Racial correction and the X-ray machine – The controversy over increased radiation doses for black Americans in 1968

The discovery of X-rays in 1895 revolutionized medicine. It has made it easier for doctors to diagnose and treat many medical conditions.22 The ability to image teeth has also transformed dental care. However, as x-ray technology developed in the early 20th century, false beliefs about biological differences between blacks and whites affected how doctors used this technology.

Ideas about racial differences in bone and skin thickness emerged in the 19th century and remained prevalent throughout the 20th.5 1863 by Theodor Waitz Introduction to anthropology affirmed, for example, that “the skeleton of the Negro is heavier, the bones thicker”.23 These claims reflected both beliefs about behaviors attributed to black people (e.g., violence)23.24 and the interests of white scientists and slave owners who justified slavery.16.19

Ideas have persisted even when contexts have changed. Almost a century later, in 1959, An atlas of normal radiographic anatomy describes the skull bones of blacks as “thicker and denser” than those of whites.25 Researchers continued to report racial differences in bone density throughout the 20th century.26 However, when the National Center for Radiological Health (NCRH) of the United States Public Health Service examined this question in 1968, it raised doubts about the claims (e.g., “unsubstantiated”, “doubtful validity”) , noted that the reported differences could have environmental causes (e.g., nutrition, exercise), and pointed out that large variations exist within so-called breeds.27.28

The belief that black people have denser bones, more muscle, or thicker skin has led radiologists and technicians to use higher radiation exposure during x-ray procedures. A doctor in 1896 asserted that “black being perfectly opaque”, black skin “would offer a certain resistance to cathode rays”.5 A 1905 review explained how “the skin of the negro offers more resistance to x-rays than an unpigmented cuticle”. This resistance made it difficult “to obtain a good skiagraph of the spine of a negro”: “The large exposed surface (abdomen and back) contains so much pigment that a good part of the energy of the x-rays is lost.”4 The New York evening world describes a famous black boxer with an “almost impregnable” skull: it took “the greatest skill of Joseph Klober, the famous electrician and Roentgen ray operator, to get a picture of the inner workings”.5.29

Formal teaching on racial adjustment for x-rays seems to have started later. Clifton Dummett, a prominent black American dentist, described learning in the 1940s to increase x-ray exposure times for the teeth and jaws of black patients because their oral tissues were more resistant to x-rays.30

Classification of Patients, 1957.

Reprinted with permission from the American Society of Radiologic Technologists.32

General Considerations on the Body, 1964.

Reprinted from Jacobi and Paris.35

In the 1950s and 1960s, X-ray technologists were told to use higher doses of radiation to penetrate black bodies. Roentgen signs in clinical diagnosis, published in 1956, describes the x-ray examination of a black person’s skull as a “technical problem” requiring a modified technique. The author suggested increasing the exposure by 10 kilovolts (a 12.5 to 21% increase).31 A 1957 article in The radiology technician classified as “white” as “normal”. For “black or brown” patients, an adjustment has been recommended to obtain a better radiograph (eg, use a peak dose of 4 kilovolts higher than normal, an increase of 9.5 to 25%) (Figure 1).32 Racial adjustments also appeared in several other textbooks.33 The second edition (1960) of Jacobi and Hagen’s X-ray technology added the unexplained recommendation that black patients receive 40-60% more exposure than that given to white patients. These tips remained in the third edition (1964) (Figure 2).34.35

The General Electric Company (GE), then the largest manufacturer of x-ray diagnostic equipment, made its own recommendations based on the race. In the 1961 and 1963 editions of his pamphlet “How to Prepare an X-Ray Technical Chart”, he indicated that black patients needed increased exposure to radiation.28 In 1968, GE spokesman Robert Molitor explained that the recommendation reflected “current medical thinking” among radiologists.27

Blacks weren’t the only ones getting more radiation. Guidelines and textbooks also recommended higher doses for people who were “extremely obese” or “muscular”; in patients with sclerosis, osteomyelitis or Paget’s disease; and in patients wearing a cast. Meanwhile, lean patients, children, elderly patients, and those with osteoporosis were given lower doses (Figure 2).35 It is unclear which adjustments were based on hunches or anecdotal experiences and which, if any, were based on in-depth study.

Several estimates give an idea of ​​the prevalence of dose adjustment based on race. Surveys of X-ray technicians in the San Francisco Bay Area in 1968 found that 75 of 90 technicians “habitually increased Negro X-ray doses.”36 They said they did it because “‘[Black people’s] the bones are harder and denser”, “their skin is darker” and “their flesh is harder”.27 A sample of chief X-ray technicians in New York also found that black patients were receiving increased radiation doses. As Goldman explained, “a ‘significant proportion’ of X-ray techs in the state apparently routinely exposed blacks to higher radiation doses than whites.”1

We don’t know what percentage of x-rays taken on black Americans used increased exposures. We also don’t know how many people were potentially injured. The radiation received during a chest X-ray is comparable to 10 days of natural exposure.37 A 40-60% increase in radiation from a single x-ray would have little effect on a person’s lifetime risk (and the increase used for black people was lower than that used for muscular or obese people). However, the cumulative effect could have been substantial for people who received multiple exposures. This question of the harmfulness of low-risk radiation exposures has been considered by the Advisory Committee on Human Radiation Experiments.38 Even though most of these Cold War experiments probably caused little physiological harm, the research subjects suffered other harms (e.g., being used for research without consent). The situation has parallels with race-adjusted x-rays: many people have been exposed to increased (even minimal) risk, presumably unwittingly, due to unsubstantiated beliefs based on racist science.