Mercury exposure and malaria prevalence among gold miners in Pará, Brazil

Abstract

Economic development, including resource extraction, can cause toxic exposures that interact with endemic infectious diseases. Mercury is an immunotoxic metal used in the amalgamation of gold, resulting in both occupational exposures and environmental pollution. A cross-sectional medical survey was conducted in 1997 on 135 garimpeiros in Para, Brazil, because of their risks of both mercury exposure and malaria transmission. Mean levels of blood and urine mercury were well above non-exposed background levels. Twentysix subjects had malaria parasitemia: Health symptoms consistent with mercury exposure were reported, but neither symptoms nor signs correlated with mercury levels in blood or urine. We did not find a dose response relationship between mercury exposure and likelihood of prevalent malaria infection, but there was a possible reduction in acquisition of immunity that may be associated with conditions in gold mining, including mercury exposure. Key-words: Mercury. Garimpagem. Malaria. Toxicity.Resumo O desenvolvimento econômico, incluindo extração de recursos naturais, pode causar exposições tóxicas que interagem com doenças infecciosas endêmicas. O mercúrio é um metal imunotóxico usado na amalgamação do ouro, resultando em exposição ocupacional e poluição ambiental. Devido aos riscos da exposição ao mercúrio e transmissão de malária em 135 garimpeiros do Pará, Brasil, uma avaliação médica "crosssectional" foi coduzida em 1997. Níveis médios de mercúrio no sangue e na urina encontram-se bem acima dos níveis basais daqueles não expostos. Vinte e seis indivíduos apresentaram parasitemia de malária; sintomas relacionados com exposição ao mercúrio foram adquiridos, mas nenhum dos sintomas/sinais está correlacionado com níveis de mercúrio no sangue ou na urina. Não foi encontrada nenhuma relação de dose-resposta entre exposição ao mercúrio e provável infecção de malária prevalente. Entretanto, verificou-se uma possível redução na aquisição de imunidade que talvez esteja relacionada às condições de garimpagem, incluindo exposição ao mercúrio. Palavras-chaves: Mercúrio. Garimpagem. Malária. Toxicidade.

Mercury exposure, malaria, and serum antinuclear/antinucleolar antibodies in amazon populations in Brazil: a cross-sectional study

“…Urine mercury levels (4 μg/L) were lower than those found in other mining populations in Amazonia [25,26,40] (Figure 1C). Only 6 had levels ≥25 μg/L, the median value found by us in another gold mine population [40]. This may have been due to the timing of our visit, during the dry season, when gold amalgamation activities were reduced.…”

“…We have reported a suggested correlation between mercury exposures and number of past malaria infections among gold miners in another gold mine settlement, in Brazil, at Piranha [40]. We have also reported that exposure of mice to low levels of mercury both decreases host resistance to murine malaria ( Plasmodium yoelii ) and impairs acquisition of immunity to murine malaria in the Nussenzweig model [47].…”

Mercury exposure, serum antinuclear/antinucleolar antibodies, and serum cytokine levels in mining populations in Amazonian Brazil: A cross-sectional study

“…Rio-Rato is a gold mining site, and participants were directly involved in some aspect of gold extraction or refining, as described previously (Silbergeld et al, 2002; Silva et al, 2004). Urine mercury concentrations ranged from below the LOD (0.50 µ g Hg/L urine) to 81.4 µg Hg/L urine, with a median value of 3.67 (Figure 2).…”

Naturally Acquired Antibodies to Plasmodium vivax Duffy Binding Protein (DBP) in Rural Brazilian Amazon

“…33,34 In fact, malaria prevalence in Granada (3.6%) 26 is far lower than that measured in mining areas (13.8-35.0%). [34][35][36] However, the "just-in-time" hypothesis of DBP exposure 37 does not completely explain the large proportion of individuals who remain unresponsive to DBP after prolonged exposure to malaria, especially because a few dominant DBP II haplotypes seem to account for the majority of P. vivax infections in areas of high malaria transmission. 38 The reasons for this are not clear, but may relate to the complexity of immune responses in terms of genetic diversity of the human and parasite populations, and stochastic events associated with the induction of a specific antibody response.…”