Int. J. Environ. Res. Public Health 2009, 6 1647 10. Pirkle, J.L.; Bernert, J.T.; Caudill, S.P.; Sosnoff, C.S.; Pechacek, T.F. Trends in the exposure of nonsmokers in the U.S. population to secondhand smoke: 1988-2002. Environ. Health Perspect. 2006, 114, 853-858. 11. Schober, S.E.; Zhang, C.; Brody, D.J. Disparities in secondhand smoke exposure – United States, 1988-1994 and 1999-2004. MMWR Morb. Mortal. Wkly. Rep. 2008, 57, 744-747. 12. Soliman, S.; Pollack, H.A.; Warner, K.E. Decrease in the prevalence of environmental tobacco smoke exposure in the home during the 1990s in families with children. Am. J. Public Health 2004, 94, 314-320. 13. Machlin, S.R.; Hill, S.C.; Liang, L. Children living with adult smokers, United States, 2004. Statistical Brief # 147. Agency for Healthcare Research and Quality, Rockville, MD, 2006. Available online: http://www.meps.ahrq.gov/mepsweb/data_files/publications/st147/stat147.pdf (accessed February 2009) 14. Wagenknecht, L.E.; Manolio, T.A.; Sidney, S.; Burke, G.L.; Haley, N.J. Environmental tobacco smoke exposure as determined by cotinine in black and white young adults: the CARDIA study. Environ. Res. 1993, 63, 39-46. 15. Scarcinci, I.C.; Watson, J.M.; Slawson, D.L.; Klesges, R.C.; Murray, D.M.; Eck-Clemens, L.H. Socioeconomic status, ethnicity, and environmental tobacco exposure among non-smoking females. Nicotine Tob. Res. 2000, 2, 355-361. 16. Sexton, K.; Adgate, J.L.; Church, T.R.; Hecht, S.S.; Ramachandran, G.; Greaves, I.A.; Fredrickson, A.L.; Ryan, A.D.; Carmella, S.G.; Geisser, M.S. Children’s exposure to environmental tobacco smoke: Using diverse exposure metrics to document ethnic/racial differences. Environ. Health Perspect. 2004, 112, 392-397. 17. Pletsch, P.K. Environmental tobacco smoke exposure among Hispanic women of reproductive age. Public Health Nurs. 1994, 11, 229-235. 18. National Center for Health Statistics (NCHS). National Health and Nutrition Examination Survey Response Rates, 1999-2006. Department of Health and Human Services, Centers for Disease Control and Prevention: Hyattsville, MD, U.S. Available online: http://www.cdc.gov/nchs/about/ major/nhanes/nhanes_cps_totals.htm (accessed January 15, 2009). 19. U.S. Census Bureau. How the Census Bureau Measures Poverty. Available online: http://www.census.gov/ hhes/www/poverty/povdef.html 2003 (accessed May 13, 2009). 20. Office of Management and Budget. Statistical Policy Directive No. 14. Definition of poverty for Statistical Purposes. May 1978. Available online: http://www.census.gov/hhes/www/poverty/povmeas/ ombdir14.html (accessed May 13, 2009). 21. SAS Institute Inc. SAS 9.1.3 Help and Documentation. SAS Institute Inc.: Cary, NC, U.S., 2000- 2004. 22. Mannino, D.M.; Caraballo, R.; Neal Benowitz, N.; Repace, J. Predictors of Cotinine Levels in US Children. Chest 2001, 120, 718-724. 23. Ellis, J.A.; Gwynn, C.; Garg, R.K.; Philburn, R.; Aldous, K.M.; Perl, S.B.; Thorpe, L.; Frieden, T.R. Secondhand smoke exposure among nonsmokers nationally and in New York City. Nicotine Tob. Res. 2009, doi:10.1093/ntr/ntp02. 24. Hassmiler, K.M.; Warner, K.E.; Mendez, D.; Levy, D.T.; Romano, E. Nondaily smokers: who are they? Am. J. Public Health 2003, 93, 1321-1327.