What is environmental risk analysis?
Environmental Risk Analysis (ERA) or sometimes known as Quantitative Risk Analysis (QRA) is used to estimate potential environmental risks in order to protect human health or ecosystems from contaminated land and/or water.
The objectives of an ERA are to provide a quantitative or qualitative estimate of risks, as well as information in the assessment of the effects associated with the presence of possible contaminants in the soil. This assessment process will form the basis for making decisions on the acceptability of the risk and the measures to be adopted for the protection of human health or ecosystems. The ERA also allows you to determine the maximum admissible concentrations for each of the chemical compounds being analysed.
Environmental Risk Analysis methodology
The methodology used in Spain is established in the Royal Decree 9/2005, 14th January, on establishing activities related to potential soil contamination and the criteria and standards to declare soil contamination, which can be outlined in four stages: identification of hazards, toxicological evaluation, exposure assessment and risk characterisation, as is demonstrated in the flowing framework:
Stage 1: Identification of Hazards. This consists in establishing a conceptual model of the investigated site defining contamination hot spots, types of chemical compounds present and its distribution within the ground, transport mechanisms, routes of exposure and potential receptors.
Stage 2: Toxicological evaluation. The objective of the toxicological evaluation is to quantify the potential risk of exposure from the toxic compounds detected through:
- Identification of the risk: to determine whether exposure to a chemical agent will cause an increase in the adverse effects on health.
- Dose-response analysis: determine the tolerable daily intake to define a no observed adverse level to a potentially exposed population.
Stage 3: Exposure assessment.
The objective is to establish the daily doses of exposure to the potential receptors of chemical agents. This is based upon the concentration of each of the adverse chemical compounds identified and the exposure routes contemplated for the analysis. Exposure to chemical compounds can be produced in two ways:
- Direct exposure via dermal contact or ingestion of soil. The exposure concentration is considered to be equal to the concentration detected in the soil.
- Indirect exposure via inhalation of volatile compounds originating from soil or groundwater, as an example. In this case the exposure concentration can be estimated through the use of direct field measurements or by using transport models. Therefore it will be necessary to know the geological and hydrogeological properties of the medium, whether the exposure route is complete or not and whether the receptors are located in the exterior or in the interior of confined spaces such as basements, offices, sewers, etc and the construction and actual state of these.
Stage 4: Risk characterisation.
This consists in combining the toxicological information with respect to the chemical compounds identified and the exposure dosed to the potential receptors. The situation is integrated into a program to determine the quantitative risk associated to the site in question. As the result of the risk is an estimation, it is important to indicate the level of uncertainty.
In terms of protecting human health resulting from an Environmental Risk Analysis (ERA) or Quantitative Risk Analysis (QRA), the following is assumed:
- For carcinogenic substances, the level of acceptable risk is one in which the expected frequency of occurrence of cancer in the exposed population does not exceed one per hundred thousand cases (the risk value does not exceed 10-5)
- For substances causing systemic effects, it is assumed that situation of acceptable risk in which for every substance, the quotient between long-term exposure and maximum admissible dose is lower than one.
If the result of the QRA is determined that the level of risk is unacceptable then procedures must be undertaken to either eliminate or reduce to acceptable levels of concentration for potentially exposed receptors.
The ERA is a valuable tool to use in the remediation of an impacted site, enabling you to establish safe level of chemical concentrations below which the effects to potential receptors become insignificant. In other words, determine the Site Specific Target Level (SSTL) in the source area.
Environmental Risk Analysis in Spain
In order to facilitate and standardise the implementation of ERA within the various autonomous regions of Spain, some such as Madrid, the Basque country and Andalusia have published guidelines for quantitative analysis and risks to human health and ecosystems.
- ERA guide (in spanish) Comunidad de Madrid
- ERA guide (in spanish) Andalucía
- ERA guide (in spanish) País Vasco, being currently revised.
Tools to used to perform an Environmental Risk Analysis in Spain
Computer programs are used to assist in determining the risk analysis such the widely used RBCA Tool Kit or BP RISC. All of them use the conceptual model of a site, the relationship between source, transport routes, receptors and the specific properties in question.
The use of these programs requires some experience as it is necessary to carry out a correct interpretation and validation of the results, as well as an adequate analysis of the uncertainties of the data used and the sensitivity of the model used. It is crucial to ensure that there has not been an underestimation or overestimation of the risks.
Finally, should be clear that this type of risk analysis methodology differs from that used in the analysis of environmental risks to obtain a financial guarantee required by business or industrial activities affected by Law 26/2008 of October 23rd, on Environmental Responsibility
Publicado el 15/04/17