Search

Abstract: Leaking underground storage tanks are a worldwide problem nowadays, therefore gasoline degradation and distribution in the subsurface have been widely studied. Brazil is the only country to currently use ethanol as fuel and as an oxygenate additive to gasoline, in amounts varying from 20 to 26% v/v. Consequently, both gasoline and ethanol may contaminate the environment when spills and leaks occur. Some authors suggest that despite the high degradability of gasoline, its degradation in the aquifer is hindered by the preferential biodegradation of ethanol, which would delay gasoline degradation; however, processes in the unsaturated zone are far less understood. The present study concentrates on degradation and distribution processes of ethanol-amended gasoline in tropical soil under unsaturated conditions. A multi-parametrical approach was adopted to assess the effects of ethanol on the fate of gasoline. Undisturbed natural soil was used to evaluate biodegradation processes while tank experiments determined differences in infiltration, distribution and retention of gasoline in unsaturated artificial porous medium. Physical, chemical and microbiological results suggest that ethanol enhances BTEX retention in soil, boosts microbial activity but delays BTEX biodegradation. [Copyright &y& Elsevier]

Abstract: Selenium (Se) is an essential element and a well-known anti-oxidant. In the Lower Tapajós River region of the Brazilian Amazon, biomarkers of Se range from normal to very high. The local traditional diet includes important Se sources such as Brazil nuts, chicken, game meat and certain fish species. Some studies have reported alterations in keratin structure, gastrointestinal problems and paresthesia in populations with high Se intake. The objective of the present study was to evaluate cutaneous and garlic odor of the breath signs and sentinel symptoms of Se toxicity (selenosis) in relation to Se status in communities along the Tapajós River. Participants (N =448), aged 15–87years, were recruited from 12 communities. Se concentrations were measured in blood (B-Se) and plasma (P-Se) by ICP-MS. A nurse performed an examination of the hair, nails, skin and breath for signs of Se toxicity. Interview-administered questionnaires were used to collect information on socio-demographics, medical history and possible symptoms of Se toxicity. In this population, the median levels of B-Se and P-Se were 228.4μg/L (range 103.3–1500.2μg/L) and 134.8μg/L (range 53.6–913.2μg/L) respectively. Although B-Se and P-Se surpassed concentrations considered toxic (B-Se: 1000μg/L (U.S. EPA, 2002)), no dermal or breath signs or symptoms of Se toxicity were associated with the biomarkers of Se status. In the present study population, where Se intake is mostly from traditional diet, there is no evidence of selenosis. These findings support the need to re-assess Se toxicity considering factors such as the chemical form of Se exposure, route of exposure (inhaled versus ingested), co-exposures to toxic elements such as mercury. Considering the current food transition towards a western diet in the Amazon, further studies should address the possible association between high Se status and cardiometabolic health in this study population. [Copyright &y& Elsevier]

Abstract: Selenium (Se) intake is generally from food, whose Se content depends on soil Se and plant accumulation. For humans, adequate Se intake is essential for several selenoenzymes. In the Lower Tapajós region of the Brazilian Amazon, Se status is elevated with large inter-community variability. Se intake in this region, where Hg exposure is among the highest in the world, may be important to counteract mercury (Hg) toxicity. The present study was conducted in 2006 with 155 persons from four communities of the Lower Tapajós. The objectives were: i) to evaluate Se content in their typical diet and drinking water; ii) to compare food Se concentrations with respect to geographic location; and iii) to examine the contribution of consumption of different food items to blood Se. More than 400 local foods and 40 drinking water samples were collected. Participants responded to an interview-administered food frequency questionnaire and provided blood samples. Food, water and blood Se levels were assessed by ICP-MS. Since Brazil nuts may also contain significant levels of barium (Ba) and strontium (Sr), these elements were likewise analyzed in nuts. The highest Se concentrations were found in Brazil nuts, but concentrations were highly variable (median: 13.9µg/g; range: 0.4–158.4μg/g). Chicken, game meat, eggs and beef also contained considerable levels of Se, with median concentrations from 0.3 to 1.4μg/g. There was no particular geographic distribution of food Se. Se concentration in drinking water was very low (<1.4µg/L). Blood Se covered a (103–1500μg/L), and was positively related to regular consumption of Brazil nuts, domestic chicken and game meat. Brazil nuts were found to contain highly variable and often very high concentrations of Ba (88.0µg/g, 1.9–1437µg/g) and Sr (38.7µg/g, 3.3–173µg/g). Further studies should address multiple nutrient/toxic interactions in the diet and related effects on health. [Copyright &y& Elsevier]

The direct and close relationship between fish consumption and blood and hair mercury (Hg) levels is well known, but the influence of fish consumption on inorganic mercury in blood (B-IHg) and in urine (U-Hg) is unclear. Objective: Examine the relationship between fish consumption, total, inorganic and organic blood Hg levels and urinary Hg concentration. Methods: A cross-sectional study was carried out on 171 persons from 7 riparian communities on the Tapajós River (Brazilian Amazon), with no history of inorganic Hg exposure from occupation or dental amalgams. During the rising water season in 2004, participants responded to a dietary survey, based on a seven-day recall of fish and fruit consumption frequency, and socio-demographic information was recorded. Blood and urine samples were collected. Total, organic and inorganic Hg in blood as well as U-Hg were determined by Atomic Absorption Spectrometry. Results: On average, participants consumed 7.4 fish meals/week and 8.8 fruits/week. Blood total Hg averaged 38.6±21.7 μg/L, and the average percentage of B-IHg was 13.8%. Average organic Hg (MeHg) was 33.6±19.4 μg/L, B-IHg was 5.0±2.6 μg/L, while average U-Hg was 7.5±6.9 μg/L, with 19.9% of participants presenting U-Hg levels above 10 μg/L. B-IHg was highly significantly related to the number of meals of carnivorous fish, but no relation was observed with non-carnivorous fish; it was negatively related to fruit consumption, increased with age, was higher among those who were born in the Tapajós region, and varied with community. U-Hg was also significantly related to carnivorous but not non-carnivorous fish consumption, showed a tendency towards a negative relation with fruit consumption, was higher among men compared to women and higher among those born in the region. U-Hg was strongly related to I-Hg, blood methyl Hg (B-MeHg) and blood total Hg (B-THg). The Odds Ratio (OR) for U-Hg above 10 μg/L for those who ate >4 carnivorous fish meals/week was 4.00 [1.83–9.20]. Conclusion: This study adds further evidence to a positive relation between fish consumption and IHg in both blood and urine, which may result from absorption of IHg from fish or from demethylation of MeHg. The findings support the importance of assessing IHg exposure in fish-eating communities. Further studies should examine the potential toxicity of IHg in heavy fish consumers. [Copyright &y& Elsevier]

Abstract: Contaminated fish poses a difficult challenge throughout the world, on the one hand, fish is a very nutritious food source, while on the other hand it accumulates many toxic substances, including mercury (Hg). As part of our efforts in the Brazilian Amazon to maximize nutritional input from fish consumption, a dietary mainstay, and minimize toxic risk, we have been studying the role of selenium (Se), an essential element, that may influence the distribution of Hg in the body and influence Hg neurotoxicity. Se, which is naturally present in the soil, is ingested through consumption of various foods, notably fish, mammals and certain plants. The objectives of the present study were: (i) evaluate whole blood Se (B-Se) and Hg (B-Hg); (ii) characterize B-Se variations with respect to socio-demographic and dietary variables; and (iii) examine the relation between B-Se and B-Hg. A total of 236 persons from six riparian communities of the Tapajós River Basin, a tributary of the Amazon, participated in this study. Whole blood Se and Hg were measured and interview administered questionnaires were used to obtain data on socio-demographic variable, smoking and drinking habits, and fish and fruit consumption. The results show that B-Se are in the upper normal range (median=284.3 μg/L, range=142.1–2029.3 μg/L). No individuals presented B-Se deficiency, but 9 participants from the same extended family had relatively high B-Se levels, potentially a threat to their health. B-Se varied between communities, was significantly higher among alcohol drinkers and farmers, but not associated with age, sex or tobacco consumption. A significant positive relation between B-Se and B-Hg was noted, independently of the overall fish consumption. B-Se increased with consumption of Peacock bass (Cichla sp.), a piscivorous fish species, and coconut pulp (Cocos nucifera L.). The B-Se intercommunity variations may reflect geographic differences in local soil Se levels as well as traditional land use practices in the different ecosystems of the Tapajós River Basin. In this population with relatively high exposure to Hg, Se may play an important role. Further studies should examine, in this region, the sources of Se, its transmission through the terrestrial and aquatic ecosystem and its role with respect to human health. [Copyright &y& Elsevier]