J Occup Environ Hyg 2011 May; 8(5):D31-D36
Real-time and near real-time methods for assessing workplace exposures are becoming increasingly available. While many conventional exposure assessment methods require collecting the agent of interest on some type of sampling media and subsequently sending it to a commercial laboratory for analysis, some workplace hazards are already routinely monitored in real time. Noise is the primary example of a workplace hazard that is monitored by direct-reading instruments, with the regulation governing the allowable exposure also specifying the operating characteristics for the monitors Advancements in the technology for monitoring the range of workplace hazards have led to increased usage of real-time monitoring either as a supplement to or a replacement for conventional workplace sampling. Direct-reading methods are also being used in innovative ways, such as for identifying workplace factors that influence exposure (determinants of exposure). Such characterization is possible because these methods have unique capabilities for measuring peak concentrations and for differentiating exposures across different work tasks or manufacturing processes; such determinations are not usually possible with conventional time-weighted average (TWA) exposure assessment methods. Direct-reading exposure assessment methods may be either real-time (instantaneous readings) or near real-time (field-based analysis providing shorter turnaround times between sample collection and result determination than is typical with laboratory analysis). Methods considered real-time generally rely on field-portable instruments that give instantaneous measurements, often as a visual display on the body of the instrument. In addition to monitors for noise and radiation, real-time monitors are widely available for gas and vapor or aerosol measurements, and new technologies are emerging for other workplace hazards, such as force strength monitors for ergonomic assessments. In the case of near real-time monitoring, advances in developing field portable versions of what were previously laboratory methods have expanded capabilities for short turnaround times between sample collection and analysis. Examples include field portable gas chromatographs for volatile and semivolatile compounds; X-ray fluorescence detectors for metals determinations; and immunochemical assay kits for methamphetamines, microorganisms, and other kinds of immunologically active contaminants. Rapid response times and immediate or near-immediate results provided by direct reading methods have great potential for workplace interventions by identifying hazardous conditions or exposures prior to adverse effects on workers. The level of performance required from these methods will be in direct proportion to the accuracy and precision requirements for determining the hazard. Other important considerations will be the sensitivity or specificity of the method for the agent of interest and whether any potential bias may exist across the range of exposures encountered in the workplace. The allowable tolerances across the measured parameters must be decided prior to designing the exposure assessment strategy. Once those parameters are decided, then understanding the capabilities of a given method for meeting that level of performance will be important for ensuring the quality of the exposure assessment. This column will provide different examples of the ways in which direct-reading methods or instruments have been used in industrial hygiene and will discuss some of the aspects of utilizing the output from these methods for making decisions about worker exposure.
Sampling; Sampling-equipment; Sampling-methods; Exposure-assessment; Workplace-monitoring; Health-hazards; Noise; Noise-exposure; Regulations; Industrial-hygiene-programs; Monitoring-systems; Monitors; Measurement-equipment; Quality-control; Analytical-instruments
Terri Pearce, National Institute for Occupational Safety and Health, Division of Respiratory Disease Studies, Laboratory Research Branch, 1095 Willowdale Road, MS2703, Morgantown, WV 26505
Journal of Occupational and Environmental Hygiene