Respiratory exposure estimation

The collection of air samples using air tubes and/or filters is of value during the course of the field research when performing SDDBM studies. The air tube/air filter data can be used to estimate the portion of the total body burden, which originates from respiratory exposure to the active ingredient. Of course, if an organic vapor respirator is used by the worker as a matter of course, the respiratory exposure component should be backed out of the final exposure calculation. 

In a report comparing community responses to low-level exposure to a mixture of air pollutants from pulp mills, Jaakkola et al. (1990) reported significant differences in respiratory symptoms between polluted and unpolluted communities. The pollutant mixture associated with the pulp mills included particulates, sulfur dioxide, and a series of malodorous sulfur compounds. Major contributors in the latter mixture include hydrogen sulfide, methyl mercaptan, and methyl sulfides. In this study the responses of populations from three communities were compared, a nonpolluted community, a moderately polluted community, and a severely polluted community. Initial exposure estimates were derived from dispersion modeling these estimates were subsequently confirmed with measurements taken from monitoring stations located in the two polluted communities. These measurements indicated that both the mean and the maximum 4-hour concentrations of hydrogen sulfide were higher in the more severely polluted community (4 and 56 g/m3 2.9 and 40 ppb) than in the moderately polluted one (2 and 22 g/m3 1.4 and 16 ppb). Particulate measurements made concurrently, and sulfur dioxide measurements made subsequently, showed a similar difference in the concentrations of these two pollutants between the two polluted communities. 

Actual exposure of the hands was reduced by approximately 95% and 87% for applicators and harvesters, respectively, wearing gloves. Respiratory exposure did not differ significantly between the two trials and was estimated to contribute approximately 4% to the excreted amount of metabolite in urine. Median IPP excretion was reduced 42% and 38% for applicators and harvesters, respectively. IPP excretion of the harvesters was strongly correlated with... 

The total respiratory exposure (RE) during the application or harvesting period was estimated using the following equation ... 

The internal dose of propoxur was measured by assessing the total amount of 2-isopropoxyphenol (IPP) excreted in the urine, collected over a period of 24 hr from the start of exposure, and described in detail in previous studies (Brouwer et al., 1993 Meuling et al., 1991). Volunteer kinetics studies revealed a one-to-one relationship of absorbed propoxur and excreted IPP on a mole basis. Based on the results by Machemer et al. (1982), a pulmonary retention of 40% was used to calculate the relative contribution of the respiratory exposure to the internal exposure. To estimate the contribution of the dermal exposure, the calculated respiratory portion was subtracted from the total amount of IPP excreted in urine. 

In addition to its presence in the ambient atmosphere, diazinon also has been monitored in both outdoor and indoor air associated with its use in a variety of domestic, commercial, and occupational exposure situations. Exposure to diazinon from its use in lawn and home garden applications was evaluated by Davis et al. (1983). Diazinon was mixed with water and sprayed using compressed air sprayers or hose-end sprayers, and potential respiratory and dermal exposures were estimated from residues collected from respirator filters, body pads, and hand rinsings. These authors reported mean respiratory exposures of 1.9,... 

Estimation of Respiratory Exposure 23 Estimation of Dermal Exposure 23 Surrogate Skin Techniques 23 Chemical Removal Techniques 25 Fluorescent Tracer Techniques 27 Estimation of Exposure to Children in the Home 27 Biological Monitoring 28... 

Whatever their design, passive samplers will collect only pesticide vapors. Therefore, air measurements made with them will not always be appropriate for estimating total respiratory exposure, especially in the case of low-volatility pesticides and pesticides tracked indoors on soil particles. In addition, some pesticides may undergo chemical degradation on sorbents or in solvents over such long sampling periods. Therefore, internal standards or other means will need to be used to assure acceptable analyte recoveries. 

Table 3-1 and Figure 3-1 also show that signifrcantly increased mortality rates associated with asbestosis or other nonmalignant respiratory disease have been reported in groups of exposed workers with cumulative exposure estimates ranging from 32 to 1,271 f-yr/mL (Albin et al. 1996 Brown et al. 1994 Case and Dufresne 1997 de Klerk et al. 1991 Dement et al. 1994 Finkelstein 1983 Henderson and Enterline 1979 Hughes et al. 1987 Liddell et al. 1997 Nicholson et al. 1979 Peto et al. 1985 Sluis-Cremer 1991). 

Smith, T. J., Hammond, S. K., Laidlaw, R, and Fine, S. (1984). Respiratory exposures associated with silicon carbide production Estimation of cumulative exposures for an epidemiological study. Br J Ind Med 41, 100-108. 

These exposure estimates [for benzo[a]pyrene] and the determinations of the tumorigenic potential of [polycyclic aromatic hydrocarbons] in bioassays strongly suggest that [polycyclic aromatic hydrocarbons] play a significant role in the induction of respiratory tract cancer in smokers... 

The experimental design for respiratory exposure necessarily depends on several assumptions and disparate pieces of available data. The excretion kinetics of the pesticide employed must be known. If the total dose is excreted by small animals in 24-48 hr., the same may also be true of humans, and a simple experimental design may suffice. If the dose Is excreted over a period of a week, a simple design correlating dose with the Immediate effect on urine will not correctly assess respiratory exposure. The difficulty with longer sampling periods, occasioned by longer excretion kinetics, derives from the variation normally observed in the urinary exposure estimation for field experiments. It Is not... 

Table II. Mean Estimated Respiratory Exposure for Three Pesticides...

Toxicity of 2-Ghloroethanol. Ethylene chlorohydrin is an irritant and is toxic to the Hver, kidneys, and central nervous system. In addition, it is rapidly absorbed through the skin (73). The vapor is not sufficiently irritating to the eyes and respiratory mucous membranes to prevent serious systemic poisoning. Contact of the Hquid in the eyes of rabbits causes moderately severe injury, but in humans corneal bums have been known to heal within 48 hours. Several human fataUties have resulted from inhalation, dermal contact, or ingestion. One fatahty was caused by exposure to an estimated 300 ppm in air for 2.25 hours. In another fatal case, autopsy revealed pulmonary edema and damage to the Hver, kidneys, and brain (73). 

Hawthorne, A., et al. (1987) Models for estimating organic emissions from building materials formaldehyde example. Atmos. Environ. 21, No. 2. Lewis, R. G., et al. (1986) Monitoring for non-occupational exposure to pesticides in indoor and personal respiratory air. Presented at the 79th Annual Meeting of the Air Pollution Control Association, Minneapolis, MN. 

One of six workers died 12 days after exposure to a mixture of half dimethyltin dichloride and half trimeth-yltin chloride vapour during cleaning of a cauldron at a chemical plant in Germany in 1981. Maximum exposure time was 1.5 h over a 3-day period no estimates of exposure concentration were made. Symptoms preceding death included excretion of high levels of tin in the urine, respiratory depression, and coma (Rey et al.,... 

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