Exposure reconstruction

Montgomery, J., P. Budd, A. Cox, P. Krause, and R.G. Thomas. 1999. LA-ICP-MS evidence for the distribution of Pb and Sr in Romano-British medieval and modem human teeth imphcations for life history and exposure reconstruction. In Metals in Antiquity Proceedings ofthe International Symposium. S.M.M. Young, A.M. Pollard, P. Budd, and R.A. Ixer (eds.). Oxford Archaeopress. 

EXPOSURE RECONSTRUCTION AND CANCER RISK ESTIMATE DERIVATION... 

This chapter consists of two primary sections. The first section presents a framework or methodology for reconstructing exposures of interest, which can then be used to produce exposure estimates appropriate for conducting cancer risk assessments. The second section discusses the application of reconstructed exposures to the determination of dose estimates and cancer potency. Although the methods discussed here can be used in both occupational and nonoccupational exposure scenarios, the focus of this chapter is primarily on occupational exposure reconstruction methods. 

When preparing to conduct an exposure reconstruction, data organization is critical, particularly for reconstructions that potentially involve hundreds or perhaps... 

Data gaps can often be addressed by using a combination of exposure reconstruction techniques simultaneously this approach is common, and there are many examples of it in the peer-reviewed literature. A number of these studies are discussed and compared below. The use of a combination of methods may also be the most effective approach for exposure reconstruction for a particular scenario, given a unique dataset with certain robust elements and otho- relatively weak elements. Uncertainty analyses, such as a Monte Carlo statistical assessment, can also be used to address data gaps generated by uncertainty in existing data or information, as well as to increase the likelihood that true exposures are captured (Cohen Hubal et al. 

The appropriate selection of a method for reconstruction and estimation is extremely important, whether for an exposure assessment, risk assessment, or epidemiological study. Some of the factors affecting the selection of an exposure reconstruction method include the characteristics of the outcome of interest (such as carcinogenic latency and dose of concern) the effectiveness of analytical methods to identify and measure the substance of interest (such as ability to distinguish from similar substances or interferences caused by mixtures of substances) and the consideration of exposures by multiple routes, including inhalation and dermal exposures. 

Use of Exposure Data Matrices to Reconstruct Exposures. Exposure data or job exposure matrices have been used since the 1940s, and continue to be a valuable method for exposure reconstruction (Coughlin and Chiazze 1990). A job exposure matrix (JEM) aims to incorporate aU somces of available data in order to link information about job categories and likely exposures (Coughlin and Chiazze 1990). The types of information used in a JEM, if available, include exposure data, current data combined wilh otho- information extrapolated to previous job tasks or working conditions, exposure time durations, job titles, work locations or... 

Qualitative Estimation Methods. Qualitative techniques have also been used to conduct or refine exposure reconstructions. The use of exposure determinants to classify exposures is a technique that has been performed qualitatively in some cases based on available data. Other qualitative techniques can include the use of expert or professional judgment and self-reported exposures. While self-reported exposures have been found to be convenient and helpful when no other exposure information is available, the method has been shown in at least one validation study to be inadequate for use as the sole data source in an exposure reconstruction. When self-reported exposures have been compared to professional judgments by experts, they have been found to have high specificity but low sensitivity (Fritschi et al. 1996). 

Process analysis and modeling based exposure reconstruction were used to augment, extrapolate, or interpolate available exposure data Comprehensive process analysis and modeling estimates... 

TABLE 30.8. Selected Examples of Exposure Reconstruction Studies Using Monte Carlo Analysis in the Peer Reviewed Literature... 

Regardless of the chosen exposure reconstruction method, it is important to document the exposure estimation process, and, whenever possible, evaluate any uncertainties inherent in the selected methodology and the results obtained using Monte Carlo or a similar technique (Benke et al. 2001 Stewart et al. 1996, 2003). Uncertainty analysis techniques are increasingly common in exposure reconstruction, and can be critical to understanding the variability and uncertainty in the estimates generated. 

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