NRM 304Risk Analysis and Management

14 September 2010

Dr. Robert A. Perkins, PE

UAF Civil and Environmental Engineering

• Course goal: Provide the student with the tools necessary to make natural resource management decisions in the face of complexity, uncertainty, and competing values and to enhance students’ critical thinking skills.

From NMR 304 Learning Goals

• Apply critical thinking skills when evaluating information and be able to distinguish between fact, theory, and opinion.

• Independently find reliable sources of information to support positions in natural resource issues.

Risk Analysis and Management

• Risk Management vs. Risk Assessment

• Steps in Risk Assessment

• Human Health Risk

• Environmental Risk

• Some Probability

• Risk Information, Fact and Fiction

What is “Risk?”

Risk is just a statement of the probability and severity of some harm."If you go snowboarding, you will probably break a bone." Is this a statement of risk?

What does it say about the "probability?"

How about the "severity"?

• "About 1 out of 750 unprotected workers with high exposure to vinyl chloride develop angioscarcoma (a rare liver cancer)."

• Although by "unprotected" and "high," it states the probability and severity of a harm. (I guessed at the 750, the rest is true.)

Safe Skydiving

• Let's say the chances of being hurt while skydiving are: one minor injury per 500 jumps and one serious injury or death per 10,000 jumps. (I made up those numbers too, but let's assume they are true.)• Is this a statement of risk?• Would you describe skydiving as "safe?"

Think about it. We agree on the risks of skydiving, but do not agree if it is "safe." That is often the case. Why? The definition of "safe" is, Absence of unacceptable risks. (Or its equivalent, the presence of only acceptable risks. You can restate that defining "unsafe" similarly.)

• So now, when you read or hear that something is "safe," you should immediately ask yourself ?

• Again, safe and unsafe are words we often use, but they are very subjective.

• “Hazardous”

Evaluate Risks, Qualitative

• Experts

• Committees– (could use to get parameters for quantitative)

• Ordinal risk matrix

• Use to decide what risks are worth tracking closely

Ordinal Risk Matrix

Risk Process - 1983

• Risk Assessment in the Federal Government: Managing the Process

• National Academy of Science (NAS)

• Two Phases:

• Risk Assessment

• Risk Management

Reality Check

• Hazard Identification at DNR

Dose-Response

• Science of Toxicology

Toxicology Slides

Copyright Society of Toxicology

18

19

Toxicology Evaluations

Are Necessary to

Predict Risk and Safety

of Chemicals: Drugs

Cosmetics

Pesticides

Pause Points to Ponder

• Response depends on dose.

• Need to know exposure dose

• Often computed from a concentration

Computing Exposure

• Environmental Engineering

• Chemistry

• Geology

• Hydrology Metrology

• Statistics

• Experts – demographics and land use, others

Exposure Point Concentration

C = Concentration of chemical in medium (i.e., mg of Z / L of water, or mg of Z / kg of beansCR = Contact rate with medium, or the amount of medium contacted per period of time (i.e., L of water drank / day, or kg of beans eaten / day.)EF = Exposure frequency, or how often the medium is contacted (days of contact / calendar year)ED = Exposure duration, or how long the exposure (contact with the contaminant) occurs ( years until receptor moves away, or years until contaminant disappears)BW = Body weight of receptor (kg, default to 70 kg for adults)AT = Averaging time (days) if we are considering carcinogenic effects of chemical Z, the AT is 365 days / year times 70 years.

Environmental Receptors• AKA Ecotoxicity

• This is a relatively simple model, but note: the material enters fish two ways, directly from the sediment and via the micro invertebrates. We might measure contaminant concentration in the sediment, the invertebrates, and/or the fish depending on the concerns.

Some issues• LD what? Test what?

– Generally some damage is acceptable.– Test species: Relevant and Convenient

• Convenient– amenable to laboratory testing

• Relevant– important to the ecosystem in question,

recognized by the public, sensitive to the chemical.

• Must settle for indicator species at best

Ecotox Terms• Bioconcentration

– Concentration in fish is greater than in water

• Bioaccumulation – Increase in concentration in fish with time, rate

of absorption greater than rate of excretions (“depuration”)

• Biomagnification – Whales eat the fish, concentration in whales

greater than fish

Uncertainty

“Clouded his future is…The future is always in motion”

Estimation of Future Events

• AKA “divining”

• Oracle at Delphi to my financial analyst

• Pigeon guts, Roman augers

• “The diviners have seen a lie, and have told false dreams; they comfort in vain (Zechariah 10. 2).

• Certainty– If we have full knowledge (we believe) of the future. We

might approximate that if we have a firm quote from a bonded sub or supplier.

• Risk– Many estimating decisions are made under “risk.” In

technical terms, “risk” means we feel we can state the probability of the events. For example, we know the price of concrete in the summer is likely to be $200/CY but may vary by 15%.

• Uncertainty– We recognize alternate states of nature may happen, but

we don’t have a clue how likely they are. – Note the difference between the technical use of terms and

the common usage. While the entire future is “uncertain,” if we feel confident we know the probability of the future we say there is “risk” and limit the use of “uncertain” to situations where we do not know the probability of events.

• Knowns

• Known-unknowns

• Unknown-unknowns

Combining Probabilities

• Most cannot be combined

• Monte Carlo Method

• Inserts random numbers in probability statements

• Computes outcome

• Repeats 1000 or 10,000 times or more

Crystal Ball

• Best since sliced bread

Law and Ethics

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Science v. Law

• Science: Investigates and attempts to explain natural phenomena. It is cautious, incremental, and truth seeking.

• Government regulation: Seeks to affect human behavior and settle human disputes. It is episodic and preemptory and seeks resolution rather than truth.

• Government regulators are often forced to intervene, and make a decision before knowledge is complete.

• American regulation is bound up in the concept of "rule of law." – Not negotiation between affected parties– Must have a “bright line”

– American regulation must make rules based on the legislative intent and must explain the reasons or facts that form a basis for these rules.

– This allows opponents of the rules numerous opportunities to contest facts.

– Often the facts are weak and both sides have great opportunities to construe what facts there are in a manner suitable to their case.

– This forces the regulators to defend their decisions based on the weak facts and sometimes "distort the current knowledge," often by putting more weight on evidence that the underlying science can bear.

• "The statute laws often describe a desirable social outcome, and may demand more of science that it can provide."

• [Material above and quotes from the Regulatory Toxicology chapter by Richard Merill in Casarett and Doull's Toxicology.]

Burden of Proof

• Who has the responsibly for demonstrating a substance is harmful or safe?

• Established by the statute. – food additives, the manufactures must prove they are

safe before they are put in food.

– OSHA must demonstrate that a substance is harmful before its use is restricted.

• How about EPA?– Many different statutes

Risk Allowed

• Some laws specify no risk is allowed. – Any chemical that causes cancer in laboratory animals

is not permitted as a food additive.

• A negligible risk will permitted– A 1 in one million increase in cancer rate is considered

negligible.

• Tradeoff approaches. – Often use the word "feasible," which implies risk is

permitted, if it is economically impractical to remove or reduce the risk.

Take Home Ideas

• Many practical engineering decisions governed by regulations

• Regulations are made by an agency, but must conform to the intent of a statute law

• Regulations (“rules”) are promulgated by a definite process defined by law.

• FR, CFR• Laws and Regulations are not “science”

Public

• In 1996 the NRC

Two “Extrapolations”

• High to Low Dose Extrapolation

• Animal to Human– Not an extrapolation in the mathematical sense– Then in what sense?

Here is the result of an animal study of the carcinogenic chemical Z. This study used 1400 rats and fed them Z each day for two years, then killed the animals and examined them for tumors. The study used 100 males and 100 female rats at each of six doses plus an unexposed control group. The study cost $1,400,000.

At the lowest dose tested, 10 mg / kg day, the study found 2% of the rats had tumors - 3 males and one female. If you are doing a risk assessment in anticipation of using chemical Z in toothpaste, what sort of risk would you be comfortable with? 1 tumor in 10,000 or 1 in 100,000? If we knew the dose of Z that produced tumors in one of 100,000 rats, we could work backwards and estimate how much Z can safely be put in toothpaste. How many rats would you need? How about 800,000, I'd guess. That would be 100,000 males and that many females in each of four groups. With some economy of scale, you might treat them for $500 each, then the testing would cost only $400,000,000.

Besides the obvious practical problem, money, space, time, and finding enough pathologists to perform necropsies on 800,000 rats, there are several theoretical problems. As you move to lower and lower doses, the curve flattens out and large changes in dose result in small changes in effect. Lower doses are inherently more difficult to measure and analyze.

Straight Line Method

We just stretch a straight line from the lowest data point we have, 2% at 10 mg/kg-day, to 0% at 0 dose. (We converted from a log to a arithmetical axis.) From here it is easy to compute the dose that could cause a tumor in 1 out of 100,000 male rats. It would be :

Validity

• Unknown

• Many chemicals have clear thresholds– Tolerated doses

• Rats are not mice, neither is human

• Testing Procedures

Apocalypse When“Predictions of ecological doom, including recent ones, have such a terrible track record that people should take them with pinches of salt instead of lapping them up with relish. For reasons of their own, pressure groups, journalists and fame-seekers will no doubt continue to peddle ecological catastrophes at an undiminishing speed. These people, oddly, appear to think that having been invariably wrong in the past makes them more likely to be right in the future. The rest of us might do better to recall, when warned of the next doomsday, what ever became of the last one. “

• ``The whole aim of practical politics'', said H.L. Mencken, ``is to keep the populace alarmed-and hence clamorous to be led to safety-by menacing it with an endless series of hobgoblins, all of them imaginary.‘’

Ethics and Precaution

• Precautionary Principle

• Not science based

• (Sure sign you are dealing with an interest group)

• See Appendix A in handout

Comparative Risk Assessment

• Don’t do it

Why not?

MTD

• Maximum Tolerated Dose

• Dose at which there are not apparent ill effects, usually in six weeks

• See Ames and Gold Paper– Believe most cancer in lab animals comes from

mitogenesis due to MTD– (I think they are right)

Oil and Dispersants

• History

• Tested by EPA and equivalent international agencies for toxicity and efficacy

• Modern dispersants are less toxic than oil

• Help biodegradation by microorganisms

• Work in cold water

Latest on Gulf Spill• On Tuesday, at a meeting of the International Society for Microbial Ecology

in Seattle and online in the journal Science, Dr. Hazen and his colleagues [California's Lawrence Berkeley National Laboratory] eported their preliminary findings, based on measurements made when the well was still gushing oil.

• They found that several species of oil-eating bacteria were thriving in the cold waters of the submerged plume, degrading the oil "faster than expected." And the evidence so far shows that oxygen consumption levels are low, with no sign of developing dead zones.

• At the meeting, Dr. Hazen reported that water samples he and his colleagues have collected since the damaged well was capped last month suggest the plume of petroleum hydrocarbons is now undetectable, either consumed by oil-eating bacteria or carried away from the immediate vicinity of the damaged well by currents. That observation isn't included in the Science article.

• Dr. Hazen and other microbiologists are convinced that bacteria have already eliminated the hazard posed by the plume. "We no longer see any deep plumes that can be attributed to the leak," Dr. Hazen said.