Precautions concerning HF band
It is relatively safe because of the long wavelengths compared to body dimensions as well as the absorption of body tissue is small. Countering this is the high powers sometimes used (multiple megawatts.)
The only dangers are if you are physically standing right next to a transmitting antenna tower for an AM radio or TV station. You can be electrocuted from some of these transmit towers if you touch the metal while standing on the ground.
There are very real dangers with HF exposure. While not as dangerous as microwave, they are still very real. If you are working around HF antennas where there is any kind of significant power, or you are planning on installing HF antennas where they might expose people without their knowledge, you should get hold of the following book:
http://www.arrl.org/catalog/6621/
"RF Exposure and You" published by the ARRL (amateur radio).
I have Yagi antennas at 23 meters high radiating up to 1 KW of power with antenna gain of up to around 8-9 dBd, 1.8 - 50 MHz. They are more than 80 meters from any home where someone might be located for a period of time, so all is OK, at least according to the book. The field of RF exposure is still being researched, so one should minimize exposure just to be as safe as possible.
When dealing with non-technical types, the word "radiation" immediately brings to mind big ugly cancer tumors, radioactive monsters, etc. Be sure to emphasize that HF is "non-ionizing", it does not have enough energy to kick electrons off of DNA atoms, so the only problem is heating. Something like ultraviolet radiation from the sun, however, is ionizing, and is a very firmly established to be a strong cause of cancer. So if you find someone who is very concerned about radiation causing cancer, make sure they stay out of the sun at all times!
http://www.fcc.gov/Bureaus/Engineeri...56/oet56e3.pdf
has a table of values. From this note the variable levels in the HF range.
http://www.fcc.gov/Bureaus/Engineeri...et65/oet65.pdf
has some tables and graphs.