A study published by India's Center for Science and Environment (CSE) has found out that New Delhi is the most polluted city of the world, taking the title from China's capital, Beijing.

According to the study, New Delhi's air has the most harmful pollutants called PM2.5 and the concentration of these pollutants is measured at 575 micrograms per cubic meter. Measurements were taken from November to January.

PM2.5 is the collective term given to air pollutants such as nitrates, sulfates, ammonia, and carbon. These pollutants are small enough to enter a person's bloodstream and cause respiratory ailments such as cancer and emphysema.

Source of pollutants in New Delhi include the city's taxis and buses. New Delhi sees 1,400 new cars a day and Indian car manufacturers are only required by Indian law to create their cars with basic emission-reducing equipment. Aside from the vehicles, other sources of pollution of the Indian city are industrial emissions, including smog from the country's power stations which are fueled with coal, and the smoke coming from burning garbage, CNN reports.

The toxic amounts of pollutants found in New Delhi's smog may also cause other diseases such as eye disorders, Vitamin D deficiency, and respiratory-related illnesses.

The report said, "Originally designed as compact entities to reduce the length of travel ... [Indian cities] are becoming victims of killer pollution, congestion ... and a crippling car-dependent infrastructure."

The researchers also discussed the improvements that the Chinese government did to reduce the pollution in Beijing. The CSE described Beijing's "consistent and aggressive efforts" which include limiting the car sales made for each year and banning odd and even-numbered cars when the "red alert" status is raised for pollution, and imposing fines to local government agencies which fail to decrease smog and emissions.

In contrast, the report described India's pollution-reducing efforts as "weak ... stringency ... and enforcement" of their pollution control policies.

The third spot for the most polluted city went to Ahwaz, the capital city of Iran's province which is one of the country's main sources for oil.