Mercury was not detected in eleven out of twenty HFCS samples analyzed (detection limit 0.005 μg mercury/g). A single manufacturer produced nine of these eleven samples. These samples were likely manufactured using caustic soda produced by a membrane chlor-alkali plant which does not use mercury in its manufacturing process. Eight of the nine HFCS samples exhibiting mercury levels between 0.065 μg to 0.570 μg mercury/g HFCS were produced by the other two manufacturers. This could indicate the use of mercury grade caustic soda or hydrochloric acid in the manufacturing processes used by these two manufacturers. Such use would account for the mercury in these HFCS products. With key aspects of the HFCS manufacturing process considered proprietary information, we could not confirm the composition of the raw materials used by the individual HFCS manufacturers and the subsequent source of the mercury. While more sophisticated methods produce lower detection limits, the CVAAS method used in these analyses was sufficient as it clearly and reliably demonstrated significant levels of mercury in 45% of the HFCS samples analyzed. Clearly the sample size of this preliminary trial is too small but there was no support to collect additional samples for analyses. When university researchers outside of the government attempted to obtain additional HFCS samples direct from the manufacturer they were unable to get them. However, with 45% of the HFCS samples containing mercury in this small study, it would be prudent and perhaps essential for public health that additional research be conducted by the FDA or some other public health agency to determine if products containing HFCS also contain mercury. In 2004, several member states of the European Union reported finding mercury concentrations in beverages, cereals and bakery ware, and sweeteners [14] – all of which may contain HFCS. FDA does not currently have a mercury surveillance program for food ingredients such as added sugars or preservatives manufactured with mercury grade chlor-alkali products.

The FDA does analyze some foods for mercury through the ongoing surveillance program known as the Total Diet Study (TDS). The TDS, however, does not test all foods for mercury. Mercury is routinely detected by the TDS in fish, liver, and poultry because farmers routinely use fishmeal and/or fish oil as feed for certain livestock to include chickens, swine, dairy cows, and farmed fish. Animals that are fed fishmeal can bioconcentrate monomethyl mercury in protein matrices that are then passed on to the consumer in the fat components of derived foods [15]. A list of the foods that were recently tested for total mercury along with the results of the analyses may be found at the FDA website [16]. In 2003, FDA tested 48 foods for mercury during the TDS and of those only three may have contained HFCS. Average daily US consumption of HFCS for the year 2007 was approximately 49.8 g per person according to the US Department of Agriculture website [17]. High-end consumers of beverages sweetened with HFCS could easily be ingesting more HFCS than the average person. Results of a recent study of dietary fructose consumption among US children and adults indicate that fructose consumption by Americans represents ten percent (10%) of calories consumed in a 24-hour period [18]. Seventy four percent (74%) of this fructose came from foods and beverages other than fruits and vegetables.

With respect to product labeling, FDA requires food manufacturers to list on the food product label ingredients in descending order of weight from most to least [19]. For example, HFCS is commonly listed as the first ingredient in chocolate syrup on the product label, therefore all that can be known is that of all the ingredients in chocolate syrup, there is more HFCS in the product than any other ingredient. Product labels listing HFCS as a first or second ingredient may contain detectable levels of mercury if the HFCS was manufactured with mercury grade chlor-alkali chemicals. As part of the review process for this article, the authors contacted manufacturers for more information on the % concentration of HFCS in their products and the common response back from manufacturers was that this information is proprietary. With the reported average daily consumption of 49.8 g HFCS per person, however, and our finding of mercury in the range of 0.00 to 0.570 μg mercury/g HFCS, we can estimate that the potential average daily total mercury exposure from HFCS could range from zero to 28.4 μg mercury. This range can be compared to the range of total mercury exposure from dental amalgam in children reported by Health Canada [20]. In the report issued by Canada, daily estimates of total mercury exposure from dental amalgam in children ages 3–19 ranged on average from 0.79 to 1.91 μg mercury. Canada and other countries do not recommend the use of mercury amalgam in pregnant women or children.

Current international food processing standards allow 1.0 μg mercury/g caustic soda [21, 22] and there is no standard for mercury in food grade hydrochloric acid. Both of these chemicals may be used to make HFCS. The FDA has approved HFCS for use as an added sugar in food products but a review of food product labels reveals that it is often added to a product in addition to sugar presumably to enhance product shelf life. Regardless of its intended use, it is imperative that public health officials evaluate this potential source of mercury exposure, as HFCS is presently ubiquitous in processed foods and therefore significantly consumed by people all over the world.

Mercury in any form – either as water-soluble inorganic salt, a lipid-soluble organic mercury compound, or as metallic mercury- is an extremely potent neurological toxin [23]. Organic mercury compounds such as methylmercury that are fat-soluble and readily cross the blood brain barrier are especially damaging to developing nervous tissues [24, 25]. For example, prenatal exposure as low as 10 mg/kg methylmercury, as measured in maternal hair growing during pregnancy, may adversely affect the development of the fetal brain [25, 26]. Confounding associations and concerns with various stages of brain development related to cumulative early life exposure to mercury include the following sources of mercury: maternal fish consumption during pregnancy, the thimerosal (sodium ethylmercurithiosalicylate, approximately 49% mercury weight) content of certain vaccines and dental amalgam [27].

Mercury regulation varies from country to country. While the US government only regulates methylmercury in fish, several other governments regulate all forms of mercury in all foodstuffs. In the US, the current action level of 1 μg methylmercury/g fish or seafood was set in 1977 during court proceedings of the United States of American v. Anderson Seafoods, Inc. [28]. The data used to determine the action level in fish came from a poisoning incident that occurred in Iraq under Saddam Hussein's regime in 1971–1972. There was not a chain of custody for the specimens taken from the victims of that poisoning that were tested by World Health Organization or American researchers, and an appropriate epidemiological study was not undertaken [29]. Further risk assessment for methylmercury has been conducted using human data from the massive episodes of mercury poisoning in the tragic Minimata Bay incident in Japan, as well as from large scale epidemiological studies concerning childhood neurodevelopment and neurotoxicity in relation to fetal exposure in various fish eating communities around the world [24, 25]. There has never been a blinded, placebo, controlled study published giving humans mercury or methylmercury, nor would this kind of study be ethically considerable. Quantitative information on long-term effects of inorganic mercury compounds on humans does not exist [30]. Inorganic mercury compounds react with DNA and are clastogenic [30]. Because the mechanisms of these reactions remain unknown, it is currently impossible to establish a no adverse-effect-level for mercury in humans. Sensitive populations such as neonates lacking the ability to efficiently excrete mercury or individuals that retain mercury in their body due to impairments in detoxification pathways may not be protected by any exposure limit. The implications for mercury in ingested HFCS are not known and clearly more epidemiological and neurotoxicological studies are required.