I don’t even think about it. Here’s some info about xrays:
A unit called a “rem” is used to measure radiation. A rem is a large unit, much like a mile is a large unit of length, so we usually use a millirem (mrem) instead, much as you would measure in inches instead of miles for most purposes. (It takes 1000 mrem to equal one rem.) A typical dental x-ray image exposes you to only about 2 or 3 mrem. The National Council on Radiation Protection (NCRP) says that the average resident of the U.S. receives about 360 mrem every year from background sources. This comes from outer space, radioactive materials in the earth, and small amounts of radioactive material in most foods we consume.Some typical sources that may expose you to radiation also include smoke detectors (less than 1 mrem per year), living in a brick house instead of a wood one (about 10 mrem per year due to radioactive materials in the masonry), cooking with natural gas (about 10 mrem per year from radon gas in the natural gas supply), reading a book for 3 hours per day (about 1 mrem per year due to small amounts of radioactive materials in the wood used to make the paper), and even from flying in an airplane (about 5 mrem for one cross-country flight because of the increased altitude.) In fact, you receive about 2 mrem per year from sleeping next to someone! This is because all of us have very small amounts of naturally occurring radioactive materials in our bodies. (source).
At low doses, such as what we receive every day from background radiation, the cells repair the damage rapidly. At higher doses (up to 100 rem), the cells might not be able to repair the damage, and the cells may either be changed permanently or die. Most cells that die are of little consequence, the body can just replace them. Cells changed permanently may go on to produce abnormal cells when they divide. In the right circumstance, these cells may become cancerous. This is the origin of our increased risk in cancer, as a result of radiation exposure. (source)
The site you linked mentions watts per kg of body weight absorbed. I couldn’t find anything to convert the measurements of radiation from the cell phones to rems to get a good comparison.