Related Experiment Video
Updated: Jan 9, 2026
04:17
Analysis of Organochlorine Pesticides in a Soil Sample by a Modified QuEChERS Approach Using Ammonium Formate
Published on: January 20, 2023
3.7K
Revisions to Spacecraft Maximum Allowable Concentrations for 2-Butanone
Aerospace Medicine and Human Performance
|December 8, 2025
Summary
NASA has updated 2-butanone exposure limits for spacecraft, increasing Spacecraft Maximum Allowable Concentrations (SMACs) for various durations based on new toxicity data. These revisions ensure astronaut safety with updated risk assessments.
Area of Science:
- Aerospace Medicine
- Occupational Health
- Toxicology
Background:
- 2-butanone is an irritant with potential central nervous system effects at high concentrations.
- Previous Spacecraft Maximum Allowable Concentrations (SMACs) were established in 1996 based on limited 1940s data.
- Existing limits did not cover long-duration missions (1000 days).
Purpose of the Study:
- To revise Spacecraft Maximum Allowable Concentrations (SMACs) for 2-butanone based on updated toxicity data.
- To establish limits for long-duration space missions.
- To ensure current spacecraft design incorporates appropriate safety margins.
Main Methods:
- Conducted a literature search of inhalation toxicity studies for 2-butanone published post-1996.
- Assessed studies used for existing occupational limits and exposure guidelines.
- Reviewed historical data and risk assessment methodologies.
Main Results:
- Several post-1996 toxicity studies were evaluated.
- The adequacy of the existing occupational limit of 200 ppm was assessed.
- Revised SMACs were determined for acute, 7, 30, 180, and 1000-day durations.
Conclusions:
- SMACs for 2-butanone were significantly increased across all durations.
- Acute SMACs rose from 50 ppm to 200 ppm.
- New SMACs for 7, 30, 180, and 1000 days are 67 ppm, 22 ppm, 22 ppm, and 22 ppm, respectively.
- Updated limits ensure conservatism in spacecraft design using current evidence.
More Related Videos
Related Concept Videos
01:24π Molecular Orbitals of 1,3-Butadiene
11.2K
Conjugated dienes have lower heats of hydrogenation than cumulated and isolated dienes, making them more stable. The enhanced stabilization of conjugated systems can be understood from their π molecular orbitals.
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
11.2K
03:08Hydroboration-Oxidation of Alkenes
11.0K
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
11.0K
02:20Conformations of Butane
17.5K
Unlike ethane and propane that have only two major conformations, butane has more than two conformers. The staggered form of butane in which the bulky methyl groups on the two carbons are placed on opposite sides, that is, at a dihedral angle of 180°, is the lowest energy, most stable form — called the anti conformer. This conformation is stabilized due to the absence of steric repulsion between the largely spaced out methyl groups. The other two staggered conformations are...
17.5K
02:05Prochirality
4.8K
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
4.8K
02:18Conformations of Ethane and Propane
16.7K
In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered...
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered...
16.7K
01:23Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
3.4K
The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.
3.4K