| Effects of 1,3-Butadiene, Isoprene, and Their Photochemical Degradation Products on Human Lung Cells Melanie Doyle,1 Kenneth G. Sexton,1 Harvey Jeffries,1 Kevin Bridge,1 and Ilona Jaspers2 1Environmental Sciences and Engineering, and 2Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapel Hill, North Carolina, USA Abstract
Because of potential exposure both in the workplace and from ambient air, the known carcinogen 1,3-butadiene (BD) is considered a priority hazardous air pollutant. BD and its 2-methyl analog, isoprene (ISO) , are chemically similar but have very different toxicities, with ISO showing no significant carcinogenesis. Once released into the atmosphere, reactions with species induced by sunlight and nitrogen oxides convert BD and ISO into several photochemical reaction products. In this study, we determined the relative toxicity and inflammatory gene expression induced by exposure of A549 cells to BD, ISO, and their photochemical degradation products in the presence of nitric oxide. Gas chromatography and mass spectrometry analyses indicate the initial and major photochemical products produced during these experiments for BD are acrolein, acetaldehyde, and formaldehyde, and products for ISO are methacrolein, methyl vinyl ketone, and formaldehyde ; both formed < 200 ppb of ozone. After exposure the cells were examined for cytotoxicity and interleukin-8 (IL-8) gene expression, as a marker for inflammation. These results indicate that although BD and ISO alone caused similar cytotoxicity and IL-8 responses compared with the air control, their photochemical products significantly enhanced cytotoxicity and IL-8 gene expression. This suggests that once ISO and BD are released into the environment, reactions occurring in the atmosphere transform these hydrocarbons into products that induce potentially greater adverse health effects than the emitted hydrocarbons by themselves. In addition, the data suggest that based on the carbon concentration or per carbon basis, biogenic ISO transforms into products with proinflammatory potential similar to that of BD products. Key words: 1, 3-butadiene, air pollution, atmospheric chemistry, hydrocarbons, in vitro, interleukin-8, irradiative chambers, isoprene, lung epithelial cells, photochemical products. Environ Health Perspect 112:1488-1495 (2004) . doi:10.1289/ehp.7022 available via http://dx.doi.org/ [Online 16 August 2004]
Address correspondence to I. Jaspers, Center for Environmental Medicine, Asthma, and Lung Biology, CB #7310, 104 Mason Farm Rd., Room 528 EPA Human Studies Facility, Chapel Hill, NC 27599-7310 USA. Telephone: (919) 966-8657. Fax: (919) 966-9863. E-mail: ilona_jaspers@med.unc.edu This work was funded by U.S. Environmental Protection Agency (EPA) grants R829762 and CR829522 and American Chemistry Council grant 2324. This publication has not been formally reviewed by the American Chemistry Council. The views expressed in this document are solely those of the authors. Although the research described in this article has been funded wholly or in part by the U.S. EPA, it has not been subjected to the agency's required peer and policy review and therefore does not necessarily reflect the views of the agency, and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. The authors declare they have no competing financial interests. Received 11 February 2004 ; accepted 16 August 2004.
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