Calomel, a mercury-containing medical treatment (Photo: H. Selin)
It probably comes as no surprise to many who are reading this that exposure to mercury is dangerous to human health. We begin our book in chapter 1 with the story of how fishers and their families in Minamata were seriously harmed (and hundreds died) as a result of eating fish high in methylmercury. People today living all over the world continue to be exposed to methylmercury through their consumption of seafood. This is of particular concern for pregnant women and small children that can suffer developmental effects. Over thousands of years, mercury miners were exposed to high concentrations of mercury vapor in narrow mining shafts and during extraction from cinnabar, and experienced serious and often lethal health impacts. Through centuries, people engaged in gold and silver mining also suffered from being exposed to mercury vapor. Today’s artisanal and small-scale gold mining communities are sites of continuing mercury exposure (we address this further in chapter 7). At the same time, and despite of all the known harms that mercury has caused, mercury in different forms has been used for millennia in medicine. In some cases, this had beneficial and sometimes even lifesaving effects (such as in vaccines), but in others, uses continued despite no evidence of benefits and ample evidence of harm.
In the process of researching linkages between mercury use and human health for Mercury Stories, we uncovered a rather curious fact about medicinal uses of mercury (spoiler alert!): People have, over time, intentionally inserted mercury or mercury compounds into every possible bodily orifice. The use of mercury in medicine dates back many thousands of years. It was used in ancient China, India, Greece, Rome, and the Arab world, and in medieval Europe. Uses continued into the 21st century. Mercury-containing medicines were used extensively against syphilis starting in the 15th century; high-dose applications led to mercury poisoning, but its symptoms were often mistaken for those of syphilis itself. Patients were often treated while sitting in a tub, and the children’s rhyme “rub-a-dub-dub, three men in a tub” is thought to be a reference to syphilis treatment. The use of mercury in dentistry goes back at least to the first century CE in China, and has grown sharply over the past two hundred years. Doctors used cinnabar to tattoo the surrounding area as a treatment against pruritus ani (intense anal itching). Soldiers starting during World War I were administered mercury-containing solutions as a preventative measure against the spread of syphilis and gonorrhea. In the mid-20th century, mercury was also an active ingredient in contraceptive suppositories used by women. Some more recent examples include the use of mercury compounds as a preservative in eye and ear drops and nasal sprays.
One of our favorite stories about mercury use in medicine involves its subsequent fate: Members of the Lewis and Clark Expedition in the U.S. in the 1800s used mercury-containing laxatives, nicknamed “Thunderbolts” or “Thunderclappers” for their effectiveness, as their diet during the arduous journey took its toll on their digestion. Years later, traces of mercury in latrine pits helped researchers track some of the expedition’s route from St. Louis to the Pacific coast.
Vintage WWII sign featuring mercury-containing prophylactics for syphilis and gonorrhea (Photo: N. Selin)
It is important to note that some mercury use in medicine, both historical and present, has had decidedly positive impacts. For example, ground-breaking mercury-containing medical devices such as thermometers and sphygmomanometers greatly advanced diagnostic and treatment capacity starting in the 1700s (we cover the history of the thermometer more extensively in chapter 6). Mercury’s use in dental amalgam provided effective oral health care to hundreds of millions of people. While dental use of mercury is being substituted for other alternatives in a growing number of countries and regions, mercury-containing amalgams still facilitate necessary and affordable oral health care in many places in the world. The antimicrobial properties of mercury made mercury compounds effective preservatives in a variety of medical products. This includes the eye and ear drops discussed above, as well as vaccines. Ethylmercury, the type of mercury in thimerosal used in vaccines, is different from other mercury forms. This use has had tremendous health benefits in preventing the spread of dangerous diseases worldwide. The presence of very small amounts of ethylmercury reduces the need for cold storage and allows vaccines to be transported to and used in remote areas. While there is no scientific evidence to support this claim, some, including anti-vaccine groups, have falsely linked its use to autism in children. During the negotiations of the Minamata Convention, the World Health Organization, GAVI (The Vaccine Alliance) and the United Nations Children’s Fund (UNICEF) successfully argued that the use of mercury in vaccines be exempted from requirements on mercury in products, due to its importance in global health protection.
The challenge of balancing benefits and harms in the context of sustainability is a theme that emerges in chapter 4, and which we return to throughout the book. The harms of mercury were often disregarded: doctors continued to prescribe damaging treatments, and governments only recently began to actively mitigate health dangers of mercury use and exposure. But governance strategies need to be designed to ensure they do not have damaging consequences. Efforts to advise vulnerable populations such as pregnant women to avoid eating fish high in methylmercury need to be designed to ensure the targeted populations keep eating healthy fish choices containing important nutrients. Reducing mercury use in dental amalgam and childhood vaccines can be appropriate where there are safe alternatives, but need to be implemented carefully to avoid feeding misinformation about the safety of life-saving vaccines. It also raises important equity issues about access to safe alternatives among poorer and wealthier communities and countries.
We argue in Mercury Stories that the history of mercury, including its use in medicine, provides important lessons for the multifaceted sustainability challenge of how to make informed decisions that enhance human well-being for all in the present and into the future.