Factors that contribute to biomarker responses in humans including a studyin individuals taking Vitamin C supplementation

It is possible in many situations to identify humans exposed to potentially toxic materials in the workplace and in the environment. As in most human studies, there tends to be a high degree of interindividual variability in response to chemical insults. Some non-exposed control individuals exhibit as high a level of damage as some exposed individuals and some of these hav e levels of damage as low as many of the controls. Thus, it is only the mea n values of the groups that can substantiate an exposure-related problem; t he data on an individual basis are still of limited use. While human lympho cytes remain the most popular cell type for monitoring purposes, sperm, buc cal, nasal, epithelial and placental cells are also used. However, for inte rpretation of responses, the issue of confounding factors must be addressed . There are endogenous confounding factors, such as age, gender, and geneti c make-up and exogenous ones, including lifestyle habits (smoking, drinking , etc.) There are biomarkers of exposure, effect/response and susceptibilit y and the last may be influenced by the genotype and polymorphism genes exi sting in a population. From our own studies. confounding effects on cytogen etic damage and ras oncoproteins will be considered in relation to workers exposed to vinyl chloride and petroleum emissions and to volunteers taking Vitamin C supplementation. Smoking history, exposure and duration of employ ment affected the worker studies. For petroleum emissions, so did gender an d season of exposure. For the non-smoking volunteer Vitamin C supplementati on study, cholesterol levels, plasma Vitamin C levels, lipid peroxidation p roducts and DNA damage in the Comet assay were also measured. Gender affect ed differences in Vitamin C levels, antioxidant capacity and the number of chromosome aberrations induced by bleomycin challenge in vitro. The results were the same for both high and low cholesterol subjects. The relationship between biomarkers and the various factors which affect them is complex. S ometimes the variables are not completely independent of each other. (C) 20 01 Elsevier Science B.V. All rights reserved.