While diving off the coast of Hawaii, I encountered multiple green sea turtles in the shallow areas around the shore. Adult green sea turtles are primarily vegetarians and feed on sea grass and algae. Juvenile turtles are reported to eat crabs and jellyfish, in addition to sea grass and algae. When fully grown, green sea turtles may weigh between 300 and 350 pounds, with one very large turtle reportedly weighing nearly 700 pounds.
The name “green sea turtle” refers to the color of its dermal fat (layer of fat beneath the skin). The turtle’s shell is typically brown in color, as in the video. In some parts of the eastern pacific, green sea turtles have shells that are reportedly olive to black. Greens sea turtles have also been reported to be one of the few turtles to leave the water for reasons other than to lay eggs. They range across the tropical and subtropical waters of the earth.
In subtropical areas and temperate areas, where shallow water temperatures during the winter are cold, green sea turtles may experience cold stunning. When this occurs, their hear rate and blood circulation decrease, they become lethargic, and barely move. They often appear to be “dead” but may be very much alive. If the turtle remains in a prolonged state of cold stunning, they may die. Being unable to swim also makes them vulnerable to various types of accidents or drowning. In 2013, there were a record number of turtles reportedly stranded by cold stunning along the Atlantic coast, but fewer in subsequent years. Along the Texas gulf coast, cold stunning does not occur as frequently and is not prolonged, but does occur. Warming sea temperatures may result in fewer cold stunning events, but may also result in other changes more detrimental to green sea turtles.
Green sea turtles are listed as endangered by the IUCN (International Union for the Conservation of Nature), and the U.S. Fish and Wildlife service lists breeding populations along the Florida and Pacific coast of Mexico as endangered. Divers, swimmers and snorkelers may swim and photograph the turtles, but are prohibited from harassing or capturing green sea turtles and their eggs.
In the United States, there are approximately 6,997 power plants with a capacity to generate at least one megawatt of electricity (United States Energy Information Agency [EIA], 2013). Each of these power plants may operate one or more electric power generators resulting in an estimated 19,023 individual generators (EIA, 2013). It is estimated that U.S. power plants produced 3.8 billion kilowatt-hours (KWh) of electricity in 2013 (EIA, 2014). Plants combusting fossil fuel (coal, oil, natural gas) supplied approximately 66% of the U.S. electrical energy needs, nuclear power plants provided 19% and renewable energy plants provided another 13% (EIA, 2014).
The public health risks associated with power plants are largely dependent upon pollutants released from the fuel used to generate heat. The primary pollutant emissions from coal combustion include particulate matter, nitrogen oxides, sulfur oxides, carbon monoxide, methane, carbon dioxide, mercury, volatile organic compounds (VOCs), and heavy metals (United States Environmental Protection Agency [EPA], 2013). Natural gas-fired plants also emit nitrogen oxides, carbon dioxide and methane, but in lower quantities than coal-fired power plants. Sulfur oxides and mercury emissions from natural gas combustion are negligible (EPA, 2013a). Nuclear power plants and renewable power plants do not have emissions from combustion; however, nuclear plants discharge large quantities of high temperature water used for cooling. In addition, nuclear power plants generate nuclear waste that is difficult to dispose and remains hazardous for thousands of years (Chapman, 2012).
Here I focus on risks associated with fossil fuel power generation; however, it is important to recognize that risks occur along the entire fuel cycle, from resource extraction to waste disposal. The public and occupational health risk from nuclear power generation is primarily related to radiation exposure during all stages of the fuel cycle (Hamilton, 2011). Secondary health risks include trauma (Hamilton, 2011). Among five renewable energy categories (geothermal, hydropower, photovoltaics, wind, and solar), trauma is the primary occupational hazard during power production operations. Exposure to toxic brines, hydrogen sulfide and radon are also occupational and public health risks at geothermal plants (Hamilton, 2011).
Fossil Fuel Power Benefits and Risks
Fossil fuel power production has allowed unprecedented industrial and population growth from a fairly low dollar cost energy source. Wilkinson et al. (2007) noted that the exploitation of fossil fuels is integral to modern living and has been a key element of the rapid technological, social and cultural changes during the past 250 years. Their review paper noted that 2.4 billion of the world’s population, disadvantaged by a lack of access to clean energy, are exposed to high levels of indoor air pollutants from inefficient burning of biomass fuels.
Community health risks associated with fossil fuel power plants are unique, not because they are the only sources for certain pollutants, but because of the quantities of pollutants emitted. For instance, according to the EPA 2011 national emissions inventory data, fossil fuel power plants accounted for 69% of all anthropogenic emissions of sulfur dioxide (SO2) (EPA, 2014). The majority of power plant SO2 emissions are from coal (98%), further distinguishing them from natural gas-fired and oil–fired power plants (0.7%). Short-term exposure to SO2 has been associated with an array of adverse respiratory effects, including bronchoconstriction and increased asthma symptoms (EPA, 2014). Fossil fuel power plants emit approximately 51% of all anthropogenic mercury emissions, of which coal-fired plants account for 97% (EPA, 2014). Mercury may remain in the atmosphere for long periods of time before depositing into the environment where it can bioaccumulate. Fossil fuel power plants also emit other hazardous heavy metal air pollutants, including arsenic (62%), nickel (28%) and chromium (22%) (EPA, 2014).
Risks to the natural environment from fossil fuel power plants include heavy metal discharges into water and ground water from coal pile runoff; leachate from coal ash landfills; discharges related to equipment maintenance and cleaning; cooling tower blowdown; discharges from wastewater treatment; and heavy metal air emissions that deposit into water and onto land surfaces. EPA surveys of groundwater near ash landfills and surface impoundments have demonstrated that arsenic may exceed human health thresholds by more than four orders of magnitude and poses the greatest risk for heavy metal discharges from coal plants (EPA, 1998). At oil-fired plants, arsenic, vanadium, and potentially nickel, are of greatest concern.
Another risk to the natural environment that does not involve a pollutant discharge is that of water withdrawals for cooling. To generate power, many power plants boil water to generate steam. The steam spins a turbine which generates electricity. After the steam passes through the turbine, it must be cooled to be recycled. To cool this water, power plants pull water from streams, rivers and estuaries for use in cooling towers or heat exchangers. A single power plant is able to pull hundreds of millions of gallons of water for use in cooling. In the United States, fossil fuel power plants account for 91% of all cooling water withdrawals (EPA, 2014). Large water withdrawals from lakes, rivers, estuaries and other water bodies may result in aquatic organisms being impinged on screens meant to filter debris. Small fish and eggs may be entrained, leading to a loss of early life stages needed to maintain healthy populations. A majority of power plants (71%) are also located within two miles of water bodies that are impaired due to excess nutrient loadings or other forms of pollution (EPA, 2014g). Thus, impingement and entrainment may exacerbate the loss of species and critical habitat from pollution.
The risks associated with fossil fuel power are not evenly distributed across fuel types or within fuel types. A study of non-climate change-related damages caused by air emissions from 406 coal-fired power plants estimated that 50% of the plants with the lowest damages together produced 25% of the net generation of electricity, while 10% of the plants with the highest damages also produced 25% of the net generation (National Research Council [NRC], 2010). Similarly, a review of 498 natural gas-fired facilities noted that there were major differences in pollution generation. Ten percent of the gas-fired plants accounted for 65% of the damage (NRC, 2010).
Greenhouse Gas Emissions from Fossil Fuel Power Plants
Greenhouse gas (GHG) emissions from power plants have been identified as a long-term risk causing worldwide climate change (Schaeffer et al., 2015). The current and future impact from climate change depends upon a large number of factors, making risk estimation a complex and difficult undertaking. Haines et al. (2000) identified GHG risks to human health that include direct exposure to thermal and weather extremes, and indirect effects that include alterations in vector-borne infectious diseases, water quality and quantity, and changes in agricultural productivity. An example of vector-borne disease risk from climate change includes that of the St. Louis encephalitis virus. The virus, which can cause inflammation of the brain when transmitted to humans, depends on meteorological triggers for virus amplification between mosquitoes and wild birds (Day, 2001). Several researchers reported that climate change has caused an earlier onset of the spring pollen season in the Northern Hemisphere, potentially exacerbating asthma symptoms (D’Amato et al., 2002; Weber, 2002; Beggs, 2004). Other impacts from climate change include regional declines in fish populations (Brooks et al., 2002). Moore et al. (2008) identified potential impacts in marine and fresh water systems that include lower pH, changes to vertical mixing, precipitation and evaporation, and harmful algal blooms.
Forty percent of all greenhouse gases are emitted by fossil fuel power plants (75% of these are from coal-fired plants) (EPA, 2014). As of 2011, fossil fuel power plants in the United States that emit 25,000 tons or more of carbon dioxide equivalent (CO2e) greenhouse gases must report annual emissions to the EPA. The list of chemicals regulated under the program includes carbon dioxide, methane, nitrous oxide, and a number of fluorinated hydrocarbons. Fossil fuel power plants primarily emit carbon dioxide, with smaller quantities of methane and nitrous oxide. While carbon dioxide is the greenhouse gas emitted in large quantities, methane and nitrous oxide have larger global warming potentials (GWP). Methane has a 25 times larger GWP and nitrous oxide has a 298 times larger GWP than CO2.
Compared to other industries, occupational injury numbers and rates in the United States are generally low among power generating facilities. The Electric Power Research Institute (EPRI) collects and publishes information on the number of occupational injuries and illnesses reported by participating power facilities. EPRI reported that the most frequent types of injury (1995-2011) was sprains and strains (38.5%); cuts, lacerations and punctures (15.2%); and contusions and bruises (8.5%) (EPRI, 2013). The greatest occupational risks are associated with fossil fuel power plants. The United States Department of Labor (DOL) shows one fatality per year in 2012 and 2013 among fossil fuel electric power generating plants (DOL, 2014). In 2013, 82% of the approximately 2,200 recordable injuries within the power generation industry occurred at fossil fuel power plants. Nonfatal injury incident rates per 100 full-time employees at fossil fuel power plants was 1.4 in 2013, which interestingly is lower than hydroelectric power generation (2.3), but higher than nuclear power generation (0.2) (DOL, 2014). Illnesses such as respiratory conditions, poisonings from chemicals, and skin diseases are generally low at fossil fuel power plants. Hearing loss, however, represents the highest illness category among fossil fuel plants. In 2013, hearing loss incident rates per 10,000 full-time employees at fossil fuel plants was 20.1, or approximately 55% of all the reported illness incidents (DOL, 2014).
Exposure to coal dust at coal-fired power plants has not resulted in illness rates similar to those in coal mines (DOL, 2014). The reason is not completely understood. While coal ash (material remaining after coal combustion) contains many of the same mineral and metal constituents as coal dust, it does not appear to be as toxic (Borm, 1997).
To address these risks the EPA has proposed a number of regulations to protect the community and natural environment, particularly for coal-fired and oil-fired power plants. Many are the result of continuing efforts that began decades ago to further reduce pollutants associated with a number of potential health effects.
Beggs, P.J. (2004). Impacts of climate change on aeroallergens: past and future. Clinical and Experimental Allergy, 34, 1507-1513. doi:10.1111/j.1365-2222.2004.02061.x
Brooks, A. J., R. J. Schmitt and S. J. Holbrook. (2002). Declines in regional fish populations: have species responded similarly to environmental change? Marine and Freshwater Research, 53(2), 189-198. doi:10.1071/MF01153
D’Amato, G., Liccardi, G., D’Amato, M., Cazzola, M. (2002). Outdoor air pollution, climatic changes and allergic bronchial asthma. European Respiratory J., 20, 763-776. doi:10.1183/09031936.02.00401402
Electric Power Research Institute (EPRI). (2013). Occupational health and safety database 2012: annual data reporting years, 1995-2011. Retrieved from http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000003002000997.
Haines, A., McMichael, A.J., Epstein, P.R. (2000). Environment and health: 2. Global climate change and health. Canadian Medical Association J., 163(6), 729-734.
Moore, S.K., Trainer, V.L., Mantua, N.J., Parker, M.S., Laws, E.A., Backer, L.C., Fleming, L.E. (2008). Impacts of climate variability and future climate change on harmful algal blooms and human health. Environmental Health, 7, 1-12. doi:10.1186/1476-069X-7-S2-S4
Schaeffer, M., Gohar, L., Kriegler, E., Lowe, J., Riahi, K., Van Vuuren, D. (2015). Mid- and long-term climate projections for fragmented and delayed-action scenarios. Technological Forecasting and Social Change, 90, 257–268. doi:10.1016/j.techfore.2013.09.013.
United States Department of Labor. (2014). Industry injury and illness data. Retrieved from Bureau of Labor Statistics website: http://www.bls.gov/iif/oshsum.htm#13Summary_News_Release.
United States Environmental Protection Agency. (2014). Cleaner Power Plants Mercury and Air Toxics Standards (MATS) for Power Plants US EPA. Retrieved from http://www.epa.gov/mats/powerplants.html.
United States Energy Information Agency. (2013). How many and what kind of power plants are there in the United States? FAQ U.S. Energy Information Administration (EIA). Retrieved from http://www.eia.gov/tools/faqs/faq.cfm?id=65&t=2.
United States Energy Information Agency. (2014). Monthly Energy Review – Energy Information Administration (DOE/EIA-0035(2014/10)). Retrieved from http://www.eia.gov/totalenergy/data/monthly/index.cfm#coal.
Weber, R.W. (2002). Mother Nature strikes back: global warming, homeostasis, and implications for allergy. Annals of Allergy Asthma and Immunology, 88, 251-252. doi:10.1016/S1081-1206(10)62004-2
With regulatory and market forces chipping away at the profit margins for coal-fired and oil-fired power plants, will the next few decades usher in a surge in more cost competitive renewable energy projects throughout the United States? Not likely. The reason is that most renewable energy sources are also facing similar challenges in addition to technological barriers.
Currently, renewable energy sources make up only 13% of the power generation in the U.S., with hydroelectric power being the largest renewable energy source at 63%. By 2040, renewable energy as a percentage of total power production is only expected to reach 16%, while coal is expected to drop from 42% to 35%. Natural gas will replace the lost coal capacity and is expected rise from 25% to 30%. Why is there not a larger growth in renewable energy as a percentage of total energy production?
Take wind power for instance. Many of the best locations for wind generated electricity are off-shore where the wind gusts are frequent and strong enough to keep the blades turning profitably. The problem is that offshore turbines need maintenance to keep them running, which requires specialized equipment and procedures. Also, salt water increases corrosion and can wreak havoc on the electronics. That makes off shore maintenance a costly endeavor. The U.S. Energy Information Agency states that less than 2% of global wind capacity is located offshore, likely because of the high capital cost to build in the ocean.
One potential solution is to build the wind turbines on shore and construct them in places like the Great Plains where the wind is plentiful and maintenance costs are low. In fact, one-fifth of the United States possible wind resource is located in North and South Dakota (Bret Harper, 2005). Here the issue is that there are not enough transmission lines to carry the power to the places where it is needed. No company is willing to build wind turbines in a location where there are no transmission lines or build transmission lines where there is no power being generated. There are a few locations that are both near transmission lines and where there is sufficient wind, but the best locations are being snapped up quickly, leaving new projects to compete for less desirable locations.
Lastly, the love affair with wind power is rapidly becoming limited to those who don’t have to live anywhere near them. The public is more aware of the complaints from wind farm neighbors concerning turbine noise, its impact on birds and bats, and the amount of land it takes to collect enough wind to make a project worth doing. The result is that it is becoming increasingly more difficult to get projects approved in a reasonable time period.
Solar power is hardly worth even talking about in terms of a viable solution to the energy needs in the United States, at least with the current technology. Who by now has not heard about the number of solar power companies that have gone under due to high production costs and low wage competition from China. Even if we can get cheaper solar panels from overseas, solar power is very expensive to produce, whether being generated by giant light collecting mirrors harnessing sunlight to boil water to make electricity or using solar panels to make electricity directly. The places where sunlight is plentiful tend to be places that are dusty and hot. A thin layer of dust that is barely perceptible to the human eye can reduce the light power 20% or more. Also, high temperatures tend to cause problems with solar panels that are made with semiconductor devices that are sensitive and unreliable when temperatures get too hot. And, as with wind, there is the chicken and egg problem, because some of the best locations for generating solar power are not on the grid.
Biomass is a catchall that can refer to burning plant or animal derived materials to make power and includes municipal garbage. When biomass is burned it has the benefit of lowering the amount that needs to be landfilled and is considered a renewable resource. While biomass power plants are more easily located near transmission lines and fuel sources, they typically have other challenges that make them less competitive with fossil fuel-fire power plants. Most biomass plants are operated on a much smaller scale than traditional power plants, which means that they don’t produce enough power to keep the lights on without the aid of fossil fuel burning plants. Among the reasons is that biomass fuels do not have the same energy density (i.e. the amount of energy that can be generated per unit mass) as fossil fuels. In addition, air emissions such as acid gases can be comparable to a similar sized coal plant. Wood burning power plants, in fact, tend to have higher nitrous oxide and methane emissions when compared to a similar sized coal plant. Nitrous oxide and methane are 31 to 300 times more potent in absorbing heat than carbon dioxide. The fact that wood-fired biomass plants emit more potent greenhouse gases (GHG) makes Environmental Protection Agency’s statement of the benefits of renewable energy posted on their website somewhat awkward:
“Environmental and economic benefits of using renewable energy include: generating energy that produces no anthropogenic GHG emissions and reduces some types of air pollution”
For more information on renewable energy resources see the following links:
Are Green sea turtle populations increasing along the Texas gulf coast? Along the Texas Gulf Coast there appears to be an uptick in the number of sightings of Green Sea Turtles (Chelonia mydas) and Green Sea Turtle nests on North Padre Island. While reported sightings are not uncommon, experts do appear to agree that in 2012 and the beginning of 2013 there has been an increase in the number of sighting reports. Also increasing, is the number of turtles requiring rehabilitation due to injuries from boat encounters that too often result in the immediate death of turtles, or more frequently, leave deep disfiguring wounds that are prone to infection.
The increased sightings have some scratching their heads as to what might be occurring. A few people have suggested that there are more turtles due to the reopening of Packery Channel between Mustang Island and Padre Island. These islands form a barrier between the Texas coastline and the Gulf of Mexico, cutting off Corpus Christi Bay from the ocean and giving rise to a shallow water body known as the Laguna Madre that stretches the Texas coastline from Corpus Christi into northern Mexico. Padre Island is the longest barrier island in the world and because it separates the Laguna Madre from the ocean there is only limited mixing with ocean water, which also means limited ways for sea turtles to get in. Now that Packery Channel is open, perhaps Green Sea turtles, whose favored habitat is shallow coastal areas, are visiting more frequently than was possible before.
The turtles may also be attracted by the large gardens of sea grass that grow in the Laguna Madre. Sea grass populations have grown in the upper Laguna Madre and, because the Laguna Madre has an average depth of 3.6 feet (1.1 m), there is plenty of light from the sun and nutrients in the sandy bottoms to allow healthy growth of sea grass. In fact, 75% of all of the sea grass cover along the entire Texas coast is found in the Laguna Madre. Three species of grass dominate with shoal grass being the most abundant, followed by a moderate distribution of manatee grass and a small distribution of turtle grass. There is speculation that all of this grass is just too tempting for the vegetarian Green Sea turtle to pass up, especially in light of the fact that sea grass beds in and around other gulf coast areas have disappeared from both natural causes and human activities.
Whether the increased number of sightings is the result of an increase in the Green Sea Turtle population or more sea turtles getting in through Packery Channel may never be known. Measuring any sea turtle population is a challenge, not just because there are not enough resources to make accurate estimates, but because making the measurements often requires disturbing turtles that may lead them to abandon their nesting grounds never to return. A second difficulty is that Green Sea Turtles that do come to shore are primarily females looking for good places to build nests. Adult males and juvenile turtles tend to stay out in the open water making population estimates unreliable.