The American Conference of Governmental Industrial Hygienists (ACGIH) is an American organization dealing for many years with the safety in workplaces. One of the primary activities of this organization is the periodical publication of exposure limits for various substances to which workers may be exposed.
These limits do not have a direct legal value, but can be rather considerable as a "recommendation" by experts of the sector being constantly updated in consequence of studies related to industrial hygiene.
For such reasons and in consideration of the recognized reliability of this association, limits recommended by ACGIH are often taken over from national legislation to protect workers in various Countries.
The limits established by ACGIH are known as Threshold Limit Values (TLV®) and are expressed with various acronyms having different meanings for the exposure of workers:
• TLV-TWA (time-weighted average): is the average concentration limit weighted throughout the working period (8 hours per day for 40 hours per week).
• TLV-STEL (short term exposure limit): is the concentration limit for short exposures that shall be shorter than fifteen minutes and only occasional.
• TLV-C (ceiling): is the maximum limit not to be exceeded under any circumstance.
The ACGIH has recently decided to amend the formaldehyde exposure limits in workplaces as a result of the recent evolutions in the classification of this substance. The new limits established by the American association are the following:
• TLV-TWA = 0.1 ppm (parts per million, corresponding to 0.12 mg/m3)
• TLV-STEL = 0.3 ppm (parts per million, corresponding a 0.37 mg/ m3)
The classification of ACGIH also reports information on skin and respiratory sensitization in addition to the classification of formaldehyde as a carcinogenic substance.
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