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Work Environment Measurement (WEM)


Work Environment Measurement, or WEM, is a branch of Industrial Hygiene aimed at evaluating levels of workers’ exposures from various physical and chemical hazards emanating from workplace operations and recommending appropriate control measures for the improvement of the working environment.  WEM is conducted through various sampling methodologies and/or direct measurement using direct reading instruments to:

  • Determine the level of harmful substances (airborne contaminants) such as but not limited to dust, mist, fumes, solvents and gases
  • Measure the level of physical hazards generated from various operations such as noise, heat, vibrations and radiation
  • Assess the illumination levels in different work areas
  • Evaluate the performance of the general and local exhaust ventilation installed

Results of WEM are evaluated or compared with the local and international standards.  Among the standards being used as references are the TLV (Threshold Limit Value) of the ACGIH or American Conference of Governmental Industrial Hygienist and PEL (Permissible Exposure Limit) of OSHA or Occupational Safety and Health Administration of the United States of America.  The Occupational Safety and Health Standards (OSHS) of the Department of Labor and Employment (DOLE) adopted most of the TLVs of the ACGIH.

WEM is a requirement for all operations.  Rule 1070 – Occupational Health and Environmental Control of the OSHS, prescribed that “The working environment measurement shall be performed periodically as may be necessary but not longer than annually”.  WEM is also a mandatory requirement of ISO 9001 and OHSAS 18001.

There are many types of Environmental Monitoring identified as follow:

  • Personal Monitoring – the measurement of a particular employee’s exposure to airborne contaminants.  The measuring device is placed as close as possible to the contaminant’s entry port to the body.  For example, when monitoring an air contaminant that is toxic, the measuring device is placed close to the breathing zone of the worker.  The data collected closely approximates the concentration of contaminants to which the worker is exposed.
  • Area/Environmental Sampling – the measurement of a contaminant concentration in the workroom.  The measuring device is placed adjacent to the worker’s normal workstation or at fixed locations in the work area.  This kind of monitoring does not provide a good estimate of worker’s exposure but helps to pinpoint work areas with high or low exposure levels of contaminants.
  • Biological Monitoring involves the measurement of changes in the composition of body fluids, tissue or expired air to determine absorption of a potentially hazardous material.  Examples are measurement of lead and mercury in blood or in urine.