The main source of mercury introduced into the environment is coal-fired power plants, according to The New York Times. Mercury is a known neurotoxin that can cause birth defects, tremors, speech impairment, and brain damage, and it's hard to eliminate from the body once consumed.
This should be a clarion call to Congress to mandate advanced scrubbing technologies to remove more mercury from power-plant emissions.
Ken Salazar, secretary of the Interior, doesn't mince words in the study's release: "This study shows just how widespread mercury pollution has become in our air, watersheds, and many of our fish in freshwater streams. This science sends a clear message that our country must continue to confront pollution, restore our nation's waterways, and protect the public from potential health dangers."
Beyond the surprising geographic dispersion of the problem, the study revealed other unexpected findings. Streams draining from undeveloped forests in South Carolina, Georgia, Florida and Louisiana had among the highest levels of mercury in the study. Extremely elevated levels were also found rural and undeveloped areas in the Northeast and Upper Midwest, where fishing in streams is very common and widely assumed to be safe. "Conditions were just right for those locations to take inorganic mercury in the atmosphere and convert it into methylmercury, the most toxic form," says Barbara Scudder, the lead scientist on the study.
How the mercury gets into fish is well-documented. Mercury particles in power-plant smoke shoot into the atmosphere. The particles are absorbed in clouds and return as toxic rain, filling streams and lakes, where fish ingest the particles. Mercury tends to accumulate in higher levels up the food chain; larger fish in streams have a proportionally higher level of mercury, on average. "The primary way Americans get mercury in their bodies is by eating fish and shellfish," Scudder says.
The U.S. runs neck-and-neck with China as the world's largest producers of coal-fired energy. The vast majority of American plants were built more than 20 years ago and are no longer state-of-the-art either in emissions safety or energy efficiency.
In 2004, the Bush Adminstration weakened and delayed laws that would have forced coal-fired power plants to remove more mercury from their emissions. This is particularly troubling because mercury toxicity is cumulative and can have subtle but insidious impacts. Scientists suspect that low-levels of mercury exposure to developing fetuses can reduce the IQs of newborns and result in moderate but permanent brain damage.
The USGS cautioned the the sample is not statistically bulletproof, due to the extremely large number of U.S. streams. Further, the study noted that 59 of the stream sites could have been impacted by mining activities. But of the 79 sites found to have levels of mercury higher than government safety recommendations, 55 had not been impacted by mining activities. This implies that the majority of the nastiest contamination came from coal-fired plants.
Cleaner coal-fired plants are already being built in China, and to a lesser degree in the U.S., where the coal industry has balked at the added costs associated with building cleaner plants. No one seems to have tallied the costs of permanently lowering the IQs of thousands of babies, however.