Reformation

Deharmonization

It’s kooky and inane, but RfDeontology has spread like a contagious disease over the last three decades.  Not only has it thoroughly infected the EPA where it was founded, it has also spread throughout the Public Health Service.  In addition, it has thoroughly corrupted the academic discipline of toxicology, and it also adversely affects the practice of many quantitative disciplines, particularly statistics, epidemiology and risk analysis.   Perhaps worst of all, it has infected academic curricula in toxicology and public health and, as a result, given many students a distorted picture of what both science and government are really about.

RfDeontology only flourishes because the government pays for it.  Believing that a policy is a fact is a career for many people.  They might still have a career without it, but it wouldn’t be the same.  A really good first step towards the eradication of RfDeontology would be to rewrite the bible that still resides on an EPA server.   This document was written to make it sound like the procedure used by the agency to evaluate chemical safety is entirely scientific.  It needs to be replaced by a document that makes it clear that it isn’t.  First and foremost, for God’s sake, stop calling the Reference Dose a “risk assessment”.   Risk assessment is something else entirely.

Repackaging

Safety Assessment could be called something else.  I have referred to it as safety assessment throughout this collection of essays both because that is what it was called when it was invented and because I think it connotes the element of policymaking that is associated with it.  Something like “Chemical Safety Evaluation Procedure” would work too.  But, I will still call it Safety Assessment for now.

The most important thing is to rename the end result.  Maybe the “Acceptable Daily Intake” isn’t quite right for EPA purposes, but the “Reference Dose” has to go.   The Agency for Toxic Substances and Disease Registry calls their number a “Minimal Risk Level” (MRL), but that also makes it sound like some determination of risk has been made when it hasn’t.  Perhaps the best alternative, which comes from the bible itself (EPA, 1993), is the phrase “Regulatory Dose” that appears in section 1.4:

That is, after carefully considering the various risk and nonrisk factors, regulatory options, and statutory mandates in a given case (i), the risk manager selects the appropriate statutory alternative for arriving at an "ample" or "adequate" margin of exposure [MOE(i)]. As shown in Equation 2 below, this procedure establishes the regulatory dose, RgD(i) (e.g., a tolerance under FIFRA or a maximum contaminant level under SDWA), applicable to the case in question:

RgD(i) = NOAEL / MOE(i). (Equation 2)

How cool is that?  Each program office can work out their own procedure for determining an ample or adequate margin of exposure and boom, each program gets to have its own procedure for making policy.  In fact, the Office of Pesticide Programs already does this – they call their number the “Population Adjusted Dose”.  So, why do we need the “Reference Dose” again?  Well, we don’t.  Die, RfD, Die.  Long live the RgD (and Equation 2).

Another main theme of the bible that needs to be ditched is the idea that Safety Assessment is applicable to everything but cancer.   The only thing that really makes cancer special is the Delaney clause.  Cancer isn’t the only nasty disease, it isn’t the only “stochastic” disease, and it isn’t the only disease to worry about after years of exposure.   A safety factor of 100 or so applied to a dose that has no observable effect is still a lot, even for cancer.  However, an extra factor for the severity of the disease might be a good policy for at least some applications.

Of lesser importance, giving the multitude of factors applied in the conduct of a Safety Assessment more specific names might be good idea too:

• Adjustment Factor.  A factor applied to account for known differences, like calculating human equivalent doses from studies with laboratory animals.
• Variability Factor.  A factor designed to address concerns for individuals who may be more susceptible.
• Precautionary Factor.  A factor designed to provide a greater margin of safety for a specific reason, e.g. an extra factor applied for inadequate data or severity of the disease.

The main reason for doing this is that different types of factors might be appropriate for different statutes.  For example, a variability factor might be appropriate for a "may render injurious" evaluation, but not for an "ordinarily Injurious" evaluation.  A precautionary factor may be justifiable for a premarket approval evaluation, but not for naturally occurring or legacy chemicals.

Refocusing

The other thing that really needs to happen is that it needs to be made clear that Safety Assessment is not the one and only possible response to issues involving chemicals in food or the environment.   Safety Assessment is aptly thought of as a form of civil law that is specifically designed to codify procedures for premarket approval.  It is far less useful for decisions and statutes that do not involve premarket approval like the Clean Air Act, the Safe Drinking Water Act, Superfund cleanup, and unintentional contaminants in food.  The most common and best use for these applications is for screening purposes, where the goal is to identify chemical exposures that are NOT a problem.  In fact, this is the recommended use for the MRL which is primarily intended for be used by the Superfund program (ASTDR, 2014):

MRLs are intended to serve as a screening tool to help public health professionals decide where to look more closely. They may also be viewed as a mechanism to identify those hazardous waste sites that are not expected to cause adverse health effects.

One of the presumptions built into Safety Assessment is that the eventual goal is to achieve a specific level of exposure.  Even in premarket approval applications, this is only possible when use is very tightly controlled.   For other applications it may be next to impossible.  While it may be possible to reduce exposures across the board, guaranteeing that everyone will have an exposure below a specific level that is generally considered to be safe may not be.  Is that really a problem?  You won’t get an answer to that question using Safety Assessment, because providing information is not the intended purpose.  If you want to look more closely, you are going to need a risk assessment.   

References

ATSDR (2014).  Minimal Risk Levels (MRLs). 

USEPA (1993).  Reference Dose (RfD): Description and Use in Health Risk Assessments. 

Official Post Soundtrack

Rundgren, T (2004).  Mammon.  In: Liars, Track 6.

Post Notes

Thesis Post #42.  Yeah, the zombies finally ran me out.  Besides being part of the Public Heath Risk Analysis Thread, this is a proposed solution to the problems outlined in the "Protection" essay.  Soundtrack link is for entire album; Mammon starts at 24:30.