Macro, meso, micro and nanoplastics in horticultural soils in Argentina: Abundance, size distribution and fragmentation mechanism

Soil contamination with plastics is a major worldwide concern. However, data on plastic pollution in horticultural soils from Latin America is scarce. Furthermore, there is limited information on the fragmentation process that plastics undergo in environmental conditions. In this study, we investigated the abundance of macro, meso, micro and nano plastics in a previously studied horticultural soil (2015) from Buenos Aires, that has not been used for any productive activity since. Although the mass of macroplastics was conserved, the number of plastic fragments per square meter increased significantly, indicating a possible natural fragmentation process. Black polyethylene (PE) mulch film was the most abundant plastic found. For this material, when considering the mass of plastic fragments per square meter, the relative abundance was, in decreasing order: macroplastics (65.1-79.1 %) > mesoplastics (15.6-24.8 %) > microplastics (5.3-12.4 %) > nanoplastics (0.1 %). However, when considering the number of plastic items per square meter, the order was: microplastics (2383-3815) > mesoplastics (1019-1076) > nanoplastics (509-550) > macroplastics (25-46). The size distribution of plastic debris was analyzed using the natural logarithm of abundance versus the square root of the mean decile area, with good linear correlations (0.7749 < R2 < 0.9785). These results provide evidence for an ongoing dynamic fragmentation process (Mott model). We hypothesize that the breakdown of plastic into smaller pieces could be explained by a random fragmentation process based on soil volume changes between natural hydration/dehydration states. These data suggest that soil under natural conditions could act as an 'environmental plastic grinder'.

Thermal paper as a potential source of bisphenol A for humans and the environment: migration and ecotoxicological impact

The objective of this work was to evaluate thermal paper (TP) tickets used in Argentina as a potential source of bisphenol A (BPA) that could impact humans and the environment. BPA in TP was measured by HPLC ranging from 11.1 to 30.5 mg BPAg^-1. In order to estimate the impact on humans, dermal BPA estimated daily intake was calculated as being 79.3 ± 19.5 μgd^-1 for workers and 1.6 ± 0.4 μgd^-1 for the general population. To evaluate TP's impact on the environment, BPA migration from TP to water and soil was studied. In the case of water, 99.6% of the BPA tickets content migrated in 30 h, while 78.0% moved into the soil in 96 h. BPA degradation kinetics in soil and water were also carried out; while in soil 61.9% of BPA degraded in 120 h, no degradation was observed up to 120 h in tap or river water.Additionally, ecotoxicological effects of BPA on the earthworm Eisenia andrei, a representative terrestrial indicator, were studied performing bioassays on lethality, avoidance, and reproductive and enzymatic activity. BPA showed to be very toxic to E. andrei (LC₅₀ value in contact paper test of 17 μgcm^-2, 95% confidence interval 6-46 μgcm^-2, 24 h exposure) and also caused an increase of total cocoons for earthworms exposed to 10 and 50 mg BPA kg^-1 soil. Evasion response was observed at a concentration of 50 mg BPA kg^-1 soil, while no effect was observed on cholinesterases, carboxylesterases, and glutathione S-transferases activities (1, 10, and 50 mg BPA kg^-1 soil). Finally, a simple BPA degradation technology using water peroxide and radish (Raphanus sativus) tissue as catalyst was explored as a simple and domestic potential treatment to avoid BPA migration to the environment.

Environmental fate of dibutylphthalate in agricultural plastics: Photodegradation, migration and ecotoxicological impact on soil

Phthalic acid esters (PAEs) were determined in polyethylene covers used in horticultural production units located at Moreno and La Plata districts (Buenos Aires, Argentina), detecting 0.69-8.75 mg PAEs kg^-1 plastic in greenhouse and tunnel films. The PAEs found were diisobutylphthalate (DIBP), dibutylphthalate (DBP) and diethylhexylphthalate (DEHP). DBP was chosen as a model molecule to carry out the photochemical degradation studies that led to the formation of monobutylphthalate (MBP) and phthalic acid (PA). DBP, MBP and PA migration from plastic covers was studied, finding that while DBP and MBP moved to soil and atmosphere in short times (<48 h), PA remained in the agricultural covers. Further experiments with DBP were made to explore the effect on migration of temperature (20 °C, 50 °C), film thickness (25 μm, 100 μm) and plastic ageing by solarization, observing that temperature increase, film thickness reduction and ageing by solarization favored DBP migration to the environment. DBP and MBP impact on soil were evaluated by avoidance and reproduction tests using Eisenia andrei as bioindicator. Both compounds reduced cocoon viability decreasing the number of juveniles at the lowest concentration assayed (0.1 mg kg^-1 of soil). At higher DBP and MBP concentrations the reproductive parameters (number of total cocoons, hatchability and number of juveniles) also showed alterations compared with the controls. Carboxylesterases (CaE), cholinesterases (ChE) and glutathion-S-transferases (GST) activities were analyzed in E. andrei exposed to DBP; cholinesterases activities were reduced at 1 and 10 mg DBP kg^-1 soil, and glutathione S-transferases activities were increased at 10 mg DBP kg^-1 soil while no effect was observed on carboxylesterases activities. These results emphasize the need to continue studying the impact of PAEs and their photodegradation products on the environment.

Human exposure and mass balance distribution during procymidone application in horticultural greenhouses

The purpose of this study was to analyze the impact of procymidone application in periurban horticultural greenhouses, especially on workers (applicators and assistants) and soil and plastic mulching, when mechanically pressurized application systems were employed. The mean Potential Dermal Exposure (PDE) was measured using the Whole Body Dosimetry technique. The PDE for the applicators was 188 mL h⁻¹ ± 103 mL h⁻¹, and 14.7 mL h⁻¹ ± 6.3 mL h⁻¹ for the assistants. In the first case, the most exposed body sections were the upper right and left (46.8 mL h⁻¹ ± 23.4 mL h⁻¹; 47.0 mL h⁻¹ ± 23.5 mL h⁻¹) and lower (20.8 mL h⁻¹ ± 10.4 mL h⁻¹; 17.3 mL h⁻¹ ± 8.7 mL h⁻¹) legs, while in the case of assistants, hands and legs were the most impacted limbs. Regarding the Margin of Safety (MOS) during the mix and load stage, two of three pesticide preparations resulted unsafe, while for the applicators, six of six spraying operations were unsafe. For the assistants, five of five operations were safe, but three of them were close to the safety limit.

Procymidone distribution between drift (0.03% ± 0.07 %), applicator (0.20% ± 0.15 %), polyethylene mulching (8.5% ± 4.5 %) and soil (3.0% ± 1.1 %) was determined with respect to the total pesticide applied. Procymidone soil impact was also evaluated using Eisenia andrei behavioral tests, finding positive correlations between procymidone application and avoidance and reproduction tests.

Human and soil exposure during mechanical chlorpyrifos, myclobutanil and copper oxychloride application in a peach orchard in Argentina

The objective of this study was to measure the impact of the mechanized chlorpyrifos, copper oxychloride and myclobutanil application in a small peach orchard, on humans (operators, bystanders and residents) and on the productive soil. The mean Potential Dermal Exposure (PDE) of the workers (tractor drivers) was 30.8mL·h^-1±16.4mL·h^-1, with no specific pesticide distribution on the laborers body. Although the Margin of Safety (MOS) factor for the application stage were above 1 (safe condition) for myclobutanil and cooper oxycloride it was below 1 for chlorpyrifos. The mix and load stage remained as the riskier operation. Pesticide found on the orchard soil ranged from 5.5% to 14.8% of the total chlorpyrifos, copper oxychloride and myclobutanil applied. Pesticide drift was experimentally measured, finding values in the range of 2.4% to 11.2% of the total pesticide applied. Using experimental drift values, bystander (for one application), resident (for 20 applications) and earthworm (for one application) risk indicators (RIs) were calculated for the chlorpyrifos plus copper oxychloride and for myclobutanil treatments for different distances to the orchard border. Earthworm RI was correlated with experimental Eisenia andrei ecotoxicological assays (enzymatic activities: cholinesterases, carboxylesterases and glutathione S-transferases; behavioral: avoidance and bait-lamina tests) with good correlation.

Polyethylene film incorporation into the horticultural soil of small periurban production units in Argentina

Horticulture makes intensive use of soil and extensive use of polyethylene (PE) sheeting and pesticides, producing an environment where the dynamics between soil and plastics can affect pesticide fate. We have determined that the presence of plastic residues in the horticultural soil of small production units equals 10% of the soil area, being meso and macro-sections the predominant fragment sizes. All soil samples were taken from different plots located in Cuartel V, Moreno district, in the suburbs of Buenos Aires city, Argentina. Laboratory experiments were conducted to see the relations among pesticide, soil and PE film. Endosulfan recovery from LDPE films (25μm and 100μm) was studied, observing evidence that indicated migration to the inside of the plastic matrix. To further analyze the dynamics of pesticide migration to soil and atmosphere, experiments using chlorpyrifos, procymidone and trifluralin were performed in soil-plastic-atmosphere microenvironments, showing that up to 24h significant amounts of pesticides moved away from the PE film. To determine whether PE residues could act as potential pesticide collector in soil, column elution experiments were done using chlorpyrifos, procymidone and trifluralin. Results showed an important pesticide accumulation in the mulch film (584μg-2284μg pesticide/g plastic) compared to soil (13μg-32μg pesticide/g soil). Finally, chemical and photochemical degradation of deltamethrin adsorbed in PE film was studied, finding a protective effect on hydrolysis but no protective effect on photodegradation. We believe that a deeper understanding of the dynamics among soil, plastic and pesticides in horticultural productive systems may contribute to alert for the implications of PE use for plastic sheeting.

Interventions for preventing venous thromboembolism in adults undergoing knee arthroscopy

BACKGROUND

Knee arthroscopy is a frequent surgical procedure. Arthroscopy procedures are considered minimally invasive. However, some patients will need extended surgical time, suffer injury and immobilization thus increasing the risk for thromboembolic events. Incidence of deep venous thrombosis (DVT) in patients undergoing knee arthroscopy is reported to be from 0.6% to 17.9% depending on the diagnostic method used. Different approaches are available for thromboprophylaxis (mechanical or pharmacological).

OBJECTIVES

To assess the effectiveness and safety of thromboprophylaxis to reduce the incidence of DVT in patients undergoing knee arthroscopy.

SEARCH STRATEGY

We searched the Cochrane Peripheral Vascular Diseases Group Specialized Register (last searched October 2006) the CENTRAL (last searched Issue 4, 2006), MEDLINE (1966 to 2006), EMBASE (1980 to 2006), and Lilacs (1988 to 2006). We contacted specialists known to be involved in phlebology and interested in post thrombotic syndrome for details of unpublished and ongoing trials.

SELECTION CRITERIA

Randomized clinical trials (RCTs) and controlled clinical trials (CCTs), whether blinded or not (i.e. double blinded, single blinded or unblinded) of all type of interventions, whether mechanical or pharmacological, single or in combination, used to prevent DVT in males and females over 18 years old undergoing knee arthroscopy. There was no restriction on language.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Four trials involving 527 predominantly male participants were included. The main weakness of the studies was the lack of correct stratification of the arthroscopic intervention. The relative risk (RR) of thrombotic events was 0.20 (95% confidence interval (CI); 0.07 to 0.57) comparing any type of low molecular weight heparin (LMWH) versus placebo. All thrombotic events but one (pulmonary embolism in the LMWH group) were distal venous thrombosis. Adverse events were most common in the intervention group than in the control group, RR 2.11 (95% CI 1.26 to 3.55). There were 66 episodes of adverse events. The number needed to harm was 20 for any adverse events.

AUTHORS' CONCLUSIONS

This meta-analysis suggests that LMWH reduces the incidence of distal DVT diagnosed by sonogram. The clinical benefit of this is uncertain. No strong evidence was found to conclude thromboprophylaxis is effective to prevent thromboembolic events and safe, in people with unknown risk factors for thrombosis, undergoing knee arthroscopy.

Efficacy of octreotide and sclerotherapy in the treatment of acute variceal bleeding in cirrhotic patients. A prospective, multicentric, and randomized clinical trial

BACKGROUND

Sclerotherapy is the most widely used method for treatment of acute variceal bleeding. Previous reports have suggested that octreotide infusion is as effective as sclerotherapy. Our aim was to investigate the efficacy and safety of octreotide in comparison with sclerotherapy in controlling variceal bleeding.

METHODS

Seventy-six cirrhotic patients were randomized to receive either sclerotherapy (n = 37) or octreotide (n = 39) infusion of 50 microg/h intravenously for 48 h after a bolus of 100 microg, followed by subcutaneous injection of 100 microg/8 h for an additional 72 h.

RESULTS

The two groups were similar in base-line data. A similar initial control of bleeding was obtained in 94.6% for sclerotherapy and 84.6% for octreotide (NS). No difference was observed between sclerotherapy and octreotide in rebleeding (23% versus 33%) and treatment failure (22% versus 36%, respectively). Furthermore, the overall success of treatment was 78% for sclerotherapy and 64% for octreotide. No significant difference in mortality was observed between treatments (eight patients for octreotide and three patients for sclerotherapy, NS).

CONCLUSIONS

These results show that both treatments present a very high and similar initial and final control of bleeding. However, there is a trend that could be clinically important towards better results in the patients treated with sclerotherapy.