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Archived Comments for: Mercury from chlor-alkali plants: measured concentrations in food product sugar

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  1. Letter to the Editors Re: Dufault et al. in Environmental Health (2009) 8:2

    Arthur Dungan, The Chlorine Institute, Inc.

    11 February 2009

    February 9, 2009

    To the Editors:

    While we share public concern about the safety of our food supply, we believe that you did a vast disservice to your readers and the chlor-alkali industry by publishing an article [Dufault et al. in Environmental Health (2009) 8:2] that, without any scientific evidence whatsoever, claims that chlor-alkali plants are the source of the mercury they found in samples of high fructose corn syrup and other food products. The report, “Mercury from chlor-alkali plants: measured concentrations in food product sugar,” carries nothing more than unsubstantiated, unwarranted speculation concerning a purported relationship between such plants and mercury in foods.

    While the study raises important questions regarding mercury in the diet, careful evaluation is needed to survey all potential sources and exposures before characterizing a source for consumers’ potential health risk. Simple conjecture born of irresponsible science only serves to misinform and mislead the public. Moreover, deliberate misrepresentation of findings has no role in a peer-reviewed technical journal.

    I urge the readers and scientific reviewers of Environmental Health to demand a higher standard of reporting and one that is consistent with research conducted using the scientific method. We are chagrined that the authors of such a study would allow such idle speculation to be prominently reported in the study’s findings. We are outraged that none of the peer reviewers pointed out this obvious speculation or called for changes.

    Contrary to the authors’ speculation, it is neither physically nor chemically possible for caustic soda to be the source of the mercury levels identified in this study. The study correctly points out that most of the caustic soda produced in the United States is produced by chlor-alkali plants that do not use mercury cell technology. However, the mercury levels the authors report are some 50 times higher than what can be attributed to any trace amounts of mercury in caustic soda produced by chlor-alkali plants that do not use mercury cell technology.

    Food-grade caustic soda is safe to use in the food-processing industry. Caustic soda used in food processing must meet stringent international Food Chemicals Codex standards established by the World Health Organization, Food and Agriculture Organization and international governments. Furthermore, the report fails to account for the possibility of other mercury sources. It is important to note that mercury is ubiquitous in our environment due to natural and man-made sources. For example, it is common to find measurable mercury in the soil in which we grow our food, and the U.S. Environmental Protection Agency allows up to two parts per billion in the drinking water we consume daily.

    We urge the editors of Environmental Health and the authors of the study to point out as quickly as possible that they provide no scientific link connecting caustic soda to the reported levels of mercury they found in their study.

    Very truly yours,

    Arthur E. Dungan
    The Chlorine Institute, Inc.
    1300 Wilson Boulevard
    Arlington, VA 22209
    Tel: 703-741-5760
    Fax: 703-741-6068

    Competing interests

    The author works for a trade association that represents some members of the chlor-alkali industry, the subject of this comment.

  2. Response to Chlorine Institute's Comments

    Renee Dufault, United Tribes Technical College

    11 February 2009


    We also share the public’s concern about the safety of our food supply. The order of preference for using chlor-alkali chemicals in HFCS manufacturing was provided by the manager of a high fructose corn syrup plant and stated as 1) mercury cell and then 2) membrane grade. The reason given for the preference stated was that mercury cell caustic enhances “product shelf life.”

    A literature review of the uptake of mercury by the corn plant indicated that corn has very low levels of mercury even in soils with elevated mercury caused by sludge application (1, 2, 4, 5, 6). After the steeping step in the HFCS manufacturing process, the de-germing process separates the germ from the endosperm (3). The germ is the portion of the corn most likely to contain any mercury and it is removed at that point of the HFCS manufacturing process while the endosperm is used to produce HFCS (3). So to summarize the results of our literature review, corn feedstock is actually a weak vector for carrying mercury into a wet-mill, and the little that may arrive is separated prior to HFCS production (1-3, 7).

    The conclusion we made, that mercury-cell caustic soda could be a likely source of mercury in the high fructose corn syrup samples, was substantiated because other obvious sources of mercury contamination were considered less likely. The Chlorine Institute does not provide any evidence that reassures the public that mercury grade caustic soda is safe to use in food manufacturing processes. The amount of mercury that contaminates the mercury-cell chlor-alkali products is variable and depends on quality control and plant operations. These products, which are used world wide in food processing, have not been adequately regulated. The persistence of mercury in HFCS is a cause for concern. Mercury is considered a neurotoxin in any form. It is interesting to note that Sweden recently banned the use of mercury in any form in any product (8). The Swedish Government's decision on a total mercury ban means that alternative, safer techniques will have to be used in dental care, chemical analysis and the chlor-alkali industry (9).

    We agree that most of the caustic soda produced in the United States (US) is now produced by chlor-alkali plants that do not use mercury cell technology. It has been reported that only five mercury cell plants are left - Port Edwards is still operating, although it has committed to phasing out mercury cell technology. Although thousands of tons of mercury pollution could be eliminated annually if these five remaining plants in the U.S. switched to cleaner technology, there are still many more mercury cell chlor-alkali plants operating throughout the rest of the world. The US must lead by example and provide leadership in eliminating this outdated chlor-alkali technology worldwide. In 2006, then Senator Barack Obama introduced legislation to phase out all mercury cell use in chlorine plants by 2012. He re-introduced it in 2007. Earlier in 2008, a version of this legislation also was introduced in the House of Representatives. It's time to pass this legislation.


    Dufault et al

    1. 1999 -- PUBLIC HEALTH STATEMENT MERCURY CAS#: 7439-97-6

    2. 2001 -- Distribution of Mercury in Soil and its Concentration in Runoff
    from a Biosolids-Amended Agricultural Watershed

    3. 1974 -- Heavy Metals in Food Products from Corn
    4. 2007 -- Heavy Metals (Pb, Cd, As, Hg) Contamination of Edible Grains
    Grown and Marketed in Nigeria
    5. 2007 -- A note on elevated total gaseous mercury concentrations downwind
    from an agriculture field during tilling 1: Sci Total Environ. 2007 Dec 15; 388(1-3):379-88. Epub 2007 Aug 20.

    6. 2004 -- Heavy metals in soils and crops in Southeast Asia. 1. Peninsular Malaysia Environ Geochem Health. 2004 Dec; 26(4):343-57.

    7. 1983 -- Differential Uptake of Mercury Vapor by Gramineous C(3) and
    C(4) Plants Plant Physiol. 1983 Aug;72(4):1040-1042.

    Competing interests

    None declared

  3. Comment on the paper by Dufault et al.: Mercury in foods containing high-fructose corn syrup in Canada

    Karen Rideout, National Collaborating Centre for Environmental Health

    21 July 2010

    In January 2009, contemporaneously with the Dufault et al. paper in Environmental Health [1], the Institute for Agriculture and Trade Policy (IATP), a non-profit organization focusing on food, agriculture, and trade, released a report of its own examining the mercury content of foods (such as sodas, syrups, and jams) containing high-fructose corn syrup (HFCS). Dufault et al. [1] tested 20 samples of HFCS from three manufacturers. Nine had detectable levels of mercury (≥0.005 µg/g), ranging from 12,000 to 570,000 ppt (0.012 to 0.570 µg/g) HFCS. Based on these results, the average daily exposure to mercury from HFCS could be 0 to 28.4 µg, about the same as that from dental amalgam [1]. This level of intake is potentially above the provisional tolerable weekly intake (PTWI) for inorganic mercury (i.e., all foods other than fish or shellfish) of 4 µg/kg body weight recently set by the Joint FAO/WHO Expert Committee on Food Additives [2], particularly for children. (The PTWI corresponds to a maximum daily intake of 0.57 µg/kg/day). The ITAP tested 55 foods with HFCS as the first or second ingredient. Mercury was detected in 17 samples, with an average of 128 ppt (range ND–350 ppt) [3]. Both Dufault et al. and the ITAP attributed the finding of mercury to contamination of HFCS through the use of mercury-grade caustic soda (i.e., produced using a mercury cell process, versus diaphragm or membrane cell technology) in its fabrication [1, 3]. Glucose-fructose is produced in Canada and the US, as well as globally, from domestic and imported ingredients. However, it is difficult to ascertain the source of HFCS or raw materials such as caustic soda used in any given food product.

    These results prompted us to explore the potential risk of mercury exposure to Canadians through HFCS (referred to as glucose-fructose on Canadian food labels). Because bulk samples of glucose-fructose were not available, we selected nine Canadian national brand retail syrup products with glucose-fructose listed as the first or second ingredient. Although we did not exhaustively sample products from across the country, we tested all national brands of table syrup available at every major chain grocery store in Vancouver. We expect this to be a reasonable representation of retail products available anywhere in Canada. We limited our testing to syrup products as these contain fewer additional ingredients than other more complex food products; they also provided a consistent matrix for laboratory testing.

    Total mercury levels were measured at the Trace Metals division of the Complex Biochemistry Laboratory at British Columbia Children’s Hospital. Analysis was done using inductively coupled plasma mass spectrometry (ICP-MS) on a Perkin Elmer Elan 6100 DRC, which is the standard method for trace metal analysis on biological samples. Samples were run in duplicate, spikes were used to measure recovery, and distilled water blanks were run between each sample to prevent cross contamination.

    Mercury concentrations ranged from 220 to 1920 ppt (0.220–1.92 µg/l). These results were much lower than the raw HFCS data from Dufault et al., and approximately a factor of ten times higher than the foods sampled by IATP. This does not seem inconsistent, given that Dufault et al. tested raw HFCS and IATP sampled a variety of food products, while we sampled syrup products exclusively. However, all the foods sampled by both IATP and BCCDC contained HFCS (glucose-fructose) as the first or second ingredient. Although one might assume that syrup products would contain more HFCS than general grocery items, the actual percentage of HFCS by weight or volume is not known for any of the foods. Direct comparisons between any of the data are not possible because each investigator tested different products (pure HFCS samples were not available to IATP or BCCDC).

    The average mercury concentrations in the products we tested are listed below:
    – “Brand A” Golden Corn Syrup – 0.22 µg/l
    – “Brand B” Pancake Syrup – 0.25 µg/l
    – “Brand B” Original Pancake Syrup – 0.45 µg/l
    – “Brand C” Concord Grape Spread – 0.49 µg/l
    – “Brand D” Original Syrup – 0.52 µg/l
    – “Brand E” Syrup – 0.60 µg/l
    – “Brand F” Golden Corn Syrup – 0.84 µg/l
    – “Brand G” Corn Syrup – 0.90 µg/l
    – “Brand F” Original Syrup – 0.92 µg/l
    – “Brand H” Organic Light Corn Syrup – 1.07 µg/l
    – “Brand I” Original Syrup – 1.09 µg/l
    – “Brand J” Original Syrup – 1.92 µg/l
    Although the manufacturer’s website for the organic product (Brand H) states that it is not high-fructose corn syrup, we included it as a possible control, otherwise similar to those containing glucose-fructose.

    We calculated several scenarios of mercury intake from glucose-fructose syrups based a diet consisting of 10%, 20%, or 50% of energy intake from retail table syrup. Given the prevalence of glucose-fructose as a sweetener in packaged foods, it is plausible to assume that some individuals might consume 50% of their energy as glucose-fructose. With a mercury concentration of 1.92 µg/l, daily consumption of 300 ml syrup — corresponding to approximately 50% of energy intake — would provide a mercury intake of 0.576 µg/day, i.e., 0.00823 µg/kg/day for a 70 kg man.

    None of the mercury in these samples was characterized. Assuming the source of any mercury contamination in HFCS is mercury grade caustic soda, it is likely that it is in the inorganic (rather than more toxic methylated) form. The World Health Organization (WHO) estimates that average daily inorganic mercury exposure from food is 4.2 µg (0.6 µg from fish and 3.6 µg from non-fish sources [4], which is a factor of ten higher than our worst case scenario estimate based on BCCDC data. As well, our scenario is a factor of 1000 times below the JECFA PTWI for inorganic mercury. Even if the mercury in HFCS were methylated during processing, levels are well below Health Canada guidelines. (The maximum provisional tolerable daily intake of methyl mercury for pregnant women, women of childbearing age and young children is 0.2 µg/kg/day) [5].

    Despite low levels and questions regarding chemical speciation, detection of mercury in HFCS should not be ignored as a contribution to total mercury exposure. Moreover, unlike fish, for which consumption is recommended despite methyl mercury contamination, HFCS provides no health benefits. Given that alternatives to mercury grade caustic soda are available and mercury cell technology presents environmental and occupational health risks, it would be prudent to avoid its use in food production.


    Karen Rideout1, Vanita Sahni2, Ray Copes3, Mark Wylie4, and Tom Kosatsky1,2

    1 National Collaborating Centre for Environmental Health
    2 Environmental Health Division, British Columbia Centre for Disease Control
    3 School of Population and Public Health, University of British Columbia
    4 Complex Biochemistry Laboratory, BC Children’s Hospital

    1. Dufault, R., et al., Mercury from chlor-alkali plants: measured concentrations in food product sugar. Environmental Health, 2009. 8(1).
    2. JECFA, Joint FAO/WHO Expert Committee on Food Additives, Seventy-second meeting, Summary and Conclusions. 2010, Food and Agriculture Organization of the United: Rome. [cited 2010 July 20]; Nations & World Health Organization Available from:
    3. Wallinga, D., J. Sorensen, Mottl, P., and B. Yablon, Not so sweet: missing mercury and high fructose corn syrup. 2009, Institute for Agriculture and Trade Policy: Minneapolis, MN. [cited 2009 April 30]; Available from:
    4. WHO, Elemental Mercury and Inorganic Mercury Compounds: Human Health Aspects. 2003, World Health Organization: Geneva. [cited 2010 April 13]; Available from:
    5. Health Canada. Mercury: Your Health and the Environment. 2004 December 14, 2007 [cited 2010 April 13]; Available from:

    Competing interests

    The authors have no competing interests to declare.