revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 414
5. POTENTIAL FOR HUMAN EXPOSURE
Ontario, region of Canada had total mercury concentrations of 3.5–11.4 ng/L (ppt), with organic mercury
constituting 22–37% of the total mercury (Schintu et al. 1989). Mercury was detected in water samples
from Crab Orchard Lake, Illinois, at 70–281 ng/L (ppt) (Kohler et al. 1990). Total mercury
concentrations in surface waters of California lakes and rivers ranged from 0.5 to 104.3 ng/L (ppt), with
the dissolved particulate fraction being dominant (89%; 0.4–12 ng/L [ppt]) (Gill and Bruland 1990).
The baseline concentration of mercury in unpolluted marine waters has been estimated to be less than
2 ng/L (2 ppt) (Fowler 1990). In contrast, the New York Bight, an inshore coastal area near the
industrialized areas of New York Harbor and northern New Jersey, contained dissolved mercury
concentrations in the range of 10–90 ng/L (ppt) (Fowler 1990).
Near-surface groundwaters in remote areas of Wisconsin were found to contain approximately 2–4 ng/L
(ppt) of mercury, of which only a maximum of 0.3 ng/L (ppt) was determined to be methylmercury,
indicating that groundwater was not a source of methylmercury in the lake (Krabbenhoft and Babiarz
1992). Mercury was found at levels greater than 0.5 µg/L (ppb) in 15–30% of wells tested in some
groundwater surveys (EPA 1985b). Drinking water is generally assumed to contain less than 0.025 µg/L
(ppb) (EPA 1984b). A chemical monitoring study of California’s public drinking water from
groundwater sources was conducted by Storm (1994). This author reported that mercury was analyzed in
6,856 samples, with 225 positive detections and 27 exceedances of the maximum contaminant level
(0.002 mg/L [200 ppb]). The mean mercury concentration was 6.5 ppb (median, 0.62 ppb; range, 0.21 to
300 ppb).
Mercury has been identified in surface water, groundwater, and leachate samples collected at 197, 395,
and 58 sites, respectively, of the 714 NPL hazardous waste sites where it has been detected in some
environmental media (HazDat 1998).
5.4.3 Sediment and Soil
In a review of the mercury content of virgin and cultivated surface soils from a number of countries, it
was found that the average concentrations ranged from 20 to 625 ng/g (0.020 to 0.625 ppm) (Andersson
1979). The highest concentrations were generally found in soils from urban locations and in organic,
versus mineral, soils. The mercury content of most soils varies with depth, with the highest mercury
concentrations generally found in the surface layers. Mercury was detected at soil concentrations ranging
from 0.01 to 0.55 ppm in orchard soils in New York State (Merwin et al. 1994).