**2. Description of air pollution and characterization of monitored atmospheric pollutants**

Air pollution, both for indoor or outdoor environments, is caused by several causes like chemical, physical, or biological modification of the natural characteristics of the atmosphere. Most common household combustion devices, motor vehicles, and industrial process are anthropogenic sources of air pollution, but also natural sources are very important for air pollution assessment as the forest fires and volcanoes emissions. Particulate matter, carbon monoxide, ozone, nitrogen dioxide, and sulphur dioxide today are the most important pollutants for their serious health risks [1].

In Europe, emissions of many air pollutants have decreased significantly the last 30 years, and air quality has improved across the region. However, excess of air quality standards still occurs, especially in metropolitan areas, and air pollutants released in one country may be transported in the atmosphere, polluting or degrading the air quality in neighbouring countries. On the basis of this statement, air pollution can be considered as a local, pan-European, and hemispheric issue [2].

At present, particulate matter, nitrogen dioxide, and ground-level ozone are recognized as the three most dangerous pollutants that affect human health, ranging in severity of impact according to long-term and peak exposures. Moreover, benzo(a)pyrene is a carcinogenic substance of increasing concern, as its concentrations are above the threshold set to protect human health in several urban areas, especially in central and eastern Europe. Air pollution could also represent a danger for the environment, producing acidification, eutrophication, and damage to agriculture.

There are various sources of air pollution, both anthropogenic and of natural origin, in turn divided in stationary and mobile sources. The most common anthropogenic sources of pollutants are combustion processes used for electricity generation, transport, industry and households, industrial processes and solvent use, agricultural crops and livestock, waste incinerator and landfill. A stationary source of air pollution, also known as a point source, refers to a fixed emission source, represented by factories, power plants, dry cleaners, resi‐ dential wood burners, dry lakebeds, and landfills. A mobile source of air pollution is a source capable of moving under its own power. "On-road" transportation is related to all vehicles; however, there is also a "non-road" or "off-road" transportation, including the gas-powered machines for garden maintenance or recreational vehicles.

of quantity and cost. In order to assess the related risk of air pollution, it is certainly very important to establish the effects of pollution on human health, but it is also needful to consider

Considering all these aspects, our proposal includes a chapter about atmospheric and urban pollution describing their relative and assessed effects on human health, with a detailed regard on risk assessment. In the last decades, a large number of legislations have been issued accepting international subscribed agreement, such as the Kyoto protocol, to save public health and restrict the effects of pollution on climate change. We will also focus on indoor pollution, with its insufficient data and relative problems and difficulties in management, on method‐

Air pollution, both for indoor or outdoor environments, is caused by several causes like chemical, physical, or biological modification of the natural characteristics of the atmosphere. Most common household combustion devices, motor vehicles, and industrial process are anthropogenic sources of air pollution, but also natural sources are very important for air pollution assessment as the forest fires and volcanoes emissions. Particulate matter, carbon monoxide, ozone, nitrogen dioxide, and sulphur dioxide today are the most important

In Europe, emissions of many air pollutants have decreased significantly the last 30 years, and air quality has improved across the region. However, excess of air quality standards still occurs, especially in metropolitan areas, and air pollutants released in one country may be transported in the atmosphere, polluting or degrading the air quality in neighbouring countries. On the basis of this statement, air pollution can be considered as a local, pan-

At present, particulate matter, nitrogen dioxide, and ground-level ozone are recognized as the three most dangerous pollutants that affect human health, ranging in severity of impact according to long-term and peak exposures. Moreover, benzo(a)pyrene is a carcinogenic substance of increasing concern, as its concentrations are above the threshold set to protect human health in several urban areas, especially in central and eastern Europe. Air pollution could also represent a danger for the environment, producing acidification, eutrophication,

There are various sources of air pollution, both anthropogenic and of natural origin, in turn divided in stationary and mobile sources. The most common anthropogenic sources of pollutants are combustion processes used for electricity generation, transport, industry and households, industrial processes and solvent use, agricultural crops and livestock, waste incinerator and landfill. A stationary source of air pollution, also known as a point source, refers to a fixed emission source, represented by factories, power plants, dry cleaners, resi‐

some health determinants such as genetic factors, age, sex, and lifestyle habits.

**2. Description of air pollution and characterization of monitored**

ologies of study, and on some case reports.

pollutants for their serious health risks [1].

European, and hemispheric issue [2].

and damage to agriculture.

**atmospheric pollutants**

420 Current Air Quality Issues

People or their activities do not cause natural "air pollution," and emission sources generally comprise volcanic eruptions, windblown dust, sea-salt spray, wild animals in their natural habitat, and plants releasing volatile organic compounds [2].

In the evaluation of pollution effects, it must be kept in mind that dangerous substances can be emitted as primary or secondary pollutants. Primary pollutants are emitted directly into the air from pollution sources, while secondary pollutants are formed when primary pollutants undergo chemical changes in the atmosphere. For example, NOX and SO2 are directly emitted into the air following fuel combustion or industrial processes. In contrast, O3 and the major part of PM form in the atmosphere following emissions of various precursor species, and their concentrations depend strongly on meteorological conditions, such as high air temperatures and sunlight.

At present, the attention of scientist and legislator is focused on the major sources of dangerous substances, represented by urban and industrial activities.

In the evaluation of urban pollution, it is important to consider regional pollution, city pollution, real and *hot spot* events, determined by peaks of pollutants higher than average followed by gradual restoration of normal limits. Of these three components, the first two have direct effects on human and environmental health, as they expose population to contaminants for a longer time, causing chronic effects.

As regards industrial pollution, there are various unwanted substances and losses generated by industrial activities both for qualitative and quantitative aspects [3].

For this reason, to assess significant trends and to discern the effects of reduced anthropogenic precursor emissions, long time series of measurements and a continuous monitoring of air quality are needed [4].

The application of European Directives contained the emission of many pollutants, conse‐ quently reducing their levels in the atmosphere. However, while restrictions are imposed on industries, technologies are developed to reduce pollutants from road transport and the most harmful substances in the air are continuously monitored, air pollution is still a major problem and it is necessary to focus attention on its effects on human health and on methods to reduce these effects.

At present, based on "*The Clean Air Act",* Quality Standards are set for six common air pollutants, also known as "criteria pollutants". They are particulate matter, ground-level ozone, carbon monoxide, sulphur oxides, nitrogen oxides, and lead. These pollutants can harm human health and the environment and cause property damage. The set of limits based on human health is called primary standards. Another set of limits intended to prevent environmental and property damage is called secondary standards [5].

The main pollutants measured to characterize and monitor the quality of the environment are shown below.

#### **2.1. Particulate Matter (PM)**

PM is one of the most important pollutants in terms of potential to harm human health, as it penetrates into low regions of the respiratory system. PM is a complex heterogeneous mixture of solid particles and liquid droplets found in the air, whose size and chemical composition change in time and space, depending on different emission sources and atmospheric and weather conditions. These particles come in many sizes and shapes and can be made up of hundreds of different chemicals. PM includes both primary and secondary PM; primary PM is the fraction of PM that is emitted directly into the atmosphere from construction sites, unpaved roads, fields, smokestacks, or fires, whereas secondary PM forms in the atmosphere following the oxidation and transformation of precursor gases (mainly SO2, NOX, NH3) and some volatile organic compounds (VOCs) that are emitted from power plants, industries and automobiles.

Particle pollution includes "inhalable coarse particles," with diameters larger than 2.5 µm and smaller than 10 µm, and "fine particles," with diameters that are 2.5 µm and smaller. Smaller sizes of PM such as PM2.5, with a diameter up to 2.5 µm, are considered particularly harmful due to their greater ability to penetrate deep into the lungs.
