Selenium and Mercury in the Brazilian Amazon: Opposing Influences on Age-Related Cataracts

BACKGROUND: Age-related cataracts (ARCs) are an important cause of blindness in developing countries. Although antioxidants may be part of the body's defense to prevent ARC, environmental contaminants may contribute to cataractogenesis. In fish-eating populations of the lower Tapajos region, elevated exposure to mercury (Hg) has been reported, and blood levels of selenium (Se) range from normal to very high (> 1,000 mu g/L). OBJECTIVES: We examined ARCs in relation to these elements among adults (>= 40 years of age) from 12 riverside communities. METHODS: Participants (n = 211) provided blood samples and underwent an extensive ocular examination. Inductively coupled plasma mass spectrometry was used to assess Hg and Se in blood and plasma. RESULTS: One-third (n = 69; 32.7%) of the participants had ARC. Lower plasma Se (P-Se; < 25th percentile, 110 mu g/L) and higher blood Hg (B-Hg; >= 25th percentile, 25 mu g/L) were associated with a higher prevalence odds ratio (POR) of ARC [adjusted POR (95% confidence interval), 2.69 (1.11-6.56) and 4.45 (1.43-13.83), respectively]. Among participants with high P-Se, we observed a positive but nonsignificant association with high B-Hg exposure, whereas among those with low B-Hg, we observed no association for P-Se. However, compared with the optimum situation (high P-Se, low B-Hg), the POR for those with low P-Se and high B-Hg was 16.4 (3.0-87.9). This finding suggests a synergistic effect. CONCLUSION: Our results suggest that persons in this population with elevated Hg, the cataractogenic effects of Hg may be offset by Se. Because of the relatively small sample size and possible confounding by other dietary nutrients, additional studies with sufficient power to assess multiple nutrient and toxic interactions are required to confirm these findings.Canadian Institutes of Health Research (CIHR)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Canadian Natural Sciences and Engineering Council (NSERC)International Development Research Centre (IDRC) - Canad

A preliminary study of mercury exposure and blood pressure in the Brazilian Amazon

BACKGROUND: Fish is considered protective for coronary heart disease (CHD), but mercury (Hg) intake from fish may counterbalance beneficial effects. Although neurotoxic effects of methylmercury (MeHg) are well established, cardiovascular effects are still debated. The objective of the present study was to evaluate blood pressure in relation to Hg exposure and fish consumption among a non-indigenous fish-eating population in the Brazilian Amazon. METHODS: The study was conducted among 251 persons from six communities along the Tapajós River, a major tributary of the Amazon. Data was obtained for socio-demographic information, fish consumption, height and weight to determine body mass index (BMI), systolic and diastolic blood pressure, and Hg concentration in hair samples. RESULTS: Results showed that overall, systolic and diastolic blood pressure, were relatively low (mean: 113.9 mmHg ± 14.6 and 73.7 mmHg ± 11.0). Blood pressure was significantly associated with hair total Hg (H-Hg), age, BMI and gender. No association was observed between fish consumption and blood pressure, although there were significant inter-community differences. Logistic regression analyses showed that the Odds Ratio (OR) for elevated systolic blood pressure (≥ 130 mmHg) with H-Hg ≥ 10 μg/g was 2.91 [1.26–7.28], taking into account age, BMI, smoking, gender and community. CONCLUSION: The findings of this preliminary study add further support for Hg cardiovascular toxicity

Annexe 5. Les processus de méthylation du mercure en milieu amazonien

LA MÉTHYLATION DU MERCURE : BREF HISTORIQUE L’accident de Minamata au Japon, qui s’est déclenché vers 1953 mais a été reconnu seulement en 1968, nous a révélé les effets neurotoxiques du méthyl-mercure (MeHg) sur des populations humaines exposées par voie alimentaire. Cet accident ainsi que celui de Niigata survenu à la même époque réunissaient des conditions particulières, à savoir une source ponctuelle de Hg très intense située à proximité d’une baie fermée, elle-même peuplée de villageois ..

Annexe 5 : consommation de poissons et Hg inorganique

In ARCHIV 126838Background: 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 10μg/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

Annexe 8 : exposition au mercure et pression sanguine

Published in the Environmental health : a global access science source, 2006, 5:29In ARCHIV 126838Background: Fish is considered protective for coronary heart disease (CHD), but mercury (Hg) intake from fish may counterbalance beneficial effects. Although neurotoxic effects of methylmercury (MeHg) are well established, cardiovascular effects are still debated. The objective of the present study was to evaluate blood pressure in relation to Hg exposure and fish consumption among a non-indigenous fish-eating population in the Brazilian Amazon. Methods: The study was conducted among 251 persons from six communities along the Tapajós River, a major tributary of the Amazon. Data was obtained for socio-demographic information, fish consumption, height and weight to determine body mass index (BMI), systolic and diastolic blood pressure, and Hg concentration in hair samples. Results: Results showed that overall, systolic and diastolic blood pressure, were relatively low (mean: 113.9 mmHg ± 14.6 and 73.7 mmHg ± 11.0). Blood pressure was significantly associated with hair total Hg (H-Hg), age, BMI and gender. No association was observed between fish consumption and blood pressure, although there were significant inter-community differences. Logistic regression analyses showed that the Odds Ratio (OR) for elevated systolic blood pressure (≥ 130 mmHg) with H-Hg ≥ 10 μg/g was 2.91 [1.26–7.28], taking into account age, BMI, smoking, gender and community. Conclusion: The findings of this preliminary study add further support for Hg cardiovascular toxicity

Annexe 20 : bande dessinée o mercúrio no Tapajós

Texto en portugúesEn ARCHIV 12683

Annexe 4 : confirmation épidémiologique des fruits

In ARCHIV 126838Also published in "Environmental research, 105 (2007) 183-193"Background: Since deforestation has recently been associated with increased mercury load in the Amazon, the problem of mercury exposure is now much more widespread than initially thought. A previous exploratory study suggested that fruit consumption may reduce mercury exposure. Objectives: To determine the effects of fruit consumption on the relation between fish consumption and bioindicators of mercury (Hg) exposure in Amazonian fish-eating communities. Methods: A cross-sectional dietary survey based on a seven-day recall of fish and fruit consumption frequency was conducted within 13 riparian communities from the Tapajós River, Brazilian Amazon. Hair samples were collected from 447 persons, and blood samples were collected from a subset of 227, for total and inorganic mercury determination by Atomic Absorption Spectrometry. Results: On average, participants consumed 6.6 fish meals/week and ate 11 fruits/week. The average blood-Hg was 57.1 ± 36.3 μg/L (median: 55.1 μg/L), and the average hair-Hg was 16.8 ± 10.3 μg/g (median: 15.7 μg/g). There was a positive relation between fish consumption and blood-Hg (r = 0.48; p < 0.0001), as well as hair-Hg (r = 0.34; p < 0.0001). Both fish and fruit consumption entered significantly in multivariate models explaining blood-Hg (fish: β = 5.6, p < 0.0001; fruit: β = - 0.5, p = 0.0011; adjusted model R2 = 36.0%) and hair-Hg levels (fish: β = 1.2, p < 0.0001; fruit: β = - 0.2, p = 0.0002; adjusted model R2 = 21.0%). ANCOVA models showed that for the same number of fish meals, persons consuming fruits more frequently had significantly lower blood and hair Hg concentrations. For low fruit consumers, each fish meal contributed 9.8 μg/L Hg increase in blood compared to only 3.3 μg/L Hg increase for the high fruit consumers. Conclusions: Fruit consumption may provide a protective effect for Hg exposure in Amazonian riparians. Prevention strategies that seek to maintain fish consumption while reducing Hg exposure in fish-eating communities should be pursued

Annexe 6 : teneurs élevées en sélénium

Published in the Science of the total environment, 366 (2006)In ARCHIV 126838Contaminated 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 Tapajo´ s 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 Ag/ L, range=142.1–2029.3 Ag/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 Tapajo´ s 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

Annexe 10 : réseaux sociaux et recherche de solutions

In ARCHIV 12683

Annexe 14 : analyses de genre dans le réseau Communautaire

In ARCHIV 126838Transdisciplinarity, gender analysis, social equity and participation are the methodological pillars of the Ecohealth approach, whose main goal is to improve human health and wellbeing while simultaneously maintaining a healthy ecosystem. In the present study, social network analysis is presented as an innovative tool to address gender, equity and community participation in Ecohealth research, by drawing upon experiences and results from the Caruso project which studies environmental dynamics and health effects of mercury in the Brazilian Amazon with the objective to reduce mercury exposure. As a participatory research tool, social network analysis is used to analyse the relationships between community action to reduce mercury exposure and 1. the distinctive roles of men and women; 2. the involvement of the different social groups and 3. the patterns of community participation. As a participatory development tool, social network analysis can contribute to the promotion of gender and social equity as well as local participation