As a scientist who has spent the past ten years studying the science of mercury (Hg) and the biologically toxic form of mercury, methylmercury (MeHg), I was taken aback by the clear misuse of the phrase “good science” in a recent letter by Florida DEP’s director of the Division of Environmental Assessment and Restoration (published in the Florida Times-Union newspaper).
The director referred to FDEP’s draft report in setting a strict mercury limit in Florida’s river, stream, lake, and coastal waters, which was released May 24. After a careful examination of the draft report, however, I have come to the conclusion that it contains serious flaws such that the strict mercury limit proposed by FDEP is not scientifically defensible.
First, FDEP’s notion that mercury “pollution” in our air, water, and land is a new, manmade phenomenon is simply wrong. While FDEP cited a 2008 paper that reported mean mercury levels of 0.25 parts per million (or ppm) in the hair of a group of women of childbearing age (16 to 49) in the Florida Panhandle, a study of 550-year-old Alaskan mummies reported average hair mercury levels of 1.2 ppm for four adults and 1.44 ppm for four infants. One mummy had hair mercury levels as high as 4.6 ppm!
Even more importantly, the FDEP draft report failed to consider the 17-year-long Seychelles Islands study, which found no harm, nor any indications of harm, from mercury in children whose mothers ate 5 to 12 servings of fish per week. In establishing the exposure risk of MeHg by fish consumption (most relevant to Floridians), the authors of this study argued that no consistent patterns of adverse associations existed between prenatal MeHg exposures and detailed neurological and behavioral testing. They concluded that despite the risk of MeHg to expectant mothers, “ocean fish consumption during pregnancy is important for the health and development of children and that the benefits are long lasting.” Indeed, the latest Centers for Disease Control data show blood mercury levels for U.S. women and children are already below EPA’s “safe” levels for mercury—the most restrictive mercury health in the world.
It is useful to note the FDEP draft report cited a 1972 study that confirmed tuna mercury levels in the past were higher (or at least not substantially lower) than tuna caught in the world’s oceans today. Although expecting to find a 9 percent to 26 percent increase in levels of MeHg, Princeton University scientists found no increase (actually, a minor decline) in fish tissue mercury levels after comparing Pacific Ocean tuna samples from 1971 and 1998. Those scientists concluded fish mercury level “is not responding to anthropogenic emissions irrespective of the mechanisms by which mercury is methylated in the oceans and accumulated in tuna.”
Second, it is curious that the FDEP draft report failed to note that forest fires in the state of Florida alone were estimated to emit more than 4,000 lbs of mercury per year from 2002 to 2006 alone. This single source of local mercury emissions is comparable to, if not significantly higher than, the mercury emitted for 2009 from all manmade mercury sources in Florida, including coal-fired power plants (which emit less than 1,500 lbs per year).
The FDEP draft report also repeatedly mentioned volcanoes as an important source of global mercury emissions but somehow fell short in conveying the full scale of this natural source of mercury. A new study in the January 2012 issue of the journal Geology noted a truly huge emission of mercury during the Latest Permian era (about 250 million years ago) where the event was estimated to emit about 7,600 tons per year! This is about four times larger than current estimates of the amount of manmade Hg emissions globally, and it persisted for nearly 500,000 years.
Such large sources of mercury resulting from the natural environment can explain why it is not surprising to find high levels of mercury in old samples taken before contamination by modern sources of mercury emission. These high levels have been observed in the hair of Florida panthers and south Florida raccoons as well as fish and aquatic life.
It is equally important to dispel the false impression from the FDEP draft report that mercury “pollution” in Florida’s watersheds and fishes is increasing. A note of caution from the U.S. EPA is clear: Contaminants in fish have been increasingly monitored since the 1970s, which has resulted in more advisories being issued due solely to increased sampling by the various states and “not necessarily due to increased levels or frequency of contamination.”
I would further note there is a serious flaw in FDEP’s draft report that sets a mercury limit of 1.25 parts per trillion (or 0.00000125 ppm) as the new standard for Florida’s inland and coastal waters. It is tacitly assumed by the FDEP that water mercury levels are directly related to fish tissue mercury levels. In fact, no such relationship exists, and indeed the FDEP draft report admits on page 58 that “Using the data collected for the [Florida Mercury Project], no relationship is observed when comparing total mercury in the water column to total mercury in fish tissues.”
Perhaps it is time for FDEP to reconsider the scientific basis of its mercury rulemaking.
Why is the FDEP so intent on setting mercury levels below those existing in nature? Why is it so difficult for the FDEP to fully disclose or explain such publicly available information from the scientific literature to all concerned citizens of Florida? Scientific inquiry must be above political pressure and partisan advocacy. Good decisions can arise only if the scientific evidence and knowledge are examined fully, without a selective bias.
Willie Soon is an independently minded Ph.D. scientist who has been studying the biogeochemical nature of mercury in our environment and ecosystem for the past 10 years.