less data are available about the possible effects of drugs on levels of biological indicators. It has been shown that aspirin can interfere with the trans-duction in xylene methylhippuric acid, and the fenilsa-salicylate, a drug widely used as an analgesic, can significantly increase urinary levels of phenol. The use of aluminum antacids can increase plasma and urinary levels of this metal. It
marked differences were observed in different ethnic groups in the metabolism of widely used solvents such as toluene, xylene, Trichloroethylene, Tetrachloroethylene and methyl chloroform.
acquired pathologic states can alter the levels of biological indicators. The critical organ can behav-ate coverage anomalous with respect to biological control tests, due both to the specific action of the toxic agent as other reasons. An example of the first type of situation is the behavior of urinary levels of cadmium, when a tubular disease caused by cadmium, urinary excretion is greatly increased and the levels of proof no longer reflect the degree of exposure. An example of the second type of situation is the increased levels of erythrocyte protoporphyrin cite observed in subjects with iron deficiency and no abnormal absorption of lead. Physiological Changes
biological media urine eg, based on measurements of biological indicators, can modify the values \u200b\u200bof the test. For practical purposes, it is only possible to obtain spot samples of urine of individuals at work, and since the density of these samples can vary, it means that indicator levels may fluctuate widely in the course of a day.
To overcome this difficulty is advisable to remove the samples after excessively diluted or concentrated, depending on values \u200b\u200bof specific gravity or creatinine selected. In particular, it must dispose of urine relative density less than or greater
1,010 to 1,030, or with creatinine levels below 0.5 g / l or greater than 3.0 g / l. Several authors also propose to adjust the values \u200b\u200bof the indicators according to the relative density or express these values \u200b\u200baccording to urinary creatinine content.
pathological changes in biological media also significantly affect the values \u200b\u200bof the biological-cal. For example, anemic subjects exposed to
metals (mercury, cadmium, lead, etc.) blood levels of the metal can be lower than would be expected according to the exhibition, this is due to the low number of red blood cells to transport existing the toxic metal into the bloodstream.
Therefore, when the determination of toxic substances or its metabolites bound to erythrocytes in whole blood are made, it is always advisable to determine the hematocrit, which provides a measure of the percentage of blood cells in whole blood.
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