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Mercury and methylmercury concentrations were evaluated in two marine fish species captured and consumed in Mexico, snapper (Lutjanus sp.) and mackerel (Scomberomorus sp.), obtained from several fish ports on the Pacific Ocean and the Gulf of Mexico. Significant differences were found between the median total mercury concentrations in snapper and mackerel, which were 0.187 and 0.125 μg/g (ww), respectively. Differences in the total mercury concentration in snapper were observed between the different oceans; snappers from the Gulf of Mexico registered a higher median mercury concentration (0.233 μg/g) than those caught in the Pacific Ocean (0.150 μg/g). Ninety-three percent of all samples presented had mercury concentrations that did not exceed the maximum limit (0.5 μg/g) specified by Mexican regulations, although 21% exceeded the US EPA limit of 0.3 μg/g, and three samples had mercury concentrations that were above the FDA recommended limit of 1 μg/g. Mackerel and snapper collected in the ports of Tampico and Mazatlan (economically important industrial cities and fishing sites) had the highest concentrations of total mercury, compared with those obtained from Acapulco and Ensenada (important touristic centers), which showed the lowest values. Recommendations should be made for the maximum allowed consumption of these fish in Mexico, especially for populations settled in shorelines where fish is essential for the daily diet.

Deficient management of cinnabar mining left the San Joaquín region with high concentrations of mercury in its soils (2.4 – 4164 mg kg-1). Numerous cinnabar mines have contributed to the dispersion of mercury into agricultural (0.5 –314 mg kg-1) and forest (0.2 – 69 mg kg-1) soils. Sediments are a natural means of transportation for mercury, causing its spreading, especially in areas near mine entrances (0.6 – 687 mg kg-1). The nearness of maize crops to mines favors mercury accumulation in the different plant structures, such as roots, stems, leaves, and grain (0.04 – 8.2 mg kg-1); these being related to mercury volatilization and accumulation in soils. Mercury vapor present in the settlements could indicate a constant volatilization from lands and soils (22 – 153 ng m-3). The mercury levels found in the soils, in maize grain, and in the air resulted greater than the standards reported by the Official Mexican Norm (NOM) and the World Health Organization (WHO). Mercury in rainwater is due mainly to the presence of suspended atmospheric particles, later deposited on the surface (1.5 – 339 μg |-1). Mercury dissolution was found in the drinking water (10 – 170 ng |-1), with concentrations below those established by the NOM and the WHO. The contamination existing in the San Joaquín region does not reach the levels of the world’s greatest mercury producers: Almaden (Spain) and Idrija (Slovenia). It is, however, like that found in other important second degree world producers such as Guizhou (China). The population of San Joaquín, as well as its surrounding environment, are constantly exposed to mercury contamination, thus making a long term monitoring necessary to determine its effects, especially to people.