Carbonyl species characteristics during the evaporation of essential oils Hsiu-Mei Chiang a , Hua-Hsien Chiu b , Yen-Ming Lai c , Ching-Yen Chen c , Hung-Lung Chiang c, * a Department of Cosmeceutics, China Medical University, Taichung, 40402, Taiwan b Center for Biomedical Technology Research and Development, Fooyin University, Kaohsiung, 831, Taiwan c Department of Health Risk Management, China Medical University, Taichung, 40402, Taiwan article info Article history: Received 13 September 2009 Received in revised form 1 February 2010 Accepted 14 February 2010 Keywords: Essential oil Carbonyl compound Formaldehyde Emission factor abstract Carbonyls emitted from essential oils can affect the air quality when they are used in indoors, especially under poor ventilation conditions. Lavender, lemon, rose, rosemary, and tea tree oils were selected as typical and popular essential oils to investigate in terms of composition, thermal characteristics and fifteen carbonyl constituents. Based on thermogravimetric (TG) analysis, the activation energy was 7.6e8.3 kcal mol 1 , the reaction order was in the range of 0.6e0.7 and the frequency factor was 360e2838 min 1 . Formaldehyde, acetaldehyde, acetone, and propionaldehyde were the dominant carbonyl compounds, and their concentrations were 0.034e0.170 ppm. The emission factors of carbonyl compounds were 2.10e3.70 mg g 1 , and acetone, propionaldehyde, acetaldehyde, and formaldehyde accounted for a high portion of the emission factor of carbonyl compounds in essential oil exhaust. Some unhealthy carbonyl species such as formaldehyde and valeraldehyde, were measured at low-temperature during the vaporization of essential oils, indicating a potential effect on indoor air quality and human health. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Essential oils with aromas have been widely used in ENTH- medicine, food and cosmetics. They exhibit antibacterial, antiviral, antifungal, sedative, antispasmodic and/or anti-inflammatory effects, depending on the components of the oil (Schnaubelt, 1998; Baudoux, 2000; Longbottom et al., 2004; Tampieri et al., 2005; Pibiri et al., 2006; Inouye et al., 2006; Takemoto et al., 2008). Some essential oil compositions could inhibit the metabolic func- tions of microorganisms, i.e., growth (e.g., lavender oil [Inouye et al., 2003] and tea tree oil [Fletcher et al., 2005; Van de Sande et al., 2007]), reproduction (Cowan, 1999) and microbial fermen- tation in the rumen of animals (Calsamiglia et al., 2007). In addition, the essential oils and their volatile constituents are used to prevent and treat human diseases, such as cancer (Hammer et al., 2006; Edris, 2007) and cardiovascular diseases (atherosclerosis and thrombosis) (Edris, 2007). Generally, the major constituents of essential oils are primarily oxygenated monoterpenes, monoterpene hydrocarbons, sesqui- terpene hydrocarbons and oxygenated sesquiterpene (Mohamed and Abdelgaleil, 2008). Therefore, terpenes could be an important species in the bioactivity of essential oil components. Some studies have indicated that b-pinene, pulegone and a-terpineol are the main toxic compounds in Baccharis salicifolia essential oil, causing neurotoxicity (Garcia et al., 2005), and sesquiterpene iso- intermedeol from lemon grass could induce apoptosis of cancer cells (Kumar et al., 2008). In addition, monoterpenes have been shown to be toxic to insects, but camphene, camphor and myrcene revealed weak inhibition (Abdelgaleil et al., 2009), and the terpene alchols were the major constituents of essential oils (i.e., tea tree, lavender and rosemary oils) shown to effectively control bacterial action at high vapor concentration in a short time (Inouye et al., 2001). However, despite these advantages, there are some hidden risks associated with the use of essential oils that should be carefully considered. It has been reported that exposure to essential oils or perfume can cause respiratory problems, especially in high-risk populations (Millqvist et al., 1999; Hammer et al., 2006), and the compositions of evaporating essential oil gas involving terpenes and aromatics can contribute to these adverse effects (Hammer et al., 2006; Su et al., 2007). Some allergic reactions and toxic effects on animals and humans are due primarily to the excessively high doses of these substances via skin contact or ingestion (Orafidiya et al., 2004). Limited data are available to describe the frequency of human poisoning with essential oils like tea tree oil (Hammer et al., 2006). However, sufficient scientific evidence about their specific effects and the mechanisms causing these hazards are still lacking (Lahlou, 2004). * Corresponding author. Tel.: þ886 4 22079685; fax: þ886 4 22079687. E-mail address: hlchiang@mail.cmu.edu.tw (H.-L. Chiang). Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2010.02.017 Atmospheric Environment 44 (2010) 2240e2247