Margarida Malta

Genotoxic endpoints in the earthworms sub-lethal assay to evaluate natural soils contaminated by metals and radionuclides

Eisenia andrei was exposed, for 56 days, to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure, to assess metals bioaccumulation, coelomocytes DNA integrity and cytotoxicity. Radionuclides bioaccumulation and growth were also determined at 0 h, 14 and 56 days of exposure. Results have shown the bioaccumulation of metals and radionuclides, as well as, growth reduction, DNA damages and cytotoxicity in earthworms exposed to contaminated soil. The usefulness of the comet assay and flow cytometry, to evaluate the toxicity of contaminants such as metals and radionuclides in earthworms are herein reported. We also demonstrated that DNA strand breakage and immune cells frequency are important endpoints to be employed in the earthworm reproduction assay, for the evaluation of soil geno and cytotoxicity, as part of the risk assessment of contaminated areas. This is the first study that integrates DNA damage and cytotoxicity evaluation, growth and bioaccumulation of metals and radionuclides in a sub lethal assay, for earthworms exposed to soil contaminated with metals and radionuclides.

Evaluation of the sensitivity of genotoxicity and cytotoxicity endpoints in earthworms exposed in situ to uranium mining wastes

Earthworms were exposed for 56 days to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The exposure occurred in situ: the containers with contaminated soil were placed near the mine pit; the containers with reference soil were placed in a reference site. For the assessment of metals bioaccumulation, DNA damages, cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation, organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure. For the assessment of radionuclides bioaccumulation, animals were sampled after 0, 14 and 56 days of exposure. As for growth, organisms were sampled after 0, 14, 28 and 56 days of exposure. The reproduction assay was performed according to the OECD (2004) guideline. DNA damages were assessed by comet assay and flow cytometry was used to determine cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation. Results have shown a myriad of effects in the organisms exposed to the contaminated soil, namely: the inhibition of reproduction, growth reduction, DNA damages, cytotoxicity, changes in eleocytes fluorescence intensity, coelomocytes proliferation and bioaccumulation of metals and radionuclides. Our results showed that the evaluation of genotoxicity and cytotoxicity endpoints, along with other parameters at an individual level in standard reproduction assays conducted in situ, are important to improve the risk assessment process of areas contaminated with uranium and other radioactive mining wastes.

Radioactivity from Fukushima nuclear accident detected in Lisbon, Portugal.

The radioactivity released from the Fukushima Dai-ichi nuclear accident was transported around the globe by atmospheric processes. Several artificial radionuclides were detected and measured in aerosols and atmospheric surface depositions in the Lisbon area during late March and early April 2011. The highest concentrations measured in aerosols were those of particulate (131)I, 1.39 ± 0.08 mBq m(-3). Cesium-134, (137)Cs and (132)Te were also determined but at lower concentrations. The total atmospheric depositions on the ground were higher on the first week of April with values for (131)I, (134)Cs, and (137)Cs of 0.92 ± 0.11, 0.59 ± 0.06, and 0.62 ± 0.12 Bq m(-2), respectively. The four artificial radionuclides measurable, (131)I, (132)Te (134)Cs, and (137)Cs, caused little radiation exposure to the members of the public, that was five orders of magnitude lower than the ionizing radiation effective dose limits for members of the public for one year (1 mSv y(-1)).

Histopathological changes in the earthworm Eisenia andrei associated with the exposure to metals and radionuclides

Earthworms were exposed for 56 d to a contaminated soil, from an abandoned uranium mine, and to the natural reference soil LUFA 2.2. Histological changes in earthworms body wall (epidermis, circular and longitudinal muscles) and gastrointestinal tract (chloragogenous tissue and intestinal epithelium) were assessed, after 0, 14 and 56 d of exposure. Results have shown alterations in all the studied tissues after 14 d of exposure (except for the intestinal epithelium), yet more severe effects were registered after 56 d of exposure. Herein we report histopathological alterations as a good biomarker for the evaluation of soil quality. We also demonstrate that morphological changes in the body wall and gastrointestinal tract, are important endpoints that could be added to earthworms standardized tests, for the evaluation of soil toxicity, as part of the risk assessment of contaminated areas.

Uranium mining wastes: The use of the Fish Embryo Acute Toxicity Test (FET) test to evaluate toxicity and risk of environmental discharge

Active and abandoned uranium mining sites often create environmentally problematic situations, since they cause the contamination of all environmental matrices (air, soil and water) with stable metals and radionuclides. Due to their cytotoxic, genotoxic and teratogenic properties, the exposure to these contaminants may cause several harmful effects in living organisms. The Fish Embryo Acute Toxicity Test (FET) test was employed to evaluate the genotoxic and teratogenic potential of mine liquid effluents and sludge elutriates from a deactivated uranium mine. The aims were: a) to determine the risk of discharge of such wastes in the environment; b) the effectiveness of the chemical treatment applied to the uranium mine water, which is a standard procedure generally applied to liquid effluents from uranium mines and mills, to reduce its toxicological potential; c) the suitability of the FET test for the evaluation the toxicity of such wastes and the added value of including the evaluation of genotoxicity. Results showed that through the FET test it was possible to determine that both elutriates and effluents are genotoxic and also that the mine effluent is teratogenic at low concentrations. Additionally, liquid effluents and sludge elutriates affect other parameters namely, growth and hatching and that water pH alone played an important role in the hatching process. The inclusion of genotoxicity evaluation in the FET test was crucial to prevent the underestimation of the risks posed by some of the tested effluents/elutriates. Finally, it was possible to conclude that care should be taken when using benchmark values calculated for specific stressors to evaluate the risk posed by uranium mining wastes to freshwater ecosystems, due to their chemical complexity.

Exposure to radionuclides in smoke from vegetation fires

Naturally occurring radionuclides of uranium, thorium, radium, lead and polonium were determined in bushes and trees and in the smoke from summer forest fires. Activity concentrations of radionuclides in smoke particles were much enriched when compared to original vegetation. Polonium-210 ((210)Po) in smoke was measured in concentrations much higher than all other radionuclides, reaching 7,255 ± 285 Bq kg(-1), mostly associated with the smaller size smoke particles (<1.0 μm). Depending on smoke particle concentration, (210)Po in surface air near forest fires displayed volume concentrations up to 70 m Bq m(-3), while in smoke-free air (210)Po concentration was about 30 μ Bq m(-3). The estimated absorbed radiation dose to an adult member of the public or a firefighter exposed for 24h to inhalation of smoke near forest fires could exceed 5 μSv per day, i.e, more than 2000 times above the radiation dose from background radioactivity in surface air, and also higher than the radiation dose from (210)Po inhalation in a chronic cigarette smoker. It is concluded that prolonged exposure to smoke allows for enhanced inhalation of radionuclides associated with smoke particles. Due to high radiotoxicity of alpha emitting radionuclides, and in particular of (210)Po, the protection of respiratory tract of fire fighters is strongly recommended.

Radionuclides in marine mammals off the Portuguese coast.

Radionuclide analyses were performed in tissue samples including muscle, gonad, liver, mammary gland, and bone of marine mammals stranded on the Portuguese west coast during January-July 2006. Tissues were collected from seven dolphins (Delphinus delphis and Stenella coeruleoalba) and one pilot whale (Globicephala sp.). Samples were analyzed for (210)Po and (210)Pb by alpha spectrometry and for (137)Cs and (40)K by gamma spectrometry. Po-210 concentrations in common dolphins muscle (D. delphis) averaged 56 ± 32 Bq kg(-1) wet weight (w.w.), while (210)Pb averaged 0.17 ± 0.07 Bq kg(-1) w.w., (137)Cs averaged 0.29 ± 0.28 Bq kg(-1) w.w., and (40)K 129 ± 48 Bq kg(-1) w.w. Absorbed radiation doses due to these radionuclides for the internal organs of common dolphins were computed and attained a 1.50 μGy h(-1) on a whole body basis. (210)Po was the main contributor to the weighted absorbed dose, accounting for 97% of the dose from internally accumulated radionuclides. These computed radiation doses in dolphins are compared to radiation doses from (210)Po and other radionuclides reported for human tissues. Due to the high (210)Po activity concentration in dolphins, the internal radiation dose in these marine mammals is about three orders of magnitude higher than in man.

Radioactivity of anthropogenic origin in the Tejo Estuary and need for improved waste management and environmental monitoring

The Tejo Estuary is a large water body surrounded by seven municipalities and industries with liquid effluent discharges containing contaminants that reach the estuary. This is the case for man-made radionuclides used in nuclear medicine, present in liquid effluents discharged by medical facilities. Radionuclide measurements in seaweeds, mussels, fish, water and sediments sampled along the North bank of the estuary revealed the presence of 131I and 99mTc, originating from nuclear medicine facilities in Lisboa. Concentrations reached 90 Bq kg−1 (wet weight) of 99mTc in fish, and 18 Bq kg−1 (wet weight) of 131I in mussels, and were even higher in the water. Another anthropogenic source of radionuclides is industrial waste, such as phosphogypsum the by-product of phosphoric acid production stockpiled at the South bank of the estuary. Main radionuclides present in phosphogypsum are 226Ra, 210Pb, 210Po and uranium. Concentrations of 226Ra in phosphogypsum are about 1000 Bq kg−1, which is a high value in comparison with 226Ra in soils of the Tejo valley, <100 Bq kg−1. 226Ra, in particular, is dissolved by rainwater from phosphogypsum stacks and seeps into the estuary. Other potential sources of radioactivity are discharges from naval nuclear powered vessels and merchant ships transporting radioactive materials that berth in the Lisboa harbour. A whole survey of the estuary indicated low concentrations of 137Cs in sediments, mostly attributed to radioactive fallout. Since waste discharges are undergoing deep modifications due to enhanced urban waste treatment, but economic activities have changed and the use of radiopharmaceuticals increases, the periodic radioactivity monitoring of the Tejo Estuary is advised and should provide feedback to enhanced waste management.

Radioactivity and Water Quality in Areas of Old Uranium Mines (Viseu, Portugal)

Radionuclides were determined in streams and rivers receiving mine drainage from old uranium mines at the center of Portugal. Results showed enhanced radioactivity levels in some areas impacted by uranium mining and milling wastes, but levels were lower than several years ago due to current water treatment of mine drainage. In some areas, such as at the village of Cunha Baixa, water from wells was contaminated by acid mine drainage, and it is not suitable anymore for human consumption and irrigation of horticulture plots. In the present, villages and towns near those old uranium mines have tap water from public networks supplied from artificial lakes built in major rivers of the region. This tap water showed compliance with the recommended limits of total alpha and total beta radioactivity, and it is suitable for human consumption. Radiation exposure of the population was therefore controlled, but current water supply is much more costly than it was with local water sources.

Radionuclides and radiation doses in heavy mineral sands and other mining operations in Mozambique.

Sites at the littoral of Mozambique with heavy mineral sands exploited for ilmenite, rutile and zircon and inland mineral deposits exploited for tantalite, uranium and bauxite were surveyed for ambient radiation doses, and samples were collected for the determination of radionuclide concentrations. In heavy mineral sands, (238)U and (232)Th concentrations were 70±2 and 308±9 Bq kg(-1) dry weight (dw), respectively, whereas after separation of minerals, the concentrations in the ilmenite fraction were 2240±64 and 6125±485 Bq kg(-1) (dw), respectively. Tantalite displayed the highest concentrations with 44 738±2474 Bq kg(-1) of (238)U. Radiation exposure of workers in mining facilities is likely to occur at levels above the dose limit for members of the public (1 mSv y(-1)) and therefore radiation doses should be assessed as occupational exposures. Local populations living in these regions in general are not exposed to segregated minerals with high radionuclide concentrations. However, there is intensive artisanal mining and a large number of artisanal miners and their families may be exposed to radiation doses exceeding the dose limit. A radiation protection programme is therefore needed to ensure radiation protection of the public and workers of developing mining projects.