Ecological risk assessment exposure analysis

The second phase of ecological risk assessment, the analysis phase, includes two principal activities characterization of exposure and characterization of ecological effects (Figure 28.1). 

Studies may be designed for estimating exposures to a wide array of wildlife, including birds, mammals and amphibians. Many regulatory requirements involve birds, and less emphasis is currently placed on other species. As regulatory requirements evolve, ecological risk assessments will be required for more species. This may require alternative approaches for food item analysis to allow estimates of pesticide ingestion. 

A number of EIA theorists believe in incorporating formal RA methods into EIA as a way to cope with uncertainties, especially in impact prediction where a formal framework for ecological risk assessment (EcoRA) is already developed. It includes three generic phases problem formulation, analysis, and risk characterization followed by risk management. The analysis phase includes an exposure assessment and an ecological effects assessment (see, e.g., US EPA (1998)). 

Another important reason for using multiple scenarios is to represent major sources of variability, or what-if scenarios to examine alternative assumptions about major uncertainties. This can be less unwieldy than including them in the model. Also, the distribution of outputs for each separate scenario will be narrower than when they are combined, which may aid interpretation and credibility. A special case of this occurs when it is desired to model the consequences of extreme or rare events or situations, for example, earthquakes. An example relevant to pesticides might be exposure of endangered species on migration. This use of multiple scenarios in ecological risk assessment has been termed scenario analysis, and is described in more detail in Ferenc and Foran (2000). 

There is some USEPA precedent for use of statistical meta-analysis in a regulatory context, including the recent meta-analysis of organophosphate-related acetylcholinesterase inhibition data and meta-analysis of epidemiological studies on effects of 2nd hand tobacco smoke exposure. Warren-Hicks and Moore (1998) provide some discussion of the potential applicability of meta-analysis to ecological risk assessments. 

Reinert KH, Giddings JM, Judd L. 2002. Effects analysis of time-varying or repeated exposures in aquatic ecological risk assessment of agrochemicals. Environ Toxicol Chem 21 1977-1992. 

Analysis of effects A phase in an ecological risk assessment in which the relationship between exposure to contaminants and effects on endpoint entities and properties is estimated along with associated uncertainties. 

As mentioned before, the ecological risk assessment is characterized by a problem formulation process, analysis containing characterizations of exposure and effects, and a risk characterization process. Several outlying boxes serve to emphasize the importance of discussions during the problem formulation process between the risk assessor and the risk manager, and the critical nature of the acquisition of new data, verification of the risk assessment, and monitoring. The next few sections detail each aspect of this framework. 

Characterization of exposure — A portion of the analysis phase of ecological risk assessment that evaluates the interaction of the stressor with one or more ecological components. Exposure can be expressed as co-occurrence or contact, depending on the stressor and ecological component involved. 

Exposure profile — The product of characterization of exposure in the analysis phase of ecological risk assessment. The exposure profile summarizes the magnitude and spatial and temporal patterns of exposure for the scenarios described in the conceptual model. 

Hope BK, Generating probabilistic spatially-explicit individual and population exposure estimates for ecological risk assessments, Risk Analysis, 20, 573, 2000. 

The output of the analysis phase of an ecological risk assessment consists of an exposure profile and a stressor-response profile (Eigure 9.1). The profiles include estimates of uncertainty, which, as in human health risk assessments, are a constant and essential ingredient of ecological risk assessments. The exposure and effect profiles, together with their associated uncertainty estimates, set the stage for the final phase of the risk-assessment process. 

There are two components to the analysis phase characterization of exposure and characterization of effects. Overall, this phase is similar to the exposure and toxicity assessment components of a human health risk assessment. The primary differences relate to the variety of ways in which exposure and toxicity can be measured in an ecological risk assessment. 

In formal EcoRA framework three phases of risk analysis are identified problem formulation, analysis, and risk characterization followed by risk management. The analysis phase includes an exposure assessment and an ecological effects assessment (see Figure 2). 

In assessing risks posed by toxic chemicals, exposure (see exposure analysis below) refers to mechanisms of direct contact, ingestion, inhalation, or indirect accumulation through the consumption of contaminated food. The concept of exposure has been expanded to include analogous pathways and mechanisms that define the intersection in space and time of other stressors with individual organisms or their ecological support systems. 

See also Carcinogen Classification Schemes Dose-Response Relationship Exposure Assessment Exposure Criteria Hazard Identification Risk Assessment, Ecological Risk Based Corrective Action (RBCA) Risk Characterization Risk Communication Risk Management Uncertainty Analysis. 

Any individual with a professional interest in exposure analysis is invited to join. The Society seeks broad participation from various disciplines such as exposure assessment, chemistry, biochemistry, risk assessment, biostatistics, physiology, toxicology, epidemiology, ecology, environmental engineering, and others. There are currently several hundred members of ISEA, with a US focus but international representation. Students and international professionals with an interest in exposure assessment are especially encouraged to join. 

Risk Assessment. Identification of potential risks (step one) was based on an analysis of the taxonomic and ecological characteristics of the parental organisms, the functional changes in the microorganisms brought about by the genetic alteration, the mechanism of pesticidal action, and the nature and scope of the proposed field trials. Evaluation of these four areas was the basis for identification of potential hazards and mechanisms for exposure, which in turn were used to formulate the risk issues. ... 

---