Pacific Volcanoes, Mercury Contaminated Fish, and Polynesian Taboos

To the Editor:

Fish provide an affordable and sustainable source of lean protein and healthy omega-3 fatty acids 1. Yet fish can also accumulate dangerous levels of mercury, which can in turn do serious and permanent harm to developing children, both during the mother's pregnancy and after birth 2. In North America today these risks drive governmental policies limiting fish consumption through formal advisories, which can have strong impacts on modern dietary choices 3.

We assume that mercury contamination is a new problem, since industrial pollution is the primary cause today. However, volcanic eruptions can produce dramatic emissions of mercury such as those at Krakatau (1883) and Tambora (1815) in Indonesia, which are detectable in the glacial ice of Wyoming in North America (Fig. 1) 4. These sometime exceed the levels of modern industrial emissions, although they occur as sudden events of short duration rather than continual accumulations over centuries. These natural mercury pulses would have been converted in the oceanic ecosystem into methylmercury and bioaccumulated in piscivorous pelagic fish, thereby affecting fish-eating populations around the world.

FIG. 1. From U.S. Geological Survey (USGS) Fact Sheet, FS-051-02, June 2002, Krabbenhoft and Schuster (2002).

Polynesian taboos may represent an old and ecologically sophisticated solution to the problem of methylmercury-contaminated fish. Dellinger, in discussions with Murphy in 2004 and 2005, learned that Tahitian women have a specific taboo banning e i'a tua “outside fish” (meaning outside the lagoon) during pregnancy and while nursing. Subsequent literature review identified other accounts of Polynesian taboos that required Hawaiian women to avoid aku and 'opelu, both pelagic piscivorous fish, during pregnancy 5. By limiting themselves to the smaller and often nonpiscivorous species in the lagoons, Polynesian women reduced the risk of methylmercury related adverse health effects: developmental, neurological, and immunological 2. At the same time, they retained the nutritional and developmental benefits of a fish-rich diet. Traditional ecological knowledge (TEK) is a term used by anthropologists that includes this type of cultural dynamic, whereby healthy and sustainable behaviors become part of ritually sanctioned knowledge (e.g., tapu in Tahitian or taboo in English).

Archaeology documents that Polynesian culture has over 2000 years of heavy dependence upon fish 6, so natural pulses of volcanic mercury would have had critical impacts, and would be a likely arena for the development of a TEK-based taboo to protect susceptible populations. The Tahitian taboo, “Eiaha te vahine hapü 'e te feiä ma'i e 'amu i te i'a tua, e 'öpani 'eta'eta roa hia” (when pregnant or sick you cannot eat “outside fish”) may well have served as one of the first “fish consumption health advisories against mercury emissions.” In collaboration with the Association Te pūátitiá (a Polynesian community organization covering five archipelagos of the Pacific), the authors are collecting additional data on fish toxicity and Polynesian taboos to explore this hypothesis.

This combination of modern environmental health science with traditional knowledge and anthropological perspectives, as well as the time-depth that geophysical, archaeological, and linguistic studies can contribute, has a number of interesting implications. It gives us a new set of working hypotheses about the role of traditional dietary taboos in mitigating environmental health risks. It gives us practical insights into how to build modern health advisories that incorporate long-term ecological knowledge, and communicate the balance of benefits and risks more effectively. Given the global potential of fish as a sustainable and affordable source of protein and omega-3 fats, and the global impacts of environmental pollution, such insights are important for populations world-wide, now and in the future.