The Risk Assessment Paradigm

An Old Story

They say it began in 1983.  But that’s not really true.  Alternative decision paradigms were the stuff of Greek philosophy.  But since Hume (1739) wrote in English, let’s start with that:

In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary ways of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when all of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, 'tis necessary that it should be observed and explained; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. But as authors do not commonly use this precaution, I shall presume to recommend it to the readers; and am persuaded, that this small attention would subvert all the vulgar systems of morality, and let us see, that the distinction of vice and virtue is not founded merely on the relations of objects, nor is perceived by reason.

Yeah, it’s 18^th century English.  So, here’s the 21^st century translation:  What is known does not dictate what ought to be done.  Or, more to the point of current discussion; even when the law empowers toxicologists to decide, the science of toxicology cannot dictate how safe we ought to be.

The National Academy of Sciences Redbook

The formal origin of the Redpill paradigm comes from a report from the National Academy of Sciences report (1983) entitled “Risk Assessment in the Federal Government: Managing the Process”.   As the cover was red, it is often referred to as the Redbook.  The essential idea behind the “new” paradigm was pretty simple; scientific analysis and the political development of regulations should be separate processes.  The rediscovery of the is-ought problem can be easily understood as a repudiation of the Safety Assessment Paradigm:

• Level Setting Plus.  The Redbook paradigm can be used to set levels, but the level is not dictated by a semi-technical analysis.  It can also be used to inform other regulatory strategies.
• Democracy.  Scientists can be politicians too, but with the Redbook paradigm scientific assumptions need to be defended with data and scientific arguments instead of regulatory policy.
• Policy Choices.  Precaution is allowed, but not required.  Regulatory decision making always requires some arbitration.  Public decision making requires more transparency than the Safety Assessment Paradigm can provide.
• Risk Estimates.  The estimation of chemical risks provides and endpoint where the technical analysis ends and the regulatory policymaking must begin.  

In addition to separating science from policy, the Redbook divides the risk assessment process into four steps:

Comparison of these four steps to the Safety Assessment Paradigm further reinforces some of the essential differences:

1. Hazard  Identification.  A Safety Assessment also begins with the identification of an adverse effect.  However, a risk assessment may consider more than one effect, instead of just the one that occurs at the lowest dose.
2. Exposure Assessment.  In order to set a concentration level that a regulatory agency will consider to be acceptable, an estimate of the amount of food consumed must generated.  This is typically a single number that is usually intended to be representative of individuals with higher exposures.   An exposure assessment for a Redbook process will be more complex, with consideration of the full range of exposures in the population.
3. Dose-Response Assessment.   Dose-response modeling is generally not a part of a safety assessment.  A Benchmark Dose may be used in place of a No Observed Effect Level, but potential effects to be expected at actual levels of exposure are never characterized – which is something that a Redbook assessment will do.
4. Risk Characterization.  A Safety Assessment determines a regulatory level without ever characterizing the risk.  A Redbook risk assessment will estimate a risk that may or may not justify setting a level.

Formulation Problems

The Redbook attempted to separate science from policy, but in a lot of ways it really didn’t In particular, it failed to grapple with scientific uncertainty.  It bought into the idea of default inference options that are justified by regulatory policy.  The Redbook also gives a cartoonish view of the way regulatory decisions really get made that is so far from reality that it fails to structure the decision process at all.  It also fails to identify exactly when the new paradigm should be used instead of the old Safety Assessment Paradigm.  All of these problems are fixable, and in fact have been addressed by subsequent NAS Reports (NRC 1994, 1996, 2013):

• Uncertainty.  It is widely appreciated that the key to separating science from policy is to acknowledge uncertainty.  But, there are two hindrances.  First, the methodology for representing uncertainties that are not statistical in nature (e.g. the probability of causes) has not been put into practice.  But the bigger problem is that many people like to think they are getting the benefit of the doubt.
• An Iterative Process.  The Redbook portrays risk assessment and risk management as a linear process that starts with data and ends with a decision.  Not true.  Hazard Identification does not spring from data.  If you look closely, it comes from a previous risk assessment, perhaps a subjective one.  So, instead of characterizing the risk once and for all, formal risk assessment is best understood as a process for improving risk characterization.  A risk assessment may be good enough to justify a decision, or not.  If not, it’s back to the drawing board.
• Squeaky Wheels.  A formal risk assessment is not needed for every issue.  Safety Assessment still works for premarket approval regulations.  Screening analyses based on accepted Safety Assessment procedures are quite adequate for concluding that exposure to some contaminants is not an issue worthy of a public debate.  But if you are contemplating a regulation that is going to cost big bucks, or telling the public not to consume food X because it has chemical Y in it, "not safe” really isn’t a meaningful reason; it’s time to break out the risk assessment paradigm.

References

Hume. D. (1739). A Treatise of Human Nature, EC Mossner (ed.), London: Penguin Books.

National Research Council (1983).  Risk Assessment in the Federal Government: Managing the Process. National Academy Press, Washington, DC.

National Research Council (1994).  Science and Judgment in Risk Assessment.  National Academy Press, Washington, DC.

National Research Council (1996).  Understanding Risk: Informing Decisions in a Democratic Society.  National Academy Press, Washington, DC. 

National Research Council (2013). Environmental Decisions in the Face of Uncertainty. National Academy Press, Washington, DC. 

Official Post Soundtrack

King Crimson (1981).  Frame By Frame.  In: Discipline, track 2.

Post Notes

Thesis post #15.  Hume had a really cool Guillotine.  Had to settle for a live version for the soundtrack.