Lead in clams and fish of dietary importance from Coatzacoalcos estuary (Gulf of Mexico), an industrialized tropical region.

With the aim of knowing seasonal variability of lead in fish and bivalve species from Coatzacoalcos estuary, biota collected during three seasons was examined. In muscle tissue of fish, the highest level (5.4 microg g(-1)) was found in the longnose gar Lepisosteus osseus from San Francisco stream (a highly impacted site); the lowest value (0.2 microg g(-1)) was registered in yellowfin mojarra Gerres cinereus from Ostión lagoon (control site). In bivalves, concentrations in soft tissue ranged from 1.5 microg g(-1) in Polymesoda caroliniana from Calzadas river, to 0.1 microg g(-1) in Corbicula fluminea from Hidalgotitlán (control site).