02/21/2012 02:01 pm ET Updated Apr 22, 2012

If Songbirds Are Dying From Mercury Poisoning, Are We Next?

Mercury pollution -- nothing to worry about if I don't live in the rural Northeast and don't eat tons of fish, right?

Guess again, says a new report done by the Biodiversity Research Institute (BRI) in conjunction with The Nature Conservancy. The report, "Hidden Risk," details the wide spread and deep impacts of mercury pollution in terrestrial nature -- particularly on animals such as songbirds and bats. Researchers are discovering how mercury is causing big declines in reproductive success among these species as well as physiological oddities -- like developmental asymmetries and an inability of some birds to hit high notes.

And the same rain that brings mercury pollution down from the sky falls on us, too. So are these species a kind of canary in the coal mine for mercury's effects on other vertebrates, including people? And will strict new federal standards limiting U.S. power plant pollution be enough in a world where mercury pollution is on the rise from China and other nations?

According to Chris Shade, Ph.D., at Quicksilver Scientific, the leading mercury testing and treatment lab in the country, methylmercury (MeHg), is the most highly researched form of mercury present in nature.  It is an organic mercury species commonly found in fish and other animal tissues.  Although methylmercury is mobile and easily absorbed, it is difficult for organisms to eliminate. Instead, the methylmercury accumulates in biological tissues.  For example, while digesting its prey, the predator absorbs the methylmercury contained in its victim.  As a result, animals higher on the food chain tend to have more methylmercury in their tissues than those lower on the food chain.  This process of methylmercury exposure is known as bioaccumulation. Bioaccumulation can result in fish having more than 1 million times higher methylmercury concentrations than the water in which they swim.

Inorganic Mercury

Inorganic mercury is the term used to refer to mercuric ion (HgII).  Inorganic mercury is highly toxic but not very mobile.  Inorganic mercury in sediments, soils and food sources does not pass easily into biological tissues.  However, once inside of the tissue, inorganic mercury is very difficult to remove.   Inorganic mercury accumulates in tissues when a more mobile form of mercury such as elemental mercury vapor, methylmercury or ethylmercury enters the tissue and breaks down into inorganic mercury. In biological tissues, most organic forms of mercury will eventually break down into inorganic mercury.

New Scientific Report Shows High Levels of Mercury in Many Wildlife Species

Mercury accumulation, previously considered a risk for aquatic ecosystems, is also found in many wildlife species living on the land. This new scientific data is presented in a new report published by BRI in partnership with The Nature Conservancy. "Hidden Risk: Mercury in Terrestrial Systems of the Northeast" highlights BRI's scientific findings on high levels of mercury contamination in songbirds and bats throughout 11 northeastern states.

The human health effects of mercury contamination are well documented: adverse effects include impacts on cardiovascular health, IQ, workplace productivity and motor control. Similarly, mercury negatively affects wildlife populations by hindering behavior and reproduction. Past investigations have emphasized adverse impacts to fish-eating wildlife, such as common loons, bald eagles and river otters.

Major Findings

Current environmental mercury loads have the ability to significantly reduce reproductive success in several songbird species of conservation concern in the northeastern U.S. including the saltmarsh sparrow and rusty blackbird.

Bats also build up significant body burdens of mercury; individuals from multiple species from all 10 areas sampled in the northeastern U.S. exceeded the threshold level of adverse impacts.

At-risk habitats and associated indicator species are identified based on the species' level of conservation concern, relative abundance, and ability to build up mercury in their bodies.

Despite rising global mercury emissions, there are actions that both managers and policy makers can take to limit future ecosystem degradation, ranging from cleaning up legacy mercury dump sites to controlling emissions from coal-fired power plants.

Through greater understanding of both the extent of wildlife exposure and harmful impacts to ecosystem health, it is now clear that increased conservation efforts are necessary to reduce this neurotoxin in our environment for the benefit of wildlife and people.


Lalsasz, Robert. 'Hidden Risk': Mercury Pollution's Costs to Wildlife and People