Respiratory exposure sampling devices

Farm worker exposure to pesticides has been studied extensively over the past 30 years.This scientitic discipline has evolved from the days when respiratory exposure of farm workers was measured using gauze dosimeters placed inside respirators to collect airborne pesticide residues to very sophisticated air sampling devices and remarkable dosimeter devices to measure dermal exposure to farm workers. ... 

Air sampling for occupational exposure to pesticides normally consists of measurement of pesticide concentrations in the worker s breathing zone, with a portable air-sampling pump and a sampling train which includes some type of collection device. The latter device, or sampling media, selected are based on the physical and chemical properties of the compound to be measured. Field workers may be exposed to chemical vapors, solid particulates or water-based aerosols. Examples of sampling media include membrane filters, sorbent tubes, polyurethane foam and charcoal. A discussion of pesticide exposure provides a useful review of methods for respiratory exposure measurement (Nigg etal, 1990). 

Several approaches to the measurement of respiratory exposure are available. The first was developed by Durham and Wolfe ( ) and employs a respirator with the collection pads protected by cones from direct spray. The second common method uses the personal air sampler with a pump carried by the worker and a collection device In the general breathing zone. The third method involves a more careful experimental design. In this case, the worker wears a pesticide respirator for a certain period of time with the respirator removed for an equal amount of time. Twenty-four hour urine samples are collected each day, with any observed Increase in urinary metabolites Indicating the degree of respiratory exposure. 

Recordkeeping The anployer must keep an accurate record of all measurements taken to monitor employee exposure to asbestos. This record is to include the date of measmanent, operation involving exposure, sampling and analytical methods used, and evidence of their accuracy number, duration, and results of samples taken type of respiratory protective devices worn name, social security number, and the results of all employee exposure measurements. This record must be kept for 30 years. 

An alternative approach, adopted by Albery et al. [59-61], is to determine the mechanism giving rise to the sensor response and to use this information together with the measured data at short times to calculate the final response. This was used for an electrochemical sensor system incorporating cytochrome oxidase where the steady-state responses of the measurement system were insufficiently fast for useful measurement of respiratory inhibitors such as cyanide, hydrogen sulphide, etc. By using mechanistic information, it was possible to successfully calculate the concentration in a test sample by real-time analysis of the sensor signals at short times after exposure to the test sample. The analysis could cope with the gradual loss of enzyme activity commonly found in these biosensor devices. 

Because one has to consider unpredictably higher concentrations, especially in the case of the last two jobs mentioned, the use of respiratory protection is often necessary. For selection of the most suitable devices, concentration measurements have to be performed. It is important to consider the surrounding environment of workplaces if other persoimel occasionally work in these areas without respiratory protection. If jobs are of short duration, short-term measurements need to be performed to assess the exposure. A risk assessment of short-term exposures on the basis of an 8-h measurement is only possible in exceptional cases. For short-term exposure measurements, not every sampling technique is suitable. In this case, special sampling methods must be used in order to achieve a sufficiently low detection limit during short measurement times, especially for complex mixtures of substances. In many cases of this type thermodesorption has been proved to be the method of choice. 

---