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APPENDIX A: Dose Estimation

The observed radiation background for similar residences was 6-7 microrad per hour (µrad/hr).Average dose rates in affected areas ranged from 15.4 to 39.1 µrad/hr. One thousand µrads areequivalent to one millirem for gamma radiation. The National Council on Radiation Protection andMeasurements (NCRP) states that some building materials can contain naturally occurringradioactive materials and should only be remediated if annual doses exceed 500 millirem per year(8).

Table 1.

Stauffer Chemical Vicinity Properties - Residence 1
Location: Residence 1 µrad/hr (waist level) µrad/hr ground level Average
#1 basement 42 49 45
#2 basement 38 44 41
#3 basement 43 48 46
#4 basement 47 51 49
#5 basement 44 51 47
#6 basement 31 41 36
#7 basement 45 46 45
#8 basement 30 44 37
#9 basement 46 53 49
#10 basement 42 48 45
#11 bedroom 31 41 36
#12 bedroom 30 39 35
#13 1st floor 14 17 16
#14 1st floor 20 28 24
#15 1st floor 10 9 10
#16 1st floor 19 26 22
#17 1st floor 26 29 27
#18 1st floor 25 31 28
#19 1st floor 11 12 11
#20 1st floor 9 11 10
#21 driveway 29 38 34
#22 driveway 29 39 34
#23 driveway 60 73 67
Average living areas 16.7 (1st floor)
Annual Dose from Building Materials (mrem) 210

Note: One thousand microrad (µrad) are equivalent to one millirem (mrem) for gammaradiation.

To calculate an Annual Dose, because there were small children in the home, took anaverage of the one meter and ground level measurements, then for each area (e.g.bedroom, 1st floor) took an average of readings, then subtracted the local backgroundof 6 µrad/hr and assumed 12 hours per day in the bedroom, 5 hours in the basement, onehour on the first floor and one hour on the driveway for 350 days per year.

Table 2.

Stauffer Chemical Vicinity Properties - Residence 2
Location: Residence 2 µrad/hr (waist level)
Annual Dosefrom buildingmaterials76 (mrem)

Note: One thousand microrad (µrad) are equivalent to one millirem (mrem)for gamma radiation. To calculate an Annual Dose, averaged the readings,then subtracted local background of 6 µrad/hr and assumed 12 hours per dayin the bedroom and 5 hours in other parts of the house for 350 days per year.

Table 3.

Stauffer Chemical Vicinity Properties - Residence 3
Location: Residence 3 µrad/hr (waist level)
#1o/s slab25
#2o/s slab25
#3o/s slab19
#4o/s slab19
#5o/s slab22
#6o/s slab29
#7o/s slab22
#8o/s slab23
#9living room22
#10living room19
#11living room19
#12living room20
#16o/s bathroom15
#17side bedroom8
#18back left bedroom7
#19back right bedroom15
#20back right bed7
Annual Dose from buildingmaterials41 (mrem)

Note: One thousand microrad (µrad) are equivalent to one millirem (mrem) forgamma radiation. To calculate an Annual Dose subtracted local background of6 µrad/hr, then for each area (e.g. bedroom) took an average of readings,and assumed 12 hours per day in the bedroom, 5 hours in other areas of thehouse and 1 hour on the outside slab for 350 days per year.

Table 4.

Stauffer Chemical Vicinity Properties - Residence 4
Location: Residence 4 µrad/hr (waist level)
#7foyer (by door)13.0
#8adjacent bath12.1
#9adjacent bath9.8
#10back door11.4
Annual Dose from buildingmaterials50 (mrem)

Note: One thousand microrad (µrad) are equivalent to one millirem (mrem)for gamma radiation.. To calculate an Annual Dose, subtracted localbackground of 6 µrad/hr, then for each area (e.g. garage, foyer) took anaverage of readings, and assumed 12 hours per day in the house and 5 hoursin the garage for 350 days per year.

Table 5.

Maximum Contaminant Concentrations in Parts per Million (ppm)
Contaminant Driveway Pavement Driveway Base Yard Soil Comparison Value
Antimony 0.0566 0.252 0.0469 20 (Chronic RMEGs Child)
Arsenic 4.85 3.84 0.829 20 (Chronic RMEGS Child)
Beryllium 1.24 1.92 0.749 100 (Chronic RMEGS Child)
Chromium 27.7 22.3 49.6 200 (Chronic RMEGS Child)
Lead 18.2 11.7 31.8 400 (EPA Screening Level)
Thallium 0.70 0.614 0.0658 5 (Chronic RMEGS Child)
Vanadium 33.9 26.3 17.2 200 (Intermediate EMEG Child)
Radium-226 70.2 (pCi/g) 6.21 (pCi/g) 25.1 (pCi/g) 5 pCi/g to 5 cm depth
15 pCi/g below 5 cm
(40 CFR 192 )
Key: Reference Media Exposure Guideline (RMEGS)
Environmental Media Exposure Guideline (EMEG)
EPA Standards for Uranium and Thorium Mill Tailings {40 CFR 192 (1983)}
Code of Federal Regulations (CFR)

APPENDIX B: Public Comments

The ATSDR responses to the following comments are in italics.

The ATSDR should be commended on this report since it conveys the radiological situation inTarpon Springs to the public in a manner that is easy to understand. In addition, the radiation dosesare put into proper perspective by comparison with the LOAEL and natural background. Theyshould also be commended for their use of the word "guidelines" instead of "standards" whenreferencing the 100 mrem per year recommended dose limit. However, the report requiresclarification on a number of issues.

The ATSDR should clarify that these guidelines do not apply to slag but are used to put theestimated doses into perspective. Phosphate slag is not a man-made radioactive material or alicensed radioactive material. It is a naturally-occurring radioactive material. It is appropriate to usethese guidelines as a means of putting these estimated doses into perspective; however, the reportfails to clarify this point.

Clarified throughout document that phosphate slag is a naturally occurring material.

As an example, the reports states that at one residence, the levels of ionizing radiation exceed bothnational and international guidelines for exposure by more than a factor of two. The report shouldindicate that these guidelines do not apply to phosphate slag, but only to licensed radioactivematerials. The only guideline which could apply to phosphate slag is 500 mrem per year asrecommended by the NCRP for continuous exposure to natural sources in remediation situations. Inreference 6 (ICRP 60), the International Commission on Radiological Protection specifically stateson page 44 that situations such that in Tarpon Springs are outside the scope of the dose limits forpublic exposure. Similarly, in reference 8 (NCRP 116), the National Council on RadiationProtection and Measurements states on page 45 that their recommended public dose limit of 100mrem per year applies only to man-made sources of radioactivity. The radioactive material inphosphate slag is not man-made but naturally-occurring radioactivity. Yet, on page 7 of the ATSDRreport, the reader is left with the impression that this guideline applies to exposures from phosphateslag. While the 100 mrem per year criterion is useful for comparison purposes, the public deservesto know that this criterion does not apply to radiation exposures from phosphate slag.

Corrected to make clear that the guideline for naturally occurring radioactive material inbuilding materials comes from NCRP 116 and that this is not a man made radioactive material.

The report uses units of µrads, millirems, millrads, rems and rads. I would suggest that all the unitsbe converted to millrems for clarity and ease of understanding. The reader is much more likely tounderstand a comparison between 300 mrem per year and 10,000 mrem than the comparison inConclusion 3 between 300 mrem per year and 10 rem; and the comparison on page 7 between 100millirem per year over a lifetime and 10 to 25 rem in one exposure. On page 7, for example,wording such as "The lowest observed adverse effect level from ionizing radiation is from 10,000 to25,000 mrem in one exposure..." would be more understandable and provide a more usefulperspective for the reader. The ATSDR should also be commended for the use of the LOAEL, sincethe public deserves to know that adverse health effects are not observed at dose levels such as thosewhich are estimated in this report. The ATSDR should also list the occupational dose limit of 5,000mrem per year as a level considered safe for occupational radiation workers.

Converted all units discussed to millirem.

The report indicates that the PIC is calibrated in µrad per hour. It is my understanding that a PIC isdesigned to measure gamma radiation in air, which is properly measured with the unit Roentgensper hour or micro-Roentgens per hour. The rad describes the absorption of energy in tissue, not air,although the conversion from Roentgens to rads is simple. I do not, however, recommend the use ofthis unit since all the units in the report should be converted, as accurately as possible, to millirem toavoid confusion. However, my understanding of the definition of the Roentgen indicates that thestatement of calibration of the PIC may be incorrect.

The PIC is calibrated using a NIST traceable standard, so that readings can be converted toµrad per hour. The chamber is constructed from a tissue equivalent material, so that readingsare tissue equivalent and energy independent.

On page 7, the report refers to "high" concentrations of radium-226 in phosphate slag. From aradiation protection standpoint, the concentrations of radium-226 found in phosphate slag cannot beconsidered high since concentrations of radium-226 can be found in the natural environment whichexceed these levels. A more appropriate characterization would be "elevated" such as wasappropriately used at the top of page 8 and in other parts of the report.

Changed to "elevated", as suggested.

This report goes to great lengths to educate the public as to the potential radiation doses which mightbe received by persons who may be exposed to phosphate slag in their homes and in theenvironment. The ATSDR's use of the LOAEL provides a comparison which is easy to understand ifit is listed in the same units. However, the ATSDR should inform the reader as to the proper use ofthe radiation protection guidelines which are referenced in the report.

Attempted to clarify the proper use of ICRP and NCRP guidelines.

Radioactive materials off-site appear similar to radioactive materials on the SMC site. The slag,regardless of where it occurs, has a low-- but elevated-- level of radioactivity. Simply put, the degreeof danger from any radioactivity is directly proportional to the amount of slag nearby.

Slag contains naturally occurring radioactive materials, which is considered part ofbackground. Doses did not exceed any applicable guideline.

Prior to these studies, it was thought there might be "hot spots" from particularly radioactive batchesof slag. This would be difficult to determine on-site due to the enormous amounts of slag. However,off-site it could manifest as unusually radioactive driveways or foundations. Fortunately, thesestudies show this is not the case.

No change necessary.

Since there is a proportional relationship between the amount of slag and radioactivity, the site itselfrepresents the largest hazard to the community; however, some areas where large amounts of slagwere incorporated into building foundations can represent a lesser threat. In particular, the residenceconstructed using "hurricane-proof" methods that incorporated slag into walls and sub-floorsrepresents an obvious potential hazard to its occupants. There is too little data and far too muchspeculation on health effects in the PHA to support the conclusion that this residence is completelysafe from slag radioactivity. Extrapolating from bomb data on the one hand, versus speculating ongranite buildings on the other hand, is poor science.

A conservative dose estimate for a maximally exposed child residing in residence #1, was lessthan half the remediation guideline of the NCRP (8).

A study has been proposed for some time that would give residents radioactivity-sensitive filmbadges to accurately gauge individual exposure. This type of study affords another opportunity toview actual exposure, and such studies have been performed in other communities where there is aquestion of exposure. This data is needed before the full conclusions of the PHA can be accepted.

Film badges would not be sensitive enough and tend to fade. The ATSDR would recommend thatany homeowner interested in measuring their individual dose obtain a Thermo-LuminescentDosimeter (TLD) from a local accredited lab.

Conclusions in the PHA addendum regarding off-site arsenic cannot yet be accepted at face value.First, the report concludes arsenic is entirely trapped in vitreous "glass-like" material and thereforebiologically unavailable. The studies authors seem to have jumped to this conclusion based on verylittle real data; to date the EPA has not provided compelling studies proving the "trapped arsenic"hypothesis. Secondly, the levels of arsenic considered toxic seem to be in debate. As far as can bedetermined, the ATSDR is deferring to the EPA, which is deferring to the State of Florida, whichseems to be unable to offer any rationale for an arsenic threshold. Based on the discussions related sofar it is doubtful if the state has a true policy regarding arsenic, and unlikely that any policy usesresidential rather than commercial exposure level scenarios. Part of the picture is certainly political.According to a literature survey, arsenic has been a byproduct of numerous mining andmanufacturing processes in Florida, as well as widely utilized in environmental control processes atgolf courses and military institutions. Clearly, the State may not want to set a precedent forresidential arsenic cleanup. Partly, the confusion over arsenic relates to its many different forms inthe environment. As an element, arsenic will never be broken down, but arsenic can exist as solublesalts that are more toxic that the sintered form thought to occur in local Tarpon Springs residentialareas.

EPA's samples of off-site slag were below health comparison values for arsenic.

There are soil extraction and toxicity tests that can answer some of the questions surrounding thesafety of off-site materials. These studies could be designed to provide the toxicity answers therebyreducing community concerns. At the public meeting presenting the off-site findings, the EPAsuggested that slag in the community be locally remediated as solid waste. This is also a logicalopportunity to cancel the threat, or perceived threat, to local residents.

The ATSDR does not feel further sampling is warranted, based on current sample results.

The most obvious shortcoming, of this health assessment is that the findings on which it is based areincomplete and standards are either absent, presented without explanation (Table 5), ignored ordismissed.

There are not always good or consistent guidelines available to make public health evaluations.The ATSDR strives to make public health evaluations of completed or potential exposures. Ifthere is no exposure possible, then there is no health risk.

Mathematical projections of radiation exposure have been made, which may or may notapproximate the actual exposure of affected individuals. This would be acceptable if there were noalternative way to collect experiential data. This is not the case, however. A sampling of affectedresidents needs to be given radioactivity-sensitive film badges to wear (over a period of time to bedetermined by the scientific community) to more accurately measure individual exposures. The localcitizens deserve to be advised on the basis of information about what exposure is actually happening,rather than OD projections that do not take into consideration the life style of the individualsinvolved. Since techniques do exist to monitor the actual accumulation of exposure to radioactivity,and since the costs associated with that technique are not outrageously high, it seems to us thatprudence would dictate that any scientist - and we assume that these results are being analyzed byscientists, not actuaries or risk managers- would not only recommend but urge that this extra step betaken to measure the actual, not the projected, exposure of the affected citizens.

Film badges would not be sensitive enough and tend to fade. The ATSDR would recommend thatany homeowner interested in measuring their individual dose obtain a Thermo-LuminescentDosimeter (TLD) from a local accredited lab.

The solubility, and thus the toxicity levels, of arsenic in offsite materials have not been investigated.The theory that arsenic is trapped and chemically/biologically unavailable is unsubstantiated. Therehave been no specific studies indicating that this is the case in any or all contaminated areas beingincluded in these generalized conclusions. Pursuant to this lack of convincing data of the solubilityof arsenic and other chemical contaminants, the questions relating to potential groundwatercontamination have gone unasked and unanswered. Wells located in any areas with significant slagneed to be tested for the contaminants of concern. The question of contaminated groundwater belowcontaminated offsite areas has been ignored.

EPA samples were leach tested for heavy metals including arsenic and the lack of measurablequantities of arsenic and other heavy metals in leachate demonstrate that the material isinsoluble and therefore not bioavailable.

There appears to be no agreement on what standards for arsenic are acceptable. While local citizenswere once led to believe that 10 -6 risk levels for arsenic were to be applied as clean-up levels (.4ppm or .8 ppm, depending on whether federal or state guidelines are referenced), this no longerseems to be the case. The PHA Draft itself makes no mention of the current disagreement overstandards, and instead lists an RMEGS Comparison Value of 20, which has the affect of minimizingthe high arsenic concentrations found, leading to the average reader's perception that the arseniclevel is substantially below "standards." While the lack of clarity and the misleading nature of theinformation in Table 5 could be construed as an attempt to confuse local citizens concerning thedegree of contamination found in the study, we must assume that there was no ill intent. We believethe problem is one of inattention to communication skills. Specifically, there is no definition andclarification of the actual meaning of the information in the "Comparison Value" column. The briefreference to this term on page 8 is not particularly enlightening or reassuring. In addition there is noinformation concerning the "commercial" and "residential" standards for the various heavy metalcontaminants. We recognize that there is disagreement between the EPA and FDEP concerningcertain standards and feel that this is of such importance that comment on the issue should haveappeared in this report.

It is true to say that there is considerable disagreement on a standard for arsenic in variousmedia. Because the ATSDR is not a regulatory body, we use media specific guidance from ourstaff of board certified toxicologists.

The Public Health Implications (page 8) contain a number of confusing and inconsistent statements.While acknowledging that both the ICRP and the NCRP recommend limiting annual exposure toexternal radiation to 100 mrem/yr above background levels, and that the annual dose to a personliving in Residence #1 could be over twice that limit, it goes on to predict that no adverse healtheffects would be expected from residing in that home. Within the space of the paragraphs, standardsare described, a case in which the contamination considerably exceeds those standards is cited, andthen the statement is made that no ill effects are anticipated. It is also stated on page 8 thatcontaminated slag does not appear to contain sufficient heavy metals to represent a public healthhazard, ignoring the fact that levels of arsenic are well over the State of Florida's acceptable levels.Thus, there appears to be an arbitrary use of standards in this document. They are invoked whenconvenient. and at ether times ignored. The PHA lists standards for radiation and arsenic in someareas of the text, and then proceeds to ignore them in the Conclusion.

The 100 mrem/yr standard is mentioned only for comparison, as the source of radiation is fromnaturally occurring radioactive materials. Naturally occurring radioactive materials areconsidered part of background, and the 100 mrem/yr standard is to protect from man-madeexposures. The NCRP (8) has recommended remediation only if the annual dose from naturallyoccurring radioactive material in building materials exceed 500 mrem/year.

How is the ATSDR able to legitimately state that no ill effects are expected when standards areviolated? It appears that the ATSDR chooses which standards to ignore and then does not give anyrationale for so doing. The words "arbitrary" and "capricious" are used in the legal and communityto describe this lack of consistency in applying applicable rules and standards.

No health guidelines have been exceeded.

This report has done very little to allay the fears of concerned residents, or to convince them thatthey are being protected.

The ATSDR has taken the following steps to explain that there is no public health threat from thelimited use of phosphate slag in buildings and roads:

  1. Met with individual homeowners on numerous occasions,
  2. Held public meetings and availability sessions,
  3. Coordinated with the EPA and the State of Florida Department of Health,
  4. Responded to numerous letters and phone calls from the press, the public and elected officials,
  5. Preparing public health education in conjunction with the State of Florida Department of Health.

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