Humans, monitoring exposure

It is difficult to assess human exposure to pesticides. Several studies have measured pesticide residues in human fat (MAFF, 1995) or human milk (MAFF, 1997), as both matrices are good indicators of long-term exposure, but they tell little of the subject s exposure to short-lived pesticides such as the OPs or pyrethroids. 

In a MAFF study (MAFF, 1995) of pesticides in human fat in the UK, 99% of samples analysed (n = 203) had detectable residues of DDT (as p,p -DDT, o,p-DDT, p,p -TDE and/or p,p -DDE). Since the fat samples were taken at routine autopsy, it is likely that most of the subjects were at least 70 years old and therefore had lived through times when DDT was permitted in the UK. Their residues reflect their lifetime exposure. Twenty-three per cent of the subjects had DDT fat residues between 1 and 9.3 mg.kg 1 which suggests higher exposures. These people might have been exposed directly during DDT s heyday, or might have been fond of oily fish which contains higher residues of OCs than most other foods. 

In the same MAFF study other long half-life OCs were also found in human fat (Table 10.7). Again these residues are indicative of the subjects lifetime exposures to these pesticides rather than indicating recent exposure. It is interesting that the shortest environmental half-life OC, namely lindane, has the lowest human fat residue frequency. 

Levels of pesticide residues in human milk from women from different countries give an indication of exposure to pesticides in their respective countries (Table 10.8). For example, in the USA, p,p -DDT was found at 0.039 mg.kg 1 (Mattison et al., 1992) in human milk, whereas in milk from women in Faridkot in India a 

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A Computerized Bibliographic Literature Information System for Total Human Exposure Monitoring Research... 

Vahter, M. and Friberg, L. (1988) Quality control in integrated human exposure monitoring of lead and cadmium, Fresenius J. Anal. Chem. 332, 726. 

Human exposure to environmental contaminants has been investigated through the analysis of adipose tissue, breast milk, blood and the monitoring of faecal and urinary excretion levels. However, while levels of persistent contaminants in human milk, for example, are extensively monitored, very little is known about foetal exposure to xenobiotics because the concentrations of persistent compounds in blood and trans-placental transmission are less well studied. Also, more information is needed in general about the behaviour of endocrine disruptive compounds (and their metabolites) in vivo, for example the way they bind to blood plasma proteins. 

Human exposure to radiation is monitored by reporting the absorbed dose and... 

Reliable evaluation of the potential for human exposure to endosulfan depends in part on the reliability of supporting analytical data from environmental samples and biological specimens. In reviewing data on endosulfan levels monitored or estimated in the environment, it should also be noted that the amount of chemical identified analytically is not necessarily equivalent to the amount that is bioavailable. 

Exposure Levels in Humans. This information is necessary for assessing the need to conduct health studies on these populations. Trichloroethylene has been detected in human body fluids such as blood (Brugnone et al. 1994 Skender et al. 1994) and breast milk (Pellizzari et al. 1982). Most of the monitoring data have come from occupational studies of specific worker populations exposed to trichloroethylene. More information on exposure levels for populations living in the vicinity of hazardous waste sites is needed for estimating human exposure. 

Vahter M (1982) Assessment of human exposure to lead and cadmium through biological monitoring. Natl Swed Inst Environ Med, Stockholm. 

Table 4 Other Biomarkers Used in Biological Monitoring of Human Exposure to Organophosphates...

Unchanged compounds or metabolites in blood and urine can be used to monitor human exposure to some carbamates. Table 5 shows some biological indices of internal dose used to monitor carbamate exposure. Urine carbamate metabolites may provide a good estimate of the internal dose because the half-life of most compounds is very short, samples collected soon after the end of the exposure are preferable for analysis (WHO, 1986). 

Dithiocarbamates are chemically characterized by the presence of metals in the molecule (iron, manganese, zinc, etc.) therefore, the measurement of these metals in urine has been proposed as an alternative approach to monitor exposure. For instance, increased urinary excretion of manganese has been reported in workers exposed to mancozeb (Canossa et al., 1993). Available data are at present insufficient to confirm the possibility of using metals as biomarkers of human exposure to DTC. 

Catenacci, G., Barbieri, F., Bersani, M., Ferioli, A., Cottica, D., and Maroni, M. (1993) Biological monitoring of human exposure to atrazine, Toxicology Letters, 69 217-222. 

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