***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.
***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.
Q. Just a comment on the timing of the class, I really like
being able to adjust my schedule to fit this online class. However,
I work weekdays to have weekends free. I actually prefer having
the modules due by Wed rather than Mondays especially if you are
late to post the new module.
A. See announcements.
Q. For the Stem and Leaf method that we used in for doing the homework, there didn't seem to be a pattern to the order that the exposure was listed. I was curious as to whether they should be in order of most harmful to least?
A. I've never heard of that, although it is logical. Simplicity and following the lines and boxes usually dictates the format. We will talk a little more about that in Module 7.
Q. The literature states that the Koc is a measure of the tendency for organic compounds to be adsorbed by soil and sediment. What number would represent a high Koc?
A. We'll work with this more in food chain transport. There are two important parameters, the first is Koc and the second is the percent of organic carbon, by weight, in the soil.
Q. The NSC site on pentachlorophenol states that it exists in two forms. Are those two forms and their chemical differences relating to solubility in water due to differences in chemical structure?
A. There are several errors on that site. Chemically, there is only one version of PCP.
Q. The same site states that pentachlorophenol rapidly degrades in air, on land, and in water. What quantifies rapid - minutes, hours, days, weeks? That statement as written does not seem to give the reader very good information on the chemical.
A. Another error on that site, PCP does not degrade rapidly.
Q. The NSC site states "Pentachlorophenol is a non-flammable solid, which does not evaporate easily". I think "liquids" evaporate and "solids "sublime into the air.
A. Yes, if it changes directly to vapor without becoming a liquid, which is probably the case with PCP.
Q. On the SCEM model, with the addition of irrigation water. Lawns, as in cemeteries, are generally watered using a sprinkler or some other airborne method. At least the big ones in Denver were. I have seen flood irrigation of smaller patches of grass in Tucson. I think incidental ingestion and dermal absorption of that water by the workers might be a pathway. I don't know if blueberries could be irrigated using flood irrigation or if they would require an airborne method as well.
A. I don't know either, I dream up these examples to illustrate a point; I don't intend them to get complex. But you are right, you would need to consider the workers. We also realize that for each receptor we identify, we generate lots of analysis. Usually, unless you have a reimbursable contact with a big budget, you try to identify the most heavily exposed receptor in each category and work to that. For example you would do the workers in the cemetery, not the visitors. The final report needs to mention the visitors, and that you assumed they were exposed less than the workers, but beyond that you would not treat the visitors separately. Then when you submit the draft report for the public meeting, you will find out that someone visits the cemetery every day and you should have considered him in your analysis.
Q. I have looked through the RAGS chapter 6 but haven't found
a comprehensive list of transport mechanisms. I am really unsure
of how to check that all the possible means of transporting the
chemical have been covered in a site model. Any suggestions?
A. Exhibits 6-3, and 6-6 have most of the things I can think of.
Q. Looking at the site assessment for the module 5 Ghost Road Lake leads to questions regarding transport mechanism to the vegetation. Major variables are going to be groundwater flow direction (i.e. seasonally and annual average) and additional sampling to determine exact location of primary source. Further sampling to determine local concentration levels can pinpoint the primary source. Groundwater elevation data via measurements through monitoring wells and laser elevation surveys can then determine leach direction.
The combination can then provide the needed information to
properly determine risk assessment. ** Are the contaminates coming
from the lakeshore or are they leaching through the ground into
the lake? Eolian sediment can be a major risk through inhalation,
ingestion, and dermal contact, but data shown only represents
present risk. Risk including exposure increases from future activities
(which is the reason for the study) can only be determined by
indicated knowledge.
** yes, for the exposure assessment.
Am I realistic?
A. In order to keep the problem simple, it was stated that there were no drinking water wells and that the only contamination from the water is via the water pumped for irrigation. Groundwater, somewhat like wind, tends to both advect and disperse contaminants. There are also chemical processes and sometimes biological process that further reduce the contamination. So how far away does the nearest well have to be, before you do all the groundwater studies? That's a study in itself. But you need to determine this.
Q. The mistake that jumped off the page at me was that "the non-polar form dissolves easily in water while the other does not." It seems to me that just the opposite would be the case.
A.That's the one I had in mind.
Q. Would the contaminated lake necessarily lead to contaminated groundwater? In this case, the lake water is used for irrigation instead of groundwater, but if you collect a surface water sample and find it contaminated, can you then conclude that the groundwater is also contaminated?
A, Probably, see above.
Q. Why are many polycyclics quite toxic while some are not?
A. The polycyclic that cause cancer are not carcinogenic themselves
but are metabolized, and some of the metabolites are very toxic.
Different polycyclics are metabolized differently. Often there
are several different routes to different metabolites most of
which are not toxic, but some are toxic. For many polycyclics,
because of their prevalence in air pollution and cigarette smoke,
a lot of details are know.
Q. Is there any one CSM that is generally more used and accepted
when doing a risk assessment?
A. Regarding CSM format, the stem and leaf is a good tool and
is probably the most common. For written reports, the table is
used and for public presentations the graphical is often used.
Q. Would we bother with RA at all, it the wind was blowing in opposite direction all the time?
A. We would "address" or consider it. We may not do much analysis if it obviously is not a problem. Even if the winds prevail from one direction, they sometime blow in other directions. This is shown in a "wind rose" which displays the frequently of winds from various directions. For many places you are safe to only consider the prevailing wind.
Q. Another question is not related to the Module directly.
It came to my mind when I was thinking about paper topic. Say,
we have international project, and we deal with transboundary
pollution. What happens if standards of one country are lower
that in neighboring and water in the river leaves one country
clean but enters another one dirty, according to respective country
standards? How are situations like that solved?
Thank you,
A. In the European Union, they try to address them by consensus standards. In a sense we had this in the US before 1970. One state's industries would pollute another state. There were some regional standards, but they were largely voluntary, and poorly enforced. Up until sometime in the 1960's most people simply accepted pollution as a necessary consequence of an industrial society and would accept pollution as the downside of a prosperous society. Today wealthy industrialized countries want both prosperity and a clean environemnt.
There have been several international conventions that dealt with dumping of Hazardous Waste, I have a list of 233 international treaties that deal with this and similar issues. The best known are the Basel Convention and the Rio Declaration, you can search and read about them. Both had many nations that signed. Perhaps more important is that the World Bank is no longer financing pollution generating industries, so at least heading in that direction. It is very difficult for a society to enforce pollution laws, when most of the population is stressed by lack of goods and services.