Mercury Contamination in Sediments and Fish from an Urban Tropical Estuary: Ecological and Human Health Risks

This work examined mercury concentrations in Rodrigo de Freitas Lagoon (RFL; Rio de Janeiro, Brazil) to support ecological and human health risk assessments associated with the consumption of Hg-contaminated fish. Sediments and fish samples (Mugil liza and Geophagus brasiliensis) were collected for total Hg determination. Potential application of a model for estimating Hg in fish was also evaluated by comparing estimated Hg contents with those found in fish muscle samples. To assess human health risks for non-carcinogenic effects, the hazard quotient (HQ) was calculated for fishermen and market consumers. Hg contents in human hair and blood were estimated by using a single-compartment model proposed by WHO, based on the frequency of fish ingestion and mercury concentration in fish. No sediment sample (0.122 +/- 0.079 mg/kg; n = 17) exceeded the safety Brazilian limit for aquatic biota (0.3 mg/kg). The northern section of RFL presented the highest Hg contents correlated with organic enrichment and mud. Mercury concentrations in M. liza (0.0065 +/- 0.0050 mg/kg; n = 30) were lower than those found in G. brasiliensis (0.0580 +/- 0.0745 mg/kg; n = 31), probably due to the sampling of younger M. liza organisms, which are also at a lower trophic level. Estimated mercury concentration in fish was consistent for G. brasiliensis. Potential hazard on fishermen's health was detected (HQ = 2.1). Hg estimation in fishermen's hair (14.93 mu g/g) exceeded the safe limits indicated by WHO. Regarding market consumers, no potential risk was detected (HQ = 0.3), and the Hg concentrations in blood (2.11 mu g/L) and hair (0.53 mu g/g) were in accordance with the limits established by WHO.