Total respiratory exposure

This final value in terms of pg/kg body weight per day is the total respiratory exposure (TRE). 

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

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. 

Hand Exposure (% of total) Respiratory Exposure (% of total)... 

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. 

Calculations of total respiratory and dermal exposure as well as calculation of chlorpyrifos body burden from urine data... 

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. 

Table 3 Total Actual Dermal and Respiratory Exposure Results for 15 Operators Using Tractor-Drawn Sprayers...

Table 3 Range, Median, GM, and GSD of Assessed Total Dermal and Respiratory Exposure to Thiophanate-Methyl and Methiocarb...

Following a single 70-minute inhalation exposure of rats to green nickel oxide ( NiO 9.9 mg nickel/rrf AMAD 1.3 pm), the fraction of the inhaled material deposited in the total respiratory tract was 0.13, with 0.08 deposited in the upper respiratory tract and 0.05 deposited in the lower respiratory tract (Benson et al. 1994). During the 180 days postexposure, nickel was not detected in extrarespiratory tract tissues. Following a single 120-minute inhalation exposure of rats to nickel subsulfide ( Ni3S2 ... 

Davis et al. (1983) reported that dermal exposure to diazinon from spray applications of the compound for home and garden applications ranged from 5,700 to 29,000 pg/hour depending on the type of sprayer used. The mean respiratory exposures ranging from 1.9 to 7.4 pg/hour, were negligible compared to the dermal exposures. In addition, these authors reported that dermal exposure of the hands, which accounted for 85% or more of the total dermal exposure, could be easily reduced by the use of protective gloves. 

Egle (1972) exposed anesthetized dogs to concentrations of acrolein between 172 and 262 ppm for a brief period of time (1-3 minutes) and observed that acrolein uptake by the total respiratory tract at ventilatory rates of 6-20 respirations/minute averaged 80-85% of the inhaled dose. Retention was independent of the respiratory rate. The author estimated that only about 20% of the inhaled dose reached the lower respiratory tract. Exposure of the lower respiratory tract alone resulted in 65-70% concentration-independent retention, but decreased slightly with increases in tidal volume from 100 to 160 mL. Although the study by Egle (1972) does not provide information on the disposition of the retained acrolein or on whether the uptake rates represent steady-state values, it indicates that... 

Murphy et al. (3A17) reported that exposure of guinea pigs to low concentrations of acrolein (propenal) resulted in an increase in total respiratory flow resistance plus decreased respiratory rates and increased tidal volume. 

Respiratory exposure was assessed with personnel-type air samplers (see Table 5-2). Total dermal exposure to applicators to chlordane was 2.5 pg/kg/hour. The most exposed body regions in descending order were hands, forearms, head, lower legs, thighs, back trunk, front trunk, upper arms, and back neck. Approximately 25% of the clordane on the exterior surface of clothing was likely to penetrate through the fabric. Respiratory exposure was 0.04 pg/kg/hour. 

Recent mothers who were employees of the largest steel producing plant in India, located in the Steel City (Bhilai), had elevated concentrations of total mercury in breast milk and blood when compared to recent mothers who did not work at the plant but were residents of the Steel City both groups had higher levels than recent mothers from a reference site 100 km distant. In Bhilai, mercury concentrations in breast milk and blood increased with increasing age of the mother, and this may be related to increasing respiratory exposure to mercury-contaminated dust. 

In comparing these methods, the direct entrapment procedures give the advantage of providing an absolute value for a discrete exposure even within a sequence of repetitive exposures to the same pesticide. They can also be used to differentiate the relative contributions of oral, dermal, and respiratory exposure to the total exposure picture. 

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... 

A study, conducted in the workplace, that measures the protection provided by a properly selected, fit-tested, and functioning respirator when used intermittently for only some fraction of the total workplace exposure time (i.e., sampling is conducted during periods when respirators are worn and not worn). EPFs are not directly comparable to Workplace Protection Factor (WPF) values because the determinations include the time spent in contaminated atmospheres both with and without respiratory protection therefore, EPFs usually underestimate the protection afforded by a respirator that is used continuously in the workplace. See also Protection Factor Stndy Workplace Protection Factor (WPF) Study. 

Benson et al. (2011) presented a respiratory exposure study using -labeled sulfur mustard. Anesthetized rats with transorally placed tracheal catheters were exposed to 250mg sulfur mustard vapor/m for lOmin. A total of 18.1 3pg sulfur mustard per animal was absorbed. Within 2h postexposme, inhaled sulfur mustard was distributed and more than 70% were deposited in the carcass and pelt. 

Nickel carbonyl should be used in totally enclosed systems or under good local exhaust. Plants and laboratories where nickel carbonyl is used should make use of air-monitoring devices, alarms should be present in case of accidental leakage, and appropriate personal respiratory protective devices should be readily available for emergency uses. Monitoring of urinary nickel levels is useful to help determine the severity of exposure and identify appropriate treatment measures. Some large-scale users of nickel carbonyl maintain a supply of sodium diethyldithiocarbamate, or Antabuse, a therapeutic agent, on hand for use in case of overexposure. 

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