The identification of potential aeroallergen/irritant(s) from oilseed rape (Brassica napus spp. oleifera): volatile organic compounds emitted during flowering progression.

Volatile organic compounds emitted by growing intact oilseed rape plants have been detected using an entrainment apparatus enabling volatile headspace analysis by thermal desorption coupled to capillary gas chromatography-mass spectrometry. In total, 22 volatile compounds were identified as being emitted during the flowering period. The main constituents were alpha-farnesene (a sesquiterpene); beta-myrcene (a monoterpene); linalool (a monoterpene alcohol) and the 'green leaf' volatile (E)-3-hexen-1-ol acetate. These compounds constituted between 50 and 87% (mean 68%) of the total volatiles emitted in all of the entrainments carried out with flowering oilseed rape plants. The remaining constituents consisted of a range of compounds including other terpenoids, the characteristic 'green leaf' volatile (E)-3-hexen-1-ol, short chain alcohols and ketones, organic sulphides and nitrogen-containing compounds. These were generally present as minor constituents but some plant entrainments revealed that higher relative amounts could be emitted. This was particularly apparent for dimethyl disulphide, 3-methyl-2-pentanone, 3-hydroxy-2-butanone, sabinene, isomyrcenol and (E)-3-hexen-1-ol. The possible role of the 22 compounds in respiratory mucosa and conjunctiva irritation associated with airborne releases from oilseed rape is discussed.