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Title: PROPERTIES OF COMMON PLASTICS USED IN UV EXCLUSION STUDIES

Author
item Krizek, Donald
item Mirecki, Roman

Submitted to: American Society for Photobiology
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2003
Publication Date: 7/5/2003
Citation: Krizek, D.T., Mirecki, R.M. 2003. Properties of common plastics used in uv exclusion studies [abstract]. Programs and Abstracts, Annual Meeting, American Society for Photobiology. July 5-9, 2003. p. 17

Interpretive Summary:

Technical Abstract: UV exclusion studies afford researchers and policy makers an attractive means of assessing the biological effects of ambient solar UV radiation. In order to conduct meaningful UV exclusion experiments, careful consideration should be given to selecting appropriate plastic filters. Such filters should have the proper spectral cutoff, be relatively stable under ambient UV, and be free of artifacts. Cellulose diacetate (CA) filters have been widely used in UV-B enhancement experiments because of their ability to exclude germicidal wavelengths emitted by fluorescent sun lamps that are commonly used in these studies. Cellulose diacetate has a UV cutoff at ca. 292 nm, close to the spectral cutoff of sunlight. Cellulose diacetate has also been used in UV-B exclusion studies along with Aclar (polychlorotrifluorethylene, PCTFE) and Teflon FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene) since each filter is transparent to terrestrial UV-A and UV-B radiation. Recently we conducted UV exclusion experiments at the Beltsville Agricultural Research Center, using four combinations of Teflon and CA filters (one layer on top of the other). We observed phytotoxic effects on cucumber when CA was used as the bottom filter but not when Teflon was used as the bottom filter or in open uncovered treatments. These findings suggest that toxicity is caused by the CA itself rather than by solar UV, possibly as a result of outgassing of a phthalate known to be used as a plasticizer in the manufacture of CA or some breakdown product. To avoid possible confounding effects from use of CA and to obtain maximum transmission of UV and visible radiation, we recommend that Teflon or Aclar be used in lieu of CA in UV exclusion studies. The properties of each of these filters will be described.