"These data help relieve worry and concern," Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention, said Thursday.
The CDC released its first National Report on Exposure to Environmental Chemicals in 2001 and has updated it every two years. For its latest findings, the CDC took blood and urine samples from about 2,400 people in 2001 and 2002 and tested for 148 environmental chemicals, including metals, pesticides, insect repellants and disinfectants.
The CDC stressed that the presence of an environmental chemical in blood or urine "does not mean that the chemical causes disease."
In the early 1990s, 4.4 percent of U.S. children ages 1 to 5 had elevated lead levels. That dropped to 1.6 percent between 1999 and 2002, according to the latest study.
"This is an astonishing public health achievement" that is related to the removal of lead from gasoline and other efforts to screen and treat children for lead exposure, Gerberding said.
Gauging the effect of secondhand smoke, the CDC tested for nonsmokers' levels of cotinine, a product of nicotine after it enters the body. Levels dropped by 75 percent in adults and 68 percent in children between the early 1990s and 2002, the CDC said.
Gerberding said the decrease came from restrictions on smoking.