Colorado’s permissive standard for plutonium in soil

In Democracy, Environment, Jefferson Parkway, Nuclear Guardianship, Plutonium, Public Health, Rocky Flats on June 23, 2013 at 2:09 am

People often express shock at recent residential and commercial developments near Rocky Flats. I’m often asked, are there no restrictions on such development in that area? For an answer to this question, one needs to look at the history of the Colorado standard for plutonium in soil in areas off the Rocky Flats site.

The dawning of public awareness about Rocky Flats 

After a major fire in one of the plutonium processing buildings at Rocky Flats on Mother’s Day 1969, NCAR radiochemist Ed Martell and Stuart Poet sampled soil east of the facility and found elevated levels of plutonium. In February 1970 when they reported their results to officials from Rocky Flats and the Colorado Health Department (CDH) they were told that what they’d found came not from the 1969 fire but either from a fire that occurred on September 11, 1957, or from leaks from thousands of drums of plutonium-laced waste stored outside in the plant’s 903 area from 1954 till 1968. These two events had not been previously revealed by either Rocky Flats or CDH. Thus began public awareness that Rocky Flats endangered public health.
Government scientists map plutonium contamination

In 1970 Atomic Energy Commission scientists P. W. Krey and E. P. Hardy produced this map showing plutonium contamination in soil on and off the Rocky Flats site in becquerels per square meter (one becquerel equals one disintegration or burst of radiation per second).

Microsoft Word - Krey-Hardy Clean.doc

Colorado sets a standard for plutonium in soil
In response to these revelations, in January 1973 Colorado adopted a very stringent standard of 0.2 disintegrations per minute per gram of soil (dpm/g), declaring land that exceeds this standard is unfit for residential, commercial or industrial uses.”1 Less than two months later the state increased by tenfold the amount of plutonium to which exposure was allowed, from 0.2 to 2.0 dpm/g, while at the same time it dropped its prohibition against residential, commercial, or industrial uses in areas too contaminated to meet the new, more relaxed standard. Hereafter it would merely require “special techniques” for construction in such areas, such as plowing plutonium under.2 Thus the state gutted its initial fairly protective standard for one that is essentially worthless.

Dust sampling stops a residential development near Rocky Flats
In December 1974 a Jefferson County Commissioner asked Carl Johnson, Director of the Jefferson County Health Department, whether the commissioners should permit a new residential development on land just east of the Rocky Flats site. The CDH had already approved the project, despite having found plutonium in surface soil there up to seven times the state standard (they would require plowing prior to construction). Johnson and two U.S. Geological Survey colleagues employed the innovative method of sampling only respirable dust. Dust samples taken at 25 locations showed plutonium concentrations on average 44 times greater than what had been measured at the same locations by the state using whole-soil samples. Several readings exceeded previous ones by 100 times or more, one by 285 times.3 In
September 1975, when the County Commissioners saw the results, they vetoed the residential development.

Johnson proposes that the state sample dust, not soil

In October 1975 Johnson formally proposed that for, purposes of assessing health risk, the state set a new standard based on plutonium in respirable dust on the surface of the soil. “The coarser materials which are not inhaled and retained,” he pointed out, “have no bearing on the actual hazard to health and serve only to dilute the amount of radioactivity found by analysis, and may yield a spurious low concentration of plutonium that is misleading.”4   The CDH did not welcome Johnson’s proposal.  To resolve the issue, the Colorado Land Use Commission brought in Karl Z. Morgan, former chair of the internal dose committee of both the National Council on Radiation Protection and Measurements and the International Commission on Radiological Protection and recently retired from DOE’s Oak Ridge Lab. Morgan was asked whether for assessing the public health risk from plutonium in surface soil it was better to follow Johnson in using dust samples or the CDH in collecting whole-soil samples. Morgan sided with Johnson, in favor of using samples limited to “the respirable portion, less than 5 microns dust particles.” Employing Johnson’s method, he realized, would make the State’s 2.0 dpm/g plutonium standard far more protective, since, for samples taken at the same location, Johnson’s method shows concentrations 40 or more times greater than the CDH whole-soil approach.5 Colorado officials, having gotten from Morgan the advice they sought, chose to ignore it.

Ed Martell criticizes the state standard
At an EPA hearing in Denver in 1975, Martell said that the state standard of 2.0 dpm/g equals 0.9 picocurie per gram of soil. Rounding this number off, he said that allowing 1.0 pCi/g of plutonium in surface soil “will give rise to an estimated 10 to 100 pCi/g of insoluble airborne dust of respirable size.” It thus is far from clear, he said, that the state standard “is safe and acceptable.” It may be “at least 20 times too high.”6


This review shows that the Colorado standard for plutonium in soil fails to protect the public in several ways:
1. The shift from an initial strict 0.2 dpm/g standard for plutonium in soil to the 2.0 dpm/g standard increased by tenfold the quantity of unregulated plutonium in off-site soil.
2. Ending the original prohibitions against residential, commercial and industrial uses gave a green light for development on contaminated land near Rocky Flats.
3. The state’s refusal to adopt the method of sampling respirable dust on the surface of soil, as recommended by Carl Johnson and Karl Morgan, means, as Martell pointed out, that people in the area are far more likely to inhale airborne particles of plutonium, the worst way to be exposed to this highly toxic material.


1.  Cleere, R.L. 24 January 1973. Public notice of plutonium contamination in the area of the Dow Chemical Rocky Flats Plant, signed R. L. Cleere, Executive Director, CDH.
2.   Amendment to the State of Colorado Rules and Regulations Pertaining to Radiation Control, Subpart RH 4.21.1, adopted Colorado State Board of Health, 21 March 1973.
3.   Johnson, C., Tidball, R. R., and Severson, R. C., “Plutonium hazard in respirable dust on the surface soil.,” SCIENCE (6 August 1976), 193:488-490.
4.  Johnson, C., to Colorado Board of Health, “Proposal of a new interim standard to define the potential airborne-plutonium particle hazard in terms of concentration of plutonium in respirable dust on the surface of the land,” 14 October 1975.
5.   Morgan, K. Z., 21 January 1976, Transcript of Presentation, Colorado Land Use Commission Meeting, pp. 12-13.
6.  Martell, E. A. January 1975. Basic considerations in the assessment of the cancer risks and standards for internal alpha emitters. Statement presented at the public hearings on plutonium standards, US EPA, Denver, pp. 17, 20.

  1. Reblogged this on kjmhoffman.

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