Travelling by car is injurious to health. A recent study undertaken by the state pollution control board has revealed that people in cars are exposed to as much as five times more toxins in the air than pedestrians and cyclists in Calcutta. The pollution level inside airconditioned cars is almost just as bad. People travelling in cars pass through a "tunnel of pollutants", with toxins emitted by the exhausts of the car in front ending up inside the one behind. Those inside a car are also exposed to volatile organic compounds up to six times more than a person walking or cycling alojng a busy Calcutta street.