At the bottom of this page are some ideas about your paper.
Q. Are there specific relationship between Kow and Koc? If a chemical has high Kow, that means there will be high amount in the biota. If a chemical has high Koc, that means there will be high amount in the soil? I’m not sure if my assumptions are right, but if they are true, a chemical with high Kow should have low Kow.
A. Just the opposite, High Kow and High Koc go together, the more lipophilic the chemical, the higher the number in both. While Kow is a simple concept using three chemicals: water, octanol, and the test chemical, it is often hard to measure in much detail. However Koc can be a much more complex problem, since the “c” is not chemical carbon, but carbon that is part many forms of organic molecules in a matrix of mineral particles and water. In general, Mackay uses the relation Koc=0.41Kow. .
Q. Question about tox tutor Would you say risk characterization falls more under risk assessment or risk management or both? In the picture it looks like they overlap. Picture seems misleading because I think risk characterization is made in the risk assessment and when risk is characterized we can then manage the risk.
A. The picture is trying to show that risk characterization is the output of the risk assessment phase and input into the risk management phase.
***Q. There are people who want "zero tolerance" for contaminants in
food, but don't discuss the fact that this is a global problem and even if Alaska
became toxic free (I would applaud that), there are many factors that would enable
toxics to enter the Alaskan environment. Water and air currents from other countries
(Russia, China, etc.) bring these contaminants. If risk assessment is not the
answer, then what is the solution?
A. Risk assessment just answers (or tries to) the question, "How dangerous is it?" It is very different from Risk management, which answers the question, "What are we going to do about it." At first risk management always answers that question by saying, "Right now, nothing." Then goes on from there, "When we get the money (or time, etc.) we propose to do this and/or that."
***Q. For the SCEM a view in the future is required. Which time fame makes
sense, is possible or common, related to contaminant transport and accumulation
A. Good question. I am currently working with a risk assessment for an underground nuclear test site that should consider the next 10,000 years. The scope of the risk assessment is a risk management decision. Many contaminants fade with time (natural attenuation) so there is a time in the not too distant future where they will not be a problem and that defines a logical time to end the assessment.
***Q. I'm not sure I understand the difference between Exposure Assessment
vs. Risk Assessment as described in the RAIS tutorial. It seems like both assessments
analyze the same types of hazards.
A. That's not the best part of RAIS. The Risk Assessment is summed up in the Risk Characterization. That Risk Characterization is based on two things, a Dose-response Evaluation and an Exposure Assessment.
***Q. Do risk assessment professionals always or generally always perform a
CSM? Is this standard practice or is it really established for public presentations
after the fact?
A. You must do one, at least on the back of an envelope, to define the situation. Sometimes, especially for emergency situations, there is a release, transport path and receptor that are obvious and must be addressed first.
***Q. I am a little unclear why the Koc would be so variable. That seems a little unpredictable and untrustworthy. How can you get an accurate Koc?
A. My guess is the problem, with most chemicals of interest, is that there is very little in the water phase. What is in the water must be extracted very carefully for quantitation. I have never done a Koc test myself, but with petroleum products there are many problems: mixing time, settling time, and the presence of micro-droplets of oil in the water. This would be the case with many hydrophobic chemicals.
***Q. A question that I have had on several sites is what is the land use of a particular site. For example, what is a pipeline facility or a loading/unloading facility where the only thing that happens is that a chemical goes through the site?
A. "Industrial" land use is generally permitted more contamination that "residential." This is largely because of the "healthy worker phenomenon." Environmental regulations are designed to protect the very young, very old, and the sick, for 24/7 exposure. Workers in industry are presumed healthy and only exposed 40 hour per week. Then there is the issue of "breakdown of institutional controls," sometime in the future the company goes bankrupt and there are no security guards and the fences fall down, etc. So if the company has money, you make them clean it up now. Beyond that we get to political and social issues, should polluters be punished? But all these are risk management, not risk assessment.
*** Q. This differences in chemical properties that are published (ie the Koc value for PCP that you mentioned) when doing partitioning calculations how do you know which one to use? The one that gives you the most conservative estimate?
A. In the list of professions needed for risk assessments (in Module 1) are listed chemists. But you hit it on the head, you would do the risk assessment using the high and low values and determine which resulted in the highest risk, that is the value you would use. Computer modeling helps with this.
*** Q. Under "Identify Exposure Pathways and Potential Intake Routes", it is mentioned the source could be leaking drums or contaminated soil. Why isn't contaminated water considered as a source? For example during the gulf war tones of crude oil was spilled in water which caused death of a large no of aquatic organisms and the smoke from the burning oil was carried to distant places like the Himalayas. What would be the source in such a case?
A. In the natural attenuation process, which lasts a long time for some compounds, contaminants are moved from place to place, either by bulk transport or diffusion. When we are hired to do a risk assessment, we start by defining what hazard we are trying to assess. For most environmental contaminants, that defines the source, for the purposes of the risk assessment we are doing. Secondary sources are interesting, if they identify some change in the transport process. For example, after we remove all the drums, the contaminated soil where the drums were remains a source. Identifying it as a different type of source may help us analyze the situation better.
**Q. The Tox Tutor identified lifestyle choices as the primary cause of cancers.
I have always been taught that while the lifestyle choices most certainly will
affect the occurrence of cancer, it cannot occur without a genetic predisposition.
This was touched on briefly, but never really stated in the tutor. Do you believe
that the two are mutually exclusive?
A. Not exclusive. But lets clarify terms. At conception, a conceptus starts with a genome from its parents. That could be called the "heredity" of the conceptus. Cancer involves a change to a cell's "genome." If you assume that it takes 8 mutations to cause cancer, the conceptus might "start out" with two of them by heredity, then it would be that much easier for cancer to occur. Some of the 8 mutations could be caused by lifestyle and some by workplace exposures, and some by radiation, none are exclusive. There are some forms of cancer that almost completely hereditary. These are very rare cancers, but have been heavily studied to try to understand the genetic process of cancer.
**Q. Why is Oak Ridge considered the "background" levels for so many
sights? When we accept these numbers are we saying that background levels in
fertile organic soil in Tennessee is the same as in Phoenix Arizona?
A. I think that is just a DoE system. But it is hard to find a true background. You need to find a nearby site that is similar in every way, except for the contamination, but this never really possible. It can be informative, though, for example in Nome, there are very high levels of arsenic in the soil in many places. It's hard to label a site "contaminated" if you cannot find an uncontaminated site nearby.
***I think I will have trouble narrowing my topic down for my paper. I look forward to additional details on your expectations, etc.
Pedagogically (a word I did not use until last year) the paper serves several purposes: It gives the students an opportunity to dig into a topic or situation that interests them, and then they are more likely to remember the things they find. By tying the paper to class concepts, they are learn the concepts better through this application. By reading other student's papers, each student will learn more about topics that are different from what the student is familiar with, and this broadens their knowledge. It improves the students' writing and communication skills. For my student's paper I want them to learn about electronic searching and also the valuation of literature. (There may be others.)
In writing the below, I hope to answer your question without forcing students into any particular conclusion:
Most papers will start with some sort of situation in which some hazard was identified, then a risk assessment that was done to analyze that hazard. Your paper will describe that process critically, that is compare and contrasts the assessment with what we learned in class. (By critical I do not mean antagonistically, but rather analytically.)
So for most papers the students will need a situation and a record of the risk assessment for that situation. The problem here may be that the situations that catch your attention, in the media, are not likely to have a risk assessment done, yet. While the risk assessments you find, are older. That is one advantage of the UAF library's access to the newspaper and magazine databases that go back several years.
Some sources of situations and/ risk assessments:
All the proposed environmental and worker safety regulations and changes in them must be published in the Federal Register. Often these have lengthy preambles. (See module 1).
The RAIS site of the DoE has lots of stuff. DoE is that nation's largest polluter of record (most of which they inherited from earlier agencies) and has a very active program to fix this.
Go to the EPA Superfund site and look at RODs and active sites. The ROD is essentially a risk management document, but it usually references a risk assessment.
Pick any chemical you like (or don't like) and do a search on that chemical and "risk assessment."
Go to the newspaper and magazine database and do the same search.
I read "Soil and Groundwater Cleanup" magazine, but that is not on the web yet.
Most public agencies put such document on the web; many consultants are proud of these and reference them on the web site. You might call some consultants and ask them if they have these. (They do not have to be electronic.) The Corps of Engineers web site might reference risk assessments on remote cleanup.
The important thing is that you are dealing with a risk assessment, but the documents you refer to do not have to use those exact words.
Module 5 Index