Mercury at chlor-alkali manufacturing plants represents one of the main sources of anthropogenic mercury (i.e. mercury contamination originating from human activities). This source of mercury contamination will be gaining more attention in 2009 with the reintroduction of a bill in Congress to stop this unnecessary mercury exposure.
Since the late-1800’s, chlor-alkali plants have used large vats containing several tons of elemental mercury as a catalyst to convert salt water into common chemicals such as caustic soda (sodium hydroxide), potash (potassium hydroxide), chlorine gas, chlorine bleach (sodium hypochlorite), hydrogen gas, and hydrochloric acid. It is well-established in the chemical industry that this process causes some level of mercury contamination in those chemicals. Further, chlor-alkali plants have been the source of extensive mercury contamination via emissions and waste-water effluent, such as the Minimata mercury poisoning incident in Japan. Mercury emissions are measured and accounted for at U.S. chlor-alkali plants. An additional 20 - 100 tons of mercury annually has been unaccounted for (“lost”, but not due to emissions), with some of this mercury contaminating consumer products. Advances in technology have successfully allowed these plants to cost-effectively convert to a mercury-free process. However, as this technology’s use is not federally mandated, there are chlor-alkali plants in the U.S. that continue to use the mercury-based process. Plants using mercury as a catalyst are called “mercury-cell chlor-alkali plants”, and chemicals produced at those plants are known as “mercury-grade” (e.g. “mercury-grade caustic soda”) or alternatively as “rayon-grade”.
Chlor-alkali chemicals are widely utilized as an ingredient in consumer products as diverse as polyurethane flooring, polyvinyl chloride (PVC), and food additives such as MSG, sodium benzoate, and potassium benzoate. Chlor-alkali chemicals are also used to process the raw ingredients and to adjust pH levels in many chemical processes, including most notably the corn wet-milling process that produces High-Fructose Corn Syrup (HFCS), dextrose, corn starch, and other corn sweeteners for human consumption. Corn wet-milling products are used to produce citric acid and aspartame (NutraSweet). Corn wet-milling products not destined for human consumption are used as livestock feed for cattle, turkeys, pigs, and chickens. Chlor-alkali chemicals are also used to produce products such as pharmaceuticals, bleach, and toothpaste, and are important for water purification.
The industrial standard on chlor-alkali products allows for up to 1 ppm (part per million) of mercury in caustic soda and 0.5 ppm mercury in hydrochloric acid. Mercury contamination in these chemicals makes its way into common products. For example, some types of polyurethane flooring used in schools contain mercury and may give off mercury vapors, especially when damaged (see section 10.2 of the CDC ATSDR report HERE).
Potentially more ominous is the mercury contamination in the food supply. A peer-reviewed study by Renee Dufault et al was published in January 2009 on mercury levels in HFCS (see HERE). The HFCS samples, which were collected at the FDA in 2005, contained total mercury in the 0.000 – 0.570 mcg Hg per gram of HFCS (i.e. 0.000 – 0.570 ppm). As comparison, fish at 1 ppm methylmercury exceed the FDA action level and are not allowed to be sold. Per capita consumption of corn sweeteners grew rapidly from 9 to 40 grams (2 to 10 teaspoons) per day from 1978-1985, primarily due to introduction of HFCS into soft drinks and dextrose into foodstuffs, and is currently at about 50 grams (12 teaspoons) per day. Corn sweeteners are used as a primary ingredient in a wide range of food products, including many that are not readily obvious, such as the dextrose used in IV feeding solutions for premature infants and certain types of baby formula. Further, per the Dufault study, there seems to have been a preference by corn sweetener producers to utilize mercury-grade caustic soda (rather than other grades of caustic soda) due to its preservative qualities. The Corn Refiners Association (CRA) claims that their members had all switched from using mercury-grade caustic soda as of several years ago. Given the results of the Dufault study, the CRA claim presumably would mean that the manufacturers with mercury-contaminated HFCS in the study have converted to other grades of caustic soda since 2005. To date, CRA has yet to provide tangible evidence that these conversions have occurred, or when they occurred. The non-profit Institute for Agriculture Trade & Policy recently published test results of mercury levels in grocery products in 4th quarter 2008 containing HFCS, as part of a report that provides a good explanation of the overall issue (see “Not So Sweet: Missing Mercury and High Fructose Corn Syrup” HERE). Questions have been raised about whether those test results indicate that mercury-grade caustic soda is still utilized today in the production of corn sweeteners in the USA.
SafeMinds has been investigating whether past, or ongoing, contamination of the food supply by chlor-alkali mercury has contributed to the increase in neurological disorders. The type of mercury in HFCS is unknown but indications are that the type is not methylmercury, the type of organic mercury found in fish. Methylmercury ingestion has been extensively studied, but there has been much less research on the effects of ingestion of other forms of mercury that might theoretically be derived from mercury-grade caustic soda and hydrochloric acid such as mercury salts (e.g. mercuric hydroxide, mercuric chloride). There are numerous possibilities as to how a daily regimen of ingested mercury might have contributed to the autism epidemic, perhaps laying the groundwork for the damage done by the increased vaccine schedule of the late 1980’s. Could ingested mercury have damaged the immune system, similar to how ethylmercury damaged dendritic cells in Dr. Isaac Pessah’s research in 2006 (“Uncoupling of ATP-Mediated Calcium Signaling and Disregulated IL-6 Secretion in Dendritic Cells by Nanomolar Thimerosal”, July 2006 edition of Environmental Health Perspectives)? Could ingested mercury have contributed to low glutathione levels, reducing the natural protection against toxins? Could ingested mercury have damaged mitochondrial function? What are other hypotheses? Comments and suggestions would be appreciated. With the support of our community, we’ll keep working on this issue to get answers.
As for stopping this mercury contamination, there is potentially good news. Oceana is an environmental organization that has been pressing for a ban on the use of mercury in chlor-alkali production. Oceana has produced informative reports on when certain USA chlor-alkali plants have converted to mercury-free manufacturing and which ones still utilize the mercury chlor-alkali process (see HERE). In 2007, then-Senator Barack Obama sponsored an Oceana-inspired bill to eliminate the mercury-cell chlor-alkali manufacturing process. Indications are that Oceana plans to re-introduce this bill in the current session of Congress. Internationally, governments are encouraging or mandating the conversion of chlor-alkali plants to mercury-free technology.
Mercury-cell chlor-alkali plants represent a major source of mercury contamination that is totally unnecessary given that more cost-efficient mercury-free processes have been available for decades, and common sense dictates that they should be eliminated expeditiously. SafeMinds asks for the support of our community on this issue and will continue to report on developments that will eliminate this unnecessary exposure.
Scott Laster is an engineer, a SafeMinds board member, and chair of the SafeMinds Environmental Committee. The SafeMinds Environmental Committee is tasked with raising awareness on environmental mercury exposures that may be contributing to autism prevalence. Scott lives in Atlanta with his wife and two sons.