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  1. Contamination
  2. The ATSDR reviewed the report of the radiological survey that EPA Region IV conductedduring the week of August 23, 1998 (2). The gamma radiation surveys were taken at fourresidences near the Stauffer Chemical Superfund site in Tarpon Springs, Florida. Slag andsoil samples were taken at 10 residences and chemically analyzed (3) to determine if therewas a toxicological risk to the public and also to compare the contaminants in the off siteslag to those at the Stauffer site. Slag appeared to be in a sintered form (i.e., a glass likematerial), consistent with an arc furnace extraction process. Samples were analyzed foraluminum, antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cobalt,copper, iron, manganese, mercury, nickel, radium, selenium, silver, thallium, vanadium,fluoride, and zinc.

    ATSDR staff also reviewed relevant tests conducted by EPA representatives (2,3) andhealth-related reports issued by the Florida Department of Health (FDOH). The FDOH,through a cooperative agreement with the ATSDR, has issued a public health assessment forthe Stauffer site (4) and a health consultation for the Gulfside Elementary School in Holiday,Florida (5).

    Appendix A contains the radiological survey and sampling data from the site visit (StaufferChemical Vicinity Properties) during the week of August 23, 1998.

    Static gamma radiation surveys were taken in four residences using a pressurized ionchamber (PIC). This instrument is calibrated in microrad per hour (µrad/hr) and wasprovided and operated by the EPA's National Air, Radiation and Environmental Laboratory(NAREL) . Comparison surveys were taken at the same locations with a Bicron Micro Remmeter, S/N B792W, calibration date of August 4, 1998. Measurements were taken at bothwaist level (normal standard for exposure surveys) and ground level for comparisonpurposes.

    The hurricane proof construction style of residence #1 (see Table 1) is different from that ofany other home encountered. The floors and some walls on both levels are poured concretethat use phosphate slag as aggregate. This resulted in the basement floors having more than twice the gamma dose rate of the upstairs living space.

  3. Quality Assurance and Quality Control
  4. In preparing this public health assessment (PHA), the ATSDR relied on the informationprovided in the referenced documents. The agency assumed that adequate quality assuranceand quality control measures were followed with regard to chain-of-authority, laboratoryprocedures, and data reporting. The validity of the analyses and the conclusions drawn inthis document was determined by the availability and reliability of the referencedinformation.


As of June, 1998, there was a completed exposure pathway from ionizing radiation from elevatedbackground, but not at levels expected to cause adverse health effects. EPA samples of selectedresidences found that driveways, yard fill, home foundations, and other concrete structures containedphosphate slag with measurable concentrations of the natural radium isotope Ra-226 (3). Phosphateslag is a naturally-occurring radioactive material, not a man-made radioactive material or a licensedradioactive material.

Radiation dose measurements in several homes were elevated compared to backgroundmeasurements, but not sufficient to represent a health hazard. The normal background for theTarpon Springs area was about 60 millirem per year (mrem/yr), excluding the contribution fromradon. If the dose from radon for this part of Florida is included, the annual background dose isabout 160 mrem/yr. Florida has a low background dose compared to Denver, Colorado, which isabout 300 millirem (including the contribution to total dose from radon). The International Councilon Radiation Protection (ICRP) (6) and the National Council on Radiation Protection andMeasurements (NCRP) (8) both consider phosphate slag in building materials to be part ofbackground.

The NCRP, in its report number 116, on page 50, gives the average dose from background radiation(excluding contribution from radon) to be 100 millirem per year and recommends that doses frombackground should be remediated if they exceed 500 millirem per year (8). To put this inperspective, the ICRP recommends that radiation doses to the public not exceed 500 millirem in any5 year period and should be less than 100 millirem per year over a lifetime, excluding doses frombackground (i.e., natural sources like phosphate slag), diagnostic (e.g., x-rays) and other medicalexposures(6). The lowest observed adverse effect level (LOAEL) from ionizing radiation is from10,000 to 50,000 millirem in one exposure and is seen as a slight decrease in blood cell count (7).

Radon samples in homes were all below EPA's action level of 4 pCi/L. There was no radon gascoming from slag containing radium. The lack of radon would be expected from the glass-likecharacter of the slag. Although phosphate slag contains heavy metals, leach testing of the samplestaken by EPA, did not find measurable heavy metals. The glass-like property of the slag would alsoexplain why heavy metals were not detected in leachate.

We made theoretical radiation dose calculations for the four properties in which gammameasurements were taken. We assumed a more conservative (high) occupancy factor of 18 hoursper day in residence #1 and one hour on a slag aggregate driveway for 350 days per year, because ofthe young child present. For the other residences sampled, we assumed an occupancy factor of 17hours in parts of the residence containing slag aggregate for 350 days per year. The calculated dosesfrom building materials ranged from a high of 210 millirem per year (mrem/yr) at residence #1 (seeTable 1 in Appendix A) to a low of 41 mrem/yr at residence #3 (see Table 3 in Appendix A). Noinfants or elderly individuals, who might be expected to be home more than 18 hours per day, livedin the homes with the greatest amounts of slag aggregate. Using a conservative exposure model for amaximally exposed child in the most affected home, the expected annual dose was well below theNCRP's remediation recommendation of 500 mrem/yr (8).


All the radium levels sampled at off site residences and the associated gamma radiation wereelevated above the local average for background radiation. The National Council on RadiationProtection and Measurements (NCRP), in its report number 116 on page 50, states that somebuilding materials can contain naturally occurring radioactive materials and should only beremediated if annual doses exceed 500 millirem per year (8). The lowest observed adverse effectlevel (LOAEL) from ionizing radiation is from 10,000 to 50,000 millirem in a short period of time(i.e., less than a week) and is seen as a slight decrease in blood cell count (7). (Note: A millirem isequivalent to a millirad for gamma radiation.)

Of the four homes sampled in the Tarpon Springs area, only one exceeded 100 millirem per year,from structural building materials. Residence #1 had elevated radiation levels, especially in thebasement. Using a conservative scenario, the annual dose to a young child living in a basementbedroom could receive about 210 mrem/yr additional background dose, which is well below theNCRP's 500 mrem/yr guideline (8).

The ICRP and NCRP recommendations are very conservative and are a factor of 100 below theLOAEL for acute exposure to ionizing radiation. Even though the total dose including radon wouldbe 310 mrem/yr, this is still roughly the national average background dose in the United States of300 mrem/yr (9). No adverse health effects would be expected from residing in the most affectedhome.

Phosphate slag at sampled vicinity properties does not appear to contain sufficient heavy metals torepresent a public health hazard, based on current medical, epidemiological and toxicologicalinformation. For non-radioactive chemicals and metals, the ATSDR uses comparison values(contaminant concentrations in specific media and for specific exposure routes believed to bewithout risk of adverse health effects) to select contaminants for further evaluation. The ATSDRand other agencies have developed the values to provide guidelines for estimating mediacontaminant concentrations that are not likely to cause adverse health effects, given a standard dailyingestion rate and standard body weight. Table 5 lists environmental media exposure guidelines(EMEGs) and reference media exposure guidelines (RMEGs).

Many of these values have been derived from animal studies. Health effects are related not only tothe exposure dose, but to the route of entry into the body and the amount of chemical absorbed bythe body. Several comparison values might be available for a specific contaminant. To protect themost sensitive segment of the population, the ATSDR generally selects the comparison value thatuses the most conservative exposure assumptions.

Natural Background Radiation

Natural radiation and naturally occurring radioactive materials in the environment provide themajor source of radiation exposure to the public. For this reason, natural background radiation isoften used as a comparison for man-made sources of ionizing radiation. Background radiationcomes from cosmic sources, naturally occurring radioactive materials including radon, and globalfallout as it exists in the environment from testing of nuclear explosive devices. Although numerousepidemiological studies have attempted to relate the health effects to exposures from elevated naturalradiation, none has provided definitive results (10).

The average annual effective dose in the United States population from natural backgroundradiation circa 1980 - 82 was 300 millirem per year (mrem/yr). Radon and its decay productsaccount for roughly 200 mrem/yr. Cosmic radiation contributes 26 mrem/yr at sea-level and greaterthan 50 mrem/yr in Denver. Terrestrial gamma radiation from the earth and building materialcontributes an average of 28 mrem/yr, but in certain areas with uranium or phosphate ore bodies andcoastal areas with deposits of monazite sands, the contribution can be as high as 2000 mrem/yr. Thecontribution from internal radioactive materials, such as potassium-40 and polonium-210, is about39 mrem/yr (9).

Special Considerations of Women and Children

Radiation doses are calculated at ½ meter (20 inches) from the floor to better estimate the dose tochildren. Although there is elevated background radiation from radium-containing slag andaggregate, the dose to children is approximately the national average background dose of 300 mremper year and is not expected to result in any adverse health effects. Phosphate slag at sampledvicinity properties does not appear to contain sufficient heavy metals to represent a health hazard towomen or children, based on current medical, epidemiological and toxicological information.

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