Gene expression profiling has been used to show that the specific genes repressed or induced upon exposure to a toxic stress vary depending on the cell type and the type of toxicants to which the cells were exposed (Troester et al. 2004).
This technique permits observation of disruption induced in living mammalian cells by at least two different types of toxicants.
A scheme for simultaneous selective detection of the fluorescent signals emitted by a bacterial biosensor array, able to detect four different types of toxicants, using a single photodetector (photomultiplier) is presented.
AMG can detect only a few heavy metals, but environmental exposures usually involve different types of toxicants, often simultaneously.
This experience suggests that the multifactorial nature of the disease makes it difficult to see the effects of incremental improvements in our environment when exposures to other types of toxicants persist or even increase.
Many chemicals display more than one type of toxicity, that is, carcinogens are often immunotoxicants, and reproductive and developmental toxicants may influence many endocrine-sensitive systems.
Others measured exposure using consumption of contaminated fish or cooking oil [ 13, 26- 29], place of residence [ 30- 32], or type of occupation, as an indicator of toxicant body burden [ 31, 33].
This information can be important to the rate of toxicant removal, the type and concentration of intermediate product(s), and the identification of conditions that limit effective toxicant removal.
However, it is important to understand the types and levels of toxicants in order to appropriately address potential health effects to the population.
Most of the previous work assumed that input of toxicant was continuous.
Moreover, the concentration of toxicant will also affect the survival of microorganisms.
