Atmospheric chemistry
Where personal-care siloxanes go in US air
Open access · cc by · source: Europe PMC
CMAQ puts cyclic siloxanes highest in cities, with oxidized products peaking downwind at far lower concentrations than the parents.
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- Paints, cleaners and personal-care products now emit as much regulated VOC as every US vehicle
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Where personal-care siloxanes go in US air
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Atmospheric lifetimes are approximately 5–10 days at typical OH.
Atmospheric lifetimes () are approximately 5–10 days at typical hydroxyl radical (OH) concentrations; accordingly, long-range transport (; ; ; ; ) of cVMS occurs.
Average D5 concentrations up to 432 ng m−3 and average o-D5 up to 9 ng m−3.
The oxidized product concentrations are significantly lower than the parent compounds with average D 5 concentrations up to 432ngm −3 and average o-D 5 up to 9ngm −3 .
Key findings
Lifetimes are about 5–10 days. Urban D5 can average up to 432 ng m−3 while oxidized D5 averages up to 9 ng m−3 downwind. Cities are emission-dominated; rural air tracks transport and OH. D4/D6 have larger errors than D5 because emissions are less certain.
Methodology
Authors added D4, D5, D6 and single-OH oxidation products to CMAQ 4.7.1 at 36 km over North America for four months in 2004, using population-based emissions and OH rate constants.
Limitations
Particle-phase oxidized siloxanes are not simulated; indoor exposure is not modeled; D6 molecular weight was capped by CMAQ’s dry-deposition limit.
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