Final Program - Society for Risk Analysis

for growth inhibitor use and retail cross contamination, and used Latin Hypercubesampling for uncertainty iterations. The FAO/WHO dose response model was usedfor evaluating illnesses. A fixed appropriate level of protection (ALOP) risk metricwas established as a risk of illness per serving. For each uncertainty iteration, Brent’sroot finding algorithm was used to solve for the corresponding performance objective(PO) risk metric as an allowable Listeria concentration (cfu/g) at the processingplant where regulatory monitoring would occur. Over all 240 uncertainty iterations,an uncertainty distribution of this PO was formed. Points on this distribution representthe probability that the resulting risk per serving is less than or equal to the targetALOP for a given PO. Deconvolution testing confirmed that regulatory PO settingwould have the impact expected. Assuming the most likely industry response, nodose response uncertainty, and a target ALOP of -6.38 log10 risk of illness per serving(the median of the current estimated risk of illness distribution), a plant PO of-1.74, -2.75, and -3.39 log10 cfu/g would be required for 60%, 70%, and 80% confidencerespectively that the target ALOP is not exceeded. These are all more stringentthan the current typical monitoring level -1.40 log10 cfu/g. In general, uncertaintyfrom the dose-response portion of the model and from the nature of the industryresponse dominated the uncertainty. This work highlights some of the difficulties ofthe current risk metric framework with regard to uncertainty.P.9 Gamo M, Ogura I, Kobayashi N, Ema M, Nakanishi J; masashi-gamo@aist.go.jpNational Institute of Advanced Industrial Science and Technology (AIST)RISK ASSESSMENT OF NANOMATERIALS - TITANIUM DIOXIDE(TIO2) -Nanoscale titanium dioxide (TiO2) has been used for many years for variouspurpose, particularly, as cosmetics and photocatalysts. Although TiO2 itself is consideredinactive, there is concern that nanoscale TiO2 might pose a nonnegligible riskowing to its small size and resulting high specific surface area. Since risk assessmentand proposal for acceptable exposure limits of nanomaterials including TiO2 havebeen limited, the industries that produce or use nanoscale TiO2 have been facingdifficulties in developing strategies on controlling the exposure to and resulting riskof nanoscale TiO2. As one of the outputs of the NEDO (New Energy and IndustrialTechnology Development Organization) project “Research and Development ofNanoparticle Characterization Methods - Evaluating Risks Associated with ManufacturedNanomaterials” (FY2006-2010) in Japan, we have developed a risk assessmentreport on TiO2. Considering the mechanism of action of TiO2 nanoparticles, lunginflammation was considered as a health-protective endpoint for assessing health riskin the workplace. The NOAEL determined from the inhalation experiment usingrat by Bermudez et al. (2004) was converted to the corresponding exposure concentrationfor workers, and the uncertainty factors applied were prudently determined.The acceptable exposure limit was proposed as 0.6 mg/m3 (respirable dust, 8 hoursTWA). Note that the value was set as a period-limited value from the viewpoint ofadaptive management, that is, it aims at protecting workers against subchronic exposure(approximately 15 years) and should be subjected to revision in the next 10 years.Although the risk levels in most of the workplaces where nanoscale TiO2 is handledare not significant, it is considered that installing appropriate exposure controls is necessarydepending on the type of nanoscale TiO2 and the handling processes.P.51 Georgopoulos PG, Brinkerhoff CJ, Isukapalli SS, Lioy P, Dellarco M,Landrigan P; plioy@eohsi.rutgers.eduEnvironmental & Occupational Health Sciences InstituteAN EXPOSURE INDEX ESTIMATION FRAMEWORK FOR THE NA-TIONAL CHILDREN’S STUDY (NCS)Exposure Indices (EIs) are designed to capture and summarize, in a small setof numerical values/ranges, complex distributions of potential exposures to multiplecontaminants. Typically, an EI is defined in relation to health risks associated withcommon health endpoints, and takes into account location-specific contaminant informationon multiple media and exposure pathways. The EI estimation frameworkdeveloped for the NCS is intended to support formulation and testing of specificexposure-based hypotheses, to maximize the use of databases and location-specificextant data in exposure estimation, and to rank different NCS locations in relation tothe potential for environmental exposures. The NCS EI framework utilizes an ExposureInformation System (EXIS) that has been developed by aggregating, processing,and integrating diverse extant databases containing field data on environmental,demographic, behavioral, biological, etc. attributes at the Federal, regional, State, andlocal level. Within the EXIS, these data are supplemented by estimates from numericalmodel simulations of environmental quality and population exposures. The EXIShas been designed to support and to take advantage of the MENTOR (ModelingENvironment for TOtal Risk studies) and PRoTEGE (Prioritization/Ranking ofToxic Exposures with GIS Extension) systems. Initial EI applications have focusedon inhalation exposures potentially relevant to pregnancy outcomes such as low birthweight and pre-term birth rates. This framework is demonstrated here through itsapplication (a) for the set of all counties selected for the NCS, and (b) for NCS studysegments for Queens County, NY. These applications demonstrate the feasibility ofthe EI analysis in conjunction with extant data; however, they also illustrate variouschallenges due to heterogeneities and gaps in data. Systematic analyses of these challengeswill help prioritize future information collection efforts for specific NCS studycomponents.103