Acid Rains is a phenomenon related to the emission of increasing amounts of sulfur oxides (S) and nitrogen oxides (N) into the atmosphere, in the form of sulfur dioxide (SO2) and nitrogen oxide (NO). These are the main pollutants emitted during the combustion process, in particular, nitrogen oxide (NO) is always released as both nitrogen (N) and oxygen (O) are present in the air. As for sulfur dioxide (SO2), on the other hand, only in some cases is it produced because sulfur (S) is not present in the air, so it must be present in the burned material. The negative effects of acid rain cause the weakening of plants, and therefore produce damage to forests, as well as produce a chemical and physical alteration of soils and waters: this phenomenon leads to the acidification of aquifers and the disappearance of aquatic species present in lakes and rivers. In addition, the acidity of rain also leads to the disintegration of some building materials and the development of respiratory diseases. Fortunately, this problem is diminishing because coal use is decreasing.

Air Pollution is about changing the normal composition, or physical state, of atmospheric air. This change is due to the presence of one or more substances capable of:

• Altering the normal environmental conditions of health
• Constituting a direct or indirect danger to human health
• Compromising recreational activities or other legitimate uses of the environment
• Altering biological resources, ecosystems, and material goods, both public and private.

The atmospheric pollution can be:

• Natural: dust, volcanic eruptions, fires, decomposition of organic material, and electrical discharges in the atmosphere
• Anthropic: combustion processes, waste disposal, and industrial plants.

Furthermore, these types of pollution can be both local (limited to the area of ​​production of the pollution) and global (the consequences are widespread throughout the planet).

To control air pollution, air quality standards have been established which consider the level of danger of the pollutant in regard to human health. Main pollutants governed by legislation are:

• Particulate matter: any substance, solid or liquid, dispersed in the atmosphere with dimensions of less than a few microns. In urban areas, the difference is made between PM10, i.e. the particulate fraction with dimensions below 10 microns (capable of being retained in the respiratory tract and not reaching the lungs), and PM2.5, i.e. the particulate fraction less than 2.5 microns and is more dangerous than PM10. Some of the negative effects of particulate matter are due to the dirtying of the external surfaces of buildings, the corrosive effect and damage to vegetation, as well as respiratory problems.
• Sulfur oxides: they are caused by anthropogenic action, mainly coming from thermoelectric plants, industrial plants, refineries, and from the production of metals. In addition to causing acid rain, they are also responsible for problems with the respiratory system.
• Nitrogen oxides: they are toxic and irritating to the respiratory tract and are produced by combustion.
• Carbon monoxide: it is a pollutant that is produced by all combustion processes fueled with hydrocarbons and therefore by combustion engines, industrial processes, and natural emissions. It is lethal if the concentration in the body is high, it generally causes loss of concentration, altered reflexes, and migraines.

The concept of a hole in the ozone layer is improper and it is more correct to speak of a decrease in the concentration of this gas in the atmosphere. Ozone is the triatomic oxygen (O3) found about 30-40 km above the ground in the stratosphere and reduces the penetration of ultraviolet radiation to the earth. In particular, UVA is able to reach the ground, but UVB and UVC are absorbed by ozone. The main cause of the decrease in atmospheric ozone concentration is the release of chlorofluorocarbons (CFCs), which are found in refrigerants, propellants, insulation materials, and fireproofing materials. Unfortunately, CFCs are also responsible for the greenhouse effect, which is why it’s important to find sustainable materials to replace them. Protection from ultraviolet radiation occurs through a continuous process of production and destruction of molecules. In fact, radiation destroys ozone (O3), producing a diatomic oxygen (O2) and oxygen (O) molecule. Subsequently, the decomposition of CFCs generates chlorine free radicals (CL) that effectively react with ozone, taking away an atom of oxygen. This leads to the limited availability of atomic oxygen needed to complete the cycle and allow ozone regeneration.

The phenomena of Global Pollution are characterized by the presence of pollution spread throughout the planet and not limited to the geographical area where it was produced. The main phenomena related to global pollution are Acid rain, Decrease in ozone concentration, and the Greenhouse effect.

Green Economy (GE) is the economy that use energy and raw materials efficiently, intervene in ecosystems without damaging them, and consider waste as raw materials. It is a theoretical model of economic development that aims to reduce emissions and pollution, increasing energy efficiency and resources. The macro sectors of GE are:

• Renewable energy
• Green buildings
• Sustainable transportation
• Water management
• Waste management
• Land management.

The Greenhouse Effect is a natural phenomenon caused by the presence of gases such as carbon dioxide, water, methane, and nitrogen oxides in the atmosphere. These gases are transparent to incoming solar radiation, however, they are opaque to the radiation emitted by the earth, having a greater wavelength. Without the greenhouse effect, the average temperature of the earth would not be suitable to host living forms, being too low, however, anthropogenic action has increased the greenhouse gases amount in the atmosphere, mainly due to combustion processes and deforestation actions. To quantify the impact of greenhouse gases, emitted by human action, we refer to the Global Warming Potential (GWP).

Life Cycle Assessment (LCA) is an analysis methodology that allows evaluating the environmental loads associated with a product, considering the energy used to produce it, the materials consumed, and the final waste. It is used considering three different time frames:

• From cradle to grave, that is from the extraction of the raw materials (necessary during the production process) to the disposal of the product at the end of its life.
• From cradle to gate, that is from the phase of extraction of raw materials to the exit from the plant.
• From cradle to cradle, that is from the extraction of the raw materials (necessary during the production process), up to the recycling of the product at the end of its life.
• From gate to gate, that is from the entrance to the exit of the plant

Light Pollution increases the brightness of the sky, resulting in decreased visibility of celestial bodies, and it is due to the dispersion of the light flux emitted by lighting systems, in particular:

• Inadequate night lighting
• Reflection of the light flux towards the sky
• Incorrect management and maintenance of lighting systems.

This pollution has harmful effects on the environment, altering the vital rhythms of flora and fauna and reducing the possibility of carrying out astronomical research. If light pollution were controlled, energy consumption would also be reduced.

Noise Pollution causes the introduction of noise into the living and external environment, such as to cause annoyance, disturbance of rest, human activities, danger to human health, and deterioration of ecosystems. Sources of noise pollution include:

• Noise from inside the building such as conversations, TVs, sound systems, and general appliance noise.
• Noise from outside the building such as noise from construction sites, industrial areas, and vehicles such as cars, trains, and airplanes.
• Impact noise such as falling objects
• Reverberation, i.e., a sound that propagates due to resonance in very large, empty rooms.

To reduce noisy pollution two main actions can be carried out:

• Prevention, adopting good practices to produce little noise
• Protection, mitigating the effects of the noise emitted. Among the various mitigation methods, it is possible to act on the source, along the path that follows the sound or on the receiver.

Sustainable development is a concept that emerged in 1987 during the Stockholm conference and states that development should be able to meet the needs of current generations without compromising the ability of future generations to meet their own needs. The concept of sustainable development, therefore, is related to the concept of intergenerational justice. Moreover, sustainability implies social, economic, environmental, and institutional equity.

Thermal pollution is linked to the second law of thermodynamics (Carnot’s statement). In fact, using a thermal machine it is not possible to completely transform heat into work but part of the heat supplied to the machine is returned to the external environment.

The thermal pollution caused by the industries derives mainly from the use of water to cool the thermal machines. In fact, the industries subsequently release the heated water into the environment. One of the worst consequences is linked to the biological alteration, since zooplankton, phytoplankton, fish, and other species have a preferential temperature range within which reproduction and growth are favored. Outside this range, the population decreases until it becomes extinct.

Another form of thermal pollution is related to urban heat islands, i.e. the increase in temperature in urban centers. Usually, the increase is about 4-8 ° C compared to the suburbs and the countryside and is caused by the reduction of vegetation, the waterproofing of the surfaces (which would not allow evapotranspiration), by the urban geometry capable of internally reflecting the radiation infrared and the use of energy sources such as air conditioners, vehicles, and production processes.