Ultrasonic Industrial parts cleaner frequency range is 40 to 80 KHz = 80,000. Hz
Cell phone frequency range is, 800MHz to 1.800MHz = 800,000. to 1,800,000,000. Hz.
Router frequency is 2.4GHz = 2,400,000,000. Hz
Kitchen microwave oven frequency is 2.45GHz = 2,450,000,000. Hz
Radiation transmission is directly proportional to cross sectional area as light transmits from a light bulb. As you get farther and farther away from a light bulb the amount of light is many times less every time the distance doubles, that is why you can not light up an entire football stadium with ONE 100 watt light bulb and you can not heat a swimming pool with a blow torch and you can not heat your house with a birthday candle.
If you stand across the room from a 25 watt light bulb you have no ill effects, but if you put your face on the light bulb you get the skin burned off of your face. A router is low power and is no different than a light bulb.
It makes perfect sense to me if a micro wave oven can cook food a Router being the save frequency can cook plants that are too close to the transmitter and a cell phone glued to your ear can fry your brain. Brain tumors have increased several times over since the invention of cell phones and the cell phone companies continue to say, you have NO PROOF cell phones caused it!!!
Once upon a time people believed the world was flat. One day a man claimed the world is round, everyone laughed. Barbie Dolly had not been invented yet. There are none so blind as those who will not see.