Human health risks of geothermally derived metals and other contaminants in wild-caught food.

Arsenic (As) and mercury (Hg) associated with geothermally influenced lakes and rivers represent a potential health risk to communities where wild-caught food is consumed. The Rotorua Lakes region of New Zealand has extensive natural geothermal activity and a large proportion (35%) of indigenous Māori population, for whom wild food gathering is an important cultural activity. The aim of this study was to measure selected heavy metal and organochlorine (OC) concentrations in important local fish and shellfish species and assess the potential health risk to the local population of consuming these species. Following U.S. Environmental Protection Agency (EPA) protocols, consumption limits were calculated based on both excess lifetime cancer risk and noncancer risk. These were compared with local consumption rates, which were determined by questionnaire (n = 19). Median and 95th percentile contaminant concentrations were calculated to approximate random and most extreme contaminant consumption scenarios. Only Hg concentrations exceeded established Food Standards Australia New Zealand (FSANZ) guideline values of 0.5 mg/kg, namely, for rainbow trout (Oncorhynchus mykiss; 62% of the study sites) and koura (freshwater crayfish; Paranephrops planifrons; 25% of sites). The major risk was from consumption of trout, where the local consumption rate (1.5 meals/mo) exceeded the consumption limit of 0.9 meals/mo (median data) and 0.4 meals/mo (95th percentile data). Shellfish--pipi (Paphies australis) and mussel (Perna canaliculus)--collected from the only estuarine site also had local consumption rates (3.5 meals/mo) above calculated consumption limits (2.6 and 2.9 meals/mo, respectively). Our results, while based on a limited sample size and therefore exploratory in nature, nevertheless provide the basis for developing consumption guidelines. This study makes a significant contribution to broadening our understanding of the complexities of managing customary fisheries.