Why do exposure limits vary with frequency?

The primary health concern with amateur radio RF exposure is tissue heating from non-ionizing radiation. However, the human body does not absorb all radio frequencies equally. Because the human body acts somewhat like an antenna, it becomes resonant at certain frequencies, specifically in the VHF range between 30 MHz and 300 MHz. At these resonant frequencies, the body absorbs a much higher percentage of the RF energy. To keep operators and the public safe, the FCC sets much stricter exposure limits in these specific frequency ranges. Distractors suggesting that lower frequencies inherently have more energy or higher frequencies are transient are scientifically inaccurate.