ToxSci Advance Access originally published online on September 6, 2006
Toxicological Sciences 2006 94(2):440; doi:10.1093/toxsci/kfl097
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TO THE EDITOR
1 Community and Environmental Medicine, Faculty Research Facility, Room 100, North Campus University of California, Irvine, California 92697-1825 2 Community and Environmental Medicine, School of Medicine, University of California, Irvine, California 92697-1825 3 Department of Medicine, Division of Immunology and Allergy, University of California, Los Angeles, California 90095
E-mail: rfphalen{at}uci.edu.
Received August 28, 2006; accepted August 31, 2006
The comments of Drs Oberdörster and Finkelstein on our recent paper (Phalen et al., 2006
) are a welcome addition to the discussion on in vitro dosing of cells with slowly dissolving particles. We agree that the dose rate is important but that there may be limitations to lengthy exposure periods in vitro. Toxicologists conducting in vitro studies should consider their caveats, along with those listed in our paper. The purpose of our presenting several equations was twofold. First, they clearly showed our methods and assumptions. Second, a reviewer of the paper requested their inclusion.
Our thesis that the nonuniform deposition of inhaled particles implies that some individuals will receive very large local particle depositions in their tracheobronchial region is supported by strong evidence. Also, it seems reasonable to take this effect into account in in vitro dosing. As stated in our final paragraph, we believe that it is "important for others to perform similar dosimetry calculations in order to support, modify, or refute our results."
We thank Drs Oberdörster and Finkelstein for catching a typographical error in our second paragraph on page 129. We had twice correctly stated that the patch containing about 200 epithelial cells measures 0.1 by 0.1 mm. Therefore, the patch area given on page 129 should be 0.01 mm2, not 1 mm2. In reviewing our calculations, we also noted that the exponents in Table 7 are incorrect. The computer program used to generate the table apparently converted micrometer to centimeter twice, once just after data were input and again in the calculations. A revised Table 7 is presented here.
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REFERENCES
Phalen RF, Oldham MJ, Nel AE. (2006) Tracheobronchial particle dose considerations for In-Vitro toxicology studies. Toxicol. Sci. 92:1126–132.
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