The level of inorganic mercury in the blood of American women has been increasing since 1999 and it is now found in the blood of one in three women, according to a new analysis of government data for more than 6,000 American women.

“My study found compelling evidence that inorganic mercury deposition within the human body is a cumulative process, increasing with age and overall in the population over time,” said author Dan Laks, a neuroscience researcher at the David Geffen School of Medicine at the University of California, Los Angeles.

In a separate statistical analysis, he found that older women had more inorganic mercury in their blood than younger women, indicating that mercury accumulates in the blood over time.

“My findings also suggest a rise in risks for disease associated with mercury over time,” Laks said.

Laks conducted computer analyses of data from the Centers for Disease Control and Prevention in Atlanta. The CDC’s National Health and Nutrition Examination Survey, usually called NHANES, is what Laks calls the “gold standard” in assessing the health status and health risks to a representative group of Americans. NHANES is unique in that it combines interviews and physical examinations.

NHANES data also are designed and survey weighted so that results can be generalized to the nation’s entire population.

Laks examined data on blood inorganic mercury levels of 6,168 women, ages 18-49, in NHANES two year data sets from 1999 through 2006. Between 1,455 and 1,622 women were in each two-year matched group.

“The overall population average of blood inorganic mercury concentration also increased significantly from 1999-2006,” Laks wrote.

Inorganic mercury was detected in the blood of 30 percent of women studied in 2005-2006, a steep rise from the two percent of women who were found to have inorganic mercury in their blood in the 1999-2000 study.