Regulatory limits for safe levels of elements in water and foodstuffs are established by the U.S. Environmental Protection Agency and the U. S. Food and Drug Administration.
Igneous rocks (from the Greek word for fire) form from when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface.
Metamorphic rocks started out as some other type of rock, but have been substantially changed from their original igneous,
Sedimentary rocks are formed from pre-existing rocks or pieces of once-living organisms. They form from deposits that accumulate on the Earth's surface. Sedimentary rocks often have distinctive layering or bedding.