| Description |
ix, 97 leaves : illustrations ; 29 cm |
| Summary |
"In this study, the ozone uptake rate for human hair and the resulting formation of volatile aldehydes and ketones were quantified. Human hair was chosen for two reasons: 1) ozone-hair chemistry may influence personal exposure to ozone and its reaction byproducts due to the proximity to the breathing zone. and 2) ozone reacts readily with human skin oils (squalene) and personal care products (fatty acids and terpenes) that may coat hair. In this preliminary study, hair samples from three ethnic groups were collected before and after washing and/or application of various personal hair care products. Hair samples were exposed to ozone in a flow through Teflon reactor. The cumulative ozone uptake was quantified by measuring the inlet and outlet ozone concentration during a 24 hour period. Organic reaction products were identified and emission rates were quantified by sampling the reactor inlet and outlet using Tenax sorption tubes and DNPH tubes followed by thermal desorption and GCMS analysis and HPLC analysis. Cumulative ozone uptake on most hair samples was surprisingly similar. On average, the ozone uptake for the washed hair samples was (0.95 ± 0.02) x 10⁻⁵ mol O₃ g⁻¹ and for unwashed hair samples was (1.30 ± 0.02) x 10⁻⁵ mol O₃ g⁻¹ .The ozone reaction probability for hair fiber surfaces reduces over time and ranged from 0.02 x 10⁻⁴ for a washed sample exposed to ozone for 24 hours, to 2.1 x 10⁻⁴ for a fresh unwashed sample. The product yields of compounds associated with ozone reacting with sebum (geranyl acetone, 6 methyl 5-hepten-2-one, nonanal and decanal) were consistently higher for unwashed hair than for washed hair. While natural oils that coat hair contribute to ozone reactions on unwashed hair, ozone also appears to react with other unidentified compounds on washed hair"--Abstract, leaf iv. |
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