Excessive pesticides use is harmful because it can contaminate soil and water sources, harming and non target organisms like beneficial insects, pollinators and aquatic life, leading to biodiversity loss and can also directly impact human health through exposure to pesticide residue in food causing diseases like cancer, reproductive issues and neurological problem.

Although carbon-dioxide (CO₂) only make up around 0.04% of atmosphere, it plays a critical role in ecosystem by acting as a green house gas, trapping heat and significantly influences Earth's temperature which in turn impact various aspects of ecosystem, including plant growth, weather pattern and ocean acidification. when its concentration increases due to human activities like burning fossil fuels, essentially even a small percentage of CO₂ and can have a large impact on climate due to its heat trapping properties.

Only certain pollutants gases in atmosphere cause the green house effect because these special gases a molecular structure that allows them to absorb infrared radiation emitted by earth while other gases like hydrogen and oxygen do not have ability to trap heat.

 You can reduce CO emission from automobile by using vehicles that burn fuel completely, using catalytic converters and other emission control devices.

Solar energy can be used for generating electricity through photovoltaic panels, heating water with solar thermal collectors and providing heat for buildings through passive solar design.

(i) Carbon dioxide (CO₂):

Higher levels of carbon dioxide lead to increased global warming which can cause ice caps to melt and oceans to warm, causing sea levels to rise. Extreme weather changes such as heat waves, heavy rains and wild fires also occur.

(ii) Carbon monoxide (CO):
It is an extremely poisonous gas that can cause suffocation and death. Carbon monoxide is a very toxic gas that stops the red blood cells in animal's blood from carrying oxygen that the body needs.

(iii) Oxide of Nitrogen (NOₓ) NO, NO₂:
NOₓ can damage lungs, irritate the eyes and damage vegetation. It can also cause acid rain which affects buildings and statues made of limestone.

(iv) Oxides of Sulphur (SOₓ) SO₂, SO₃:
SOₓ irritates the eyes and causes breathing difficulties and acid rain.

(v) Hydrocarbons:
They can cause pneumonia, coughing, many other breathing and lung diseases. They also cause global warming.

(vi) Particulate matter:
Irritates the eyes and can also cause severe breathing problems for people with asthma. It also makes clothes dirty. Also, visibility is reduced because it produces haze in the air.

Greenhouse effect:
The progressive warming up of the Earth's surface due to blanketing effect of man-made carbon dioxide, methane, water vapours and other gases in the atmosphere is called greenhouse effect.

Explanation:
The sun emits short wave radiation that passes through greenhouse gases to heat the surface of the Earth. At night, the hot Earth's surface  emits long wave radiation that is mostly absorbed by greenhouse gases. This process of absorption prevents the radiation to reach space, reducing the speed at which Earth can cool off. This increases the temperature of the Earth and causes global warming.Higher the concentration of carbon dioxide and other greenhouse gases, greater will be the absorption of thermal radiation and greater will be increase in global warming.

Air Quality Index (AQI):

Air quality index (AQI) is a rating system that shows how bad is the atmosphere around you.

Explanation:
An AQI value under 50 is considered good in quality. This means that it is safe for you to spend time outdoors with posing a risk to your health. As AQI number increases so does the risk to health. An AQI over 300 is considered hazardous. Children under 18, adults over 65, people with chronic heart or lung disease and diabetic people are at high risk groups. Outdoor workers can also be considered at higher risk because of prolonged exposure.

(i) Reduce outdoor time:

Limit the time you spend outdoors. Also reduce the intensity of outdoor activities. According to experts the chances of being affected by unhealthy atmosphere increases if a person stays outdoor for long periods or involve in more laborious work outdoor.

(ii) Wear mask:

If you are forced to go out, then consider wearing a mask. Unfortunately, not all face masks provide adequate safety against particulate matter. Cloth or dust mask may not effectively filter out the finer particles. However certified N95 masks have better filtration capabilities and may be safer to use.

(iii) Keep indoor air clean:

Keep your indoors healthy by keeping the windows and doors closed. If it is difficult to maintain clean air in the entire room then create a clean room by switching on air conditioner or air cleaner.

(iv) Consult doctor:

If you experience any symptoms that worry you, talk to your doctor.

(v) Install carbon monoxide detector:

Install carbon monoxide detector to detect the increased level of carbon monoxide. These higher levels of CO may occur due to faulty fuel burning appliances. 
Breathing in polluted air by these high risk groups may affect their lungs, heart and brain. Air pollutants can enter their blood stream and cause coughing or itching of eyes which may lead to poor quality of life, hospitalization, cancer or even premature death.

Huge amount of pollutant gases are thrown out in the atmosphere by burning fossil fuels. Automobiles, aeroplanes, industrial machines and coal-fired electricity generating plants, etc. are mainly responsible for the extremely polluted air especially in big cities. Scientists have developed a number of different way to control this menace of pollution. Planting trees is thought to be very helpful in removing the air pollution. A well known process carried out by plants is photosynthesis in which plants clean the air through absorption of carbon dioxide and releasing oxygen. This famous reaction takes place in the presence of sunlight and it is catalysed by chlorophyll, the green planting trees / photosynthesis

6CO₂(g) ​+6H₂O (l)​  --ChlorophyllSunlight​------> C ₆H₁₂O₆(s)​ +6O₂(g)​

The particulate matter present in the atmosphere is also removed by plants when it deposits on leaves, branches and trunk surfaces. Catalytic converters are used in the exhaust system of modern-day automobiles to reduce the emissions from an internal combustion engine. Due to non-availability of enough oxygen the carbon fuel in engine does not burn completely into carbon dioxide and water. Thus, toxic by-products like CO and hydrocarbons are produced.

A three-way catalytic converter performs the following three functions simultaneously.

(i) It reduces nitrogen oxides into elemental nitrogen and oxygen:

2NOx (g)     ​⟶ N₂(g)​ + xO₂(g)

​(ii) It oxidizes CO to CO₂:

2CO(g) ​+ O₂(g)  ​⟶  2CO₂(g)​

(iii) It oxidizes hydrocarbons into CO₂ and H₂O:

Cx​H₄x(g)​  +  2xO₂(g  )​⟶  xCO₂(g) ​+  2xH₂O (l)​

Similarly, the emission of sulphur dioxide can be decreased either by:Using fuels which have significantly less sulphur contents Using flue gas desulphurization process. This process can remove sulphur dioxide gas from the exhaust gases of fossil fuels. Flue gas is the mixture of waste gases produced when fossil fuels are burnt in power plants.The desulphurization process involves the addition of adsorbents like calcium oxide which can remove up to 95% of the sulphur dioxide from the flue gas.

Major causes of high AQI in Pakistani cities - Especially in Winter

• Vehicular Emissions
• Crop Stubble Burning
• Industrial Emissions
• Burning of Fuel for Heating
• Dust & Construction
•  Weather Conditions in Winter
• Waste Burning

Reason:

In summer, due to high temperature, hot air rises up and take pollution with it and disperses it. Also strong wind and rainfall help to wash away dust and pollutants from air.

In the last five years, Pakistan has faced heavy floods and rains due to climate change. Due to rise in temperature, glaciers are melting fast. This has caused floods which destroyed infrastructure and crops badly .