,N-dimethylformamide cause intolerance of alcohol with hyperacetaldehydemia; acetaldehyde is claimed to be carcinogenic as well. The biotransformation of these three widely used substances differs among various species. Different fate of chemicals in human and animal organisms results in the necessity to consider kinetic and metabolic studies in setting limits; in microorganisms also metabolites supposed to be formed in humans should be tested. Limits for some pollutants in various media are given.     

Biodegradation of endosulfan isomers in broth culture and soil microcosm by Pseudomonas fluorescens isolated from soil

Bacterial isolates from endosulfan-contaminated soil were grown in minimal medium and screened for endosulfan degradation. The isolate which used endosulfan and showed maximum growth was selected for detailed study. Maximum degradation in shake flask culture by Pseudomonas fluorescens was 92.80% of α and 79.35% of β endosulfan isomers in 15?days at 20?mg/L concentration, followed by 50 and 100?mg/L, while the corresponding values in static condition were 69.15 and 51.39%, respectively. Endosulfan concentration degradation declined significantly at 50 and 100?mg/L. Concomitant to degradation, release of chloride ion exhibited positive relation, while pH decreased from 7.0 to 4.53 in agitating and 7.0–5.18 in static condition. The soil microcosm study revealed maximum endosulfan degradation in sterilized soil amended with P. fluorescens. Endosulfan diol and endosulfan ether were among the products of endosulfan metabolism in broth culture, but only endosulfan ether was detected in the soil microcosm. Endosulfan sulphate, a persistent and toxic metabolite of endosulfan, was not detected in either case. The study showed that P. fluorescens could be used effectively for bioremediation of the pesticide contaminated sites.     

Reproductive toxicity of nitroaromatics to the cricket, Acheta domesticus

The effect of TNT (2,4,6-trinitrotoluene) and its metabolites, 2,4-dinitrotoluene (2,4-DNT), 2-amino-4,6-dinitrotoluene (2A-DNT), and 4-amino-2,6-dinitrotoluene (4A-DNT) on cricket (Acheta domesticus) reproduction was evaluated. We previously used crickets to assess the toxicity of a nitramine explosive (RDX) and its metabolites. It is common to find that while much information on the environmental impact of the parent compound is available in the literature, such is often not the case for the degradation metabolites of the parent compound. In some instances, these metabolites are as toxic (or more so) as the parent compound and we hypothesized that this might be the case for TNT. The presence of TNT and its metabolites in sand (10 µg/g) did not adversely affect cricket egg production, but adversely affected hatching of cricket eggs as compared to controls. However, there were no differences in hatching success among TNT and metabolite treatment groups. Hatching success of cricket eggs in soil or following topical exposure decreased as concentrations of TNT and its metabolites increased. The relative toxicity of TNT and its metabolites in soil generally followed the trend of TNT < 2A-DNT < 4A-DNT < 2,4-DNT. In addition, toxicity appeared to be higher in sand than in sandy loam soil or in the topical exposure test. After 45 days of exposure in sandy loam soil, the EC₂₀ (20% effect concentration), EC₅₀ (50% effect concentration), and EC₉₅ (95% effect concentration) were 14, 116, and 10,837 µg/g for TNT: 1.7, 32, and 16,711 µg/g for 2A-DNT: 1.9, 9, and 296 µg/g for 4A-DNT: and 0.4, 5.7, and 1437 µg/g for 2,4-DNT. Overall, results suggest that parent TNT and metabolites are toxic to cricket eggs at relatively high concentrations and these toxic effects are manifested as a decrease in hatching success.     

The role of toxicity in the carcinogenicity of Endosulfan

Two studies have been undertaken on the toxicity and carcinogenicity of endosulfan, a chlorinated cyclodiene - the NCI Endosulfan Rat Study and the NCI Endosulfan Mouse Study. Histological sections have been examined and the results of this review are based on my diagnoses.Endosulfan is highly toxic for male and female Osborne-Mendel rats, particularly for male rats. The chemical causes interstitial fibrosis or acute tubular necrosis of the kidney and death. These lesions, as well as atrophy of the testes, polyarteritis, parathyroid hyperplasia, osteitis fibrosis of bone, and abscesses of the lung, interfere with the health of the animals and with the development of neoplasms.Endosulfan, even though it is extremely toxic, is carcinogenic for male and female Osborne-Mendel rats. The chemical induced malignant neoplasms at all sites in male and female rats and in the endocrine organs in male rats. Rats of both sexes developed lymphosarcomas, and female rats had neoplasms of the reproductive system. Endosulfan is also carcinogenic for the liver of female mice.     

Endosulfan, a global pesticide: A review of its fate in the environment and occurrence in the Arctic

This review investigates the fate and behaviour of endosulfan, a current-use organochlorine pesticide, in temperate environments and the Arctic. Usage data and patterns, physical-chemical properties, environmental partitioning and degradation, environmental levels, global distribution and temporal trends are evaluated and discussed in the context of criteria that designate a substance as a persistent organic pollutant. Endosulfan is one of the most abundant OC pesticides in the global atmosphere and is capable of undergoing long range transport to remote locations such as the Arctic. Degradation of the two isomers, α- and β-endosulfan, does occur in temperate/tropical soil and aquatic systems, both by abiotic and biotic processes, although this is highly dependent on the prevailing environmental conditions. Endosulfan sulfate is the major metabolite and this recalcitrant compound has been detected in air and is present in remote mountain lake sediments, although in comparison to α-endosulfan, data for this compound in the wider environment are lacking.Temporal trends from ice/snow cores as well as mountain lake sediments reveal a marked increase in endosulfan accumulation from the 1980s onwards. Furthermore, unlike other ‘legacy’ OC pesticides, levels of α-endosulfan do not show a decline in atmospheric monitoring data, reflecting ongoing use of this pesticide in the northern hemisphere. Endosulfan is present at low concentrations (relative to the pesticide, lindane) in surface Arctic Ocean waters, with the atmosphere likely to be the major contemporary source. Residues of endosulfan have been detected in marine biota for different geographical regions of the Arctic, with higher bioaccumulation factors (> 10³-10⁷) for zooplankton and various species of fish, compared to studies in warmer/temperate systems. Endosulfan is present in marine mammals, although there is uncertainty in the various Arctic biota datasets due to differences in analytical techniques. For some biota, biomagnification factors for α-endosulfan are > 1, notably from fish to seal, although there is a wide variability in values between the same species for different regions of the Arctic. There is little if any evidence of trophic magnification of α-endosulfan in well-defined marine foodwebs, with some evidence of bio-dilution at higher trophic levels, presumably due to increased metabolism.Endosulfan does fulfil several of the criteria under the UNEP Stockholm Convention for designation as a persistent organic pollutant. The α- and β-isomer have similar physical-chemical properties and environmental behaviour to some of the obsolete organochlorine pesticides, although an assessment of their persistence and toxicity should be viewed alongside endosulfan sulfate, as ‘Σendosulfan’. Persistence of ‘Σendosulfan’ coupled to ongoing use of endosulfan pesticides, will ensure continued long-range transport and contamination of remote environments.     

Role of epidemiologic studies in evaluating the carcinogenicity of chromium compounds

Epidemiologic and animal studies have identified intermediately-soluble chromates as human carcinogens. Epidemiologic studies also provide moderately strong evidence to conclude that chromates do not cause cancer at sites other than the respiratory tract. This information, combined with the evidence from animal studies and in vitro experiments, has led to the conclusion that chromates do not present a carcinogenic risk from ingestion. Unfortunately, epidemiologic studies have not provided definitive answers to other questions: (i) does trivalent chromium present a cancer risk?; (ii) is there a threshold for carcinogenic effects?; and (iii) what is the appropriate model for predicting cancer risk? Mechanistic research with supporting evidence from animal studies has provided the most useful information to answer these questions. Working hypotheses are: (i) trivalent chromium is not a carcinogen; (ii) there are probably substantial differences in carcinogenic potency between chromates, with the water-soluble compounds having lower potency than intermediately-soluble compounds; (iii) only respiratory tract cancers are caused by exposure to chromates, and ingestion and chromates does not constitute a carcinogenic risk; (iv) there is probably a threshold for carcinogenic effects from chromium due to detoxification mechanisms and lack of bioavailability of low doses; and (v) currently used models for quantitative risk assessment (e.g. the low dose linearized multi-stage model) are inappropriate to predict low dose cancer risks from exposure to chromates.     

Evaluating the effectiveness of copper sulphate,chlorine, potassium permanganate,hydrogen peroxide and ozone on cyanobacterial cell integrity

Cyanobacterial blooms are continuously critical challenges in drinking water systems which can have various negative impacts such as production of taste, odour and toxic compounds. Furthermore, the intracellular metabolites could be released into surrounding waters when the cyanobacterial membranes are destroyed. Although a variety of techniques have been developed to control cyanobacterial blooms and remove cyanobacterial cells or metabolites in water treatment processes, the effect of these treatments on the membrane integrity of cyanobacterial cells have not been systematically studied and compared. This study evaluated the effectiveness of copper sulphate (CuSO₄), chlorine, potassium permanganate (KMnO₄), hydrogen peroxide (H₂O₂) and ozone on the cell integrity and densities of Microcystis aeruginosa. All of these technologies can compromise the cell membrane of cyanobacteria to varying degrees. Chlorine showed the strongest ability to impair the cell integrity with a majority (≥88%) of the cells compromised within the first minute and with the cell lysis rates ranging of 0.640–3.82 h⁻¹ during 1–60 min. Ozone dose of 6 mg L⁻¹ also could induce 90% lysis of the cyanobacterial cells in 5 min and the cell lysis rate of KMnO₄ (10 mg L⁻¹) was 0.829 h⁻¹. CuSO₄ and H₂O₂ could not only destroy the viability of cyanobacterial cells but also showed algistatic potential over the 7 day treatment. The potential of all the oxidants (chlorine, KMnO₄, H₂O₂ and ozone) considered as algicides were discussed in this study. The benefits and drawbacks of these control and water treatment options were assessed as well.     

Biodegradation of triclosan by a wastewater microorganism

Triclosan, a synthetic antimicrobial agent, has been considered as an emerging environmental contaminant. Here we reported a triclosan-degrading wastewater bacterial isolate, Sphingopyxis strain KCY1, capable of dechlorinating triclosan with a stoichiometric release of chloride. The stain can degrade diphenyl ether but not 2,4,4′-tribromodiphenyl ether and 2,2′,4,4′-tetrabromodiphenyl ether, despite all these three compounds are structurally similar to triclosan. While strain KCY1 was unable to grow on triclosan and catechol, it could grow with glucose, sodium succinate, sodium acetate, and phenol. When grown with complex nutrient medium containing a trace amount of triclosan (as low as 5 μg/L), the strain could retain its degradation ability toward triclosan. The maximum-specific triclosan degradation rate (q_m) and the half-velocity constant (K_m) are 0.13 mg-triclosan/mg-protein/day and 2.8 mg-triclosan/L, respectively. As triclosan degradation progressed, five metabolites were identified and these metabolites continue to transform into non-chlorinated end products, which was supported by a sharp drop in androgenic potential. The activity of catechol 2,3-dioxygenase in the cell extract was detected. No triclosan degradation was observed in the presence of 3-fluorocatechol, an inhibitor of meta-cleavage enzyme, suggesting that triclosan degradation proceed via meta-cleavage pathway. Based on all the observations, a degradation pathway for triclosan by strain KCY1 was proposed.     

The Italian wall lizard (Podarcis sicula) as a bioindicator of oil field activity

The aim of this study was to develop and to validate a methodology based on biomarker responses and residue analysis on the terrestrial lizard Podarcis sicula to assess the ecotoxicological effects associated with on-shore oil extraction. The oil treatment plant investigated is located in Val d'Agri (southern Italy). Italian wall lizards were sampled on four stations along a transect determined on the basis of prevailing winds downwind of the oil plant. Cytochrome P450 1A1 activities (EROD and BPMO), AChE activity, PAH bile metabolites and contaminant levels (PAHs and trace elements) were measured. Major results in the evaluation of toxicological impact of oil field activity in the Italian wall lizards were obtained for Cd, Hg, total and carcinogenic PAH levels, and PAH metabolites in bile. Results obtained validate, for the first time, P. sicula as a terrestrial bioindicator for the assessment of the toxicological impact of on-shore extraction activity.     

Urinary metabolites of 4-n-nonylphenol in rainbow trout (Oncorhynchus mykiss).

Nonylphenol is present in surface water and aquatic sediments and because of its lipophilic characteristics shows a considerable potential to bioaccumulate in aquatic organisms. Nonylphenol inhibits testicular growth and induces vitellogenin synthesis in male rainbow trout. In order to better understand the effects of nonylphenol on fish and its impact in the aquatic environment, it is essential to elucidate the metabolic fate of this compound. A single oral dose (5 mg, 1850 KBq) of [3H]4-n-nonylphenol resulted in 1.1% and 3.0% of the ingested radioactivity eliminated in urine after 24 and 48 h, respectively. Four metabolites were separated by radio-HPLC and tentatively identified by mass spectrometry. Urinary metabolites likely resulted from the initial omega-oxidation of 4-n-nonylphenol to the putative 9-(4-hydroxyphenyl)-nonanoic acid which subsequent beta-oxidation led to 4-hydroxybenzoic acid as major metabolite. Intermediary metabolites, namely 3-(4-hydroxyphenyl) propionic acid and 3-(4-hydroxyphenyl)-2-propenoic acid confirmed the occurrence of this beta-oxidative pathway. Urinary metabolites identified in this study were quite different from biotransformation products previously described in bile of trout treated with 4-n-nonylphenol.     

Sorption of dichlorodiphenyltrichloroethane (DDT) and its metabolites by activated carbon in clean water and sediment slurries

Polyethylene-water partitioning coefficients (K_PE) and mass transfer coefficients (k_PE) for the ortho and para isomers of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) and its metabolites dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE) and, dichlorodiphenylmonochloroethylene (DDMU) were measured. These data were used to derive activated carbon (AC) sorption isotherms in clean water in the sub-nanogram per litre free aqueous concentration range for a virgin and a regenerated AC. The sorption strength of AC for DDT and its metabolites was very high and logarithmic values of the AC-water partitioning coefficients, log K_AC, ranged from 8.47 to 9.26. A numerical mass transfer model was calibrated with this data to interpret previously reported reductions in DDT uptake by semipermeable membrane devices after AC amendment of sediment from Lauritzen Channel, California, USA. The activated carbon-water partitioning coefficient values (K_AC) measured in clean water systems appear to overestimate the AC sorption capacity in sediment up to a factor 32 for DDT and its metabolites at long contact time with fine-sized AC. Modelling results show decreased attenuation of the AC sorption capacity with increased sediment-AC contact time. We infer that increased resistance in mass transfer of DDTs to sorption sites in the microporous region likely caused by deposits of dissolved organic matter in the macro- and mesopores of AC appears to be the most relevant fouling mechanism. These results suggest that DDTs may diffuse through possible deposits of dissolved organic matter over time, implying that the effects of sediment on the sorption of DDTs by AC may be more kinetic than competitive.     

Particle‐associated polycyclic aromatic hydrocarbons in a representative urban location (indoor‐outdoor) from South Europe: Assessment of potential sources and cancer risk to humans

PM₁₀‐bound polycyclic aromatic hydrocarbons (PAHs) levels were monitored at urban locations (outdoor/indoor) within the city of Madrid between May 2017 and April 2018. Fourteen PAH congeners were measured, potential emission sources were identified as were potential carcinogenic risks. The ΣPAHs averaged 0.577 and 0.186 ng/m³ in outdoor and indoor air, with a high linear correlation per individual mean PAH and month. The largest contributors to the ΣPAHs were the high‐molecular‐weight PAHs. Principal component analysis‐multiple linear regression results showed that emissions from diesel and vehicular processes explained 27% and 23% of the total variance of outdoor and indoor air, while combustion processes accounted for 30% and 25% in ambient and indoor air, respectively. During the cold season, biomass burning plus coal and wood combustion were additional sources of outdoor emissions. The heavy‐, medium‐ and light‐molecular‐weight PAH originating from outdoor sources accounted for 72%, 80%, and ~60% of the indoor levels of the three respective PAH groups. Average BaP concentration was 0.029 and 0.016 ng/m³ in outdoor and indoor air, respectively. Estimated BaPeq concentration averaged 0.072, 0.035, and 0.027 ng/m³ for outdoor, indoor, and indoor‐generated individual PAH concentrations, respectively. The estimated carcinogenic risk falls within the range of acceptable risk targeted by the US‐EPA.