###### Abstract  
This article discusses the contention in the commented-upon paper that Brillouin precursors generated by 5G New Radio (5G NR) and other cellular systems are a possible cause of tissue damage at deeper layers of tissue than the power penetration depth of the carrier frequency. The original theory for Brillouin precursors from pulsed radiofrequency signals (RF-EMF) and speculation about their possible health effects dates back to the 1990's and was based on studies of the propagation of very short (nanosecond) ultrawide-bandwidth RF pulses through water. This assumption is not correct for cellular telephone signals due to their narrow bandwidth. The commented-on paper provides no alternative rationale as to why Brillouin effects should cause tissue damage from RF-EMF radiation from cellular and other communications systems. Other inaccuracies in this paper concerning thermal responses of tissue to RF-EMF are also noted.  
Brillouin precursors; 5G new radio; thermal hazards 2  
been experimentally observed by [PERSON] et al. [3], [PERSON] et al. [4] and others, confirming the theory.  
[PERSON] and [PERSON] refer to work by [PERSON] et al. [5], who examined the propagation of \"ultrashort\" (1 ns) pulses of RF-EMF with a carrier frequency of 10 GHz in water. Those authors proposed that Brillouin precursors could \"create a disturbance in tissue at greater depth than would be expected if one were to use the depth of penetration of the basic carrier frequency\" [5]. This claim forms the basis of [PERSON] and [PERSON]'s critique. The \"greater depth\" refers to the low-frequency components of the wave packet, which represent only a small fraction of the total energy carried by the pulse.  
[PERSON] recommended \"zero human exposure to such unique precursor and generating pulses\" [6]. [PERSON]'s claims were challenged by [PERSON] [7,8] and [PERSON] et al. [3], but nevertheless have been repeated on activists' websites. Now, [PERSON] and [PERSON] have resurrected the theory even though they do not explain how such precursors might cause tissue damage.  
Simple considerations show that [PERSON]'s original model is irrelevant to band-limited communications signals such as from cellular communications systems. We consider a pulse of RF-EMF with the same parameters as in [PERSON] et al. [6], consisting of 10 cycles of 10 GHz radiation that is normally incident on the medium (water); all of the incident energy is assumed to be transmitted into the medium. This pulse is represented by a carrier wave of frequency \(\omega_{\mathrm{c}}=2\pi 10^{10}\) rad/sec and amplitude \(\mathrm{E_{c}}\) (measured just beneath the surface of the medium) that is modulated by a square wave of duration \(\mathrm{t_{p}}\) (1 ns). The surface of the medium is located at \(z=0\), and increasing z is directed into the medium.  
The wave packet immediately below the surface can be written as  
\[E(t,0)=E_{c}\mathrm{rect}(t/t_{p})\cos(\omega_{\mathrm{c}}t) \tag{1}\]  
where \(\mathrm{rect}(t/t_{p})\) is a rectangular function that is equal to 1 for \(|t|<\mathrm{t_{p}}/2,1/2\) for \(|t|=\mathrm{t_{p}}/2\), and 0 otherwise. This \"ultrashort\" pulse is vastly different, both in duration and in frequency spectrum, from 5G or other communications signals but may be a reasonable approximation for other problems (e.g., ultrawide-band radar or brief laser light pulses).