spacecraft maximum allowable concentrations

[Guest guest]

Steve:

Regarding spacecraft maximum allowable concentrations (SMACs):

" Who knew?

Talk about your inadequate ventilation.....

http://www.nap.edu/catalog.php?record_id=12529#description "

Response:

The Spacecraft Maximum Allowable Concentrations (SMACs) came out of a

progression of developing exposure limits. The National Research Council

(NRC) was commissioned by the military to develop Emergency Exposure

Guidance Levels(EEGLs), Continuous Exposure Guidance Levels (CEGLs), and

Short-term Public Emergency Guidance Levels (SPEGLs) beginning in the 1940's

and originally designed for exposure to healthy young men for the EEGLs and

CEGLs, and for exposure to civilians around military installations for

SPEGLs. The Toxicology Committee of AIHA also developed Emergency Exposure

Limits for a short time (1964) (members appear to have overlapped).

At this same time (1960s), there became a need for the spacecraft limits

wand the NRC was again " hired " to do what you will now see as SMACs by the

" Committee on Spacecraft Exposure Guidelines, Committee on Toxicology,

National Research Council " . The interesting piece about SMACs is that they

(like certain CEGLs) are for 24-hours per day (and many days such as 90 for

the CEGLs). This drove the need to look at Physiologically-Based

Pharmacokinetics (PB-PK) and especially half-lives much more closely. In

particular, it revealed considerations for: stressed detoxification

mechanisms, shortened recovery times, bioaccumulation in target tissues,

development of alternate metabolic pathways. In the mid-70s EPA looked at

this data and devised there own protocol for continuous exposure limits over

a 70-year lifespan, mostly for pesticides & herbicides. Similarly, in the

mid-70s, Brief and Scala (Exxon) published in the AIHA Journal on

adjustments of Occupational Exposure limits (OELs) using a similar but more

simple basis. Three other significant papers were published in the 3 years

after the first by others. This continued for OELS up to the most recent

extended work adjustments by the AIHA WEEL committee expected to be

published in 2009.

Refs (sorry, not at the office, don't feel like looking up the originals so

I'll cite myself):

Havics, Tony: " Understanding Exposure Limits " , The Certified Hazardous

Materials Manager, June 1994.

Havics, Tony: " Applying Exposure Levels To Emergency Situations " , The

Certified Hazardous Materials Manager, July-August 1994.

Havics, Tony: " Biological Monitoring and Exposure Limits, How biological

exposure indices can be used to assess worker exposure " , The Certified

Hazardous Materials Manager, September-October, 1994.

Havics, Tony: " Using Emergency Response Planning Guidelines (ERPGs) in your

Emergency Planning Process " presented at Ohio Safety Congress & Expo, April

1-3, 2008.

Havics, Tony, Jim Rock, and Tom Kupferer: " Pragmatic Approach to Adjusting

OELs for For " Non-Traditional " Work Schedules " , PO111, IH General Practice,

at the American Industrial Hygiene Conference & Exposition (AIHCE), 2008,

Mat 31-June 5, 2008, Minneapolis, MN.

.......................................................................

" Tony " Havics, CHMM, CIH, PE

pH2, LLC

5250 E US 36, Suite 830

Avon, IN 46123

www.ph2llc.com

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