Baring the Sole: The Rise and Fall of the Shoe-Fitting Fluoroscope

A homework problem in Chapter 16 of Intermediate Physics for Medicine and Biology asks the student to estimate the dose experienced by customers exposed to x-rays when buying shoes.

Problem 8. During the 1930s and 1940s it was popular to have an x-ray fluoroscope unit in shoe stores to show children and their parents that shoes were properly fit. These marvellous units were operated by people who had no concept of radiation safety and aimed a beam of x-rays upward through the feet and right at the reproductive organs of the children! A typical unit had an x-ray tube operating at 50 kVp with a current of 5 mA.

(a) What is the radiation yield for 50-keV electrons on tungsten? How much photon energy is produced with a 5-mA beam in a 30-s exposure?

(b) Assume that the x-rays are radiated uniformly in all directions (this is not a good assumption) and that the x-rays are all at an energy of 30 keV. (This is a very poor assumption.) Use the appropriate values for striated muscle to estimate the dose to the gonads if they are at a distance of 50 cm from the x-ray tube. Your answer will be an overestimate. Actual doses to the feet were typically 0.014–0.16 Gy. Doses to the gonads would be less because of 1/r². Two of the early articles pointing out the danger are Hempelmann (1949) and Williams (1949).

To learn more about using x-rays to fit shoes, see the wonderfully titled article “Baring the Sole: The Rise and Fall of the Shoe-Fitting Fluoroscope” (Isis, 91:260-282, 2000) by Jacalyn Duffin and Charles Hayter. The abstract states

One of the most conspicuous nonmedical uses of the x-ray was the shoe-fitting fluoroscope. It allowed visualization of the bones and soft tissues of the foot inside a shoe, purportedly increasing the accuracy of shoe fitting and thereby enhancing sales. From the mid 1920s to the 1950s, shoe-fitting fluoroscopes were a prominent feature of shoe stores in North America and Europe. Despite the widespread distribution and popularity of these machines, few have studied their history. In this essay we trace the origin, technology, applications, and significance of the shoe-fitting fluoroscope in Britain, Canada, and the United States. Our sources include medical and industrial literature, oral and written testimony of shoe retailers, newspapers, magazines, and government reports on the uses and dangers of these machines. The public response to shoe-fitting fluoroscopes changed from initial enthusiasm and trust to suspicion and fear, in conjunction with shifting cultural attitudes to radiation technologies.

Why use x-rays to size loafers? Duffin and Hayter claim “the shoe-fitting fluoroscope was nothing more nor less than an elaborate form of advertising designed to sell shoes.” They say that the device was “aimed especially at mothers…the fluoroscope became yet another instrument of experts’ advice about ‘scientific motherhood.’” These fluoroscopes were rather fancy: “Like an alter to commerce, it became a featured part of the décor in high-class stores, situated on a specially lit and often elevated ‘fitting platform’…Whether in a traditional mahogany finish or art deco shapes and colors, the design responded to the demands of interior decorating.” But these x-ray sources were dangerous. “Store personnel and the adult and child customers were at risk of stunted growth, dermatitis, cataracts, malignancy, and sterility.” The papers by Louis Hempelmann and Charles Williams were the turning point.

“In 1949, two landmark articles on the hazards of shoe-fitting fluoroscopes appeared in the 1 September issue of the New England Journal of Medicine. The first, by Charles R. Williams of the Harvard School of Public Health, contained actual measurements of the high and inconsistent radiation outputs of twelve operating machines. The second, by L. H. Hemplemann [sic], also of Harvard, described the dangers of the uncontrolled use of shoe-fitting fluoroscopes, including interference with foot development in children and radiation damage to the skin and bone marrow.”

We don’t have much evidence indicating how this exposure affected people’s health. It was not lethal like that suffered by the Radium Girls who painted luminous dials using radium-based paint, but everyone buys shoes so millions of people were exposed. The risk of widespread low-dose radiation is difficult to assess, especially years latter.

By the early 1960s the fad was over. I was born in 1960. Yikes! I just missed getting zapped. Did you?