There is concern that volatilizing mercury into the atmosphere may cause a additional problem rather than actually remediate a Hg polluted area.

As an example, the risk assessment of Hg (0) volatilization will be summarized from Terry and Banuelos’ book entitled, Phytoremediation of Contaminated Soil and Water.  Does the benefit of reducing organomercurials in the food chain outweigh the volatilization of elemental mercury into the atmosphere?  In Oak Ridge, TN, it is estimated that 80,000 Kg of Hg contaminates a 250 ha area.  Elemental Hg levels  measured in the first 1-1.5 meters above the soil were 0.004-0.01 mg/m3.  This is typical over the earth’s landmass and 4 orders of magnitude below federal levels (50 m/m3).  The maximum efflux of elemental mercury in one year at the Oak Ridge site is 10 kg.  At this rate it would take 8,000 years to reclaim this site.  It is hypothesized that merA transgenic plants could increase volatilization 400-fold and clean up the site in 20 years.  The efflux would still be 25-fold lower than federal regulations and provide minimal danger to local animals and plants.  Furthermore, it is estimated that the atmospheric levels of mercury are 1.0 x 106 kg.  This is the same amount of Hg estimated to be contaminating all Hg laden soils in the U.S.  If there was a concerted effort to clean up all of this Hg in 20 years at 5 % a year, the global pool would increase 5 % in the first year.  However, approximately 5 % of the global pool would be reoxidized and transferred back to the earth.  Therefore, from these preliminary estimations, it does not seem as though Hg (0) volatilization would pose a greater risk than the existing risk of Hg.