The Centers for Disease Control (CDC) conducts ongoing assessments of the levels of environmental chemicals in the U.S. population. This ongoing study utilizes lab samples from the individuals who are part of the National Health and Nutrition Examination Survey (NHANES). The NHANES samples from the years 1999-2000, 2001-2002, and 2003-2004 (each representing about 2,400 individuals) were used for the CDC's national reports. In the CDC Fourth National Report on Human Exposure to Environmental Chemicals ("the fourth report") complete data from the above sample years were included. Each year additional chemicals are measured; the fourth report contains information on 75 previously untested compounds, for a total of 212 compounds measured. In the fourth report, blood and urinary levels of eight different forms of arsenic are reported. The fourth report, for the first time, also includes levels of solvents (30 different compounds) and provides adult rather than juvenile values for mercury. In the majority of individuals tested, acrylamides, cotinine, trihalomethanes, bisphenol A, phthalates, chlorinated pesticides, triclosan, organophosphate pesticides, pyrethroids, heavy metals, aromatic hydrocarbons, polybrominated diphenyl ethers, benzophenone from sunblock, perfluorocarbons from non-stick coatings, and a host of polychlorinated biphenyls and solvents were found. This review provides many of the ranges for xenobiotic toxins so a clinician can identify a patient's current exposure and toxic load compared to the national averages and monitor the effectiveness of prescribed treatments.