Mercury & Human Health
Mercury is an element that has been historically used to manufacture chemicals or appliances (such as thermometers and light bulbs). But with increased industrialization came increased mercury emissions that poison our air and water, causing a ripple of ill health effects.
While some mercury emissions occur naturally (such as those released from volcanic eruptions), half of the world’s mercury emissions come from man-made sources. According to EarthShare member organization Natural Resources Defense Council (NRDC), coal-fired power plants remain one of the largest mercury pollutants, emitting around 33 tons of mercury every year and contributing to half of all mercury emissions. Other sources include chemical manufacturing plants (which emit another 10–12 tons of mercury per year) and automobile scraps that are melted down for recycling.
According to the Environmental Protection Agency (EPA), once mercury is released into the air, it can be carried great distances. Once airborne, mercury vapor can be changed into other forms of mercury and can be further transported to water or soil via rain or snow. Some forms of mercury can also be released into water and soil through pesticides and fungicides.
Once in the water, microorganisms like phytoplankton and fungi convert and release inorganic mercury to methylmercury. At this stage, the mercury can enter the food chain. Small fish feed upon organisms and plants containing methylmercury, bigger fish come along and eat the smaller fish. In a process called bioaccumulation, mercury builds up in the food chain over time. This means that bigger, older fish tend to carry the most methylmercury, as they’ve consumed many smaller fish containing mercury.
Not surprisingly, methylmercury is transferred to people as we catch and consume fish from contaminated waters. Eating fish is the main source of human exposure to mercury, according to the EPA.
Methylmercury affects more than 630,000 newborns each year, interfering with brain and nervous system development. Deficits in cognitive thinking, memory, language, motor and visual spatial skills have all been linked to children exposed to methylmercury in the womb. It’s because of these risks that women are advised to abstain from eating fish while they are pregnant or nursing.
Mercury poisoning is also a possible health risk to those who consume mercury-laden fish. Immediate symptoms of mercury poisoning include:
- Impairment of peripheral vision
- A “pins and needles” sensation in the hands, feet and around the mouth
- Lack of coordination
- Impairment of speech, hearing and walking
- Muscle weakness
You can steer clear of mercury-infected fish by keeping tabs on local water and fish advisories. Some of our member organizations, like the Environmental Defense Fund, also have safe fish charts that make it easy to select the right fish for dinner.
Most states have approved regulations and initiatives to cut back on the amount of mercury released to our shared lands and waters. You can start by getting involved at the local level. The Sierra Club Foundation, an EarthShare member organization, recommends contacting your state governor, local public health officials, and joining conservation efforts to decrease the amount of mercury in our air and water.
Mercury Statistics and Fact Sheets
- 2012 Mercury Information, Environmental Protection Agency
- Coal Plants and Mercury, Sierra Club
- Mercury Contamination Facts, Environmental and Energy Institute
For Your Health
- Health Effects of Mercury, Environmental Protection Agency
- Mercury is Toxic, Sierra Club
- Fish Consumption Advisories, Environmental Protection Agency
- Seafood Selector, Environmental Defense Fund
- Mercury Test Kit, Sierra Club
- Mercury and Compact Fluorescent Light Bulbs, Environmental Defense Fund
Mercury in the Environment
- Mercury Levels by State and Region, Environmental Protection Agency
- Mercury Maps, Environmental Protection Agency
- Handling Mercury Spills, Environmental Protection Agency
- Mercury in Aquatic Systems, U.S. Geological Survey