Subpart K: Elemental Phosphorus Plants
Subpart K protects the public and the environment from the hazards of emissions of polonium-210 and lead-210 to the ambient air from phosphorus plants. The standard limits emissions to a maximum of 4.5 curies of polonium-210 annually. The standard focuses on polonium-210 because control measures that limit polonium-210 also limit emissions of lead-210.
Elemental phosphorus plants extract pure phosphorus from ore for use in the chemical industry. There are eight (5 operational, 3 standby) elemental phosphorus plants located in four different states. However, two plants in Idaho are the major emissions concern.
Phosphate ore is high in uranium and its decay products. These decay products, especially polonium-210 and lead-210, become airborne through volatilization during the extraction process and could potentially enter the atmosphere in large concentrations. Exposure comes from inhaling the radionuclides, with the lungs receiving virtually all of the dose, causing an increased risk of lung cancer.
Except under certain conditions, owners or operators must test emissions annually and submit the results to EPA.
In addition, there are general requirements that all facilities subject to any NESHAP must meet, 40CFR61, Subpart A: General Provisions .