Metal pollution in coastal areas of Mexico

Metals are natural constituents of the earth core and can be widespread in all environments, forming part of sediments, rocks, animal and plant tissues, crude oil, hemoglobin, pigments, proteins, and enzymes. However, some of these metals, such as lead, chromium, and mercury, have been widely used in industrial and human activities, thus provoking an alteration in their geochemical balance and causing high concentrations, frequently three to four orders of magnitude higher than their natural concentrations. The aggressive industrialization and urbanization of coastal areas in Mexico have given rise to singular pollution problems in which such metals play an important role. Thus, this review identifies the main sources and quantifies the concentration levels of metals in the water, sediments, and organisms of coastal ecosystems (rivers, estuaries, coastal lagoons, Continental Shelf) in the Gulf of Mexico as well as the Mexican Pacific. The results show high concentrations of lead, chromium, and nickel in sediments and animal tissues from coastal states (Tamaulipas, Veracruz, Tabasco, and Campeche) in the Gulf of Mexico, especially in areas close to industrialized towns such as Tampico, Veracruz City, and Villahermosa. On the other hand, studies conducted on Mexican Pacific coasts indicate low levels of metals in sediments and organisms, an indication that the metal pollution here is closely tied to human, industrial, and oil activities.