Evaluation of Mercury in Urine as an Indicator of Exposure to Low Levels of Mercury Vapor
Joyce Tsuji
Environ Health Perspect. 2003 April; 111(4): 623–630.
ABSTRACT
We conducted a pooled analysis to investigate the relationship between exposure to elemental mercury in air and resulting urinary mercury levels, specifically at lower air levels relevant for environmental exposures and public health goals (i.e., < 50 microg/m3 down to 1.0 microg/m3). Ten studies reporting paired air and urine mercury data (149 samples total) met criteria for data quality and sufficiency. The log-transformed data set showed a strong correlation between mercury in air and in urine (r = 0.774), although the relationship was best fit by a series of parallel lines with different intercepts for each study R2 = 0.807). Predicted ratios of air to urine mercury levels at 50 microg/m3 air concentration ranged from 1:1 to 1:3, based on the regression line for the studies. Toward the lower end of the data set (i.e., 10 microg/m3), predicted urinary mercury levels encompassed two distinct ranges: values on the order of 20 microg/L and 30-60 microg/L. Extrapolation to 1 microg/m3 resulted in predicted urinary levels of 4-5 and 6-13 microg/L. Higher predicted levels were associated with use of static area air samplers by some studies rather than more accurate personal air samplers. Urinary mercury predictions based primarily on personal air samplers at 1 and 10 microg/m3 are consistent with reported mean (4 microg/L) and upper-bound (20 microg/L) background levels, respectively. Thus, although mercury levels in air and urine are correlated below 50 microg/m3, the impact of airborne mercury levels below 10 microg/m3 is likely to be indistinguishable from background urinary mercury levels.
The relationship between urinary mercury and airborne concentrations of elemental mercury is only reliable down to concentrations of about 10 µg/m3. Below 10 µg/m3, predicted urinary mercury levels are within background ranges. Urinary mercury is therefore not an accurate measure for understanding the exposure of persons due to most environmental air concentrations, which are typically well below 10 µg/m3.
A correlation between air and urine mercury does exist at airborne mercury levels < 50 µg/m3. However, the relationship between urinary mercury and airborne concentrations of elemental mercury is only reliable down to concentrations of about 10 µg/m3. Below 10 µg/m3, predicted urinary mercury levels are within background ranges. Urinary mercury is therefore not an accurate measure for understanding the exposure of persons due to most environmental air concentrations, which are typically well below 10 µg/m3. The effect of an air concentration at the ATSDR residential action level of 1 µg/m3 on the urinary mercury level appears negligible relative to background levels.
Evaluation of mercury in urine as an indicator of exposure to low levels of mercury vapor
