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. The Site Conceptual Exposure Model: Why is it called Conceptual? A conceptual design is required in each case (model).
A. Good point. Initially, just by looking at the site and the situation, only a few of the routes are "plausible." So we put these in the model, SCEM. That tells us what to look for the in the next step. For example, if the contaminant is a tar-like substance that stays on the surface, we don't need to put groundwater as a transport medium in our SCEM, and exposures via drinking from downgradient wells can be neglected. Later we may find other routes that can be excluded as well. Until you can exclude a route, you need to keep it in the model.

***Q. Are "exposure point" and "receptor" the same thing?
A. A receptor is a person (in human health risk assessment). An exposure point is the location where they are being exposed.

*** 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.)

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*** 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. What is the difference between your use of the term "exposure routes" and that of DOE?
A. Some of the most fundamental concepts are the hardest do define. Let's start by trying to define a "microenvironment." A human is surrounded by a microenvironment. For industrial hygiene, because it is so tightly bound by government regulations, it defines a "fishbowl" that fits over the head, that is the microenvironment for inhalation exposures. That is, the samples of "breathing air" must be taken inside that bowl. Now for a fate and transport analysis, the "exposure route" is how the chemical of concern gets into your microenvironment, i.e., playing in contaminated dirt. For a toxicity analysis, the "exposure route" is how the chemical leaves the microenvironment and enters the body, i.e. inhalation, dermal, or ingestion.

***Q. As a practical matter in doing risk assessments do "sources" and "media" need to be spelled out separately?
A. Usually they do. A contaminant is generated at a source and travels though a media to get someplace. Back to fundamental definitions, the barrels at the old dump are certainly the source. You might describe the soil beneath them as a media. After the barrels are removed, the contaminated soil is still a "source." You might describe the dust blown from the contaminated soil as a "media," or the atmosphere that blows it as the "media."

***Q. In the Chesapeake Bay Article, PCB's and DDT's are present and are bioaccumulating up the food chain. Since these chemicals are so persistent, is dredging the only way to "treat" the sediments so that the bay can be truly chemical free?
A. What a can of worms. Yes, dredging can remove them from the sediment. Then what? The contaminated dredge spoil is still contaminated, so it must be stored someplace. Both these do degrade, just very slowly. They also diffuse, slowly. What happens next is we are hired to assess the risk from the contaminated fish, etc., to humans. The risk may be small, so we leave the sediment alone. Or tell people not to eat the fish. Or?? Often there is no good solution. Most of those are "risk management" decisions, so we can just give the managers the numbers and relax.

** Q. I thought RCRA also deals with old contamination, such as metals.
A.“Old” is not the issue (although in a logical world that would be true, here we are talking the legal world.) it is the source. If it comes from a current operation that generates hazardous waste, that is, is covered by the RCRA law, it is a RCRA site. If it is from another source, it is CERCLA. These are usually older abandoned sites, and the polluter is often defunct. However sometimes these sites come into the possession of a going concern, in that case they are still CERCLA sites, even though, if the current owner made the waste, it would be a RCRA issue.

** Q. What is the difference between a chemical of potential concern (COPC) and a chemical of concern (COC)? Is it just semantics, or is there a substantive difference?
A. No difference that I know of. We may learn more later.

**Q. How was DDT able to be released into the market? Wasn't toxicological testing performed prior to its use? Also, what do you think will be the next DDT? In other words, is there anything commonly used today that you think will be the cause of future health problems?
A. Lots and lots of testing was done, to make sure it was very toxic to insects. It is not very toxic to people, at all. It is extremely persistent in the environment and is bad for certain types of eggs in egg laying animals. Recently it has been speculated that DDT could be an endocrine disrupter in humans and animals, but this is unproved.

** Q(uestion). So there is essentially four main analysis of the site before the FS and ROD? 1) Scoping, 2) PA/SI, 3) Preliminary Screening Risk Assessment, and 4) RI/FS. Why is the RI paired with the FS? The RI seems to be more Risk Characterization and the FS Risk Management within our best technology.
A(nswer). They work together. The Feasibility Study, depending on its nature, will need certain information from the Remedial Investigation. As part of the FS, Risk Assessments will be done for each of the considered options. Each of those Risk Assessments will have a Risk Characterization. Yes, feasibility studies are an important part of risk management.

** Q. I didn't read anything concerning the risk of transportation of contaminants in the Chesapeake Bay article. While chemicals are in transport from point A to point B there is the highest potential for a release or containment failure. One might presume that trapping contaminants in Bottom Sediments might be the best alternative to extracting these sediments and transporting them to a disposal point or facility with the potential of contaminating even more mediums. What part of the Risk Assessment are individual transportation and disposal risks considered?
A. Transportation options would be part of the Feasibility Study and are Risk Management issues, not risk assessment. You might do a risk assessment of a transportation mishap, but that would be a new site, and you would have to make assumptions about what is spilled and how. I agree, although its not an area I am an expert in, that if you have contaminated sediment, you would probably be better to leave it there, rather than to muck it up and re-entrain it in the water column. The issue comes when such dredging must be done for other reasons.

*Q. Shouldn't the U.S. Department of Transportation (DOT) be considered another main U.S. Federal Agency that is responsible for regulating human exposure to chemicals? (Regulatory Toxicology module 12A)
A. Only indirectly, via transporation safety. There job is be sure nothing is spilled, not what to do after it is spilled.

C(omment). It is my understanding that the State of Alaska defaults most all its Haz Mat/Waste regulations to the Feds. When working in the Haz Mat business I had to study Oregon and Washington regulations because they are more restrictive than the Federal regulations (State's Prerogative) (we completely avoided California because the prevalence of regulations made it uneconomical to dispose of waste in that state). Washington State regulations have an official designation of “Dangerous Waste;” those wastes that they had determined was of concern, but are not yet regulated by the EPA (such as some antifreezes) (We have it so easy in Alaska, except for the transportation deadlines). So we have to get our substance categorizations straight: Hazardous Waste: EPA/RCRA/CERCLA, Dangerous Material: Washington State, Hazardous Material: DOT.
R(eply). Oh so true. And lots more. When I worked for the Corps of Engineers I had to go through three days of training to learn how to make out a hazardous waste manifest – just the paperwork. We go over that a little in ENVE 649, Hazardous and Toxic Waste Management.

* Q. In the illustration on submodule 2B the routes of exposure are inhalation and ingestion. Why is absorption through the skin via showering, washing hands, etc., not listed as an exposure pathway? Are we assuming that the chemical does not penetrate the skin, or is there another reason for not including absorption?
A. It sure can be a route. I just did not use it as an example.

*Q. Since we are talking about search engines, I thought I would give a little insight here to my favorite search engine. Most search engines search the "hidden text" on Web pages for the key phrases in your query. If you put in "Labrador Retriever" most engines will bring back documents that have the word "Labrador Retriever" in the hidden text the most times. Programmers know this, and enter key words thousands of times in the hidden text just to get their web pages listed first after a query. This is the glitch. A web page does not have to be good for many search engines; it just has to have a smart programmer. Google is different. Google actually counts the number of times a web page is linked to another web page. It operates under the assumption that the most informative or popular web pages will be linked to others more often than junk sites. This is unique (or at least it was last I heard) among search engines, and it is why Google typically returns lots of good sites without a bunch of garbage.
A. Good comment. I find for technical data, there is not too much trouble with rigged pages, but for commercial or popular terms, you are correct.

Q. If a person suspects illegal chemical dumping might be occurring on private property or on government property surrounding a persons residence, does that person have the right to request an environmental sample for private testing?
A. Interesting question. Your rights to get onto your neighbors property are very limited. It the old days, before RCRA, people often dumped and their neighbors could not do a thing about it. Read the Sopranos http://www.faculty.uaf.edu/ffrap/EQE_649/Module_02/Submodule_2A/Sopranos.htm

Q. I know that RCRA typically is used for "active" facilities to manage wastes "cradle to grave", and CERCLA is typically for past releases; however, I worked for several years at a DoD Chemical Depot, that had over 52 sites that had been impacted by past activities (over 20 years), but the whole site was regulated under RCRA. There was no "current activities" that routinely produced new hazardous wastes, and the site was eligible under the NPL. The Depot was closed except for environmental activities and a storage site for mustard agent. Apparently there is some overlap between RCRA and CERCLA as illustrated at this site. I never understood how this site could be RCRA and not CERCLA, but it was. Do you have any insights or a criteria list that would clarify the distinction between the two? Do you have any thoughts on why a site like this would be a RCRA site instead of a CERCLA site?
A. I don't know. We have an environmental laws class and that is where you might get an answer, or an argument, it tough to get an answer out of a lawyer. When you say 52 sites, you probably mean 52 locations within an economic or legal entity, the Depot. These sites are often grouped together in some logical fashion into "operational areas" for the purpose of remediation or whatnot. One explanation for the RCRA designation is that the Depot was designated a "Transfer, Storage, or Disposal Site" under RCRA, for one item, perhaps the mustard gas, then that designation was applied to the whole site. Anyway, for the purposes of risk assessment, it does not matter, except that RCRA has slightly different terminology for some phases of the process.