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Air and Water:  

How Has EPA Changed Subpart R?



EPA first issued the NESHAP for phosphogypsum stacks in 1989. The 1989 standard required that all phosphogypsum be stored in stacks and did not permit any other uses, such as agricultural or indoor research and development.


In 1992, in response to several petitions, EPA revised the standard to permit alternate uses. The 1992 revision of Subpart R permitted uses that fall into three categories:


EPA is issuing changes to Subpart R in 1999 in response to issues raised by The Fertilizer Institute about the risk assessment supporting the 1992 revision. The assessment evaluated the radiation exposure risk to persons who use phosphogypsum in indoor laboratory research and development activities. EPA is also using this opportunity to streamline and clarify other portions of the standard. The 1999 rule changes the 1992 version in three ways:

Why did the EPA decide to make changes to Subpart R?

After EPA issued a final rule revising Subpart R in 1992, The Fertilizer Institute filed a petition asking reconsideration of several provisions. EPA reviewed the petition and agreed to reconsider two provisions of the final rule:

What are the 1999 changes in the amount that may be used for indoor research?

EPA specifically reviewed the portion of the risk assessment used to determine the limit on the quantity of phosphogypsum researchers could use in laboratory research. EPA found that when they used actual exposure scenarios, the 700 lb. limit could be raised to 7,000 lbs. and meet the risk limits with an ample margin of safety.

What are the 1999 changes to the sampling and measurement requirements?

The 1992 version of Subpart R required that anyone using phosphogypsum for research and development must take samples and measure for radium-226 content. However, the standard did not place any restriction on the radium-226 content of phosphogypsum used for research. In the 1999 revisions, EPA has eliminated the sampling requirement.

EPA has retained the requirement that anyone using phosphogypsum for agricultural purposes or for approved other uses must take samples and measure the radium-226 content. However, in response to comments from affected groups, we have clarified the requirement.

What are the 1999 Subpart R Revisions?

Any amendments or revisions to the 1992 version of the NESHAP for radon emissions from phosphogypsum had to meet specific criteria that EPA uses when determining the safe level of risk. These criteria are specified in Section 112 of Clean Air Act as amended in 1990. The criteria require the NESHAPs to be established in a two-step process.

Nationally, the average chance of someone’s developing a fatal cancer in his or her lifetime is about 1 in 4. The criteria in Section 112 require that the NESHAPs standards for sources of radiation be set so that no one’s chances are increased by more than 1 in 10,000.

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