Radiation exposure, especially over 5,000 milligrams yearly, can reduce immunity by reducing the white cell count. Higher altitudes are subject to more radiation exposure from the atmosphere. Fetus cannot exceed 500 milligrams during gestation. Toxicity symptoms include nausea, vomiting, fatigue and diarrhea. Those experiencing larger doses over a period of years have a higher incidence of cancer and bone marrow depression. Fema is a government agency with more info.

Very often the thyroid can be adversely affected by even low levels of radiation in the air. 

Toxic Thyroid can be applied on the throat 2-3x daily

Environmental is also very protective for the skin and for inhalants

We carry potassium iodine tablets: 130 milligrams for adults, 65 milligrams for children is suggested during exposure.