EMF (from power lines)
EMF (electro-magnetic fields) are created by anything carrying electrical current- most notably high tension power lines. There is some non-conclusive evidence that there may be health risks associated with long-term exposure to EMF.

Luckily, the intensity of the EMF depends on the closeness of the power source. Careful measurements often demonstrate that the EMF created in a home by an electric stove is greater than the EMF created by overhead power lines on the adjoining property.

Measurements can be taken on your behalf if this issue concerns you. The power company sometimes will do this as a free service.

UFFI
Urea formaldehyde foam insulation (UFFI) was a very effective material during the late 1970's for improving the wall insulation of existing homes. It could migrate inside walls to fill voids far better than any other material when thin insulation was already present in those walls.

Sometimes, particularly if formulated improperly, the UFFI would give off formaldehyde gas, especially during hot and humid weather. Formaldehyde gas is an irritant and even potential carcinogen in the extreme. UFFI was therefore promptly banned.

UFFI is practically a non-issue healthwise. Nowadays, old UFFI, however, is more apt to off-gas during prolonged hot and humid weather. Nevertheless, when it does, the formaldehyde off-gassing is still less than from the cabinetry, carpets and subflooring in newer homes. If UFFI is discovered during your home inspection, consider installing central air conditioning to control hot and humid conditions.