Explain how the excessive use of nitric fertilisers in agriculture can effects human life.

When nitrogen fertilizers are excessively used in agriculture, they affect human life in various ways:

• Excessive nitrogen fertilizers get dissolved in the soil and cause groundwater contamination. This water is unsafe for drinking especially in infants and pregnant women. When nitrate enters the infants' body through drinking water, it gets converted into nitrite by the digestive system. Nitrite binds with the oxyhemoglobin and converts it into metheglobin which can not carry oxygen. As a result, infant gets deprived of oxygen. This is known as blue baby syndrome. Infant may develop respiratory and digestive problems and the color of its mucous membranes gets blue. 
• Excessive use of nitrogen fertilizers results in the emission of nitrous oxide gas in large quantities. Nitrous oxide gas is one the greenhouse gases. So, it may cause global warming. 
• It also causes eutrophication of water bodies and formation of algal blooms. It results in death of fishes and other aquatic organisms which are consumed by humans as a food.