For Muslims, Hajj is an annual holy journey to Mecca in Saudi Arabia. Scientists have been able to record an increase in air pollution as a result of 3-4 million people migrating towards the city. The pollution is said to be very dangerous and linked to the heart failure of those in the city. Higher levels of carbon monoxide, black carbon, and other pollutants are responsible for the health risks. Saudi officials are currently assessing the situation and taking measures to tackle this issue.