Poor air quality causes nearly 122, 400 premature deaths every year in Bangladesh, says a new study.

The number has steadily climbed from an estimated 81,200 deaths a year in 1990 to 122,400 in 2015.

The study prepared by two US-based health research institutes - the Health Effects Institute and the Institute for Health Metrics and Evaluation -was published recently.

According to the study, Bangladesh and India have experienced the steepest increases in pollution since 2010 and now have the highest PM2.5 concentrations (fine particles that lodge deep in the lungs) in the world.

India's air now China's as the world's deadliest, according to the study.

India has recorded a nearly 50 per cent increase in premature deaths linked to PM2.5 between 1990 and 2015, the report found.

"India now approaches China in the number of deaths attributable to PM2.5," said the report.

Globally, there were 4.2 million premature deaths and a loss of 103 million healthy years of life in 2015, making air pollution the fifth-highest cause of death among all health risks, according to a Health Effects Institute report.

The study found that China and India were responsible for over half of the total global attributable deaths.

The report also stated that only one in 10 people live in places that have clean air.

“We are seeing increasing air pollution problems worldwide, and this new report and website details say why that air pollution is a major contributor to early death,” said Dan Greenbaum, president of the Health Effects Institute (HEI1 ), the global research institute that designed and implemented the study.

“The trends show that we have seen progress in some parts of the world - but serious challenges remain,” he added.

A UN report had last year said that Asia and the Middle East, and low-and middle-income countries are the most affected regions in terms of air pollution.

United Nation's World Health Organisation said that the major sources of air pollution were: inefficient modes of transport (polluting fuels and vehicles), inefficient combustion of household fuels for cooking, lighting and heating, coal-fired power plants, agriculture and waste burning.