Environmental toxins/chemicals

The industrial revolution brought many advances in technology it also brought increased problems with pollution and environmental toxins. Humans now live in an environment that is rich in man-made chemicals. Currently, there are more than 65,000 chemicals in common use with approximately 400 new chemicals entering the environment on a yearly basis. Not surprisingly, toxicology may assume a role of increasing importance within the realm of human health. 

Huntley, S. K., Ellis, D., Gilbert, M., Chappie, C., and Mansfield, S. D., 2003, Significant increases in pulping efficiency in C4H-F5H-transformed poplars improved chemical savings and reduced environmental toxins, J. Agric. Food Chem. 51 6178-6183. 

HBM values are derived from toxicologic and human studies and are health based (Jakubowski and Trzcinka-Ochocka 2005). Two types of HBM values exist HBM I, the concentration of an environmental toxin in human biological material below which there is no risk of adverse health effects and HBM II, the concentration above which there is an increased risk of adverse health effects in susceptible individuals in the general population (Jakubowski and Trzcinka-Ochocka 2005). An HBM I value serves as an alert level, and an HBM II value is an action level at which immediate efforts should be made to reduce exposure and further clinical examination should follow (Ewers et al. 1999). HBM values and reference values have been derived for a number of chemicals, including lead, cadmium, mercury, pentachlorophenol (PCP), and arsenic. 

One essentially unexplored area for hair analysis is its application to the investigation of environmental toxin exposure. We received a research grant during 1979 from the National Institute of Occupational Safety and Health to explore the possibility of using hair analysis for monitoring exposure to polychlorinated biphenyl compounds (PCBs). Although the analytical chemical problems of this project were successfully solved, we were unable to mount successful field studies with human subjects. 

Our negative experience in this field suggests that it may be more effective to measure environmental toxins which, in contrast to PCBs, produce measurable metabolites in hair. Since exposure to environmental toxins involves the passive endogenous and exogenous deposition of chemicals in hair, and since the latter is the predominant process, the ratio of endogenous signal/exogenous noise will be maximized more effectively if metabolites rather than the parent toxins are measured. 

See also Asbestos Biomarkers, Human Health Biomonitoring Botulinum Toxin Chemicals of Environmental Concern Ecotoxicology Epidemiology Pharmacokinet-ics/Toxicokinetics. 

Computational modeling is a powerful tool to predict toxicity of drugs and environmental toxins. However, all the in silico models, from the chemical structure-related QSAR method to the systemic PBPK models, would beneht from a second system to improve and validate their predictions. The accuracy of PBPK modeling, for example, depends on precise description of physiological mechanisms and kinetic parameters applied to the model. The PBPK method has primary limitations that it can only predict responses based on assumed mechanisms, without considerations on secondary and unexpected effects. Incomplete understanding of the biological mechanism and inappropriate simplification of the model can easily introduce errors into the PBPK predictions. In addition values of parameters required for the model are often unavailable, especially those for new drugs and environmental toxins. Thus a second validation system is critical to complement computational simulations and to provide a rational basis to improve mathematical models. 

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