Correct Answer: Option D) All are correct
Unburnt hydrocarbons (UHC) are organic compounds that have not undergone complete combustion during fuel burning processes. They include benzene and 3,4 benzopyrene: This is correct. Benzene (C₆H₆) and 3,4 benzopyrene (also known as benzo[a]pyrene) are common examples of unburnt hydrocarbons. These are polycyclic aromatic hydrocarbons (PAHs) that are formed during incomplete combustion processes.
They are mainly emitted by burning fossil fuels: This is correct. Unburnt hydrocarbons are primarily released when fossil fuels like gasoline, diesel, coal, and natural gas undergo incomplete combustion. Common sources include vehicle exhausts, industrial processes, power plants, and residential heating systems.
They are associated with lung cancer in humans: This is correct. Both benzene and benzo[a]pyrene are classified as known human carcinogens by international health organizations. Long-term exposure to these unburnt hydrocarbons has been linked to increased risk of lung cancer and other respiratory diseases. Benzo[a]pyrene in particular is one of the most potent carcinogens found in cigarette smoke and air pollution.
