Thank you Chet! Do you know what was used for monitoring at the time? Charcoal tubes/pump or badges? I am trying to find reliable monitoring options.

Regards,

Peggy Paduraru, PhD 
Chemical Safety Advisor
Safety & Risk Services
The University of British Columbia | Vancouver Campus
336-2389 Health Sciences Mall | Vancouver BC | V6T 1Z3 Canada
Phone 604 827 3409 | Cell 604 788 0550 | Fax 604 822 6650
peggy.paduraru**At_Symbol_Here**ubc.ca
http://www.srs.ubc.ca

Hi Peggy,

I’d like to share something that was prepared by our Occupational Safety Manager when he performed isoflurane monitoring a couple years ago:

Occupational Exposure Limit

There is no federal or State of Nevada enforceable regulatory permissible exposure limit for isoflurane.

A recommended exposure limit of 2 parts per million (ppm) over a 60-minute sampling period is often cited, though this value is an extrapolation from a National Institute of Occupational Safety and Health (NIOSH) recommended standard published in 1977, “Occupational Exposure to Waste Anesthetic Gases and Vapors.” The recommendation from NIOSH is based on halogenated anesthetic agents in use at the time: chloroform, trichloroethylene, halothane, methoxyflurane, enflurane, and fluroxene. Isoflurane (a structural isomer of enflurane) did not come to market until 1979. EH&S previously reviewed data that indicates isoflurane is significantly less toxic than enflurane.

Several European countries have established legal limits for the exposure to isoflurane, ranging from 2 ppm in Norway to 50 ppm in England. In the United States, California’s occupational safety agency, Cal/OSHA, has set the permissible exposure limit at 2 ppm over an 8-hour time-weighted average (TWA).

The American Conference of Governmental Industrial Hygienists (ACGIH) recommended a threshold limit value (TLV) for enflurane of 75 ppm (8-hour TWA) in 1979. In the absence of other regulation or guidance, the University of Nevada, Reno has previously applied this exposure limit to the less-toxic isoflurane. However, in 2021, ACGIH established a TLV specifically for isoflurane: 50 ppm (8-hour TWA). This value should now be considered the University’s occupational exposure limit. In addition to the 50 ppm TWA, a short-term exposure limit (STEL) is set at 150 ppm measured over a 15-minute time period and an action level is set at 20 ppm (8-hour TWA), a point at which action must be taken to monitor exposure and controls must be implemented to reduce exposure.

Table 1. University of Nevada, Reno Occupational Exposure Limits for Isoflurane (2023)

Hopefully this is helpful.  Best,

Chet

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