In a letter to the American Conference of Governmental Industrial Hygienists (ACGIH), the Z390 Committee urged the ACGIH to postpone changes to the H2S Threshold Limit Values (TLV) time-weighted average from 10 parts per million (ppm) to 1 ppm and TLV short-term exposure limits from 15 ppm to 5 ppm. OSHA currently does not have a published Permissible Exposure Limit (PEL), so the agency could potentially incorporate any changes made to the TLV.
"In the Z390 Committee's view, the science and data put forth in the ACGIH proposal is very weak and does not support lowering the current standards. The Z390 Committee recommends that the H2S exposure levels be investigated more thoroughly and advises that more research and data is needed to help determine any proposed lower levels to ensure the safety and health of workers," said Z390 Committee Chair Frank Perry, CSP, P.E.
The Z390 Committee advised that the ACGIH solicit a call to the general public for papers and studies, and also submit a request for H2S research to the National Institute for Occupational Safety and Health (NIOSH). In addition, the Z390 Committee recommended that the ACGIH consider adopting consensus procedures, and make meeting minutes and information regarding TLV revisions available to the general public.
The American Society of Safety Engineers (ASSE) serves as secretariat of the Z390 Committee, which develops and revises the ANSI Z390.1-1995 (R2001) standard. The standard provides guidance for H2S safety training and instruction of affected personnel.