Integrated biomarker response

Figure 7.1 Integrative biomarker index as star plots. The integrated biomarker response is obtained from the sum of areas of each biomarker in the test battery. For the spatial survey, it can be observed that sites 1 and 4 are more stressed or affected than the other sites. The general response of biomarkers can be appraised in temporal settings where changes are observed between sites over time.

Beliaeff, B. and Burgeot, T. (2002) Integrated biomarker response a useful tool for ecological risk assessment. Environ. Toxicol. Chem., 21, 1316-1322. 

It is noteworthy that the styrene reference concentration (RfC) in the Integrated Risk Information System is based on the biomarker-response relationship found in workers (Mutti et al. 1984 EPA 1998). The Environmental Protection Agency (EPA) used the relationship of urinary biomarker to ambient-air concentration of workers to develop an RfC that was adjusted for the difference in exposure time between the workplace and the general population. That is a valid approach because it derives a workplace concentration-toxicity relationship in workers, which can then be adjusted for the general population to account for differences in exposure time and can take uncertainty factors into account. It is different from direct adjustment of the styrene BEI to evaluate human population biomonitoring data on styrene metabolites in urine, which would have the uncertainties described above and in Chapter 5. 

Biosensors Analytical devices that incorporate biological material or a material mimicking biological membranes associated with or integrated within a physical-chemical transducer or transducing system. Biosensors are based on biochemical biomarker responses at the suborganism level. 

An important characteristic of biomarkers is that they indicate that a contaminant (or contaminants) is (are) present in the environment, that it is biologically available, and that it has reached a target tissue in sufficient quantity and duration as to elicit the observed response (Melancon 2003). In addition, because most organisms are exposed to multiple stressors over time, biomarkers can reflect an integrated exposure of cumulative, synergistic, or antagonistic effects (Adams and Rowland 2003). 

Biomarkers of exposure are an indicator of absorbed dose and may present unique advantages in exposure assessment. Biomarkers demonstrate that internal exposure has occurred and can be used to estimate chemical uptake over time and help establish the relationship between exposure and effect. They are apical in nature, in that they account for and integrate over all sources of exposure. Specifically in relation to potentially sensitive subpopulations like children, biomarkers may be able to identify increased absorption or biological response in comparison with the general population. Biomarker data alone cannot be used to establish source and route of exposure and are limited in providing information on frequency, duration, and intensity. Moreover, metabolism of any chemical... 

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