Peggy:

We recently measured isofluorane using SKC 226-81A sorbent tubes and calibrated personal sampling pumps at 0.3-0.4 Lpm for 30 minutes. Results ranged from analytical reporting limit of 0.12 ppm to 0.25 ppm, well below the California (and German) OEL of 2 ppm, and current ACGIH TLV of 50 ppm. Analyses were performed by ALS, Cincinnati, Ohio, an AIHA-acccredited Industrial Hygiene Laboratory.

Ralph A. Froehlich, M. S., CIH, CSP, QEP, FAIHA, FAWMA
Helix Environmental, Inc.
1 Elizabeth Place, Suite 160H
Dayton, Ohio 45417
(937) 226-0650 office
(937) 776-8435 cell

On Apr 30, 2025, at 1:55 PM, Paduraru, Peggy <peggy.paduraru**At_Symbol_Here**UBC.CA> wrote:

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

 

 

 

From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Chet Carpenter
Sent: Tuesday, April 29, 2025 5:13 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: Re: [DCHAS-L] Isoflurane monitoring

 

[CAUTION: Non-UBC Email]

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)

TWA (8-hour)	STEL (15-minute)	Action Level (8-hour TWA)
50 ppm	150 ppm	20 ppm

 

Hopefully this is helpful.  Best,

 

Chet

 

Cheston Carpenter

Executive Director

Environmental Health and Safety/MS 0328

University of Nevada, Reno

 

Work-phone: 775-784-4342

Cell-phone: 775-343-8806

chestonc**At_Symbol_Here**unr.edu

www.unr.edu/ehs

He, Him, His

 

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From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Paduraru, Peggy
Sent: Tuesday, April 29, 2025 2:39 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [DCHAS-L] Isoflurane monitoring

 

[EXTERNAL EMAIL]

 

Hello:

 

I am trying to find out what other universities are doing for monitoring isoflurane exposure (or other anesthetic gases). In BC it is classified as a reproductive toxin but does not have an exposure limit. We are planning to use the Cal/OSHA PEL of 2 ppm as a guideline. Isoflurane is the main anesthetic gas used in our research animal units.

 

Thank you!

 

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

 

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