Top Student, Final Exam, Instructor's remarks in green font._____________
NAME
ESM 693 Final Exam
I suggest you download this file and splice your answers after the appropriate sub-paragraphs. When you finish, send it to me via the dropbox. If anything is unclear on the exam, please email me. Also, if any glitches in the exam turn up that might affect an answer, I will post the correction in the Announcements, so you should check Blackboard from time to time before you hand the exam in. The exam must be in by May 10th, but there is no problem with sending it in early.
It is an "open book" exam, so you can use any non-human resource, including any electronic resources that are not specific to this examination.
The exam has several picture files, gif files, in it. These should open in Word as you get there. If there is a problem, let me know. Several of the gif files show results from two runs of RISC. That should be all you need for the questions. If you wanted to see the RISC output, the files are also in this exam sub-folder, and you are welcome to look at them, but you should not need them to complete the exam.
The exam will be graded out of 250 points, then scaled to 100 points, per the syllabus.
1. You are the newly hired "hazardous materials specialist" for the Alaska Department of Transportation. You get a call from the State Troopers. A railroad tank car of MethyEthylGoopanol, (MEG) a chemical you have never heard of, derailed and spilled its 40,000 gallons into a drainage ditch whence it flowed toward the Parks Highway. Fortunately the culvert under the highway was blocked. Unfortunately this formed a pool near the highway. The troopers have blocked traffic and are keeping well back from the pool. They want to know if the material in the pool is "safe" to drive past. Traffic is backing up. You tell them you will get back to them in "about half an hour." Answer the questions below in 5 or 6 paragraphs, read all sub-questions before answering any. Also, I have put a few hints in square brackets. These words might help you answer the question.
1.A. (10) A co-worker who overheard all this says, "Chemicals released into the environment never hurt people." Do chemicals released into the environment harm humans?
1.B. (15) You have the standard DOT emergency response booklets and data, including a CD, but they do not mention MEG. (The only visible placard on the tank car just said the name of the chemical, no other help. You called the emergency response number, but there was no answer.) How might you proceed to learn something about MEG? What kinds of things do you need to know, at this time?
1.C. (20) From Step 1.B, you now find lots of information on MEG. Prepare a "back of the envelope" risk assessment for your boss. Discuss in a general way the different types of hazard, receptors, fate and transport issues. [accident, illness, ecological]
1.D. (15) Your boss asks, "Does this stuff cause cancer?" You found out that the EPA considers MEG a "Group 2B" chemical. So you answer her in one sentence. Then your boss asks, "What the hell does that mean?" Explain in more than one sentence. [MTD]
1.E (10) In quick risk assessment (1.C above) you determined that the levels of MEG to which the nearby residents might be exposed was less than 10% of the concentration that OSHA says are legal for workers. Is this a good criterion for assuring the residents that MEG will not be a problem for them?
Question 2
2. (50) The material in the barrels was dumped off the truck of a "midnight dumper." most of the barrels were open and the material spilled to the ground. The barrels contained four substances: Aroclor 1242, a hydrocarbon mix that is mostly benzene, acrylonitrile, and tetrachloroethylene. Describe in one paragraph for each of those four substances: the likely exposure pathways to the farmer and the likely fate of the substance. [You could use Level I and/or RISC for some information, but I am not looking for quantitative answers from those programs. Some of the substances you will have to search for, they are not in the RISC or Level I database. A neat way to organize your answer is to start with a five column table that has those 4 substances as the column labels, and the important parameters as row labels, then put numbers or descriptions. Then your descriptions may be shorter.]
3. (50) For each of the four substances from Question 2, consult IRIS and an MSDS sheet and then describe the acute toxicity for cleanup workers and the chronic toxicity for the farmer. These responses should parallel your answers from 2. above, but in all cases assume for this question that there is enough exposure to warrant an analysis of the toxicity data. Try to explain what the data is based upon [epidemiology, laboratory] [You'll be using some numbers here, but be sure to explain, what the numbers mean. You may need to spend some more time explaining the first time the word comes up, less the second time it comes up.]
4. New situation. You are an environmental scientist/engineer working for the North End Refinery. About 20 years ago the refinery has a massive leak in its main carbon tetrachloride (CCl4) tank, and several million gallons of this chemical were released to the groundwater. The refinery put in wells and removed most of the chemical. Groundwater movement is slow and the CCl4 mixed into the groundwater. And it now appears that the residents of the subdivision nearby, where many of the residents are refinery workers, will be exposed to 0.04 mg/L of CCl4 in their water supply wells for a long time (Assume that is the same as 0.04 ppm). The expert consultants the refinery hired have determined the following risk.
You can get the RISC prj file from Blackboard, Course Information, Final Exam folder, but you should not need it.
Your boss has asked you to help on this issue and advise the "external affairs" person the refinery uses to talk to the public. Your consultants have advised that each home in the subdivision should have a charcoal filter put into the water supply lines from their wells. The filers have been advertised to reduce CCl4 from 0.04 mg/L to 0.004 mg/L. Here is the associated risk based on 0.004 mg/L:
The filters cost $750, which the refinery will pay for, plus a $1250 one-time fee to compensate the residence for maintenance of the filters. That is, each home will get a check for $2000. Your consultant tells you that the filters need to be changed every three months and cost $25. Also the consultant admits he has never used the filters, and had based his opinion on the manufacture's literature. He also tells you that filters sometimes need changing more often if there is iron in the water (and you know there is a lot of iron in the water at this location) and that the filters have never been tested in cold water.
[Look at this EPA site about CCl4
http://www.epa.gov/OGWDW/dwh/t-voc/carbonte.html]
You see two problems: First, refinery workers who live in the subdivision will not notice the CCl4, because they smell it at much higher concentrations all day. You are concerned they will use the money to change the sparkplugs in their airboats and not bother installing the filters. Second, the non-refinery workers, who have hired a lawyer and their own consultant, a former high-school science teacher, want the refinery to remove "all" the CCl4, or pipe them water from the town, 20 miles away. Both of which the refinery, state, and federal environmental agencies believe are infeasible. The $2000 offer has been in the paper, so everyone knows a little about it. The lawyer has asked you to address an informal meeting of the residents.
4.A. (30) Write a brief (two or three paragraph) memo to the refinery workers who live in the subdivision. Describe the risks and hazards if they do not install the filters. You may use some numbers for reference and in order to be technically correct, but assume the workers do not understand the numbers and you must communicate with them via your text description.
4.B (30) Prepare a set of notes that you will give to the external affairs person that you expect he will have written up for a press release and will use for notes at the public meeting. You will go to the meeting also. He already has a draft of the memo to the workers. Describe the chemical and it toxicity. Prepare some information about the risk that remains after the water is filtered. Explain why you think the residents will be "safe." Explain the residual is below the MCL. What will you say, if asked, about the MCLG. (See bottom of http://www.epa.gov/safewater/mcl.html#1 for explanation). As you did for the workers, you must use some numbers, but the explanation must be clear to people who are not facile with numbers.
4.C (20) Consider the Sandman site on outrage. Write out 3 or 4 reasons the non-refinery subdivision residents might be outraged.
4.D (30) Your memo to external affairs included information about the iron in the water and the lack of cold water experience with the filters. At the public meeting the external affairs did not bring this up, neither did you or the subdivision people. You were happy that you did have to deal with this. Now it is 2 o'clock Sunday morning, you are lying wide-awake, and berating yourself and the refinery for not mentioning the iron in the water and the lack of cold water testing. Here are two sets of principles:
Fundamental Canons from the National Society of Professional Engineers (NSPE)
http://www.nspe.org/ethics/eh1-code.asp
or
Canons of Ethical Conduct from the American Board of Industrial Hygiene (ABIH).
http://www.abih.org/Docs/Code-of-Ethics.htm
Both have similar information, six basic principles in the front and more detailed explanation further back. Select one or the other (they are similar, so tell me which you are using). Pick two or three of the fundamental principles (canons) and write two or three paragraphs (total) about applying them to your situation. Several of the principles might conflict; you should describe at least one of these conflicts.
PROBLEM 1
1.A. Chemicals released into the environment do
harm humans. Mustard gas was used
during World War I as a weapon. An
industrial chemical release of methyl isocyanate occurred in Bhopal, India,
killing over 2,500 people. Even
spontaneous releases of chemicals from geologic processes have occurred that
have killed people. For instance, in
1986, a cloud of carbon dioxide was released from Lake Nyos in Cameroon,
killing 500 people as well as domestic livestock. Very good.10
1.B. Information important in an emergency situation like this would include:
· Who manufactured this product? How can we contact them?
· What are the physical dangers posed by this chemical?
· How toxic is this chemical?
· What are the toxic levels for this chemical?
· Is this explosive? Caustic?
· What are the effects of short term exposure?
· What first aid measures or treatment should be taken for short-term exposure?
· What activities or measures should be avoided?
· What measures should be taken by those involved in cleanup?
· What are the current and forecasted weather conditions and how will this affect chemical mobility, transport, and cleanup efforts?
How might I proceed
to learn something about MEG?
After consulting the DOT response booklets and trying the emergency contact number, I would have two routes to investigate: manufacturer’s information and generic chemical information sources. It is possible that the chemical name is a brand name, and the generic chemical information sources may or may not have a cross reference for this chemical; so tracking down the shipper or manufacturer may also be necessary.
In order to contact the manufacturer, I would have to track down the shipping information from the railroad. I do not know the procedures for this (since I am new to the job), but I would start by determining who I should call within the railroad and find out all I could about the shipment: who the manufacturer was, how we could contact them, and what manifests and other documentation are available about the product.
Chemical-specific emergency response information sources on the web include:
· Material Safety Data Sheets (e.g. http://hazard.com)
· National Institute of Occupational Safety and Health (NIOSH) database for Immediately Dangerous to Life and Health concentrations (e.g. http://www.cdc.gov/niosh/npg/npgd0000.html#L)
· International Program on Chemical Safety Project’s International Chemical Safety Cards
· American Conference of governmental Industrial Hygienists (ACGIH)
· Occupational Safety and Health Administration Permissible Exposure Limits
In addition to emergency response information, these data
sources would provide basic chemical properties (such as water solubility and
vapor pressure), exposure routes, and known toxicity levels that would
facilitate a “back of the envelope” risk assessment. Other data sources could
provide portions of this information.
For instance, ChemFinder
(http://chemfinder.camsoft/com) could provide basic chemical properties, and
the IRIS or ASTDF databases could provide toxicity data associated with
different exposure routes. very good 15
1.C. I am assuming the most immediate dangers posed will be by the inhalation route, if this chemical vaporizes, because of the high mobility of gas. This would occur in a matter of minutes to hours. Next, I am assuming that a cleanup will commence within 24 hours. Here, if the site is cordoned off from the curious, the next concern would be inhalation and dermal contact by those involved in the cleanup. In the longer term, we would consider the effects of any of the chemical left in place after the cleanup, such as runoff to surface water and migration to groundwater. In addition, the chemical may be retained in the soils it was spilled on or ran over and the soils in the drainage ditch where it pooled. This residual may be mobilized by the next runoff event or dug up when the road is widened; perhaps even taken up by vegetation. Finally, we would have to consider ecological risk to plants or animals that come in contact with the soil or the vegetation.
Hazards: Illness or death due to accidental exposure to MEG, depending on its toxicity and the routes of exposure that are complete at the site that are avenues for exposure to MEG.
Human receptors include:
· Roadway travelers (automobile, bicycle, pedestrian) and, of those, some that might stop at that site
· Site workers (excavation, surveyors, cleanup crews, those folks that cut back the vegetation)
· Residents in the area
In addition, ecological receptors should be considered, including terrestrial animals, birds, and fish, and their levels of activity (resident, migrating through, nesting, etc.); invertebrates (insects); as well as vegetation.
Fate and Transport: Here are some of the transport mechanisms, discussed by environmental media, and the factors that affect whether this media and transport mechanism would be significant:
Air.
· The chemical may be transported through the air immediately as a gas. A high vapor pressure would lead to this mechanism, and this would be significant it this chemical was acutely hazardous.
· The chemical might also be released from the water it mixes with in the drainage ditch, and this release mechanism is controlled by its Henry’s Law constant (associated with both its vapor pressure and water solubility).
· The chemical may also be transported in air by aerosols, including dust, fog, or soot. This mechanism would favored if the chemical were likely to be sorbed to soot or soil particles (low octonal-water partition coefficient (Kow)) or dissolved in water droplets (high water solubility)
Water. Water, either surface water or groundwater may transport the chemical.
· In surface water, it may either dissolve (water solubility) or be transported by sorbing onto particulate matter in the water (Kow) and moves with the water. The drainage patterns in the area of the spill would control where the surface water runoff ended up – in an area where it might infiltrate, or into surface receiving waters such as lakes or streams.
· The chemical may get to groundwater either through infiltration of pooled contaminated surface water or directly by leaching from contaminated soils. In either case, water solubility as well as a low potential to be sorbed onto soil particles (Kow) govern the fraction of the chemical that will end up in groundwater.
Soil
· The amount of chemical that remains in the soil is what’s left over from partitioning to air or water. Low vapor pressure, low water solubility, and high Kow will tend to keep the chemical in the soil.
Degradation, Biological Uptake
· A low Kow will tend to predict biodegradation and metabolization by receptors, while a high Kow would predict persistence and bioaccumulation in the environment.
20
1.D. Does
this stuff cause cancer? A Group 2B
chemical is a probably human carcinogen, because there is sufficient evidence
from animal studies to support causal association between exposure and
cancer. So what does that mean? The
answer to that requires an evaluation of the risks associated with the
dose-response effect. In this case,
there has not been sufficient evidence in humans to demonstrate
carcinogenicity. But studies on animals
have identified the doses that cause cancer (dose), and the number of animals
that showed symptoms at that dose out of all that were exposed to it
(risk). In these studies, a high dose, such
as the maximum tolerated dose (the highest
dose used in an animal cancer test that can be tolerated without serious weight
loss or other toxic effects other than
carcinogenicity) is often administered in order to provide statistically
significant data. The dose from
the experimental results is scaled to humans, based on a number of
considerations, including animal strain, sex, age at start of treatment,
duration of experiment, and type of tumor (response). A probability is associated with that dose. For a carcinogen, it is assumed that any
amount of the chemical, no matter how small, can cause cancer. So for
smaller the dose, the smaller the chance of cancer or the fewer incidents per
unit population. A dose that causes 1
cancer incident per 1,000,000 (1E-6) is considered an acceptable risk by the
U.S. Environmental Protection Agency (EPA). A dose that causes 1 cancer
incident per 100,000 (1E-5) is considered an acceptable risk by the Alaska
Department of Environmental Conservation.
Good answer, actually the EPA will consider
down to 1 in 10,000 as "acceptable" sometimes for cleanups. 15
1.E. The OSHA standards are based on exposure to a chemical in a work setting, rather than in a residential setting. The OSHA standard is not necessarily a good criterion for assuring residents that a MEG is not a problem for a number of reasons:
· OSHA standards are based on healthy adults, not sensitive adults or children.
· OSHA standards are based on shorter exposure period (e.g. 40 hours a week for 30 years) rather than the longer exposure (every hour for 70 years, except for two seek vacation each year) that would be experienced in a residential setting.
· The worker exposed to the OSHA standard is doing so voluntarily.
· The OSHA standards were based on accepting a reasonable amount of risk.
Ten percent of the OSHA standard accounts for one of the
differences between the OSHA and residential model, because it makes up for the
ratio of exposure duration (2000 hour/year x 30 years vs. 24 hrs/day x 350 days
x 70 years). However, it probably does
not make up for the other differences in assumptions. Therefore, it is probably too high (i.e. not protective enough)
to be used as a screening level. very good 10
PROBLEM 2
2. Your analysis was the best in the class, and you get 50 out of 50. I went over it in more detail that I did most, because you were so diligent in its preparation. Possible exposure pathways for the farmer are listed in Table A, along with relevant chemical properties for the four identified contaminants.
· Aroclor 1242 has very low water solubility and vapor pressure. It is expected to sorb to soil particles, is not very mobile with water, and is does not degrade readily. Based on its high Kow, it is expected to enter animal tissue readily. The likely exposure pathway to the farmer is through airborne dust particles, contact with contaminated soils (incidental ingestion or dermal contact), and through the farmer’s ingestion of crops or meat or dairy products from livestock grown on contaminated soil or watered with contaminated water. Yes, but the route would have to be via dust or runoff mud to the irrigation or livestock water. It is unlikely to migrate down to the water table.
· Although benzene has a relatively high vapor pressure, it is also very slightly water-soluble. It is expected to degrade or biodegrade, but, based on its Kow, is expected to enter animal tissue. The farmer is most likely to be exposed to benzene through inhalation of the vapors, through contact with groundwater if he drinks it or bathes in it or surface water, and, to some extent, through consumption of crops and meat or dairy products.
· Acrylonitrile is highly water soluble It is "somewhat" soluble, about 7% or 7g / 100 ml , so water soluble that vaporization is expected to be low, its vapor pressure is not low and it will volatilize and it will tend to break down rather than persist through the food chain. This is a strange chemical. The monomer is reactive, but it tends to polymerize. I don't think much monomer would get very far. The farmer’s likely exposure will be through ingestion or dermal contact with contaminated groundwater or surface water. Its low Kow indicates that crops and meat and dairy products are not likely pathways.
· Tetrachlorotheylene (PCE) has a fair vapor pressure but its low water solubility tends to cause high vaporization. It is expected to degrade rather than bioaccumulate, although its Kow indicates some uptake by animals. The pathway to the farmer is most likely through inhalation, and somewhat through contact with soils and water. Yes, see below where I ran Level I and got different numbers than you. But Level I is steady state and assumes no loss. Most PCE will wind up in the air, but it may soak the ground for quite a while. Dry cleaners frequently dumped it to "dry wells" where it may have contaminated a large spot of soil for quite a while.