This is a little long, so I am going to summarize at the top. I will show that:

1) The estimates are much higher than what you cite;

2) Typical exposure when flying is much lower than what you cite;

3) Dose per unit time DOES matter;

4) The HPS article references their own position paper which doesn't mention differences with short time intervals;

5) The regulations for low-dose exposure are extrapolated from high dose data, because of a lack of studies at low doses;

6) Because of this, the HPS recommends against quantitative risk estimates, because the precise risk is hard to quantify;

7) The lack of data means they are being disingenuous when they say no, as they lack the data to establish it. Note the phrasing: "we would not expect" -- this despite the data we DO have, which establishes that units of time matter;

8) Despite that one position paper, which tries to dismiss health risks below 5-10 rem, their own position paper on backscatter scanners recommends per-screening and per-year (time limit!) maximums far below that threshold;

9) Going by the contact information and president, the HPS may have turned into an industry front. Citing HPS might be as credible on these issues as citing Philip Morris spokespeople on the dangers of cigarettes.

In order:

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1) "According to the Health Physics Society (HPS), a person undergoing a backscatter scan receives approximately 0.005 millirems (mrem, a unit of absorbed radiation). American Science and Engineering, Inc., actually puts that number slightly higher, in the area of .009 mrem."

http://science.howstuffworks.com/innovation/backscatter.htm

That's .05-.09 uSv. Secondly, as previously mentioned, Brenner estimates the effective dose is 20 times as high due to factors like less volume for absorption.

That means the estimated dosage is in the range of 1-1.8 uSv, or 50 to 90 times what you mention. Not a trivial discrepancy.

2)40,000 feet is close to the altitude ceiling for most commercial aircraft. With a 30,000-foot cruising altitude, the exposure drops in half; at 20,000 feet, it drops to a sixth; at 10,000 feet, it's about 1/35th. According to your second reference.

Short business trips may even be below 10,000 feet. It takes too much time (and fuel) to reach riskier altitudes.

So "simply sitting in an airplane" is not the same as cruising at 40,000 feet on a transatlantic flight.

3) You say:

> Second, your emphasis on "dose per unit time" (or dose rate) isn't actually important.

Let me quote from your own source:

"There have been numerous biological experiments conducted, with nonhuman organisms, that demonstrate that the rate at which radiation dose is delivered can affect the extent of biological response. Thus a sufficiently high dose delivered over a period of a few minutes may be expected to have a greater biological impact than the same dose spread over a year."

The only question is what constitutes a "sufficiently high" dose, due to extrapolation. See 5).

4) Further, the terse "no" answer looked disingenuous. The cited position paper link was broken but I tracked it down.

It appears to be "Radiation Risk in Perspective", PS010-2 (which I assume is the updated version of PS010-1).

It has nothing to say about doses over short time periods.

http://www.hps.org/hpspublications/positionstatements.html

5) The issue seems to be that there is very little data about low-dose exposures, so regulations are based on extrapolation from high-dose exposures.

See http://www.ncrponline.org/PDFs/TST_NRC%20_04-08-08.pdf (third slide)

6) What it does say is this:

"the Health Physics Society recommends against quantitative estimation of health risks below an individual dose of 5 rem in one year or a lifetime dose of 10 rem above that received from natural sources."

7) The whole point of their objection was that we lack the empirical evidence to extrapolate from high doses to low doses. Then the article you cite does exactly that. They go from saying, "we lack proof that the answer is X" to saying, "the answer is ~X".

8) The recommended standard "limits the reference effective dose delivered to the subject to 0.25 microsieverts (25 microrem) per screening. Additionally, a screening facility should not expose any individual to more than 250 microsieverts (25 millirem) reference effective dose in a year."

"Use of Ionizing Radiation for Security Screening Individuals" PS017-1

http://www.hps.org/hpspublications/positionstatements.html

How they can go from saying in the first paper, "However, below 5–10 rem (which includes occupational and environmental exposures), risks of health effects are either too small to be observed or are nonexistent" to supporting a maximum of 0.025 rem per year is entirely unclear.

9) Doing some digging, PS010-2 lists a single reference:

"National Council on Radiation Protection and Measurements. Uncertainties in fatal cancer risk estimates used in radiation protection. Bethesda, MD: NCRP; NCRP Report No. 126; 1997."

PS010-2 seems to be merely opinion.

The contact for HPS.org is from a consultancy: HPS@BurkInc.com

The current president of HPS is Edward F. Maher.

"In early 1996, Dr. Maher accepted the position as Director of the Environmental Laboratory for Yankee Atomic Electric Company. The laboratory provided ongoing environmental laboratory, remediation and consultative health physics services for commercial nuclear power, Department of Energy and Department of Defense clients. [...] In 2004, Dr. Maher joined Dade Moeller & Associates"

http://hpschapters.org/crs/maher-bio.htm

Dade Moeller:

"Hirsch then zeroed in on Dade Moeller’s radiation plan and on the controversial company itself, whose namesake testified back in the 1990s that money spent on cleaning up Cold War-era nuclear facilities was being wasted since there would be a cure for cancer.

Hirsch also questioned the lab’s integrity and pointed out that it is a major Department of Energy (DOE) contractor. The area of Rocketdyne where most of the nuclear mishaps occurred was operated by the DOE, which is responsible for cleaning up the mess. It also borders Runkle Canyon, which leads Hirsch to believe that Dade Moeller shouldn’t be overseeing radiation sampling there.

Some of Hirsch’s harshest criticism was aimed at Dade Moeller’s plan to take a “tiny soil sample” every 19 acres based on the lab’s misconstruing of EPA standards regarding soil investigations of potentially polluted properties. The proximity of Runkle Canyon to Rocketdyne, and the fact that 58 soil samples in a previous test all read high for the leukemia-causing radionuclide strontium-90, were among several critical considerations that Dade Moeller ignored, according to Hirsch.

“If you want to hire someone to make your problem go away, you hire Dade Moeller,” Hirsch asserted. “That’s a generality, the reputation. If you read the actual report, I’m afraid it is completely reinforced. Every time you can manipulate an input, make a number go down, they do so.”

Dade Moeller was the go-to lab for a covert set of strontium-90 tests of Runkle Canyon’s soil in 2005, as this reporter previously uncovered. Those tests, which took just five soil samples, were later dismissed as useless by the California Department of Health Services, the very department that conducted the secret limited sampling with Dade Moeller."

http://www.vcreporter.com/cms/story/detail/simi_we_have_a_pr...

"Hirsch said the conclusions of the report should immediately raise suspicion since the developer hired the consultant who created the report, Dade Moeller & Associates. He called for DTSC to use an independent consultant.

“The city wanted an independent study,” Hirsch said. “You can’t hand that over to the advocate for the developer.”"

http://www.vcstar.com/news/2009/jan/30/developers-radiation-...

This seems to be in stark contrast to the activities of the founder of the Health Physics Society. He was the first president of HPS, from 1955-1957, and was apparently a real thorn in the side of the nuclear establishment.

http://www.gfstrahlenschutz.de/en/morganen.htm