DNA testing for chemical exposure

24 September 2007

The BBC has reported that a new type of DNA testing “may help prove if people have had their health damaged by exposure to chemicals” (see BBC news). The technique, known as msds1™, involves exposure of DNA samples from a healthy control to the chemicals in question. A distinctive pattern of gene expression, based on which genes or are up-regulated or down-regulated in response to the chemical of interest, is produced and compared with the gene expression profile of the subject under investigation. Certain ‘molecular signatures’ of exposure to specific chemicals or toxins are used to exclude or prove past exposure to the substance or substances of interest. In some cases proteomic profiling (looking at patterns of protein production, as opposed to gene expression) may also be used. The tests have been developed using multiple control individuals of different gender and ethnicity.

The company that developed the test in association with the University of Illinois, The Cytokine Institute, says that this microarray-based technology can: “determine how human cells and their individual DNA respond when exposed to a chemical and its metabolites. By analyzing gene expression and how 36,000 parameters of an individual’s DNA are affected by specific chemical exposures—such as benzene or asbestos—this technology can determine with 99.9% certainty if a person was injuriously exposed to a particular toxin, thereby offering an impartial methodology for providing scientifically-based evidence” (see press release).

The technology is being marketed for use in employee compensation claims for health problems allegedly caused by chemical exposure in the workplace.  It has reportedly been endorsed by the American Bar Association (see Insurance Times article) and admitted as evidence, for both prosecution and defence, in more than twenty legal cases.

Assuming that it is sufficiently rigorous in its ability to discern whether or not cells have been exposed to particular environmental toxins, the test could be a useful evidentiary tool with which to demonstrate chemical exposure and support assertions regarding the potential impact of this exposure on the claimant.  As a health and safety measure, it might also be used to monitor chemicals in the workplace in a manner similar to the current monitoring of employees who handle radioactive substances.  However, in spite of its potential admissibility for certain purposes, the test does not provide conclusive evidence of the timeframe within which the exposure occurred, or that the molecular change correlated with the exposure was a causative factor in the complainant’s health problem.

This test provides an example of one of the wider potential applications of emerging genomic technologies, although it appears to have been developed using cells taken from healthy controls that were subsequently exposed to particular chemicals; the gene expression profiles were then compared with those from test subjects. It is questionable whether experimental exposure of isolated cells is truly comparable with past exposure of cells in the context of a human body, in terms of the resulting gene expression profiles. Ultimately, though, with greater understanding of the highly elaborate interactions in the human body in health and disease, at systemic, cellular and molecular levels, such tests could be used for a range of purposes, including monitoring disease processes and therapeutic effects.

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