Blood mercury levels rising among U.S. women 

from:   http://www.ksby.com/Global/story.asp?S=10981098

MONDAY, Aug. 24 (HealthDay News) -- A study involving more than 6,000 American women suggests that blood levels of mercury are accumulating over time, with a big rise noted over the past decade.

Using data from the U.S. Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (NHANES), a researcher from the University of California, Los Angeles, found that while inorganic mercury was detected in the blood of 2 percent of women aged 18 to 49 in the 1999-2000 NHANES survey, that level rose to 30 percent of women by 2005-2006.

"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," study author and neuroscience researcher Dan R. Laks said in an UCLA news release. "My findings also suggest a rise in risks for disease associated with mercury over time."

The findings come on the heels of a widely publicized report, released last week by the U.S. Geological Survey, which found that 25 percent of fish sampled from U.S. rivers and streams have unsafe levels of mercury.

Environmental sources of mercury include coal-fired electricity plants and contaminated fish, which tend to accumulate the toxin in their tissues. According to the news release, chronic mercury exposure has been linked in studies to a higher risk for autism, mental impairment and neurodegenerative disorders such as Alzheimer's disease.

The UCLA study found evidence linking inorganic mercury in the blood to tissues known to be targets for the toxin, such as the liver, the immune system and the pituitary gland.

Laks also found a connection between levels of the pituitary hormone lutropin and chronic mercury exposure, which he said might help explain mercury's link to neurodegenerative disease. Inorganic mercury can also accumulate in the brain and stay there for years, according to the news release.

Overall, "these results suggest that chronic mercury exposure has reached a critical level where inorganic mercury deposition within the human body is accumulating over time," Laks said. "It is logical to assume that the risks of associated neurodevelopmental and neurodegenerative diseases will rise as well."

The findings are published online in the journal Biometals.

Assessment of chronic mercury exposure within the U.S.
population, National Health and Nutrition Examination
Survey, 1999–2006
Dan R. Laks

Biometals
DOI 10.1007/s10534-009-9261-0

Abstract: The purpose of this study was to assess
chronic mercury exposure within the US population.
Time trends were analyzed for blood inorganic
mercury (I-Hg) levels in 6,174 women, ages 18–49,
in the NHANES, 1999–2006 data sets. Multivariate
logistic regression distinguished a significant, direct
correlation within the US population between I-Hg
detection and years since the start of the survey
(OR = 1.49, P\0.001). Within this population,
I-Hg detection rose sharply from 2% in 1999–2000
to 30% in 2005–2006. In addition, the population
averaged mean I-Hg concentration rose significantly
over that same period from 0.33 to 0.39 l/L (Anova,
P\0.001). In a separate analysis, multivariate
logistic regression indicated that I-Hg detection was
significantly associated with age (OR = 1.02,
P\0.001). Furthermore, multivariate logistic regression
revealed significant associations of both I-Hg
detection and mean concentration with biomarkers
for the main targets of mercury deposition and effect:
the liver, immune system, and pituitary. This study
provides compelling evidence that I-Hg deposition
within the human body is a cumulative process,
increasing with age and in the population over time,
since 1999, as a result of chronic mercury exposure.
Furthermore, our results indicate that I-Hg deposition
is associated with the significant biological markers
for main targets of exposure, deposition, and effect.
Accumulation of focal I-Hg deposits within the
human body due to chronic mercury exposure
provides a mechanism which suggests a time dependent
rise in the population risks for associated
disease.