What is a major issue with a broken exhaust system?

A broken exhaust system poses significant risks, among which the release of poisonous fumes into the vehicle's cab is a critical concern. The exhaust system is designed to channel harmful gases, such as carbon monoxide, away from the engine and out of the vehicle. If the exhaust system is damaged or has leaks, these toxic fumes can enter the cabin, creating a dangerous environment for the driver and any passengers. Exposure to carbon monoxide can lead to serious health issues, including loss of consciousness or even death in severe cases.

While excessive noise levels and increased fuel consumption are also potential issues related to a malfunctioning exhaust system, and a reduction in engine power can occur due to inefficiencies in exhaust flow, the most immediate and dangerous consequence is the risk of inhaling poison fumes. This makes the safety of the vehicle occupants the highest priority, confirming that the correct answer highlights a major and urgent issue associated with a broken exhaust system.