It's not so much the absolute levels, but rather the presence of a normal distribution that I feel important.
Cuenca is not the only doc whose worked on this.
Biol Trace Elem Res. 1988 Jul;16(2):151-4.
Bromine levels in human serum, urine, hair. Short communication.
Cuenca RE, Pories WJ, Bray J.
Department of Surgery, East Carolina University School of Medicine, Greenville, NC 27834.
Much is known about the essentiality of the halogens fluorine (F), chlorine (Cl), and Iodine (I), but very little has been discussed with respect to bromine (Br). As a member of the halogen family its chemical properties are comparable to those of other halogens, but its presence has been masked by the presence of I and Cl in chemical analyses. By virtue of new technology and a special computerized machine called the Kevex Model 0600 Energy Dispersive X-Ray Induced X-Ray Fluorescence Spectrometer (EDXRF), we can specifically identify bromine in different compartments and verify its concentration accurately. In order to establish standard values of Br concentrations and evaluate the nature of its presence in humans, samples of serum, urine, and hair were collected from ten healthy adult males and analyzed for bromine content. Our samples had normal distributions, with serum bromine levels ranging from 3.2 to 5.6 micrograms/mL, urine levels between 0.3 to 7.0 micrograms/mL, and hair levels determined from 1.1 to 49.0 micrograms/mL. These levels, especially those of serum bromine, have been encountered by other examiners whose samples also had normal distributions. These findings suggest to us that bromine may well be an essential trace element, as are its other halogen family members.