When sulfur-containing fossil fuels such as coal and heavy oil are burned in the process of generating electricity in power plants, sulfur oxides (SO_x) are being produced when the released sulfur is combined with oxygen. Sulfur oxides refers to a group of highly reactive gases that contain sulfur and oxygen compounds such as sulfur monoxide (SO), sulfur dioxide (SO₂), sulfur trioxide (SO₃), lower sulfur oxides, higher sulfur oxides, disulfur monoxide, and disulfur dioxide [13]. The most hazardous gas among this group is SO₂, normally called black smoke [10]. It is commonly used as an indicator representing the other gases that belong to a larger gaseous group of sulfur oxides since it has the highest concentration in atmosphere than other sulfur oxides such as SO₃ and its existence may lead to another SO_x formation. Mitigating the SO₂ may also avoid the formation of fine sulfate particles, which can affect the environment and public health [14].

Fifty percent of SO₂ annual global emission is generated from coal burning and another 25–30% from oil burning [15]. Normally, concentrations of SO₂ below 0.6 ppm will not affect human beings. However, most people start recognizing SO₂ at 5 ppm since it has a nasty, sharp smell [16]. Nevertheless, even short-term exposure between 5 min and 24 h can cause respiratory illnesses such as breathing difficulty (bronchoconstriction) [17] and aggravate asthma symptoms especially in those who are actively exercising or doing outdoor activities. Scientific evidence has shown that at-risk populations such as children, the elderly, and those who have a prior history of asthma are the most affected when exposed to SO₂ even in a short term [18]. Further exposure to 10 ppm in an hour will irritate humans through breathing problems and mucus removal. The condition will worsen if the weather is stagnant, there are high ambient temperatures and humidity as well as with aerosols mixture. Furthermore, the problem will become worse if SO₂ reacts with other compounds in the environment to form fine sulfate particles and enters the digestive system [12,19].

As compared with NO, NO₂ has more adverse health effects on humans since it affects hemoglobin-oxygen affinity. The hemoglobin functions as a transporter of oxygen and carbon dioxide in our blood. However, the existence of NO₂ in our blood will interrupt the bonding of hemoglobin-oxygen and form acid in the lungs [19,20]. It has a more harmful effect than CO for the same concentration. It can be seen in urban areas as a reddish-brown layer with a sharp odor [21]. It can also affect the breathing and respiratory system from the reaction of NO_x with other compounds such as ammonia, moisture, and others to form nitric acid vapor and other particles. This will further damage lung tissue and developing fetuses. Other than this, the critical effects on respiratory diseases are caused by small particles inhaled deep into fragile lungs, which worsens respiratory diseases such as bronchitis and emphysema and intensifies existing heart disease [22] Table 21.2.

As a prominent pollutant, NO_x have major impacts on health and the environment. Besides acid rain and ground-level ozone or smog, the release of NO_x also contribute to water pollution as can be seen at Chesapeake Bay, the largest estuary in the United States. The deterioration of water quality is mainly caused by eutrophication from excessive nutrient inflows, mainly nitrogen. Water with nitrate pollution has destroyed the nutrients’ ecosystem and affects aquatic plants and animals [22,23]. Eutrophication is a process by which water nutrients have been enriched to stimulate the dense growth of aquatic plant life, which eventually leads to oxygen depletion. Lacking of oxygen supply will decrease fish and shellfish populations.

Besides, airborne NO_x also react with organic compounds in the atmosphere to form toxic chemicals such as nitrate radicals, nitroarenes, and nitrosamines, which may cause genetic mutation. Furthermore, particles of NO₂ can cause visibility impairment since it can inhibit the transmission of sunlight, especially in urban areas. As NO is one of the greenhouse gases, the mixture of NO with other greenhouse gases in the atmosphere also affects global warming, which can cause catastrophic climate change.

These chain reactions will continuously occur and it has been estimated by scientists that 100,000 good ozone molecules can be destroyed by one chlorine atom. The most dramatic issue is that the lifetime of most CFCs is within range of 50–100 years before they are removed from the atmosphere [28]. This catastrophic effect can be seen at the Antarctic ozone hole where more than half of the ozone over the South Pole is lost during every spring due to sunlight occurrence. Due to this critical issue, the ODS usages have been controlled under the Montreal Protocol and their production has been banned by signatory countries. As a consequence, the atmospheric concentration of ODS has stabilized and declined recently [29].

Overexposure of UVB radiation to humans contributes to the risk of the most fatal skin cancer, melanoma. The risk of developing melanoma has increased more than twice since 1990. Other than this, UVB may also affect eye diseases such as cataracts and weaken the immune system. Even plants and crops are affected by this exposure, such as soybean, which leads to drops in production. Furthermore, marine life is also disturbed by UVB radiation since it leads to phytoplankton damage, which will decrease fisheries and marine food sources, as this is the base of the ocean food chain.

On the other hand, the bad or tropospheric ozone occurs when NO₂ is emitted by fossil fuels when they react with sunrays, producing NO and a free oxygen atom (O) to form O₃ at lower layers of the atmosphere [24].

This tropospheric ozone is dangerous to human health especially in lung disease since it can worsen asthmatic patients condition and make them more sensitive to SO₂. Even healthy people have difficulty breathing when exposed to ozone. Besides, it can trigger other respiratory ailments such as chest pain, throat irritation, cough, congestion, emphysema, and bronchitis. It can also damage crops and their ecosystems, which leads to reduced agricultural production, and can destroy tree seedlings prone to diseases and pests as well as harsh weather [25]. Due to these effects, ozone has been considered one of the most common air pollutants by the WHO in addition to particulate matter, nitrogen dioxide, sulfur dioxide, and carbon monoxide.

In contrast, tropospheric ozone can be converted back to NO₂ and oxygen molecules (O₂) naturally when there is an availability of NO and lack of sunlight such as during late afternoon and night:

Even though this natural process will help convert ozone to NO₂, this rapid chain reaction will continuously release ozone in the environment as long as NO is available in the atmosphere. Emission of hydrocarbon from transportation combustion will react with NO to release organic radicals. This competition between hydrocarbon and ozone to react with NO will also affect the continuous duration of ozone in the atmosphere [10].

A pure natural water pH value is 7 whereas normal rainwater is 5.6. Any pH value of less than 5 is considered to be acid rain. The acid rain will acidify lakes, ponds, or estuaries, which greatly affects their flora and fauna and ecosystems, destroying all marine life. An example of an acid rain tragedy is the acidification of 95,700 lakes in the Adirondack Mountains, USA, and Ontario, Canada, which have killed the fish population and resulted in all aquatic organisms being suppressed to survive in acidic streams [19]. Honnedaga Lake lies deep in the forest of Adirondacks and has been seen with an eerie blue color because its plankton has died due to acid rain. The acidification of water streams has a damaging effect on fisheries since it inhibits hatching and erodes the gill tissues and cellular debris between gill filaments. There are several fish species that can survive in acidic water; however, there is an increasing mercury content in their bodies. Heavy metal seeps into the rivers from soil due to acid rain. Also, this affects the ecosystem since black flies, which are a scourge during outdoor activities due to their bloody and painful bite, remain unaffected by acidic water. When most organisms die, black flies will flourish with less competition for habitat and fewer predators to control their population.

Due to the corrosive effect of acid rain, most of the hardwood forests stop growing and evergreen forests are losing their needles, which have been confirmed by the decline of red spruce forests at Camel Humps, Vermont’s Green Mountain. Acid rain has drained vital nutrients from the soils and leaches aluminum from rocks, which can destroy the roots. This prevents the plants from absorbing water and other nutrients for their growth. In addition, acid rains are also damaging the structure and finish of automobiles, which causes rapid weathering. Moreover, acid rain is also leaching poisonous heavy metals, such as mercury and lead, in the water supply. Copper is also destroying the bacteria that are beneficial to septic systems [30].

As stated by United Nations Climate Change Conference 2009 in Copenhagen, a limit of 2°C of global temperature has been established due to the dangerous climate change effects [3,4]. The increasing global temperature melts the ice caps at the North and South Poles, glaciers, and snowlines. This will lead to a rise in ocean levels of 2–2.5 m by end of this century, and will cause flooding of the fertile land along coastal areas. This abrupt change disturbs the ecosystem and obviously will reduce crop production due to limited fertile land. In addition, carbon dioxide also dissolves in the sea, which also increases the surface seawater temperature and dissipates the heat back to the atmosphere. This cycle will further intensify the effect of greenhouse effect. The increase of sea surface temperatures will also cause more destructive hurricanes and millions of people and properties will be affected. Another greenhouse effect is the heavy rainfall in some areas, which induces heavy flooding, whereas other parts will have droughts in order to balance the water cycle [16,31].

In order to minimize carbon dioxide emission, carbon footprint is a solution that can be used to investigate the summation of greenhouse gas emissions of a product or service across its lifecycle from cradle-to-grave or from the farm gate to the exit gate of the processing plants [32–34]. It is measured in units of carbon dioxide equivalent (CO₂e). It comprises two main parts, which are direct and indirect footprints. The direct or primary footprint is a direct emission of CO₂e from the fossil fuel combustion such as energy usage and transportation, whereas the indirect footprint is an indirect emission of CO₂e from the whole lifecycle of products or services [35,36]. Figure 21.1 shows comparison of carbon footprints between various energy resources.

Coal is the highest carbon footprint contributor among conventional fossil fuels, which is the main reason why coal-fired power plants are the highest producer of CO₂ per kWh. Figure 21.2 shows that other conventional fossil fuels also release carbon dioxide gas to the atmosphere per unit heat energy input.

Instead of using its dynamic diameter to classify the particulate matter, classification can also be done based on its source, which are the primary and secondary particles. The primary particles are directly suspended as a result of human activity or naturally. However, secondary particles are produced by indirect reaction from chemicals emitted by primary particles that react with sunrays. Various health problems may occur due to inhalation of these particulate matters, such as coughing, irritation in airways, breathing difficulty, worsening asthmatic symptoms, bronchitis, heart attacks, and many more. In addition, there are also other adverse effects to the environment such as visibility impairment, acidification of lakes and rivers, and changes in ecosystems at coastal water and estuaries because of nutrient imbalance and leaching of nutrients from soil, which damages forests and crops, killing diversity in the ecosystems and damaging building structures [43].

In order to control suspended particle matters in the atmosphere, several technologies have been used to filter them before they are released into the environment, such as wet particulate scrubbers, fabric filters, electrostatic precipitators, mechanical collectors, and high temperature high-pressure particulate control. The wet scrubber functions by using liquid as a filter to trap the flying particulates and sulfur dioxide before they are released into the environment. On the other hand, fabric filters will trap the particulates in bags just like the vacuum cleaner before the gas is vented to the atmosphere. This method has been used widely since 1970 and its efficiency is more than 99.5%.

Legionnaires’ disease was an emerging disease of the twentieth century and is usually referred to as an “emerging infectious disease (UID)” is an impact of human alteration to the environment [49]. The source of legionnaires’ disease is cooling towers, hot and cold water systems, spa pools, thermal pools, springs, humidifiers, domestic plumbing, and potting and compost. It can be transmitted through inhalation of the contaminated aerosol, wound infection, and aspiration. There are several contaminated places such as shopping centers, restaurants, clubs, leisure centers, sports clubs, private residences, hotels, cruise ships, camp sites, hospitals, and medical equipment [45].

Initially, cooling towers were founded to be the primary source of this disease. Cooling towers installed at public areas with dense populations, seasonal and climatic conditions, which are intermittently used, have poor engineering design, and have had little or no maintenance are the possible risks for this disease. A recent case was reported in July 2010 where a 73-year-old patient was hospitalized at Kobe University Hospital, Japan, due to alveolar hemorrhage, systemic lupus erythematosus, and antiphospholipid antibody syndrome. After 4 months in the hospital, she was then diagnosed with nosocomial Legionella pneumonia. Further treatment was given but she died because of uncontrollable pulmonary alveolar hemorrhage. Since she was diagnosed with nosocomial Legionella pneumonia, the infection control team investigated the source of the risk. The investigation revealed a link to a contaminated hospital-cooling tower; tests showed a 95% strain similarity of samples taken from the patient and the hospital cooling tower. This contaminated aerosol from the hospital-cooling tower had been inhaled by this immune-compromised patient. The actions taken by the hospital to prevent the L. pneumophila breeding was to increase the temperature of the hot water supply appropriately, increase the Legionella culture test frequency to three times annually, and introduce automated disinfectant insertion machines with BALSTER ST-40 N as an antiseptic reagent. After implementing the new preventive measures, no cases have been reported since from the hospital-cooling tower or the hot water system [50].

Moreover, the construction of a dam will block the connection between the upstream and downstream of the river, which will create a sedimentation problem behind the dam. This situation will also affect some of the fish population because they cannot migrate to their spawning ground. The slow velocity of the river flow in some bays of the reservoir will influence water quality due to the high content of nutrients in water. This will cause eutrophication where excessive growth of aquatic plants will pollute the water as happened in the Three Gorges Dam [52].

Public concern has increased due to radiation from nuclear power plant effluents as seen by vented steam and its ejection outlets at the water discharged areas. There are definitely permissible effluents that are released to the environment. However, excessive radiation will increase the risk of damage to organ and body tissues, genetic mutations, birth defects, leukemia, cancers, immune system disorders, and many more. Human body tissues are made of compounds of carbon in which isotope ₆C¹⁴ can be found in trace quantities with radioactive potassium isotope ₁₉K⁴⁰ to balance cells’ fluid quantities in the human body. Once radioactive gas is inhaled or consumed, this radiation will result in biological damage. As an example, radiation can penetrate and damage cells inside the respiratory tract passages, which induces lung cancer [63]. Human beings are also exposed to background radiation and also impose radiation. It has been reported that one Brazilian beach reached 800 mSv. The legal authorities have to consider the background radiation that the public have been exposed to, which is 2.5 mSv per year by normal activities in order to limit public exposure to radiation.

The discharged nuclear power plants’ effluents depend on the type of reactors, which are pressurized water reactor (PWR) and boiling water reactor (BWR). The reactors that have been used in Europe are PWR, which is safer than BWR because the reactor vessels are separated from the steam generators. However, the steam in BWR is directly produced in the reactor vessel and routed to the steam turbine generator to produce electricity. The steam also brings absorbed radionuclides in gaseous form. The “offgas” system will remove the radioactive gases and delay the release of radionuclides such as krypton and xenon until their acceptable decay, but the possibilities of leakage and accidental release are the main concern of the public [19,24]. Leakage in nuclear power plants is due to mechanical failure and human error will increase because nuclear power plants are getting older, are not maintained properly, and lack monitoring from legal authorities. Even the transportation of fuel from mines to the nuclear power plant also exposes the environment to radiation.

If the reactor’s temperature increases more than 1200°C, hydrogen molecules will be separated from the water and trapped at the ceiling of the reactor due to its light density. This may cause a fire if ignited and damage the containment structure. The explosion will emit radioactive steam into the air just like the Three Mile Island, Chernobyl, and Fukushima Daiichi accidents. Moreover, meltdown will happen if the reactor’s temperature reaches 2400°C where the uranium fuel will melt down and the fuel rod will become molten wax. The molten uranium will continue to melt its way downward and penetrate the ground until the heat can be absorbed by the molten rock and soil, which is about 10 ft. deep. The molten soil surrounding the fuel will harden like glass and contain the remaining fuel. However, if the molten uranium penetrates the groundwater supplies then this will have a bigger disastrous impact, and the contamination will be spread to a larger area. In fact, very high pressure from the reactor’s high temperature will explode the containment structure and release the radioactive emission into the atmosphere [24,63].

A series of tragedies have occurred due to LOCAs at nuclear power plants. As an example, severe LOCA happened in Manitoba in November 1978 where a major coolant spillage occurred due to pipe leakage of the WR-1 at Pinawa. A total of 2739 L of coolant oil leaked and discharged into the Winnipeg River. Due to the loss of coolant, the reactor reached a high temperature even though not due to meltdown temperature and damaged the three fuel elements and emitted fission products [68]. A year later, the largest nuclear disaster happened in the United States on March 28, 1979 due to loss of coolant and suffered a severe core meltdown. Fortunately, the containment structure was still intact and held almost all of the radioactive emission [69]. LOCA is the main factor that leads to meltdown and damage to the nuclear power plants. The damaging effects through radioactive release through ground soil, water supply, and atmosphere led to major health problems and even fatalities. It is not only human beings that are affected; the coolant leakage that was discharged into the river is eaten by fish and aquatic organisms. Research has been done that revealed that radiation also leads to fatalities to fish, mussels, and other aquatic species [70]. The river also provides irrigation to crops and vegetation, which then died due to the radiation; some of is eaten by humans. Livestock such as cows and sheep drink from the radiated river and provide milk and meat for human consumption. This damaging continuous food chain will surely affect humans through various carcinogenic diseases and even genetic mutation.

Nuclear power plants have radioactive wastes that should be disposed of properly in a location that is a remote and geographically stable area, such as Yucca Mountain, Nevada, in United States or the Waste Isolation Pilot Plant in the Chihuahuan Desert, New Mexico. The disposal area should be built with proper security to ensure that the highly radioactive waste is stored safely within its half-life, which can be more than a thousand years [73]. Natural disposal of radioactive waste was shown at Oklo in Gabon, West Africa two billion years ago where the radioactive materials were safely contained in that area and eventually decayed into nonradioactive elements [68]. This shows that it is possible to contain radioactive wastes in secured long-term storage until they reach a safe level in unspecified time.

The safety nuclear regulatory bodies for each country that have nuclear power plants must update their policies if necessary with recent issues in order to maintain the safety of the spent fuel storage. Critical risks such as terrorist attacks, plane crashes, tsunamis, floods, tornados, and hazards from nearby activities should be taken into account in enhancing emergency responses during these conditions. These emergency responses must be in place for quite long time, which may take billions of years, and is the major challenge for radioactive waste storage.

Furthermore, hydrogen is the raw material required for the electrochemical process in the fuel cell, which can be obtained from water, biomass, and fossil fuels. However, hydrogen supplies nowadays are produced from natural gas that releases carbon dioxide during the process. Thus, the greenhouse gases are still emitted in order to achieve this clean energy [84]. Moreover, the technology of fuel cells should be improved further as it is still in a growth stage; its technological maturity is predicted to be 2018 [85].

The extensive usage of biomass still has detrimental environmental concerns that must be taken care of. For example, biomass energy cultivation requires large areas of land and substantial amounts of water. The intensive harvesting of biomass will increase soil erosion, water degradation, and removal of nutrients. In addition, the use of pesticide and fertilizer could pollute water resources. Replacement of primary forests and natural ecosystems with massive energy crops plantations will significantly change natural habitats and food source for wildlife.

Another important issue is that the demand for biomass energy has created competition between crops used as food and biofuel supplies. This issue increases food prices in some regions because farmers have shifted to biofuel crops due to better earnings. It is considered inappropriate to convert food into fuel in areas where there are still many people suffering from starvation and malnutrition in order to mitigate greenhouse gas emissions.