University of California, Davis
Measuring postural and vibrational exposures during agricultural work
Peter Johnson, Department of Environmental Health, University of Washington, Seattle, WA
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With the advancement of electronics, new avenues for the assessment of physical exposures are opening up. In the past, the continuous assessment of physical exposures was either too costly, too time consuming to perform, or limited by the number of samples that could be collected and/or the methods used to measure the exposure. With electronics getting smaller, memory capabilities dramatically increasing, electronics becoming more power efficient, and battery performance increasing, a new age in exposure assessment is developing.
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We have developed two types of instruments for ambulatory assessment of physical exposures. One instrument, developed in conjunction with Microstrain, Inc. in Winooski, Vermont, is called the Virtual Corset. The Virtual Corset is a battery powered, pager sized logger with two inclinometers and 2 megabytes of memory. The Virtual Corset is being developed and evaluated for continuously measuring postural exposures over a whole day and over multiple days. The other instrument is a flexible ambulatory data logger system that can be used with a variety of instruments. This battery powered logger, which is 5” long, 3.5” wide and 1.5” thick, weighs only 6 ounces, has 1 Gigabyte of memory, and contains a microprocessor so it can turn itself on and off in order to collect data unattended over several days, months, or even years.
The large memory capacity of this logger opens up new avenues for ambulatory exposure assessment, particularly in areas that require high data sampling rates. Along with the hardware development there is also the development of software tools for analyzing and assessing the exposure data. Software tools include an Exposure Variation Analysis (EVA) program, which provides a 3-D representation of the exposures based on the intensity and duration of the exposures. Another software tool quantifies the changes of the exposures with respect to time and provides a standardized summary measure to assess the stability/instability of the exposure.
Finally, software tools are under development to measure, quantify, and evaluate exposures based on the temporal distribution and patterns of exposures in order to derive metrics to help assess the healthful or harmful effects of the exposure patterns. Examples using the hardware and software to assess physical exposures will be presented.
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