**4. Research proposals**

according to the Environmental Protection Agency of the United States (USEPA), as it can cause irritation in the eyes, skin, and respiratory tract and in high concentrations can destroy red blood cells causing hemolytic anemia [39], besides being considered as a possible carcino-

Another important factor is the contamination associated with heavy metals such as nickel and vanadium which depends on the oil field [40]. Another example is the Amazonia, located in northern Peru, where heavy metal pollution has been found, due to the extraction of hydrocarbons threatening wildlife and local populations that depended on subsistent hunting and fishing [41]; this risk has also been found in La Venta, Tabasco (**Figure 2B**) y en Minatitlán, Veracruz, México (**Figure 2C** and **D**). In this regard, recent studies indicate that the carcinogenic risks of 16 PAH increase with the history of oil extraction; ingestion and dermal contact are the predominant pathways of exposure of the inhabitants to PAH residues in soils [42], representing a risk to the inhabitants, farmers, fishermen, and consumers of these areas.

On the other hand, oil also has various effects on plants due to the changes they produce in the soil; oil can inhibit water retention, causing reduction of germination, emergence, growth, and accumulation of biomass, and cause nutritional imbalance, reduction in pasture produc-

**Figure 2.** (A) Burning of waste by the petrochemical La Venta, Tabasco, Mexico; (B) sludge in contaminated sites in La Venta, Tabasco, Mexico; (C) petrochemical complex of Minatitlán, Veracruz, México; (D) Santa Alejandrina reservoir

tion, and, therefore, lower percentage of livestock hectare.

adjacent to the Minatitlán petrochemical complex, Veracruz, Mexico.

genic in humans (**Figure 2A**).

6 Soil Contamination and Alternatives for Sustainable Development

The strategies would be directed toward the integral management of the investigations: (1) the epidemiological study in contaminated areas, (2) the remediation of contaminated soils, and (3) the control of atmospheric emissions.

### **4.1. Health proposals**

we recommend conducting epidemiological studies differentiated by sex, age, and chronic diseases (various types of cancer, asthma, allergic rhinitis, mental problems, depression, etc.); poor air quality, derived from industrial emissions, can influence the increase of diseases, including allergic ones, such as asthma and chronic bronchitis [43], whose pathologies are of high economic cost, in addition, its potential risks as a carcinogenic factor [42].

## **4.2. Proposals in soils**

In the case of contaminated waters and soils, physical, chemical, and biological processes can be used to remove contaminants. However, there is evidence that some of these technologies can cause damage to biota and prevent the recovery of certain habitats [44]. The use of technologies such as bioremediation and phytoremediation are recommended; we propose a mixed process involving several types of remediation, for example, phytoremediation with fibrous root grasses that promote a dense rhizosphere, being the ideal type of vegetation for phytoremediation; it would also be recommended to combine these with biostimulation and bioaugmentation of autochthonous soil remediation bacteria. The vegetal cover besides contributing to the cleaning of contaminated soils can also reduce the transport of contaminants, improving the physical and chemical properties and increasing the microbial activity with better associations of microorganisms with the root and with the toxic compounds in the contaminated soil. Despite this, another problem of great importance is the accumulation of salts, whose effects can greatly harm the growth and development of many plants, so the use of tolerant plants is recommended. It is also necessary to develop sustainable alternatives that reduce pollution and allow the recovery of contaminated resources through remediation processes of soil and water, until pollutants are below the maximum permissible limits.

#### **4.3. Proposals to control atmospheric emissions**

In the case of Mexico, it is necessary to follow the guidelines of the Official Mexican Standards on Air Pollution (NOM-085-ECOL-1994). However, it is also necessary to develop sustainable alternatives that reduce greenhouse gas emissions. In addition, to have records and controls of atmospheric emissions, this must be available through the Federal Transparency Law.
