Chemical Risk Assessment

Real-world examples portray the decision logic needed to conduct chemical sampling when assessing risk. This chapter includes a troubleshooting section/checklist to assist samplers in either choosing a consultant or appraising in-house sampling methodology.

Chemical risk assessment is a twofold process. One part occurs off-site as known chem­ical information is assessed and calculations based on accepted formulas are done. The EPA baseline risk assessments (BLRAs), screening assessments, and remedial investigation studies rely on a body of knowledge accumulated over the last 20 years. Decisions about supportive air monitoring and actual on-site monitoring required during sampling events should also be made at this time.

The second stage is the actual accumulation of data during which workers must be pro­tected against airborne hazards, including those resulting from their sampling efforts, including disturbance of the on-site medium (soil, water). Decision-making concerning personal protection and engineering controls may require air monitoring of personnel, area of influence, and the site perimeter.

In order to understand the context under which air monitoring protocols are devel­oped, an understanding of chemical risk assessment for these sites is necessary. Keep in mind that the term site is an all inclusive one for this section and may include active indus­trial and/or construction sites.

5.1 BASELINE RISK ASSESSMENT

Monitoring to determine chemical risk may lead to a BLRA consistent with U.S. EPA Comprehensive Environmental Resource Conservation Liability Act (CERCLA) guidance documents that address:

• Potentially contaminated groundwater

• Surface water runoff, sediment, and river area

• Soils

The results of the BLRA may be used to

• Prioritize the need for site remediation or abatement activities.

• Provide the basis for quantification of remedial objectives.

• Assist in planning objectives to minimize risk.

CONCEPTUAL SITE MODEL

The first step in developing a BLRA is to provide a conceptual site model that has been developed to evaluate source areas, migration pathways, and possible exposure points for receptors. Migration pathways are potential conduits for contaminants to reach on-site and off-site receptors. This model is then used to determine the medium that needs to be sampled.

Source Areas

The source areas are limited to the areas delineated by the model. Source areas such as soil areas, bodies of water, and air emissions are areas for concern. Soils in particular may be primary and secondary source areas—primary as particulates that may lead to ingestion or dermal hazard, and secondary as soils that may be dispersed in the airstream through on-site activities.

Дата добавления: 2015-11-16