Risk Analysis Contamination of Groundwater, Surface Water and Soil

The environmental risk assessment is a methodology used in the study of the risk exposure to a toxic substance introduced into the environment, and whose concentration can be harmful to people or ecosystems.

Hazard identification: This first phase involves the formulation of the problem, determining the contaminants found in the area and their properties as well as terrain features and human activities which are or can be carried out in the same. First a list of potential contaminants of interest will be a matter of study in later stages is performed. This list must include: Compounds that exceed levels established from risk criteria.

Potentially carcinogenic substances for humans: Substances for which has not established a threshold in terms of their effects on human health.

Bioaccumulative, persistent and toxic compounds: Degradation products of other compounds that can become toxic. Contaminants that exceed their baseline values.


Then a conceptual model of the site, which is a schematic representation of the following takes place:

Area source pollution
Release mechanisms pollutants
Transport of pollutants
Potential routes of exposure
Potential recipients of pollution
If an exposure pathway lacks any of these elements is considered incomplete and the possibility of risk is discarded.

Toxicological Evaluation: This step is the evaluation of the dose-response relationship between the toxicant and an organism exposed to it. This relationship represents the correlation between the amount of toxic and magnitude of the effect and toxicity tests are performed to the three routes of possible exposure: oral, dermal or inhalation. The quantitative assessment of toxicity tests used to determine the dose-response relationship is different if the toxic compound is carcinogenic if it is not:

Carcinogenic contaminants: in these cases is considered that there is a threshold of exposure below which there is no likelihood of risk to human health. This level of exposure is estimated limit for one day and for each route of exposure and is usually expressed averaged for life for chronic dose. This value is called “reference dose” or referencedose (RfD).

Carcinogenic pollutant: it is assumed that any level of exposure carries a chance of developing cancer. Validation is done through the “power factor of cancer” or slope factor (SF) indicating the increased likelihood of developing cancer, over a lifetime, chronic exposure to a unit dose of the contaminant . The likelihood of cancer is available, thus multiplying the daily dose of chronic exposure by the power factor. Toxicological data on most toxic substances of environmental concern is contained in the base Integrated Risk Information System (IRIS), belonging to the United States Environmental Protection Agency (USEPA).

Exposure Assessment: This stage will determine the daily exposure dose for each pollutant or combination of pollutants to which they will be subject receiving agencies. This daily dose represents the magnitude of exposure and is expressed in units of mass of pollutant exposed per unit of body mass per day. For its calculation it is necessary to determine the concentration of each toxic compound in each medium (water, soil …) and will be held for each of the routes of exposure (oral, dermal, inhalation).

Risk Characterization: In this final phase will integrate the results of the previous two stages, ie, the toxicological information contaminants and the estimated value of the exposure dose of each, in order to determine how quantitative risk posed by the situation assessed.