**2.5. Nitrogen oxide (NOX)**

Nitrogen oxide (NOX) is emitted during fuel combustion, by industrial facilities and the road transport. NOX contributes to the formation of secondary inorganic PM and tropospheric O3, to acid deposition and to eutrophication. Of the chemical species that comprise NOX, NO2 is associated with adverse affects on health, such as inflammation of the airways and reduced lung function.

Nitrogen dioxide (NO2) is a highly reactive gas. Other nitrogen oxides include the nitrous acid and nitric acid. EPA's National Ambient Air Quality Standard uses NO2 as indicator for the class of nitrogen oxide. NO2 is emitted from all vehicles and industrial plants, including power plants. In addition to the arising O3 and PM, NO2 is linked also to several adverse effects on the respiratory system. Both primary EPA standard (to protect health) and secondary EPA standard (to protect the public welfare) for NO2 are established at 0.053 parts per million (53 ppb), averaged annually. EPA (January 2010) established an additional primary standard at 100 ppb. Primary standards are finalized to protect public health, including health of respon‐ sive populations, people with COPD, children, and the elderly. No European and extra-European countries have been found stranger to the problem.

#### **2.6. Heavy metals**

The main heavy metals in outdoor air are arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and nickel (Ni); they are emitted mainly as a result of various combustion processes and industrial activities and generally can reside in or be attached to PM. Heavy metals are persistent in the environment and can be deposited on terrestrial or water surfaces, contami‐ nating soils or sediments, and accumulating in food-chains.

### **2.7. Polycyclic Aromatic Hydrocarbons (PAHs) and benzo(a)pyrene (BaP)**

PAHs are pollutants created during the incomplete burning of several organic substances like coal, oil, gas, wood, garbage, and also tobacco and smoked and grilled. Actually, there are more than 100 different PAHs identified. PAHs generally occur as complex mixtures of congeners. The primary sources of exposure to PAHs are inhalation of the compounds in tobacco smoke, wood smoke, and ambient air.

PAHs is a growing health concern in Europe, with particular regard to BaP, a polycyclic aromatic hydrocarbon, formed mainly from the incomplete burning of organic material such as wood and from car exhaust fumes especially from diesel vehicles. It is a known cancercausing agent in humans. A main source of BaP in Europe is domestic home heating, in particular, wood burning, waste burning, coke and steel production, and mobile sources. Other sources include outdoor burning and rubber tyre wear. In Europe, BaP pollution is mainly a problem in certain areas such as western Poland, the Czech Republic, and Austria where domestic coal and wood burning is common.

Between the PAHs, the International Agency for Research on Cancer (IARC) considers BaP as 2A class, so carcinogen. However, the carcinogenicity of BaP was demonstrated through studies carried out with animals. Benzo(a)pyrene is a known mutagen, but it must be metab‐ olized to be able to induce mutation. Exposure to BaP pollution is quite significant and ubiquitous. Central and Eastern European countries report air BaP concentrations above the target value. Approximately one quarter of the EU people were exposed to higher BaP concentrations respect to target value (1 ng/m3 ) for the period 2008–2010. But almost the entire population was exposed to BaP concentrations above WHO reference level [6]. The increase of BaP emissions in Europe over the last years is therefore an important concern for public health. Regarding BaP, the Industrial Emissions Directive [7] regulates emissions from a large range of industrial sources.

#### **2.8. BTEX**

It is a group of chemical compounds including Benzene, Toluene, Ethylbenzene, and Xylenes. BTEXs are made up of naturally occurring chemicals that are found mainly in petroleum products such as gasoline. Everyone is exposed to small amounts of BTEX compounds in the outdoor air, at work, and in their homes. Besides the common daily exposures to BTEX, larger amounts can enter the environment from leaking underground storage tanks, overfills of storage tanks, fuel spills from auto accidents, and landfills.

Short-term exposure to gasoline and its components benzene, toluene, and xylenes has been associated with skin and sensory irritation, central nervous system (CNS) problems, and effects on the respiratory system. Chronic exposure to BTEX compounds can affect the kidney, liver, and blood systems. Long-term exposure to high levels of the benzene compound can lead to leukemia and cancers of the blood-forming organs [8].

### **2.9. Physical pollution**

**2.6. Heavy metals**

424 Current Air Quality Issues

The main heavy metals in outdoor air are arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and nickel (Ni); they are emitted mainly as a result of various combustion processes and industrial activities and generally can reside in or be attached to PM. Heavy metals are persistent in the environment and can be deposited on terrestrial or water surfaces, contami‐

PAHs are pollutants created during the incomplete burning of several organic substances like coal, oil, gas, wood, garbage, and also tobacco and smoked and grilled. Actually, there are more than 100 different PAHs identified. PAHs generally occur as complex mixtures of congeners. The primary sources of exposure to PAHs are inhalation of the compounds in

PAHs is a growing health concern in Europe, with particular regard to BaP, a polycyclic aromatic hydrocarbon, formed mainly from the incomplete burning of organic material such as wood and from car exhaust fumes especially from diesel vehicles. It is a known cancercausing agent in humans. A main source of BaP in Europe is domestic home heating, in particular, wood burning, waste burning, coke and steel production, and mobile sources. Other sources include outdoor burning and rubber tyre wear. In Europe, BaP pollution is mainly a problem in certain areas such as western Poland, the Czech Republic, and Austria where

Between the PAHs, the International Agency for Research on Cancer (IARC) considers BaP as 2A class, so carcinogen. However, the carcinogenicity of BaP was demonstrated through studies carried out with animals. Benzo(a)pyrene is a known mutagen, but it must be metab‐ olized to be able to induce mutation. Exposure to BaP pollution is quite significant and ubiquitous. Central and Eastern European countries report air BaP concentrations above the target value. Approximately one quarter of the EU people were exposed to higher BaP

population was exposed to BaP concentrations above WHO reference level [6]. The increase of BaP emissions in Europe over the last years is therefore an important concern for public health. Regarding BaP, the Industrial Emissions Directive [7] regulates emissions from a large

It is a group of chemical compounds including Benzene, Toluene, Ethylbenzene, and Xylenes. BTEXs are made up of naturally occurring chemicals that are found mainly in petroleum products such as gasoline. Everyone is exposed to small amounts of BTEX compounds in the outdoor air, at work, and in their homes. Besides the common daily exposures to BTEX, larger amounts can enter the environment from leaking underground storage tanks, overfills of

) for the period 2008–2010. But almost the entire

nating soils or sediments, and accumulating in food-chains.

tobacco smoke, wood smoke, and ambient air.

domestic coal and wood burning is common.

concentrations respect to target value (1 ng/m3

storage tanks, fuel spills from auto accidents, and landfills.

range of industrial sources.

**2.8. BTEX**

**2.7. Polycyclic Aromatic Hydrocarbons (PAHs) and benzo(a)pyrene (BaP)**

Physical pollution is pollution caused by colour (change), suspended solids, foaming, tem‐ perature conditions, or radioactivity, and it is characterized by its influence on environmental conditions caused by forces and operations of physics, such as noise, microwave radiation, vibration.

#### **2.10. Microbiological factors**

Microbiological factors in the environment represent an underestimated but insidious risk factor, which concern has increased with the introduction of advanced technologies in hospitals, industry, and agriculture. Microbial agents are transported and diffused in ambient through PM [9]. The main sources of microorganisms are Flügge droplets from human airways and conditioning systems, the last containing different bacteria such as *Legionella pneumophi‐ la*, virus, and mould.

To maintain a healthy environment, a strict monitoring must be undertaken for each of the contaminants mentioned above; legislation on environment sets a benchmark and provides a series of actions to hold the values of the contaminants within the limits.

As air pollutants can be transported many miles away from the area of their emission, monitoring these substances is more difficult than monitoring contaminants in water or soil, so it was decided to record ambient air quality data focusing on major pollutants. Continuously operating automatic analysers are the most important information source on air pollution levels [10]. According to current legislation, measurements are taken at permanent sites equipped with physico-chemical monitoring devices even if these stations provide only data on exposure levels which do not facilitate making conclusions on the effects or impacts to human health and the general environment. Moreover, spatial coverage and temporal definition of the carried measurements together with meteorological conditions influence the degree of representativeness of the data compared to the real state of pollution of the study area [11].

Recently, innovative technologies have been developed and direct damage of harmful effects can be demonstrated by monitoring living organisms, called biomonitors, which provide a measure of integrated exposure over a certain amount of time taking into account also climatic conditions and enrich the substance to be determined so that the analytical accessibility is improved and the measurement uncertainty reduced. Moreover, sampling is relatively simple and no expensive technical equipment is needed. The field of biomonitoring includes bioin‐ dication of effects and bioaccumulation of pollutants [12].

The information provided by mosses, lichens, and higher plants on the deposition on the effects of air pollutants is an important complement to the data acquired with automatic systems. Distribution of tree species on a national or supranational lets you draw cheaply and in a short time maps of diffusion and deposition of persistent pollutants or the effects of tropospheric O3 and other phytotoxic pollutants [13].
