Mercury on Earth: The Heavy Metal Problem
Whether cooking, showering, reading, or at work, anyone reading this article has likely turned on a light, television, or computer at some point today. But have you ever thought about where that magical luminescence we call light comes from? What exactly does turning on a light entail? Well, the answer to the first question is relatively simple and straightforward – power plants – but what does this mean for humans, and, just as importantly, aquatic life?
The cycling of mercury in an aquatic habitat. Source: pnas.org/content/104/42/16394/F1.expansion.html.
It certainly wouldn’t be a surprise if I told you that power plants pollute the environment, but what is it that is so detrimental to the surrounding habitats – specifically aquatic ecosystems? Well, the bulk of pollution from these industrial power houses can be summed up into two simple words; heavy metals. Heavy metals are chemical elements (which can be found directly on the periodic table) which exhibit metallic properties. These include such elements as iron (Fe), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), and one of the most harmful, mercury (Hg), all of which are emitted from most power plants (Klein & Russell, 1973). What happens is that these heavy metals are released in the plant’s emissions (“smoke”) and are able to settle out around the power plant, often quite a distance from the plant itself. As such, surrounding environments become burdened with accumulations of these potentially toxic elements which can result in negative consequences for proximate (and slightly distant) ecosystems.
One of the most threatening of these elements, as previously mentioned, is mercury. Mercury, also known as quicksilver, is the only metal know today that comes in liquid form under STP conditions; the substance found in thermometers, barometers and the like. Mercury (along with other heavy metals) accumulates in the water and sediment of lakes and surrounding water bodies (as well as terrestrial ecosystems, but I will focus on aquatic ones) and is absorbed by benthic organisms and plankton, a great meal for various fish (Jackson, 2011). When ingested by fish, the mercury from these smaller organisms gets transferred and can result in altered behaviour in the fish, potentially making them more vulnerable to predators (Webber & Haines, 2002). Moreover, when humans eat these fish, the mercury again gets passed on. The subsequent result of high levels of mercury in humans is brain damage, severely impairing speech (Pierce et al., 1972). Disturbingly, these effects are most pronounced in children. As expecting mothers ingest the mercury-contaminated fish, the mercury gets absorbed by the developing fetus, resulting in the aforementioned health problems in newborn children. In a recent interview with NPR, Lynn Goldman of George Washington University stated that hundreds of thousands of babies are born each year with unsafe mercury levels.
Through ingesting plankton and various benthic invertebrates such as clams, fish can ultimately succomb to mercury poisoning, altering their behaviour and causing harful effects in humans. Source: eggplantemily.wordpress.com/2010/10/30/theres-something-in-the-water/.).
Ultimately, it is not in our best interest to avoid eating fish all together and it definitely isn’t in our interest to continue to poison our children with mercury, so what can we do? Fortunately, steps are already being taken in the right direction. By this Friday, the EPA will have implemented harsher standards for power plants, requiring many of them to cut mercury emissions by more than 90% over the next 3 years. While many companies are trying to avoid this by insisting power costs will rise, jobs will be lost, and that this is not a feasible goal over the next 3 years, others suggest that jobs will be created and that it can be done well within the allotted time, many of these companies already having implemented the protocols to meet the new standards. This will drastically reduce the amount of mercury that is accumulated and transported through major food webs, ultimately ending up in humans, inevitably reducing the severity and prevalence of the negative health effects we are seeing today.
So the next time you leave the house, remember to turn off your lights, television, or computer – you aren’t only contributing to the sustainability of the environment, but you will be contributing to the future health of our species.
References
Jackson, T.A. 2001. Accumulation of mercury by plankton and benthic invertebrates in riverine lakes in northern Manitoba (Canada): Importance of regionally and seasonally varying environmental factors. Canadian Journal of Fisheries and Aquatic Sciences 45: 1744-1757.
Klein, D.H. and Russell, P. 1973. Heavy metals: Fallout around a power plant. Environmental Science and Technology 7: 357-358.
Pierce, P.E.,Thompson, J.F., Likosky, W.H., Nickey, L.N., Barthel, W.F. and Hinman, A.R. 1972. Alkyl mercury poisoning in humans. Journal of the American Medical Association 220: 1439-1442.
Shogren, P. 2011. EPA to unveil stricter rules for power plants. NPR. Retrieved 13 Dec 2011 from http://www.nrp.org.
Webber, H.M. and Haines, T.A. 2002. Mercury effects on predator avoidance behaviour of a forage fish, golden shiner (Notemigonus crysoleucas). Environmental Toxicology and Chemistry 22: 1556-1561.
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