Mercury contamination in alligators (Melanosuchus niger) from Mamirauá Reservoir (Brazilian Amazon) and human health risk assessment

Abstract

Mercury (Hg) concentrations in muscles of wild alligators (Melanosuchus niger) from the Mamirauá Reservoir (a reference area in the Brazilian Amazon) and the human health risks associated with its consumption were assessed. The mean Hg concentration in alligator muscles was 0.407 ± 0.114 μg/g (N = 61). Close to 5 % of the muscle samples showed Hg levels above the World Health Organization guideline for fish consumption (0.5 μg/g). A positive and significant relationship was observed between Hg concentrations in muscle and the age of the specimens. The dose-response approach suggests that close to 27.4 years is required for half of the exposed specimens to attain 0.5 μg/g. The hazard quotient (HQ) is a risk indicator which defines the ratio of exposure level and a toxicological reference dose. HQ resulted above the unity for all the specimens when the ingestion rate for riverine communities (200 g of muscle per day) is considered, indicating the existence of hazard. When the ingestion rate for market consumers (28.57 g/day) is considered, the risks are much lower (mean HQ = 0.55), suggesting that such group is not at risk. The establishment of local and regional ingestion rates for riverine populations and market consumers is extremely recommended.

Total Mercury Content in the Tissues of Freshwater Chelonium (Podocnemis Expansa) and a Human Health Risk Assessment for the Amazon Population in Brazil

“…When considering the mean THg concentration in males and females for monthly or annual consumption, the HQ was <1 in all categories. Research carried out by Correia et al (2014) evaluated the HQ for alligator consumption by riverside populations and determined a value of 7.19, considering this quotient due to the higher Hg concentrations in these animals as compared to P. expansa, since they show predatory feeding behavior and are piscivores.…”

I got it from my mother: Inter-nest variation of mercury concentration in neonate Smooth-fronted Caiman (Paleosuchus trigonatus) suggests maternal transfer and possible phenotypical effects

“…In certain geographical areas (e.g., Amazon region), the abundant natural Hg in soil and biota (e.g. an average of 0.3 µg.g -1 in forest soil in French Guiana, Richard et al, 2000), human activities such as deforestation, gold mining activities and agriculture additionally contribute to increase Hg bioavailability (Roulet et al, 1998;Maurice-Bourgoin et al, 2000, Vieira et al, 2011Schneider et al, 2012;Correia et al, 2014;Eggins et al, 2015;Lázaro et al, 2015;Schneider et al, 2015;Rivera et al, 2016, Marrugo-Negrete et al, 2019, Lemaire et al, 2021.…”

Lead, mercury, and selenium alter physiological functions in wild caimans (Caiman crocodilus)

“…However, many crocodilians have a concerning conservation status, and populations of several species are currently decreasing (Targarona et al, 2008;Ferreira and Pienaar, 2011;Bezuijen et al, 2012;Van Weerd et al, 2016;Balaguera-Reina et al, 2018;Ortiz et al, 2020). Few studies which focused on a limited number of species have evaluated Pb and Hg concentrations in crocodilians (Burger et al, 2000;Jeffree et al, 2001;Correia et al, 2014;Trillanes et al, 2014;Nilsen et al, 2017b). Further knowledge on their negative effects is restricted to four crocodilian species (Alligator mississippiensis, Caiman crocodilus, Paleosuchus trigonatus and Crocodylus niloticus) and few markers (morphology, DNA and reproduction; Lance et al, 2006;Warner et al, 2016;Nilsen et al, 2017a;Marrugo-Negrete et al, 2019;Lemaire et al, 2021b).…”