Five major air pollutants which are affecting air, human health and environment

Five major pollutants which are causing air Pollution

These are the pollutants which greatly affect the environment and contribute to air pollution. There are basically five Criteria Pollutants on which monitoring occurs based on their emission level, concentration and how much they are rooting air pollution.

These are - Carbon monoxide (CO), Sulphur dioxide (SO₂), Nitrogen dioxide (NO₂), Small particulates (PM₁₀ and PM_2.5) and Ozone (O₃).

1.   Carbon Monoxide

CO is a colourless, odourless and tasteless poisonous gas. It is generally produced when carbon-containing fuel is burned under unfavourable conditions causing incomplete combustion and yields CO instead of CO₂. CO emissions in most of the countries are primarily because of transportation or vehicular emissions and secondly from those industries which burn fossil fuel.

• How it is affecting our human body:

It is an asphyxiant. It impedes the ability of blood to carry oxygen from the lungs to the body organs and tissues. CO has much greater affinity than O₂ to bind with haemoglobin to form Carboxyhaemoglobin (COHb) ie., even a small amount of inhalation can convey the transport of oxygen and greatly affects various parts of the human body specifically our brain and heart.

An expression for the amount of  COHb in human blood can be calculated as:

%COHb = X (1 – e^yt)[CO]

Where,

%COHb= carboxyhaemoglobin as a per cent of saturation

      [CO]= CO concentration in ppm

           Y= 0.402/hr

           X= 0.1% / ppm CO

           t= exposure time in hours

CO mainly affects older people, foetus and person who are suffering from cardiovascular disease. Various symptoms of exposure to CO include Headache (most commonly), dizziness, shortening of breath, confusion, blurred vision, nausea and many more.

Various Studies

It is has been studied that the concentration of CO varies at different zones –

i)       Near busy Roadways- 5 to 50 ppm

ii)      Congested highways- up to 100 ppm

iii)     Cigarette smoke- 400 ppm

iv)     Bars and restaurants- 20 to 30 ppm

But there is a bright side also, whenever a person again breathe the fresh air the effect of CO almost gets decreased and get remove from the blood in 3 to 4 hours.

Effect of exposure to Carbon Monoxide

Source: Seinfeld, 1996

2.   Sulphur Dioxide (SO₂)

The source of SO₂ emission completely differs from CO, it mainly comes from the combustion of fossil fuel (ex: Coal power plants) and about 5% from vehicular emission. Few other contributors include: Petroleum refining, Copper smelting, Cement manufacturing like industries, etc.

This gas causes air pollution especially when it turns out to be an Acid Rain. Burning of fuel causes the release of SO­₂ including traces of SO₃ or oxidation of SO­₂ also produces SO₃ which reacts with water vapours to form Sulphuric acid which is the main constituent of Acid Rain.

SO₃ + H₂O = H₂SO₄

• How it is affecting our human body and environment:

This pollutant causes less severe damage to our body because of its highly soluble nature. After inhalation, it gets absorbed in the moist passages of the respiratory tract, nose and upper airways but when it gets combines with other particulate matter it turns out to cause more detrimental effect and can bring the surge in the mortality rate.

In the case of the environment, it largely causes more damage to the vegetation (trees, plants and soil) when combine to form acid rain. Low pH changes the texture of leaves by damaging the outer covering, hampers photosynthesis process and make it difficult for plants to absorb essential nutrients from the soil because of solubilization of Aluminium which cause this problem of uptake. It equally affects the Soil by changing its pH and nutrients get easily leached out.

Inanimate objects are the one, who suffers a lot because of acid rain, a recent example was of Taj Mahal, India (One of the 7 wonders of the world). Its marble got corroded causing yellowing of marble due to acid rain. Other famous buildings include: the Acropolis in Greece, LESHAN GIANT BUDDHA, MOUNT EMEI, China and many more.

3.   Nitrogen Dioxide (NO₂)

It is a reddish-brown in colour, pungent gas and one of the 7 oxides which are known to occur but there are only two oxides which majorly contributes to air pollution (i) NO (ii) NO₂. Main sources include; burning of fossil fuel reacts with oxygen in the atmosphere, vehicular emission, heaters or gas stoves (indoors).

• NO and NO₂ reaction sequence

This reaction generally takes place during combustion when nitrogen-containing fuel burnt to release oxide of nitrogen which reacts with atmospheric oxygen to form NO.

N₂ + O₂= 2NO

It further reacts with oxygen to form NO₂

2NO + O₂ = 2NO₂

• How it is affecting our human body and environment:

In humans, it mainly affects the respiratory system. Depends upon the time of exposure its effect varies. A short period of exposures can cause coughing, sneezing, headache, nausea, difficulty in breathing whereas long period of exposures can greatly hamper the respiratory system especially can cause asthma. A person who is already suffering from asthma is generally at greater risk for health effects of NO₂.

In the case of the environment, it affects the same as SO₂ as one of the main constituent of acid rain, an increase in its concentration in the atmosphere can reduce the visibility (haziness), it also causes eutrophication and contributes to nutrient pollution in coastal waters.

4. Particulate matter

Atmospheric Particulate matters are tiny dispersed particles can be solid or liquid in form and size of its aggregates ranges from 0.005μm diameter to coarse particles up to 100 μm.

Various well-known terms are there like aerosol, fumes dust, soot and smog (smoke + fog) to categorise PM depending upon their size, phase, composition and environmental concentration.

• Sources of Particulate matter :

In general, anything which causes the production of the above mention terms become a source of PM in the atmosphere but most commonly as we all know combustion due to burning of fossil fuels is one of the major sources or release of NO_x SO_x through various industrial processes. Other sources include – Vehicular emission, burning of domestic, industrial waste, agriculture waste, forest fire, unpaved roads or fields etc.

• How it is affecting human body :

PM greatly affects the human in comparison to other pollutants, its minuscule size (PM_2.5) promotes  easy passage into the body in contrast to large size particles (PM₁₀) which  generally get trapped at the upper nasal cavity (nose hairs or the at the  lining of the nose) and can cause irritation in eyes nose, coughing, sneezing  like problems.

But, the respiratory system is the primary target of PM affecting this organ in the first instance and can cause various diseases like asthma, cardiovascular problem, emphysema and can target other organs like heart, brain, kidney and circulatory system.

There is one important lethal class of benzene like hydrocarbons known as (PAH) polynuclear aromatic hydrocarbons consist of fused benzene rings example: Benzo [a] pyrene  which is formed due to incomplete combustion. PAH are mainly released from tobacco smoke, motor vehicle exhaust, wood or coal burning, are known for causing severe health problems like lung and kidney cancer.

5.  Ozone (O₃)

As we all know the case of good or bad ozone in two different layers of the atmosphere, it is an inorganic molecule made up of three bonded oxygen atoms present in the stratosphere and working as a shield for the earth, protecting it from harmful ultraviolet sun rays which act as a potent carcinogen and protecting people by preventing skin cancer and other related diseases.

But how the formation of Ozone occurs in the troposphere, how it is turning out to be a bad one in this layer and how it is turning out to be a pollutant and affecting us and our environment. Let’s discuss it now,

When sunlight reacts with NO_x (oxides of nitrogen) and VOCs (volatile organic compound) it processes a complex chain of reactions and produces several secondary pollutants known as photochemical oxidant, Ozone is one of them.

• How it is affecting human being :

Why Ozone in the troposphere considers as a potent pollutant because of its undissolved nature in water. Unlike other pollutants which readily get dissolved in the fluids and our body can easily flush out them but ozone passes into the lungs unprocessed and causes serious health problems like coughing, burning sensations, chest constriction, shortness of breath, and throat irritation whereas long term exposure can cause premature death.

• How it is affecting the environment :

It is likewise affecting nature by suspending the growth of various tree species by damaging their foliage. It generally enters during the stomatal opening, interferes with the process of photosynthesis, reduces the productivity of the plant and causes various diseases which results in the stunted growth. Fairly enough crops get damaged because of this pollutant. Examples: corn, wheat, soybeans, peanuts, etc.

It is estimated that every year nearly $2 billion crop loss occur due to motor vehicle ozone alone.