Module 02, Closure
Questions and Answers of general interest to the class, that all students should be familiar with, are indicated with *** are are first in the queue:
*** Q. I attempted searches for
hydroquionone on Excite, Alta Vista, and Ask Jeeves. No luck.
I then tried Google.com and got several hits on hydroquionone
(even though I had misspelled it for the search
A. Yes, several students used Google. I never have. Sounds good
*** Q. I was a little unclear about what SCEM was.
A. I did not introduce the topic well. A Site Conceptual Exposure Model (SCEM) is a diagram of the sources, pathways and receptors. We will work more with these.
*** Q. What type of parameters might lead to the "do-nothing" alternative?
A. The risk characterization indicates that there is no significant risk. (We will spend a long time trying to define what "significant" means.)
*** Q. In the discussion of contaminated media (Sub-Module 2B-Page 1), if the contamination, i.e. benzene from POL contaminated soil, is migrating through groundwater to surface water (tidal lagoon), is the surface water considered a transport medium or a receptor?
A. The word "receptor" usually refers to the exposed person. The term "ecological receptor" usually refers to an animal or plant, or a collection of these. In risk assessment, when you are considering the transfer from one medium or phase to another, you just continue the evaluation until you reach the receptor of interest.
*** Q. In the Dose-Response experiment does Cheech change the fishes for each dose experiment?
A. (This was from Module 1) Yes, You would start with a new, unexposed batch of fish for each dosing level. The lesson did not make that clear.
*** Q. The sub module 2A had links to the summaries of CERCLA objectives and goals. I also decided to read the summary about RCRA and found the word "hazardous substance' being used a couple of times. Can "hazardous waste" and "hazardous substance" be used interchangeably?
A. No. Gasoline is a hazardous substance, it can burn and its vapors explode. It is not a "waste." The RCRA law and its interpretations have many details about what makes a waste, under the law.
Q. Module 2B suggests that a risk assessment is performed on the data collected during the PA/SI, after COPCs are identified. What are the criteria for including a given chemical as a COPC? Are these defined during the scoping? For instance, some screening in Alaska is done based on exceedence of promulgated criteria (the Table B1, B2 and C values). But then when the cleanup alternatives are evaluated, and the state-mandated cumulative risk calculation is performed, all pollutants exceeding 10% of the promulgated criteria must be included. Or is this issue small potatoes, and the really bad players will be ferreted out in the process anyway?
A. Very good question, but the answer would depend on the situation and who you are. This is an issue of "Hazard Identification." Let's avoid the regulatory details and go back to the law and principles. We want to avoid "any adverse effect on human health or the environment." If the situation is already affecting these adversely we want to remediate the situation. If there is an "Applicable or Relevant and Appropriate Requirement," (typically a regulation) that gives us a NUMBER, and you might assume that 10% of that number will avoid these adverse affects, and go from there. But this is an assumption, not a fact. Many substances do not have an ARAR. On a 600-acre site, how many samples do you take? What do you test the samples for? If you have an obvious chemical stain, there are several series of tests that will show if the stain is one of the common contaminants. There are about 30,000 chemicals in common industrial use today and several hundred thousands in some use. In general you have to use judgment to determine where and what to test, and often this judgment comes from an iterative process that involves investigation, observation, interviews, and careful analysis of the intermediate findings.
Q. I have seen RAs done that combined the effects of different chemicals (e.g. PCBs and BTEX) at very discrete locations on a "site" (the site being say 10 acres; the spill locations being on the order of 10 sq ft). I am interested in how these RAs characterize the risks of exposure to different chemicals, not uniform on the site and limited in extent over time (especially those, such as tributyltin, that have the potential to break down over time).
A. We will work with this quite a bit later in the course. Briefly, you evaluate the probability and severity from each contaminant and location, and then add them up at the receptor.
Q. Regarding a RI/FS, it seems to me that they are very separate steps. How can a FS be started without the results from the RI?
A. That would depend on how much data you had from the PA/SI. In many cases, the RI and FS are iterative. For example, the RI indicates the ground water is contaminated, the FS suggests a pump and treat, then the RI is extended to include more monitoring wells and some test wells and so on. For this course the important concepts are that RI provides data for the baseline risk assessment and that each feasible alternative will have a risk assessment.
Q. In your schematic: Initial
scope > PA/SI >RI/FS > ROD > RD and RA, where does
the public involvement begin?
A. We'll spend more time on this later.
Q. Why is a chemical listed in the TRI also listed in the EPA extremely hazardous substance list?
A. Because many extremely hazardous chemicals are released into the environment.
Q. If a PA/SI showed a "not so poisonous" radionuclide in ground water, which would result in formation of a more "poisonous" daughter nuclide after 10 yrs (half life period =10 yrs), would the RI wait for say 8 yrs or divert its attention to another site?
A. Interesting question. Most contaminants dissipate over time, and this is referred to as "natural attenuation." You may have thought of a case of negative natural attenuation. What you ask is really a risk management issue. Deciding the priorities. Your risk assessment would just take the time factor into consideration. We will discuss effects over time more later.
Q. Is the worker really exposed to a higher concentration than the trespasser? I would think that a trespasser would be exposed to higher concentrations because he/she may not know the danger of the contaminate. Typically, I would hope, workers are either kept away from the hazard (once identified) or are properly informed if they are going to do something with the hazard.
A. The worker would presumably be "exposed" to a higher concentration, but protected against the exposure. In worker health and safety, the exposure is always measured outside of the protective equipment.
Q. Question: What obligation is the USEPA under to initiate the PA/SI when someone comes in with a jar of bad smelling well water or a baggie of dirt?
A. I don't know. "Obligation" implies legal duty, which would depend on what the substance was, who (if anybody) spilled it, where it was, and in some cases, when it was spilled. As a practical mater, it would start some wheels turning, and someone in the agency would have to make some sort of preliminary decision about what to do next.
Q. Homework Question #4 Criticism or glitch. Should develop a list of acronyms with their corresponding meaning. I believe that the military is the only area worse for acronyms than the environmental field.
A. Yes, I have the good intention of starting a Resource Module that will have acronyms.
Q. What happens if, after the risk assessments are presented to the public, public finds it unacceptable and protests the project (whatever it's about). As far as I understood, many times full info about hazard is not available so there have to be assumptions. Is it possible to change assumptions, assume something else, or vise versa not assume something at all, in order to please the public. Is it practiced? Do these kinds of things happen?
A. That happen often. The old, quick answer is that these are risk management issues, not risk assessment. However there is a new trend to include the public in the risk assessment process. We will discuss this.
Q. There we many typos in the text. Also while I was reading I thought that many people have listening memory more developed that sight memory, i.e. they remember things better when they hear them, rather than look at them. Would probably be a good thing to have downloadable files, where students would be able to actually hear the lecture, sitting at their homes. I understand that online teaching is just getting developed, and probably in the future their will be things like I described.
A. The term "distance education" and "electronic education" include many things. Video taping lectures has been done at UAF for over 20 years. Streaming video is also available now for many courses. The system this course uses, web-based pedagogy, is quite different than recorded lectures, and it was intended to be. It requires interaction of the student with the computer, the instructor, and other students.
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