# Non-Ionizing Radiation Measurements for Trajectory Radars
## 2 Regulation of Human Exposure Limits to Non-Ionizing Radiation  
Non-ionizing radiation is a kind of electromagnetic radiation that, as opposed to ionizing radiation, does not cause an electron withdrawal from molecular structures. Nevertheless, the incidence of NIR on a material produces thermal and non-thermal effects. The thermal effects are a consequence of the increased vibration in the material's molecules caused by the NIR. Concerning the non-thermal effects, there is no evidence that they pose a danger to human health, particularly with regard to long-term exposure [14].  
The Electric and Magnetic Fields (EMF) project of the World Health Organization (WHO) has been developing a program that, among other objectives, evaluates the scientific literature and reports on health effects to facilitate the development of internationally acceptable standards for exposure to EMF. In addition, this program intends to advise national authorities, other institutions, the general public and workers about any risks arising from exposure to EMF and any necessary mitigation actions [15].  
In Brazil, law No. 11934, of 5 May 2009, establishes that the definition of exposure limits to non-ionizing radiation must follow WHO recommendations, which adopted ICNIRP numbers [16]. Currently, these limits are defined by Anatel Act No. 458, of 24 January 2019 [4]. Compliance verification is based on field measurements so that preventive procedures can be adopted to avoid the impact on human health [17; 18; 19]. Anatel Act No. 458 regulates the limits of human exposure to electric, magnetic and electromagnetic fields in the radiofrequency range between 8.3 kHz and 300 GHz, generated by radio-communication stations and user terminals. The regulation also defines evaluation methods for exposure to non-ionizing radiation and procedures to be followed for the licensing of stations.  
Different values of exposure limit are defined to the occupational and to the general population. Occupational exposure refers to that in which people are exposed as a result of their professional activity, as long as they are aware of the potential exposure, and they can exercise control over their permanence in the place or adopt preventive measures.  
Limit values are the same for the entire range from 2 GHz to 300 GHz, where the Bear radar operates. For the general population, the equivalent plane wave density should be less than 10 W/m\({}^{2}\) and, for the occupational public, 50 W/m\({}^{2}\). Other limits are shown in Table 1[4].  
The power density limits are related to the average power from the emissions. However, the peak power level from the radar emission (1 MW) is much higher than its average power. Although there is not much information about the relationship between biological effects and peak values of pulsed fields, it is suggested that, for frequencies exceeding 10 MHz, the equivalent plane wave density, averaged over the pulse width, should not exceed 1000 times the reference levels [3]. Since the peak power of the radar signal is  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Population**} & **Electric Field** & **Magnetic Field** & **Equivalent Plane** \\  & **Intensity (V/m)** & **Intensity (A/m)** & **Wave Density (W/m\({}^{2}\))** \\ \hline General & 61 & 0.16 & 10 \\ Occupational & 137 & 0.36 & 50 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Population exposure limits to Radio Frequency—Electromagnetic Fields (RF-EMF) for the 2 GHz to 300 GHz range.  
exactly 1000 times the average power value, it is within the suggested limit. Therefore, our measurements are focused on the average power density.