Integrating Mercury Concentrations in American Alligators (Alligator mississippiensis) with Hunter Consumption Surveys to Estimate Exposure Risk

Abstract

Mercury is a naturally occurring element but is also considered a widespread contaminant due to global anthropogenic activity. Even in moderate amounts, mercury (Hg) is an established neurotoxin and is associated with a range of adverse outcomes both in humans and wildlife. Humans in the United States are most commonly exposed to Hg through contaminated food or drinking water, and the consumption of game species, particularly those occupying higher trophic levels, has the potential to expose hunters to high concentrations of Hg. In the present study, we determined Hg concentrations in tail muscle and blood from American alligators (Alligator mississippiensis) inhabiting a region (Savannah River Site, SC, USA) with known Hg contamination. We then integrated these data with alligator harvest records and previously published surveys of alligator meat consumption patterns to estimate potential exposure risk. We found that the average Hg concentrations in tail muscle (1.34 mg/kg, wet wt) from sampled alligators exceeded the recommended threshold for Hg exposure based on the World Health Organization's guidelines (0.5 mg/kg, wet wt). In addition, based on regional consumption patterns reported for both adults and children, we estimated Hg exposures (x Adult ¯= 0.419 µg/kg/day, x Child ¯= 2.24 µg/kg/day) occurring well above the US Environmental Protection Agency methylmercury reference dose of 0.1 μg/kg/day. Although the two reservoirs sampled in the present study are not currently open to alligator hunting, they are connected to waters that are publicly accessible, and the extent of alligator mobility across these sites is not known. Together, the findings reported in the present study further demonstrate the need for active monitoring of Hg concentrations in game species, which can convey substantial exposure risks to the public.

Maternal provisioning interacts with incubation temperature to affect hatchling mercury exposure in an oviparous reptile

“…We noted important distinctions when assessing mercury concentrations in neonate alligators compared to adults. Liver THg concentrations in hatchlings are lower compared to concentrations in most other tissues, and blood does not appear to be as reliable an indicator as it is in adults [46,59,66]. Furthermore, incubation temperature influences the dynamics of maternally derived mercury, potentially mediating developmental cost or depuration.…”

“…Maternal transfer of mercury to eggs has been demonstrated across a range of taxa [15,26,27,30,[39][40][41][42][43][44]. When converted from its inorganic to methylated form, mercury both bioaccumulates within organisms and biomagnifies across trophic levels, making it a contaminant of concern for long-lived, high trophic level predators [45][46][47][48]. For these reasons, the American alligator has been used as a sentinel of mercury contamination in the southeastern United States for several decades (electronic supplementary material, table S1 and citations therein).…”

Heavy Metals in Poultry Chicken and Human Health Threat: A Mini Review

“…One of the most effective neurotoxins is mercury (Hg), which can have a variety of detrimental impacts on an animal's or human's health [52]. Although methyl mercury is recognized as the most hazardous type, mercury (II) is more commonly and abundantly found in the environment and can have severely detrimental effects on poultry [53].…”

Heavy metal toxicity in poultry: a comprehensive review

“…Hg is one of the most potent neurotoxins, and it has a range of negative health effects on both humans and animals ( 93 ). Hg is considered to be a significant environmental pollutant, along with other non-essential trace metals, because of its high toxicity and capacity for biomagnification and bioaccumulation ( 94 ).…”