Illustration: Luiz Hinrique Maduro
Although present exposures to methylmercury are lower than those that produced the historic epidemics of poisoning, growing evidence suggest that current exposures are sufficient to impact the developing fetal brain. A number of recent studies have identified rice, in addition to fish-consumption, as an important vehicle for exposure to methylmercury.
The story of mercury as an environmental contaminant can be said to have started in the 1950s. In Japan the Minamata disease struck, first thought to have been a nerve infection but later identified as methylmercury poisoning. Present exposures throughout the world are lower than those that produced the historic epidemics of methylmercury poisoning in Japan and Iraq. However, there is growing evidence that current exposures are sufficient to alter normal function of several physiological and developmental systems, indicating that methylmercury exposure still constitutes an important public health problem.
When our article in Ambio was published in 2007, fish consumption and fish-eating birds and mammals were the main known source for methylmercury exposure. Indigenous communities, for whom fish and/or marine mammals constitute their dietary mainstay were, and still are, among the highest exposed. There were few reports about rice Orzya sativa but, since then, a number of studies from Asian countries have identified rice as an important vehicle for exposure. For example, a recent study from China showed intellectual deficits in children exposed to methylmercury through contaminated rice.
Long-lasting effects of fetal methylmercury exposure have been described in children throughout the world. Because the developing fetal brain is so highly sensitive to mercury poisoning, it is considered the most adequate endpoint for risk assessment by governmental and international agencies. Today, throughout the globe, birth cohort studies are examining the relation between prenatal mercury exposure and childhood neurodevelopment.
We have learned a lot when it comes to the risk that environmental contaminants pose, the administrative requirements are much stricter and the available test systems far more advanced than they were. But we have not succeeded in eliminating the threats despite our discoveries and improved scientific knowledge. Our societies keep adding new chemicals to the ever longer list of environmental contaminants. It might be that the greater risks for the future may not be caused by individual chemicals in high concentrations but come from the collective synergetic effects of a huge number of substances, each of them in concentrations well below toxic threshold values.
On Ambio’s 50th anniversary, we salute the journal’s role in promoting cross-disciplinary research, relevant for decision and policy-making. The health effects of mercury, like other environmental pollutants, need to be considered in the context of an ecosystem approach to health, which seek to shift the research paradigm to one that embraces transdisciplinarity, social justice, gender equity, multi-stakeholder participation and sustainability.
Mergler, D., H. Anderson, L.H.M. Chan, K. Mahaffey, M. Murray, M. Sakamoto, and A. Stern. 2007. Methylmercury exposure and health effects in humans: A worldwide concern. Ambio 36: 3–11
All articles in Ambio's 50th Anniversary Collection: Environmental contaminants.
Jernelöv, A. 2021. What did we know and which questions did we ask with regard to environmental contaminants in the early 1970s? 50th Anniversary Collection: Environmental contaminants. Ambio Volume 50.
Behind the paper
Jensen, S. 2021. Afterthoughts from an environmental pollution discovery: Interview with Sören Jensen. 50th Anniversary Collection: Environmental contaminants. Ambio Volume 50.
Mergler, D. 2021. Ecosystem approaches to mercury and human health: A way towards the future. 50th Anniversary Collection: Environmental contaminants. Ambio Volume 50.
Wania, F. 2021. The unlikely fate of a term paper. 50th Anniversary Collection: Environmental contaminants. Ambio Volume 50.
Farrington, J. 2021. Reflecting on three influential Ambio articles impacting environmental biogeochemistry research and knowledge. 50th Anniversary Collection: Environmental contaminants. Ambio Volume 50.
Martin, J.W. 2021. Revisiting old lessons from classic literature on persistent global pollutants, and looking ahead. 50th Anniversary Collection: Environmental contaminants. Ambio Volume 50.