Sub-module 8B, Page 1

Learning Goals:


Hazard Identification

While the risk assessment process outlined in 8A is quite general, in this sub-module we will spend some time with environmental contaminants in the mode where most of us deal with them. Let's start with some philosophy. Most health risks from chemicals in the environment arise from releases. Releases might be intentional (or permitted, accent on the first syllable) or unintentional. The risks we are calculating might be due to future releases or past releases.

Intentional, past
Unintentional, past
Intentional, future
Unintentional, future

1.) Insecticides such as DDT were released into the environment in large quantities. (Intentional, Past)
2.) A local electroplating operation asks the city's wastewater treatment facility for permission to discharge water containing cadmium into the city's sewers. (Intentional, Future)
3.) An inspection reveals that a gasoline service station's tanks have been leaking for several years (Unintentional, Past)
4.) A manufacturing company wants to set up chemical storage tanks on a hill overlooking a school. (Unintentional, Future)

Risk assessments are required in all four cases. For the unintentional future release, the probability of the harm is related to the probability of the release. Will the tank burst? These are chiefly engineering decisions relating to the design of the tank. Once the engineers have analyzed the probability of a release, a human health risk assessment is needed in a "what-if" analysis of the consequences of possible future failure. In performing the human health risk assessment, the risk analyst would be given exact quantities of chemicals that would be released in order to perform the risk analysis, but the quantities would be hypothetical.

For the intentional future releases, we have a similar situation. Here the
analyst would be given an exact number for the release, or the party that plans to release the chemical would be given an upper limit on the quantity that will be permitted. You learned in the TRI exercise that many toxic releases are quite legal.

For all the past releases, both intentional and unintentional, Hazard Identification is much more difficult. We generally do not know the amounts of chemical released, and often we do not even know the chemical. Often there are several chemicals. We receive notice of them through a phone call (worse, a phone call from a reporter) or a worker/neighbor/ member of the public shows up with a Ziploc bag filled with something, or a well water sample that smells like a dry cleaning store. Perhaps a notice that "this is from the area behind the storage shed," or "this is from the place where all the vegetation is dead." What next?

Following some type of initial notice, often times as informal as noted above, a chain of events will follow. Illogical as it sounds to the uninitiated, the details of what follows will depend on the regulatory matrix: what the substance is, the location where it was found, and the nature of the party who likely put it there. 100 kg of benzene from a chemical plant is different than 100 kg of benzene from an oil spill. 100 kg of fresh benzene on its way to factory is different from 100 kg of contaminated benzene on its way to a recycler. We will try to avoid those details, but two Federal laws for which you need to know their relations to risk assessment are CERCLA and RCRA. You saw brief descriptions of those laws back in Module 2B []

Here is an overview of the "superfund" cleanup process,, no need to follow all the links, but read all the steps involved.

When Congress passed Superfund in 1980, the original law had a provision for a risk assessment, called a Hazard Ranking Score (HRS). The idea was simple, since there were many sites competing for superfund money, proponents of cleaning a particular site would fill out a simple form. The form had a numbering system, the higher numbers indicating increased risk to human receptors. The EPA (who might also be a proponent) would arrange these into a priorities list, with the highest score funded first. (I worked with a HRS in the early 1980's and I remember it was 3 or 4 pages long, the instructions were about 10 pages.) What happened was thousands of contaminated sites were discovered, the cognoscenti realized that the system could easily result in errors. Today the HRS regulations are almost 200 pages long. Here's a little about it

RCRA (pronounced "reck rah") stands for the Resource Conservation and Recovery Act. This 1976 law was modified in 1984 by the Hazardous and Solid Waste Amendments (HSWA) again, there is no need for me to talk about HSWA as distinct from RCRA. RCRA is the "hazardous waste law." It provides cradle to grave control of hazardous waste. You don't need to know any details about RCRA for this course, but you should know that RCRA deals with producers of hazardous waste and transporters and treatment facilities that handle hazardous wastes and finally store it. You should also know that RCRA has its own set of regulations that deal with clean up of chemical spills and their associated risk assessments. But on the whole, the procedure is similar to what we learn about CERCLA below. Here's a capsule on RCRA. You should look at the first definition of hazardous waste.
RCRA The key difference between RCRA and CERCLA is that RCRA usually deals with current or ongoing pollution events and usually there is some sort of viable economic entity that is responsible and heavily involved. CERCLA usually deals with past events, sometimes long ago, and either there is not an economically viable entity available, or finding that entity, and making them pay, is part of the process.

Back to your friend/client/public with the Ziploc bag. Clearly you want to investigate the situation some more. In most situations, the next thing you need to do is find the money and time to do an investigation. You certainly want the substance in the bag analyzed to determine what it is, and probably go out to the site and observe the situation. When you have done these things, you are in the middle of the
Hazard Identification part of a risk assessment. Let's assume the soil in the bag was saturated with a chemical and your quick review of the site indicates there may be a lot of soil so contaminated. Let's ignore issues of budget and regulatory matrix, but we'll use the nomenclature from the superfund process. What happens next?

We saw the process in the website above, but here it is my own words:

1.) You need to "scope" the situation. Your analysis of the gunk in the Ziploc bag and tour of the site is the start of a scoping. Depending on what you find, the next step would be,

2.) A more formal approach follows and is called a Preliminary Assessment and Site Investigation. (PA/SI) This step usually requires extensive sampling of soils and materials and a thorough investigation of the situation. Elaborate preparations and chemical analysis procedures and quality control are required. This step would determine if a significant release of contaminant occurred. If it did, the next step is called,

3.) Remedial Investigation. This step is often combined with a feasibility study and the acronym RI/FS is commonly used for this process (pronounced "riff is") The RI is now done in great detail, but the nature of the investigation is keyed to the expected cleanup alternatives. For example if the PA/SI indicated extensive groundwater contamination, the RI/FS would involve many test wells to sample the groundwater. If the PA/SI indicated the contaminants were bound up in the surface soil, the RI/FS would not drill many wells. The feasibility study is the first step in designing the remediation.

4.) Following the RI/FS, if this were a Superfund site (and there is usually an analogous procedure for non-superfund clean ups) a Record of Decision is issued by the EPA. The record of decision or ROD follows public comment and deliberation by the EPA and firms up what will be done with the site.

5.) The next steps are called Remedial Design and Remedial Action, the latter is when the site actually gets cleaned up, or monitored or whatever. The key acronyms in order are:

Initial scope > PA/SI >RI/FS > ROD > Remedial Design and Remedial Action

Back to the Ziploc bag and its chemical(s) and your evaluation of the situation. Here you do a risk assessment to determine if the matter is even worth pursuing. Your report will mention the chemicals that were in the bag. Are these chemicals toxic in the doses people are likely to be exposed to? Is the site a playground or an industrial storage yard? Based on this preliminary risk assessment, if the situation looks like it poses a significant risk, you will try to get your boss to budget the money to go to a PA/SI. If you decide there is little risk, you will try to get your friend with the bag to agree and leave the office. You might call this a back-of-the-envelope risk assessment.

Following the PA/SI a preliminary screening risk assessment is done, if the PA/SI indicates that there is significant contamination at the site. This will be a formal document that is as thorough a risk assessment as practical, given the preliminary nature of the information the PA/SI produces. This preliminary screening risk assessment will identify the Chemicals of Potential Concern (COPCs), that is the chemicals we are interested in.

During the RI, enough information becomes available to do a much more accurate risk assessment, and this is called the Baseline Risk Assessment. Its characterization of the risk is based on the information collected by the RI. During the FS, different scenarios (by that I mean sets of design alternative) of cleanup are considered. For each of these, there is a risk assessment of the alternatives, based on the likely effect of the cleanup alternative considered.

As part of the ROD, the risk assessments of all the various options studied are presented to the public. Note that the baseline risk assessment is now the risk assessment for the "do-nothing" alternative.


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