In a recent article Tim Jorgensen, an Associate Professor of Radiation Medicine at Georgetown University, wrote about the risks of getting cancer from flying in jet airplanes.  According to Professor Jorgensen, the primary health risk comes from exposure to cosmic radiation.  Sounds like scary stuff.  He wrote about one particularly frequent flyer (a Mr. Stuker), who had amassed some 18 million miles of air travel (imagine the upgrades!):

The primary health threat at this dose level is an increased risk of some type of cancer later in life. Studies of atomic bomb victims, nuclear workers and medical radiation patients have allowed scientists to estimate the cancer risks for any particular radiation dose.

All else being equal and assuming that low doses have risk levels proportionate to high doses, then an overall cancer risk rate of 0.005 percent per mSv  is a reasonable and commonly used estimate. Thus, Stuker’s 100-mSv dose would increase his lifetime risk of contracting a potentially fatal cancer by about 0.5 percent.

… …  ….

A 0.5 percent increase in risk is the same as one chance in 200 of getting cancer. In other words, if 200 male travelers logged 18,000,000 miles of air travel, like Stuker did, we might expect just one of them to contract a cancer thanks to his flight time. The other 199 travelers would suffer no health effects. So the chances that Stuker is the specific 18-million-mile traveler who would be so unlucky is quite small.[i]

The article tellingly postulated that the risk of this exposure to cosmic radiation, which equaled a one-in-two-hundred chance of contracting cancer, was really a small impact on Mr. Stuker’s overall chances of getting cancer (which Dr. Jorgensen estimated at almost 25% lifetime risk for the average American male).  Instead of a 25% lifetime risk, Mr. Stuker had a lifetime risk of 25.5%.  Too small to be measured scientifically, Dr. Jorgensen argues that it is a theoretical risk increase only.  Interesting.

Perhaps particularly interesting to the brownfield industry, which relies on risk assessment in order to determine – to the satisfaction of our regulators – how much “risk” a finished project can pose to the public.  Although never addressed in any law, regulatory authority has snagged onto what they have accepted as an allowable risk level – which – as those in the brownfield industry know – is usually one-in-a-million.  My math is shaky – but I think that is a risk level FIVE THOUSAND TIMES lower than that which Dr. Jorgensen viewed as “theoretical” when compared to a lengthy exposure to cosmic radiation.

I’ll note something that is less theoretical.  The cost of obtaining this level of “assurance” when engaged in the arithmetic of risk assessment is also measured in the millions.  Of dollars.  I doubt that my experience is unique, but I have been a team member on several projects where a consultant proposed the excavation and disposal of hazardous materials in order to get the “right” risk numbers. Sometimes this was about soil that would ultimately lie underneath the concrete floor of an underground parking lot, but was still recommended to be excavated in order to obtain a theoretical risk no greater than the mellifluous one-in-a-million.

How do we get to one-in-a-million? We start by trying to evaluate how bad is bad. Are we dealing with old petroleum products or kryptonite?  These risks are assigned to various substances by analysis and derivation of a so-called “cancer slope” – the line on a graph that links the concentration of the bad stuff and the period of its exposure to the likelihood of contracting cancer.  Not too many of the bad things have actually been tested on humans – so we study the impact of, say, dry cleaner solvent on mice, and make extrapolations.

Naturally, in the face of some uncertainty, scientists take care to err on the side of conservatism in such extrapolations.  If unsure, let’s presume the stuff has a stronger cancer producing impact because we don’t want to take risks with an unsuspecting public.  To use the technical scientific name, let’s call this the “fudge factor”.   To get a good sense of how careful we are at trying to protect the unsuspecting public from these theoretical risks we have to multiply the various impacts of; 1) using extrapolated inferences from studies on lab rats; 2) incorporating a heavy-thumbed fudge factor to whatever cancer slope is derived by that exercise and 3) using the assumption that any resultant potential risk to an individual must not be greater than one in a million.  That would be a factor of 10^-6, for all of you who enjoy this stuff.

What kind of life risks are comparable to this level of certainty?  If we consult a source such as the National Oceanic and Atmospheric Administration, we are informed that an equivalent risk is the likelihood of any one of us being struck by lightning in any given year.[ii]  I have to condition that factoid with the note they provide to the effect that one’s chance of being struck by lightning at some point in your life (assuming you live to be eighty) is 1/13,500. That’s almost getting scary.

Who decided that we hoi polloi, the great unsuspecting public, would accept no more risk than one-in-a-million?  Granted, it would possibly be a career shortening move for some public official to take on the fight for adopting more realistic risk parameters.  “More risk! More risk!” is not a catchy political slogan.  But the policy consequence of this type of conservatism is plain.  Developing new uses for old sites is costlier, in some cases hugely costlier, and unnecessarily so.

This is another, but hidden, regulatory burden placed on the redevelopment of old and dirty urban sites into new and useful purposes.  Affordable housing, for example.  Inexpensive housing in the midst of the urban core, so people can live near where they work.   I do not have the data necessary to determine how many fewer housing units exist because of the unrealistic and unsupportable assumption that we should only bear a risk no greater than one in a million, but there can be little doubt it is a significant number.  The first lawyer I ever worked for liked to remind me that to “assume” makes an ass out of you and me.  Maybe it is time for the regulatory authorities to start reexamining their assumptions about what kind of risks we can handle, and how they should be measured. Our housing stock could benefit from a level headed reappraisal of risk.

 

[i] Jorgensen, Timothy J., “Air travel exposes you to radiation – how much health risk comes with it?”, The Conversation US, June 7, 2017 ; as reported in Scientific American, www.scientificamerican.com/article/air-travel-exposes-you-to-radiation-how-much-health-risk-comes-with-it/

[ii] http://www.lightningsafety.noaa.gov/odds.shtml

 

Photo Credit: Approaching Lindbergh Field – photo by Allan Ferguson, Flckr Creative Commons