Comparative study of human exposure to mercury in riverside communities in the Amazon region

Abstract

Four populations in the Amazon area were selected for a comparative study of mercury-exposed and non-exposed populations: São Luiz do Tapajós, Barreiras, Panacauera, and Pindobal Grande. The highest mercury levels in human hair samples were found in São Luiz do Tapajós and Barreiras, greatly exceeding the limits established by the World Health Organization. Panacauera showed an intermediate level below 9 µg/g. This was the first comparative and simultaneous evaluation of mercury exposure in the Amazon area. Also, thanks to this type of monitoring, we were able to eliminate the uncertainties about the reference dose. On the basis of these data, we can conclude that the mercury levels detected in exposed populations of the Tapajós River basin may be dangerous not only because they are above the World Health Organization limits, but also because the simultaneous mercury detection in non-exposed populations with similar characteristics provided a valid control and revealed lower mercury levels. Our results support the importance of continuous monitoring in both exposed and non-exposed populations.

Daily mercury intake in fish-eating populations in the Brazilian Amazon

“…There has been the suggestion that based on the general health status of the population, ''normal'' values higher than those proposed by WHO could be established in the Amazon (Santos et al, 2002). However, another Amazonian study concluded that differences in exposed and nonexposed populations in this region would argue against an Amazonian reference level, particularly as levels surpass those of WHO (Pinheiro et al, 2006). Despite attempts to establish reference values and background parameters as well as eliminate uncertainties about the reference dose in the Amazonian context, few studies have adopted a rigorous procedure for developing risk-based reference doses (Gaylor and Kodell, 2002;Rice, 2005).…”

“…Despite many years of research and biomonitoring, adult traditional populations in the Amazon continue to be chronically exposed to high levels of mercury through their fish diet (Bastos et al, 2006, Pinheiro et al, 2006. In these populations, there is strong evidence of early nervous system dysfunction and, to a less extent, immunologic and cardiovascular effects among both adults and children (Lebel et al, 1996(Lebel et al, , 1998Grandjean et al, 1999;Amorim et al, 2000;Dolbec et al, 2000;Harada et al, 2001;Cordier et al, 2002;Mergler, 2002;Yokoo et al, 2003;Silbergeld et al, 2005;Fillion et al, 2006).…”

“…During the last decade, a large number of exposure assessments of fish-eating populations have been conducted in different countries of the Amazon (Barbosa et al, 1997;Lebel et al, 1997;Cordier et al, 1998;Dolbec et al, 2001;Santos et al, 2003;Passos et al, 2003a;Gonc¸alves and Gonc¸alves, 2004;Webb et al, 2004;Do´rea et al, 2005;Bastos et al, 2006;Pinheiro et al, 2006). However, little attention has been given to the importance of mercury intake in these populations, although a limited number of studies have tried to estimate the rates of mercury intake Henshel, 1996, 2000;Bidone et al, 1997;Hacon et al, 1997;Kehrig et al, 1998;Fre´ry et al, 2001).…”

Manifestações emocionais e motoras de ribeirinhos expostos ao mercúrio na Amazônia

“…In these studies, the Hg levels in Itaituba were significantly higher (p < 0.0001) than those in Acará. The riverside-dwelling communities in the Tapajós region have a history of long-term exposure, for approximately two decades, and are known for uncontrolled mineral exploration [5][6][7][8]26 . Riverside dwellers in Acará had low HgT levels, which can be explained by the location, which is far from mineral prospecting, and by fish consumption with low HgT levels.…”

“…With that, investigations into clinical symptoms associated with exposure levels have been the subject of research in exposed populations 4,6,24 . The Hg poisoning diagnosis should be based not only on the epidemiological findings and the high Hg levels in blood or hair samples, but also on clinical findings as stated by Harada et al 25 and Pinheiro et al 26 . This study aimed at analyzing emotional and motor symptoms of individuals exposed to MeHg through their diet, contributing to the beginning of the epidemiological, toxicological and clinical monitoring of this special group.…”