Ensayo clínico aleatorizado, controlado con placebo y doble ciego para evaluar la eficacia y la seguridad del ácido tranexámico tópico en el ahorro de pérdidas sanguíneas en pacientes tratados mediante cirugía protésica de rodilla / Randomized, placebo-controlled, double-blind clinical trial to evaluate efficacy and safety of topical tranexamic acid in saving blood loss in patients undergoing prosthetic knee surgery

Antecedentes y objetivo: Durante la artroplastia de rodilla se produce una pérdida sanguínea importante. El objetivo de nuestro estudio es valorar la eficacia y la seguridad de la administración tópica de 3 g de ácido tranexámico (TXA) en cuanto a la reducción de pérdidas sanguíneas en artroplastia de rodilla. Material y método: Se ha realizado un ensayo clínico aleatorizado, fase iii, doble ciego, controlado con placebo. Se incluyó a 150 pacientes en 2grupos paralelos de tratamiento (75 por brazo). La solución se administró de forma tópica intraarticular tras la cementación y previo al cierre capsular. Se realizaron determinaciones analíticas antes y después de la cirugía. Resultados: La pérdida total de sangre media para el grupo placebo fue de 831,5ml y 662,3ml para el grupo TXA con una diferencia entre ambos de 169,2ml, lo que supone un ahorro del 20,4%, siendo estadísticamente significativa (p<0,001). No se obtuvieron diferencias en el inicio de la deambulación, días de ingreso o escala visual analógica al mes de la cirugía. Se retiró a 10pacientes por infección del tracto urinario prequirúrgico, alergia a metales, fallo de selección, debilitamiento rotuliano, inestabilidad protésica, fractura tibial intraquirúrgica, cambio de indicación a prótesis unicompartimental y una pérdida de seguimiento. Hubo una única complicación no relacionada con el fármaco (globos vesicales de repetición). Conclusión: La administración de TXA de forma tópica tras la cementación de los componentes protésicos en artroplastia de rodilla en una única dosis demuestra que es segura y eficaz.(AU)

Background and objective: Knee arthroplasty is a major surgery with potential significant blood loss. Assess the efficacy and safety of topical administration of 3g of tranexamic acid (TXA) in terms of reducing blood loss in knee arthroplasty. Material and method: A randomized, phase III, double-blind, placebo-controlled clinical trial has been conducted. We included 150 patients in 2parallel treatment groups (75 per arm). The solution was administered topically intra-articular after cementation and prior to capsular closure. Analytical determinations were made before and after surgery to quantify blood loss. Results: Total blood loss for the placebo group was 831.5ml and 662.3ml for the TXA group. The difference between the 2groups was 169.2ml; which means a save of 20.4 per cent; this difference being statistically significant (P<.001). There were no differences in terms of the onset of ambulation, days of admission or Visual Analogue Scale at one month of surgery. Ten patients were rejected for presurgical urinary tract infection, metal allergy, selection failure, patellar weakening, prosthetic instability, intrasurgical tibial fracture, change of indication to unicompartimental prosthesis and a loss of follow-up. There was only one complication unrelated to the investigational drug (bladder balloon). Conclusion: The administration of TXA topically after cementation of the prosthetic components in total knee arthroplasty in a single dose has demonstrated being safe and effective.(AU)

[Translated article] Randomized, placebo-controlled, double-blind clinical trial to evaluate efficacy and safety of topical tranexamic acid in saving blood loss in patients undergoing prosthetic knee surgery / Ensayo clínico aleatorizado, controlado con placebo y doble ciego para evaluar la eficacia y la seguridad del ácido tranexámico tópico en el ahorro de pérdidas sanguíneas en pacientes tratados mediante cirugía protésica de rodilla

Antecedentes y objetivo: Durante la artroplastia de rodilla se produce una pérdida sanguínea importante. El objetivo de nuestro estudio es valorar la eficacia y la seguridad de la administración tópica de 3 g de ácido tranexámico (TXA) en cuanto a la reducción de pérdidas sanguíneas en artroplastia de rodilla. Material y método: Se ha realizado un ensayo clínico aleatorizado, fase iii, doble ciego, controlado con placebo. Se incluyó a 150 pacientes en 2grupos paralelos de tratamiento (75 por brazo). La solución se administró de forma tópica intraarticular tras la cementación y previo al cierre capsular. Se realizaron determinaciones analíticas antes y después de la cirugía. Resultados: La pérdida total de sangre media para el grupo placebo fue de 831,5ml y 662,3ml para el grupo TXA con una diferencia entre ambos de 169,2ml, lo que supone un ahorro del 20,4%, siendo estadísticamente significativa (p<0,001). No se obtuvieron diferencias en el inicio de la deambulación, días de ingreso o escala visual analógica al mes de la cirugía. Se retiró a 10pacientes por infección del tracto urinario prequirúrgico, alergia a metales, fallo de selección, debilitamiento rotuliano, inestabilidad protésica, fractura tibial intraquirúrgica, cambio de indicación a prótesis unicompartimental y una pérdida de seguimiento. Hubo una única complicación no relacionada con el fármaco (globos vesicales de repetición). Conclusión: La administración de TXA de forma tópica tras la cementación de los componentes protésicos en artroplastia de rodilla en una única dosis demuestra que es segura y eficaz.(AU)

Background and objective: Knee arthroplasty is a major surgery with potential significant blood loss. Assess the efficacy and safety of topical administration of 3g of tranexamic acid (TXA) in terms of reducing blood loss in knee arthroplasty. Material and method: A randomized, phase III, double-blind, placebo-controlled clinical trial has been conducted. We included 150 patients in 2parallel treatment groups (75 per arm). The solution was administered topically intra-articular after cementation and prior to capsular closure. Analytical determinations were made before and after surgery to quantify blood loss. Results: Total blood loss for the placebo group was 831.5ml and 662.3ml for the TXA group. The difference between the 2groups was 169.2ml; which means a save of 20.4 per cent; this difference being statistically significant (P<.001). There were no differences in terms of the onset of ambulation, days of admission or Visual Analogue Scale at one month of surgery. Ten patients were rejected for presurgical urinary tract infection, metal allergy, selection failure, patellar weakening, prosthetic instability, intrasurgical tibial fracture, change of indication to unicompartimental prosthesis and a loss of follow-up. There was only one complication unrelated to the investigational drug (bladder balloon). Conclusion: The administration of TXA topically after cementation of the prosthetic components in total knee arthroplasty in a single dose has demonstrated being safe and effective.(AU)

[Translated article] Randomized, placebo-controlled, double-blind clinical trial to evaluate efficacy and safety of topical tranexamic acid in saving blood loss in patients undergoing prosthetic knee surgery.

BACKGROUND AND OBJECTIVE: Knee arthroplasty is a major surgery with potential significant blood loss. Assess the efficacy and safety of topical administration of 3g of tranexamic acid (TXA) in terms of reducing blood loss in knee arthroplasty. MATERIAL AND METHOD: A randomized, phase III, double-blind, placebo-controlled clinical trial has been conducted. We included 150 patients in 2 parallel treatment groups (75 per arm). The solution was administered topically intra-articular after cementation and prior to capsular closure. Analytical determinations were made before and after surgery to quantify blood loss. RESULTS: Total blood loss for the placebo group was 831.5ml and 662.3ml for the TXA group. The difference between the 2 groups was 169.2ml; which means a save of 20.4%; this difference being statistically significant (p<.001). There were no differences in terms of the onset of ambulation, days of admission or visual analogue scale at one month of surgery. Ten patients were rejected for presurgical urinary tract infection, metal allergy, selection failure, patellar weakening, prosthetic instability, intrasurgical tibial fracture, change of indication to unicompartimental prosthesis and a loss of follow-up. There was only one complication unrelated to the investigational drug (bladder balloon). CONCLUSION: The administration of TXA topically after cementation of the prosthetic components in total knee arthroplasty in a single dose has demonstrated being safe and effective.

Randomized, placebo-controlled, double-blind clinical trial to evaluate efficacy and safety of topical tranexamic acid in saving blood loss in patients undergoing prosthetic knee surgery. / Ensayo clínico aleatorizado, controlado con placebo y doble ciego para evaluar la eficacia y la seguridad del ácido tranexámico tópico en el ahorro de pérdidas sanguíneas en pacientes tratados mediante cirugía protésica de rodilla.

BACKGROUND AND OBJECTIVE: Knee arthroplasty is a major surgery with potential significant blood loss. Assess the efficacy and safety of topical administration of 3g of tranexamic acid (TXA) in terms of reducing blood loss in knee arthroplasty. MATERIAL AND METHOD: A randomized, phase III, double-blind, placebo-controlled clinical trial has been conducted. We included 150 patients in 2parallel treatment groups (75 per arm). The solution was administered topically intra-articular after cementation and prior to capsular closure. Analytical determinations were made before and after surgery to quantify blood loss. RESULTS: Total blood loss for the placebo group was 831.5ml and 662.3ml for the TXA group. The difference between the 2groups was 169.2ml; which means a save of 20.4 per cent; this difference being statistically significant (P<.001). There were no differences in terms of the onset of ambulation, days of admission or Visual Analogue Scale at one month of surgery. Ten patients were rejected for presurgical urinary tract infection, metal allergy, selection failure, patellar weakening, prosthetic instability, intrasurgical tibial fracture, change of indication to unicompartimental prosthesis and a loss of follow-up. There was only one complication unrelated to the investigational drug (bladder balloon). CONCLUSION: The administration of TXA topically after cementation of the prosthetic components in total knee arthroplasty in a single dose has demonstrated being safe and effective.

Fractionation of U and heavy metals into the colloidal fraction in acid mine drainage conditions in the Río Tinto area (SW Spain).

The Río Tinto mining area provides ideal conditions for studying the role of colloidal particles in concentrating. All the elements are present in higher concentrations respect to their content in common natural waters. 234U/238U activity ratio ranges between 2.286 ±â€¯0.149 and 2.531 ±â€¯0.151. Concentration of Fe and Al are in the order of 104-103 mg/L; Co, Zn and Cu values are three times lower than Fe and Al, but still much greater than in natural waters; U reaches values up to 40.73 µg/L. To evaluate the partitioning of these elements into the colloidal fraction, ultrafiltration (UF) experiments were made. A permeation model describing the relationship between concentration of the elements or isotopes in the permeate solution and the concentration factor (CF) was calculated. Experiments were carried out using CF from 1.5 to 25.0. The behaviour of investigated heavy metals and U can be predicted by a permeation model that provides similar permeation coefficient (Pc) for all of them (Pc = 0.95-0.97 for 50 kDa, Pc = 0.86-0.88 for 10 kDa, and Pc = 0.80-0.86 for 3 kDa). Retention for all the investigated elements occurs, resulting in up to 23% of the element associated to the 3 kDa colloidal fraction. The increase in U and heavy metals concentrations in the retentate fraction with the increasing CF is due to the retention of the colloidal fraction. The colloidal abundance of related metals increased with decreasing membrane MWCO even though the difference is small between 3 and 10 kDa fraction for some metals Characterization of colloidal material is needed to better understand the state of play in this context.

An improved method for radium-isotopes quartet determination by alpha-particle spectrometry by using 225Ra (229Th) as isotopic tracer.

A new method for the determination of radium quartet (223,224,226,228Ra) in environmental samples by alpha-particle spectrometry with PIPS detectors is described. This uses 225Ra as yield tracer, in equilibrium at the beginning with 229Th. Thorium is removed from the sample by using AG1X8 anion-resin, and then radium isotopes are isolated and purified with a cation-exchange column Biorad AG50X8, verifying that Ac has been fully removed from the sample to ensure the good evaluation of the Ra yield (average decontamination factor > 92%). Finally, the counting source of radium is obtained by micro-precipitation with BaSO4. This method produces high spectral resolution (<35 keV), and quantitative Ra recoveries (>70%). In this new method, NH4Ac in 0.1 M HNO3 is used to remove the 225Ac contained in the sample in order to avoid its future spectral interference in the yield calculation. The method has been validated by using certified reference samples with known concentrations of radium isotopes.

From floodplain to aquatic sediments: Radiogeochronological fingerprints in a sediment core from the mining impacted Sancho Reservoir (SW Spain).

The Sancho Reservoir (SW Spain) was built in 1962, about the time of maximum 137Cs fallout, and it has been affected by acid mine drainage (AMD) particularly since the mining cease in 2001. This is a unique scenario for studying the radiogeochronological fingerprints in AMD-affected sediments deposited over the former flood plain. A sediment core sampled in 2011 was analysed for bulk density, 137Cs, 239Pu, 240Pu, 210Pb, 226Ra, 228Ra, 234Th (238U) and 40K, and studied with various radiometric dating models. Bulk density revealed unsteady compaction and likely depositional events. The activity concentrations of 226Ra, 228Ra, 234Th (238U) and 40K were uniform down-core, but declining overall in the upper 0-25cm, revealing changes in provenance except for 238U, which increased in the top 10cm likely due to its supply by AMD. The AMD fingerprint was also found in the 239+240Pu/137Cs activity ratio, which increased in the top sediment layers. The 137Cs and 239+240Pu profiles show well defined peaks at the same depth, with inventories being about four times higher than the expected integrated atmospheric deposition in the area. The unsupported 210Pb (210Pbexc) showed a complex non-monotonic profile interrupted at several sections, particularly around the 137Cs peak. The whole dataset cannot be interpreted in terms of continuous sedimentation processes. Based upon correlated features in the bulk density and 210Pbexc profiles, a series of depositional events (likely linked to peaks in the rainfall records) have been identified in the core. These events date back to the period comprised since the construction of the dam until its increase in height in 1972, which likely displaced upstream the main depositional area of riverine loads, as inferred from sediment trap data. The CRS (with a reference date) and (a piecewise) CIC models have been used for complementing and discussing the chronology.

¿Qué hay nuevo sobre traumatismos en edad pediátrica? / What’s new in children orthopaedic trauma?

Cada vez son más frecuentes la aparición en la bibliografía de artículos relacionados con problemas en edad pediátrica. Con el objetivo de actualizar información hemos realizado una revisión de la bibliografía publicada en las principales revistas relacionadas con la ortopedia y traumatología infantil durante el año 2015 seleccionando aquellos que trataban sobre traumatismos en edad pediátrica. El artículo ha sido divido en bloques por región anatómica y se resume la información más destacada de las publicaciones

Increasingly frequent occurrence in the literature related problems in childhood items. In order to update information we have conducted a review of the literature published in leading journals related to orthopedics and traumatology child during 2015 selecting those that dealt with trauma age pediatric. The article has been divided into blocks by anatomical region and the most important information is summarized publications

Calibration of a low background gas-flow proportional counter to estimate 234Th activity in coastal waters.

This paper relates the calibration of a low background gas-flow proportional counter. This calibration has been used to determine low activity of 234Th in coastal water samples. Two methods were used to prepare calibration samples: Evaporation and Electrodeposition. First method was rejected due to the lack of reproducibility because the different geometry adopted by the drops of tracer once dried on the disk. On the contrary, through the second method, similar efficiencies were obtained in all detectors with an average of 0.401±0.004. In this paper, the whole procedure to obtain 234Th activity in dissolution as well as in particulate matter has been detailed, and all the algorithms needed to calculate activities and efficiencies are shown. Finally, two experiments have been designed in order to validate the calibration of the beta counter and the method to determine 234Th in coastal waters with high concentration of particulate matter.

Application of (234)U/(238)U activity ratios to investigations of subterranean groundwater discharge in the Cádiz coastal area (SW Spain).

The activity ratios of (234)U/(238)U were used to investigate processes of subterranean groundwater discharge into coastal marine waters in a study location at Bay of Cádiz (southwest Spain). Marine waters in the bay and surrounding open ocean exhibited U concentrations of 3.4 ± 0.1 µg/L and activity ratios of 1.15 ± 0.01, in agreement with the expected composition of seawater ((234)U/(238)U activity ratio = 1.148 ± 0.002). Three water samples obtained from the discharge zone of the Guadalete River exhibited activity ratios of 1.17-1.22 along with slightly lower U concentrations compared to seawater, which is likely due to mixing between seawater and a groundwater end-member. One possible source of groundwater was characterized by sampling and analyzing a well water sample collected in the neighboring village of El Puerto de Santa María; this water sample exhibited an activity ratio of 1.34 ± 0.03 and a U concentration of 1.22 µg/L. Water from the Guadelete River estuarine zone can be explained to result from a two-component mixture of seawater and groundwater from the El Puerto de Santa María well; however, if there are several groundwater reservoirs with different U activity ratios that discharge to the coastal water, then, it may be difficult and more studies are being conducted to address this issue.

Mobility of Po and U-isotopes under acid mine drainage conditions: an experimental approach with samples from Río Tinto area (SW Spain).

Under acid mine drainage (AMD) conditions, the solubilities and mobilities of many elements are vastly different from conditions prevailing in most natural waters. Studies are underway in the Río Tinto area (Iberian Pyrite Belt), in order to understand the behavior and mobility of long-lived U-series radionuclides under AMD conditions. A set of leaching experiments utilizing typical country rocks from the Tinto River basin, waste rock pile composite materials, iron-rich riverbed sediments and gossan (weathered naturally rock) were performed towards this purpose. Initial leaching experiments using distilled water kept in contact with solid material for 300, 100, 50 and 1 h resulted in very low concentrations of U with (234)U/(238)U activity ratios close to equilibrium and activity concentrations of (210)Po < 0.03 mBq/g. Leaching experiments performed with sulfuric acid media (0.1 and 0.01 M), and contact times between the solid and solution for 24 h were conducted to quantify the amount of U-isotopes and (210)Po leached, and the radioactive disequilibria generated between the radionuclides in the leachate. These experiments show that Po mobility in acidic conditions (pH around 1-2) is very low, with (210)Po activity in the leachate to be 6% in average for the solid sample. By contrast, mobility of U-isotopes is higher than that of Po, around 1.2%.

Estimation of annual effective dose due to natural and man-made radionuclides in the metropolitan area of the Bay of Cadiz (SW of Spain).

In order to investigate the radiological hazard of naturally occurring radioactive material (NORM) and man-made (137)Cs radionuclide in the Bay of Cádiz, 149 samples of sediments have been analysed. Activity concentration in all the samples was determined using a HPGe detection system. Activity concentrations values of (226)Ra, (232)Th, (40)K and (137)Cs in the samples were 12.6±2.6 (2.5-40.6), 18.5±4.0 (2.8-73.4), 451±45 (105-1342) and 3.2±1.3 (0.2-16.0) Bq kg(-1), respectively. Outdoor external dose rate due to natural and man-made radionuclides was calculated to be 35.79±1.69 (4.71-119.16) nGy h(-1) and annual effective dose was estimated to be 43.89±2.27 (5.78-146.14) µSv y(-1). Results showed low levels of radioactivity due to NORM and man-made (137)Cs radionuclide in marine sediments recovered from the Bay of Cádiz (Spain), discarding any significant radiological risks related to human activities of the area. Furthermore, the obtained data set could be used as background levels for future research.

Radioactive impact of Fukushima accident on the Iberian Peninsula: evolution and plume previous pathway.

High activity concentrations of several man-made radionuclides (such as (131)I, (132)I, (132)Te, (134)Cs and (137)Cs) have been detected along the Iberian Peninsula from March 28th to April 7th 2011. The analysis of back-trajectories of air masses allowed us to demonstrate that the levels of manmade radionuclide activity concentrations in the southwest of the Iberian Peninsula come from the accident produced in the nuclear power plant of Fukushima. The pathway followed by the radioactive plume from Fukushima into Huelva (southwest of the Iberian Peninsula) was deduced through back-trajectories analysis, and this fact was also verified by the activity concentrations measured of those radionuclides reported in places crossed by this radioactive cloud. In fact, activity concentrations reported by E.P.A., and by IAEA, in several places of Japan, Pacific Ocean and United States of America are according to the expected ones from the air mass trajectory arriving at Huelva province.

An alternative radiometric method for calculating the sedimentation rates: application to an intertidal region (SW of Spain).

A new method using the inventory determined for the activity of the radionuclide (137)Cs, coming from global radioactive fallout has been utilised to calculate the sedimentation rates. The method has been applied in a wide intertidal region in the Bay of Cádiz Natural Park (SW Spain). The sedimentation rates estimated by the (137)Cs inventory method ranged from 0.26 cm/year to 1.72 cm/year. The average value of the sedimentation rate obtained is 0.59 cm/year, and this rate has been compared with those resulting from the application of the (210)Pb dating technique. A good agreement between the two procedures has been found. From the study carried out, it has been possible for the first time, to draw a map of sedimentation rates for this zone where numerous physico-chemical, oceanographic and ecological studies converge, since it is situated in a region of great environmental interest. This area, which is representative of common environmental coastal scenarios, is particularly sensitive to perturbations related to climate change, and the results of the study will allow to make short and medium term evaluations of this change.

Incidences of polluting episodes in sedimentary media.

There exist diverse radioactivity sources in the environment coming from anthropogenic activities that alter the natural levels of radiation. The detailed study of the environmental impact of these sources is of great interest, because it provides knowledge for subsequent decontamination works and environmental control. In this work, it is analyzed the radioactive contamination caused by the radionuclide (226)Ra in sedimentary media under a liquid sheet. In this way, the dumping of the radionuclide in sediment columns has been studied in laboratory, determining how its penetration in depth develops along time and for different grain sizes. For this purpose, a migration model based on the numeric resolution of the diffusion equation has been devised.

Sedimentology models from activity concentration measurements: application to the "Bay of Cadiz" Natural Park (SW Spain).

A previous study on seabed sediments of the Bay of Cadiz (SW of Spain) enabled us to identify several relations between sedimentological variables and activity concentrations of environmental radionuclides such as (137)Cs, (226)Ra, (232)Th and (40)K. In this paper the study has been extended to a large neighbouring inter-tidal area in order to establish if the above mentioned models can be generalized. As a result we have determined that the measured activity concentrations are closely to the values predicted by the theoretical models (correlation coefficient range=0.85-0.93). Furthermore, the proposal model for granulometric facies as a function of activity concentrations of the abovementioned radionuclides provides for the sediments distribution a representation which agrees with the values of the tidal energy distribution obtained using numeric models calibrated with experimental data from current meters and water level recorders.

Diffusion of (226)Ra and (40)K radionuclides reproduced in underwater sedimentary columns in laboratory.

The potential radiological impact of the increase of radioactive substances in the environment makes interesting the study of the migration of the contaminant radionuclides in soils and sediments, which are the last receiver system of these substances. By using a battery of sedimentary columns controlled in the laboratory, the diffusion of the (226)Ra and (40)K radionuclides has been studied, assessing their respective effective diffusion coefficients in a similar sedimentary medium. A decreasing temporal evolution is obtained, associated to the progressive 'fixation' of the radionuclides by the clay minerals of the sediment, followed by a constant tendency. A timescale of the 'fixation' by the sediment is determined, being of the order of days for (226)Ra and of the order of months for (40)K, so the progressive 'fixation' of (40)K by the clay minerals of the sediments is slower than in the case of (226)Ra.

Levels of 137Cs in muddy sediments of the seabed of the Bay of Cadiz, Spain. Part I. Vertical and spatial distribution of activities.

This is the first of a two-part paper. This first part describes a detailed study conducted of the spatial and vertical distribution of the concentration of the radionuclide (137)Cs, utilising columns of sediment extracted from the seabed of the Bay of Cadiz (Spain) as specimens. The activity concentrations have been measured by means of gamma spectrometry using a HPGe detector and (137)Cs is used as an indicator of the sedimentation and contamination processes in the zone. At the same time the relationship between the levels of activity found and other hydrodynamic and sedimentological variables characteristic of the zone have been studied. The experimental results obtained will also serve to develop a model of the distribution of (137)Cs, which will be presented in the second part of this paper.

Levels of 137Cs in muddy sediments on the seabed in the Bay of Cadiz (Spain). Part II. Model of vertical migration of (137)Cs.

This second part of the study reports the development of a model to describe the vertical migration of the artificial radioisotope (137)Cs in the sediment column on the seabed of the Bay of Cadiz. The application of the model provides an overall picture of the process of sedimentation in the Inner Bay of Cadiz. The spatial distribution of the rate of sedimentation enables us to study the sources of sediments and the means by which the sediments have been transported. A method has been derived from the rate of sedimentation to perform the dating of the layers of sediment. The model describes the behaviour of (137)Cs in the area under study, taking into account the time of residence in the zones that are the source of accumulation, the origin of the sedimentary material, together with the diffusion of the radionuclide in the sediment of the seabed.

Environmental impact of unleaded gasolines in the bay of Cádiz (Spain).

Given the strategic situation of the José León de Carranza bridge, which spans the Bay of Cádiz (in the SW of Spain) and carries very heavy motor traffic, together with knowledge of the currents and tidal flows in the zone, we have used a technique of radioactive dating of sediments to study the temporal evolution presented by contamination from lead in the sediment column. This has allowed us to observe the environmental impact, in terms of the concentration of Pb in the sea bed sediments, that has been produced in the zone by the introduction of unleaded gasolines as substitutes for traditional automobile fuels that employ organic forms of tetra methyl lead as an antidetonant agent in the fuel.