The revised National Ambient Air Quality Standards of India (NAAQS) aim to regulate and control the levels of air pollutants to ensure the protection of public health and the environment. The pollutants that are included in the revised NAAQS are as follows:

a) Lead: Lead is a toxic heavy metal that can have harmful effects on human health, particularly on the nervous system. It is emitted into the air through various industrial processes, including the combustion of fossil fuels and the smelting of metals. The revised NAAQS sets a limit on the concentration of lead in ambient air to protect public health.

b) Benzene: Benzene is a volatile organic compound (VOC) that is commonly found in petroleum and petrochemical products. It is a known carcinogen and exposure to high levels of benzene can increase the risk of developing leukemia. The revised NAAQS includes a limit on the concentration of benzene in ambient air to safeguard public health.

c) Ammonia: Ammonia is a compound that is primarily emitted from agricultural activities, such as the application of fertilizers and the management of livestock waste. It can contribute to the formation of fine particulate matter (PM2.5) and can also have adverse effects on human health, particularly on the respiratory system. The revised NAAQS includes a limit on the concentration of ammonia in ambient air to mitigate these impacts.

However, the pollutant that is not included in the revised NAAQS is:

d) Hydrogen sulphide: Hydrogen sulphide is a colorless, toxic gas that has a distinctive odor of rotten eggs. It is mainly produced by industrial processes, such as the refining of petroleum and the production of natural gas. Hydrogen sulphide can have harmful effects on human health, including irritation of the respiratory system and, at high concentrations, can lead to unconsciousness or even death. Despite its toxic nature, the revised NAAQS does not currently include a specific limit on the concentration of hydrogen sulphide in ambient air.

In conclusion, the revised National Ambient Air Quality Standards of India include limits on the concentration of lead, benzene, and ammonia in ambient air to protect public health. However, the standards do not currently include a specific limit for hydrogen sulphide.