Metabolic measures, biological monitoring

Besides alkylphosphates, OP metabolism gives rise to the production of other metabolites that can be used as exposure markers (Table 4). Unchanged OP compounds in blood or urine can also be measured to confirm exposure (Table 4), but this method is of limited use for routine biological monitoring of occupational exposure, as OP compounds are rapidly excreted in urine. Moreover, most OP pesticides are unstable, and, with a few exceptions, they are not detectable in biological specimens after a few hours. So far, the measurement of unchanged compounds in biological fluids has been performed primarily for research purposes and has limited practical applicability. 

Aniline is rapidly and extensively metabolized following oral administration. In the pig and sheep, approximately 30% of a 50-mg/kg dose of 14C-labeled aniline was excreted in the urine, as measured by 14C activity, within 3 h after administration, whereas approximately 50% of the dose was excreted in rats. Within 24 h, more than half the administered dose was excreted by pigs and sheep and 96% of the dose was excreted by rats. Fecal radioactivity was low. A-acetylated metabolites accounted for most of the excretion—/V-acetyl-/>-aminophenyl glucuronide being the primary metabolite in sheep and pig urine and /V-acetyl-/>-aminophenyl sulfate being the primary metabolite in the rat (Kao et al. 1978). Biologic monitoring of workers exposed to aniline showed that /i-aminophenol constituted 15-55% of the parent compound in the urine the o- and ra-isomers were also formed (Piotrowski 1984). 

Biological monitoring for exposure to phenol is possible by measuring blood or urine levels of the parent compound. However, it should be noted that phenol and metabolites of phenol may also come from other sources. For example, phenol is a metabolite of benzene and of protein metabolism. Urine samples taken from male workers employed in the distillation of high-temperature phenolic fractions of tar revealed a phenol excretion rate of 4.20 mg/hour compared to a control rate of 0.53 mg/hour for non-exposed workers (Bieniek 1994). Samples were taken 4 hours into the workers workday, but the worker exposure levels were not reported. 

Although it would seem reasonable to apply the electronic noses for measuring biological variables such as metabolic products and microbial activity, only a limited number of studies have been described. Of these, the following can be mentioned detection of infection bacteria activity in ulcers [10], microbial contamination in meat [11], classification of microbial strains [12,13], and monitoring of bioreactors [ 14]. 

Biological monitoring for recent, as opposed to more remote, exposure to tetrachloroethylene has also been performed by measuring concentrations of tetrachloroethylene and its principal metabolite, TCA, in blood and urine. However, TCA is not specific fortetrachloroethylene because it is also produced from the metabolism of trichloroethylene and 1,1,1-trichloroethane (Monster 1988). In a study of occupationally exposed individuals, measurements of tetrachloroethylene and TCA in the blood 15-30 minutes after the end of the workday at the end of the week were judged to be the best parameters for estimating exposure to the chemical. The best noninvasive method for determining tetrachloroethylene exposure was to measure the concentration of the parent compound in exhaled air. After exposure to a... 

Biological monitoring under the standard must be provided at least every 2 months for the first 6 months and every 6 months thereafter until your blood lead level is below 40 ng/dl. A zinc protoporphyrin (ZPP) test is a very useful blood test which measures an adverse metabolic effect of lead on your body and is therefore an indicator of lead toxicity. 

The biological monitoring of lead exposure in paediatric and adult human populations has usually involved one of two approaches (1) measurement of the internal or systemic dose of lead itself in some indicator medium, or (2) quantification of some subcritical effect of lead. The extent to which biological monitoring in humans accurately states both exposure risk and relative health risk remains the subject of much research. Of particular interest are (1) the biokinetic characteristics of the common indicators of exposure, (2) the development and use of kinetic models of lead metabolism, and (3) the relative merits of the use of biological effect indicators versus measurement of the toxicant in some medium. 

Each situation requires an evaluation of the hypotheses to be tested before the personal monitor can be designed and the identification of the types and duration of exposure that may occur. Once inhaled, the compound may be rapidly metabolized in the body short-term measurements would be appropriate for such processes. The compound may instead have a long residence time at a specific site in the lung or may be stored in an organ or tissue. Thus, the inhaled compound or one or more of its adducts or metabolites could eventually deliver a biologically effective dose to a target organ or cell (13). The monitor must be developed with consideration of the... 

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