What is the best type of desk lamp in terms of EMF ?
Desk lamps with a full AC voltage incandescent bulb are not good in terms of EMF. The 120 V AC or 230 V AC wire creates a strong AC electric field, and also some AC magnetic field. In addition to this, the incandescent bulb generates also a lot of heat, and it wastes a lot of power.
Low voltage halogen light bulbs still have some AC electric field but the electric field is much lower because the voltage of the lamp is lower. There is some AC magnetic field but it is not too high. Halogen light bulbs are almost safe in terms of EMF.
Anyway, an halogen light bulb generates still a lot of heat.
Since the halogen light bulbs are powered by a low voltage AC, like 12V or 24 V, there must be a transformer somewhere. To avoid the magnetic field, the transformer should be placed away from the user. So any desk lamp with the transformer in the base has to be discarded.
The best products of this kind are those with the transformer attached to the wall socket, so the wire from the wall to the desk carries only the low voltage.
Anyway, commercial products contain mostly rectangular transformers which have much more magnetic field dispersion. Rectangular transformers also radiate the "dirty electricity" that is found in the mains system.
It would be better if the transformer was toroidal, but we don't known any commercial product based on a toroidal transformer.
The fluorescent compact lights are extremely bad in terms of EMF they should be avoided at all costs, especially for a desk lamp which is located close to the body.
LED lights are excellent in terms of EMF but only if they are powered with smooth, "clean", DC voltage and current.
Most LED desk lamps on the market contain an electronic circuit, called the LED driver, that converts the 120/230 V AC from the mains to a sort of DC, but these circuits introduce a lot of electromagnetic noise.
The best LED desk lamp so would have a good quality, linear power supply, with toroidal transformer.
Some people are concerned abouty the excess of blue light in the light emitted by LEDs, but we don't think this problem exists anymore, since many years the white LEDs in the market generate a light that has almost the same spectrum of the natural light. Of course there are variations on white LEDs like cool white, warm white and pure white. For a prolonged use of such lights we recommend warm white or pure white. Anyway, in our opinion, blue light excess is not a big problem, it is negligible against the problem of electromagnetic fields and radiation, which are totally invisible.