Revisions to Limits for 2-Propanol in Spacecraft Air

Area of Science:

• Aerospace Medicine
• Occupational Health
• Toxicology

Background:

• Original spacecraft maximum allowable concentrations (SMACs) for 2-propanol were set in 1996.
• 2-propanol can cause irritation and central nervous system effects at high concentrations.
• Previous limits were based on limited human exposure data.

Purpose of the Study:

• To review and update NASA's spacecraft exposure limits for 2-propanol.
• To ensure current limits are protective and not overly restrictive.
• To incorporate the latest evidence and risk assessment methodologies.

Main Methods:

• Conducted a literature search for "isopropyl alcohol" toxicity and inhalation studies.
• Assessed studies used in developing occupational and acute exposure limits.
• Reviewed existing SMACs for 2-propanol.

Main Results:

• No new toxicity studies were identified since the original SMACs were established.
• A relevant study not previously included in documentation was identified.
• The 24-hour limit was increased from 100 ppm to 200 ppm.
• The 60 ppm limit was deemed appropriate for missions up to 1000 days.

Conclusions:

• The original SMACs for 2-propanol remain largely relevant.
• Updated limits are adequately protective without being overly restrictive.
• NASA periodically reviews chemical limits to ensure safety and relevance.