Background: A main route of heavy metal exposure is the consumption of contaminated food or water, resulting in negative health effects. Objectives: The objective of this study was to assess the health risk related to consumption of canned tuna and fresh fish by evaluating chromium (Cr), cadmium (Cd), mercury (Hg), and lead (Pb) concentrations. Methods: Forty-eight samples of tuna canned in water and 20 samples of different fish species sold in the city of Tijuana were used. Samples were digested by microwave-assisted digestion. Mercury was measured using the cold vapor atomic absorption spectrometry (CVAAS) method (United States Environmental Protection Agency (USEPA) method 7419b) and Pb, Cd, and Cr were measured using graphite furnace atomic absorption spectroscopy (GFAAS) (USEPA method 7010). Health risk assessment was conducted calculating the total hazard quotients (THQs) using the USEPA region III risk-based concentration table for adults. Results: The wet weight heavy metal concentrations in the canned tuna for Hg were 0.005 to 1.17 mg/kg, for Pb were 0.07 to 0.32 mg/kg, for Cd were from not detected (ND) to 0.007 mg/kg, and for Cr were 0.02 to 0.65 mg/kg. In the fresh fish samples, concentrations of Hg were 0.14 to 2.14 mg/kg, for Pb were 0.04 to 0.32 mg/kg, for Cd were 0.001 to 0.003 mg/kg, and for Cr were 0.07 to 0.38 mg/kg. The highest Hg concentrations were found in species of mako shark (Isurus oxyrinchus) and soupfin shark (Galeorhinus galeus). THQ values calculated were below one for all the samples. Conclusions: The results suggest that the consumption of canned tuna and fish in Tijuana does not represent a health risk for the general population in terms of exposure.

Even though geothermal energy is a renewable energy source that is seen as cost-effective and environmentally friendly, emissions from geothermal plants can impact air, soil, and water in the vicinity of geothermal power plants. The Cerro Prieto geothermal complex is located 30 km southeast of the city of Mexicali in the Mexican state of Baja California. Its installed electricity generation capacity is 720 MW, being the largest geothermal complex in Mexico. The objective of this study was to evaluate whether the emissions generated by the geothermal complex have increased the soil mercury concentration in the surrounding areas. Fifty-four surface soil samples were collected from the perimeter up to an approximate distance of 7660 m from the complex. Additionally, four soil depth profiles were performed in the vicinity of the complex. Mercury concentration in 69 % of the samples was higher than the mercury concentration found at the baseline sites. The mercury concentration ranged from 0.01 to 0.26 mg/kg. Our results show that the activities of the geothermal complex have led to an accumulation of mercury in the soil of the surrounding area. More studies are needed to determine the risk to human health and the ecosystems in the study area.

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