The Earth's magnetic field adds to the overall electro magnetic fields exerted on your body. The Earth's magnetic field measures approximately 0.3 Gauss (30 microteslas) to 0.6 Gauss (60 microteslas) (Georgia State University, Dept of Physics and Astronomy). Generally speaking, the magnetic field is believed to be stronger closer to the poles, but there are significant variations in the fields.
Map of the Earth's Magnetic Field (NASA)
Map of the Earth's Magnetic Field (British Geological Survey)
Location: Earth's Composition
The composition of the Earth can lessen the Earth's magnetic field. That is, the type of rock in the Earth's crust at a specific geographic location can dampen the effect of the Earth's magnetic field.
For example, areas with diamond fields typically have quartz, a type of rock which lessens electromagnetic fields. Similarly, areas with granite or gold mines will also dampen the Earth's magnetic field.
It is important to note that mining locations see significant contamination through metals leaching into the groundwater. One mine location can be the source of multiple metals.
Location: Earth's Magnetic Field
Granite
Gold
Quartz
