How Does Electronic Waste Contribute Mercury to the Environment?
Electronic waste (e-waste) contributes many harmful substances to the environment. Mercury is one of these. Mercury can enter the environment through the improper disposal of fluorescent tubes, tilt switches (switches in thermostats and other mechanical devices), older computers, batteries and even paint (epa.gov). Once in the environment, mercury can have very harmful effects, especially because it does not filter quickly.
Ecological Impacts of Mercury
Mercury is a known toxic compound which has significantly increased its prevalence in natural ecosystems over the last 30 years (Mercury report to Congress, 1997).
Mercury can exist in the environment as either a gas, liquid or as solid particles. This enables mercury to enter ecosystems through multiple avenues. Mercury is most dangerous, however, when it reacts with other chemicals to form methylmercury, an organic compound. Data gathered by Watras et al. showed that “methyl-Hg is more efficiently transferred up aquatic food chains and less efficiently excreted that inorganic Hg” (Watras et al., 1992). This aspect of mercury means that it is able to “bioconcentrate, bioaccumulate and biomagnify. In fact, mercury is one of the few metals that is known to biomagnify in aquatic food webs” (Mercury report to congress, 1997). In addition, loading of mercury will not present itself as methyl mercury within an environment immediately (Paterson et al., 2006). Thus, the currently levels of methyl mercury measures are not reflective of the current levels of mercury loading, which are much higher now than they have been in the past. The implications of this are great and far reaching.
(Mercury Reports to Congress, 1997).
Bioaccumulation and Biomagnification
Bioaccumulation refers to the uptake of a chemical in living organisms over time. Conversely, biomagnification is “the increase in chemical concentration in organisms at successively higher tropic levels in a food chain as a result of the ingestion of contaminated organisms at lowers trophic levels” (Mercury Reports to Congress, 1997). Initially, higher levels of mercury in larger organisms was thought to be a product of longer lifespan, however, studies have increasingly shown that higher concentrations are a result of biomagnification (Watras, 1992; Morel et al. 1998; Sampiano et al, 2005). This effect is compounded by mercury’s long retention time in soils; mercury can “continue to be released to surface waters for long periods of time, possibly hundreds of years” (Mercury report to congress; Johansson et al. 1991).
Sources of Exposure and Contamination
Organisms can be exposed to mercury
through contact with exposed substances, such as earthworms in soil or fish in
water, or through ingestion of already contaminated organisms or materials,
such as grazers eating plants from contaminated soil (Mercury report to
(Mercury Report To Congress, 1997)
(Mercury Report To Congress, 1997)
Mercury uptake by plants is extremely harmful. They show damage to structure and phytomass, decreased amounts of chlorophyll, as well as plant death in some species (Mhatre, 1985; Sarkar and Jana, 1986).
The effects are dangerous to aquatic
organisms as well. The effects of
mercury on fish include death, reduced reproduction, impaired growth and
development, behavioral abnormalities, altered blood chemistry, impaired
osmoregulation, reduced feeding rates and predatory success, and effects on
oxygen exchange;” mercury has can affect sensory processes as well, especially in humans (Mercury Report to Congress).
For a more detailed report of the effects of mercury on individual organisms and species, see the Mercury Report to Congress, Volume VI: An Ecological Assessment for
Anthropogenic Mercury Emissions in the United States, specifically pages 2-26 through 2-37 (http://www.epa.gov/ttn/oarpg/t3/reports/volume6.pdf).
Ecosystems at Risk
At risk ecosystems for mercury absorption need to be particularly avoided when dealing with electronic waste. These ecosystems include areas with high concentrations of avian and aquatic organisms, as these are primary targets for mercury bioaccumulation. These areas particularly at risk due to the high levels of organismal exposure to the environmental system, and thus are more susceptible to the effects, even indirectly.
Other sources for more information on the effects of Mercury in ecosystems:
Enviornment Canada also has some valuable information:
A useful, relatively recent study by the USGS on the effects of Mercury in stream ecosystems (also useful for follow up information through other sources)