Example of “Not Suitable for 

Matrix” Presentation

Kathleen Behling, SC&A, Inc.

Advisory Board on Radiation and Worker Health, 

Subcommittee for Procedure Reviews

June 21, 2023
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OCAS-TIB-009

 Rev. 0, “Estimation of Ingestion Intakes,” issued April 13, 2004

 Provides approach to estimating ingestion intakes for workers 

without bioassay monitoring data 

 Used to estimate ingestion intakes during both operational and 

residual contamination periods

 Relies on ambient air concentration measurements to estimate 

the amount of daily ingestion in the workplace
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SC&A’s review of OCAS-TIB-009

 SC&A reviewed OCAS-TIB-009 in June 2006

 SC&A identified a set of related findings that were later 

consolidated into the BRS as TIB-009 finding 1

 BRS TIB-009 finding 1: The fundamental scientific approach 

to reconstructing ingestion exposures has flaws that could lead 

to an underestimate of ingestion doses under certain 

circumstances

 SPR determined that this TIB-009 finding was an overarching 

issue, and the finding was transferred to BRS issue NIOSHOVER-0002, rev. 00, “Workplace Ingestion”
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NIOSH’s response to SC&A’s TIB-009 review

 NIOSH issued its approach to estimating ingestion intakes in a 

white paper on October 23, 2012, and presented its results at the 

November 1, 2012, SPR meeting

 NIOSH concurred that parameters used in the TIB-009 model are 

based on assumptions that have not been empirically demonstrated 

to be valid

 NIOSH agreed to revise its approach to deriving radionuclide 

ingestion rates

 NIOSH characterized SC&A’s findings into two issues: 

– Issue 1: The possible lack of an association between measured air 

concentrations in the workplace and surface contamination 

– Issue 2: The modeled transfer of the surface contamination to the GI tract 

through inadvertent ingestion
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Issue 1: NIOSH summary of SC&A findings on 

surface contamination

 Surface contamination levels are likely 

orders of magnitude higher than 

predicted by the settling velocity of 

airborne contaminants assumed at 

5 microns 

– Airborne particulates at uranium rolling 

mills likely range from a few microns to 

large or visible particles

– For larger particles, settling velocities 

increase dramatically, and there are no 

limitations for their ingestion

 Surface contamination likely builds up 

over time that may extend to weeks, 

months, or longer before reaching 

equilibrium

 NIOSH’s assumption that equilibrium is 

reached in a 24-hour period is without 

scientific basis and highly unconservative

 For select processes, surface 

contamination may not be the result of 

settling, but may include:

– liquid spills

– results from milling, grinding, cutting, 

welding, etc.
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NIOSH on issue 1: Relationship between air 

and surface contamination levels

 NIOSH analyzed air and smear sampling from:

– Simonds Saw and Bethlehem Steel uranium rolling operations

– Superior Steel during a test rolling

– Vitro Manufacturing (~240 air samples and 150 contamination smears)

 Paired data were plotted and showed measured surface 

contamination levels are proportional to air contamination

 Linear regression analysis showed estimated level of surface 

contamination (dpm/m2) equals 116.7 times measured air 

concentration (dpm/m3)
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Issue 2: NIOSH summary of SC&A findings on 

modeled transfer

 The modeled transfer of 

surface contaminations to the 

mouth that assumes a 10% 

transfer from the surface area 

of one hand during a full 

workday appears unrealistic

 In a hot and dusty work 

environment, a radiologically 

uninformed or untrained worker 

is likely to contact or wipe their 

face with both hands 

repeatedly over the course of a 

full workday

 Ingestion may involve other 

modes of intake, such as direct 

deposition on lips, smoking of 

cigarettes, etc.
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NIOSH on issue 2: Determine daily ingestion 

rate for loose surface contamination

 NRC computer program RESRAD-BUILD has an ingestion 

parameter based on an extensive review and analysis of the 

literature

 In this model, the hourly ingestion rate (dpm/h) equals the surface 

contamination measured in the workplace (dpm/m2) times effective 

transfer rate for ingestion of removable contamination (m2/h)

 NUREG/CR-5512, volume 3, considered the average value of 

1.1×10-4 m2/hr (corresponding to an ingestion of about 0.5 mg/day) 

to represent the default ingestion transfer rate

 Corresponding ingestion rate for an 8-hour workday would be 

8.8×10-4 m2/d
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Relationship between air concentration and

surface contamination, and default daily ingestion

Using the NIOSH-derived surface contamination level and 

NUREG/CR-5512 default ingestion value results in the following 

equation:

Id = 116.7 × Am

× GO

Id = 0.103 × Am

where Id = the daily ingestion of loose radioactive material in dpm/d

Am = the measured air concentration in the workplace in

dpm/m3

GO = the NUREG/CR-5512 default for ingestion in the 

workplace in m2/d = 8.8×10-4 m2/d
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TIB-009 guidance 

TIB-009 recommends estimating daily ingestion intake using the 

following relationship:

Id = 0.2 × Am

where Id = the daily ingestion rate in dpm/d

Am = the measured air concentration in the workplace in

dpm/m3
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NIOSH conclusion on TIB-009 guidance

 Using empirical data and mean value for GO (slide 9 equation), 

ingestion intakes are predicted that are approximately half those 

using the TIB-009 approach

 Even though parameters and assumptions used in TIB-009 were 

somewhat simplistic, the model produces estimates of ingestion that 

are in reasonable agreement with the NUREG predictions 

 It should also be considered that the 20% multiplier used in TIB-009 

includes an ingestion source term for a contaminated beverage or 

food item, which was not considered in the development of GO in 

the NUREG 

 Given the uncertainty inherent in these values, it is not 

unreasonable for NIOSH to continue using the TIB-009 approach for 

estimating intakes
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Additional NIOSH ingestion considerations

 Under the TIB-009 approach, ingestion will always be a fraction of the 

inhalation exposure (1 dpm/m3 of air activity results in daily inhalation and 

ingestion exposures of 9.6 dpm and 0.2 dpm/day, respectively)

 For uranium intakes, the uptake across the gastrointestinal tract is low 

 The ingestion pathway contributes less than 0.6% to the dose for soft 

tissues under all solubility types 

 The maximum contribution for ingestion would be to organs of the 

gastrointestinal tract

 For these organs, the highest contribution to a dose is 3.4% for lower 

large intestine when insoluble material (type S) is inhaled

 Additionally, NIOSH applies a geometric standard deviation associated 

with ingestion that has a minimum value of 3 and in some cases 5
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NIOSH on using TIB-009 guidance for 

residual period

 It was discovered TIB-009 has been improperly applied during the residual period at 

Dupont Deepwater Works and other sites

 After the cessation of AEC activities, it is inappropriate to use a resuspension factor to 

estimate an air concentration and then multiply that value by 0.2 to calculate a daily 

ingestion intake

– The reason is that the relationship between air concentration and surface activity in TIB-009 

assumes an active source or process is generating the airborne activity

– Airborne activity predicted using a resuspension factor (e.g., 1 x10-6/m) would grossly 

underrepresent the airborne activity that actually deposited the surface contamination 

 To apply TIB-009 during residual periods, air concentration on the first day of the residual 

contamination period should be equal to that present during the end of operations

 Ingestion can then be decreased over time using ORAUT-OTIB-0070 source depletion 

techniques

 NIOSH will comprehensively review estimation of ingestion during the residual 

contamination period at all sites and issue PERs as appropriate
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SC&A’s response to NIOSH’s TIB-009 ingestion 

assessment

November 1, 2012, SPR meeting: SC&A identified:

 Majority of data on inadvertent ingestion from hand-to-mouth 

behavior are in residential setting and may not represent industrial 

environment

 Data in NUREG/CR-5512 and RESRAD came from Pacific 

Northwest Laboratory and represent one set of data

 An independent EPA study on World Trade Center (WTC) workers 

used a model for transferring pesticides hand to mouth

– EPA study found on soft surfaces ingestion was 2.25 cm2/hr, which agrees 

with NIOSH

– EPA’s hard surface values were 11.25 cm2/hr
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NIOSH’s response to WTC study

January 4, 2013: NIOSH provided an email response to WTC study:

 EPA document was developed to identify contaminants of primary 

health concern in support of planned residential cleanup efforts 

 EPA’s methodology is oriented toward the screening analysis of 

exposures to residents living in the vicinity of the WTC and not 

toward the quantification of exposure to WTC cleanup workers

 Considering this, DCAS believes that the occupational ingestion 

parameters in the RESRAD program remain the best set of data 

from which to estimate ingestion exposures under EEOICPA
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Closure of BRS finding 1 for TIB-009 and 

OVER-0002

 SC&A concluded:

– Considering (1) the differences between the WTC study and TIB-009 

and (2) all the uncertainties involved, the amount of agreement 

between the hand-to-mouth effective transfer rates is reasonable

– Difference in hand-to-mouth ingestion model between workers and 

residents is due to exposure durations assumed, not the effective 

transfer rates

• e.g., a worker duration might be 8 hr/day, 250 days/year, and 20 years, while a 

resident’s duration might be 12 hr/day, 365 days/year, and 30 years

 SC&A therefore recommended closure

 Considering all discussions, SPR closed TIB-009 and OVER0002 finding 1 at the February 5, 2013, meeting
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Discussion on presentation approach