South Africa heavily relies on coal for its energy and that makes it a country choking with air pollution. This has also meant millions of dollars in health costs.  

Mpumalanga, an eastern province in the country, is home to a dozen of coal-fired stations operated by the national power supplier Eskom.  

Environmental group Greenpeace recently released a report that shows that the Mpumalanga Province is the world's largest air pollution hotspot. 

The province is also where almost all of South Africa's coal is mined and the resulting pollution is adversely affecting residents.  

Residents like Promise Mabilo felt compelled to become an activist after realizing that her son was heavily affected by pollution. 

She describes his suffering from bronchitis as the worst thing she's ever experienced. 

"When these people are attacked by this, they are unable to breathe, you will cry. You will be unable to even hold him because they hold up tight without breathing, without doing (seeing it), you don't know." 

Mabilo says what they really need is for the government to enforce compliance from the coal companies.  

"But we know they will take time to do that. They have to do something; the government has to do something," said her.  

Many families in this area relate similar stories. They refer to pollution as a silent but prolific killer.  

26-year-old Mbali Mathebula has two young children who are heavily affected by pollution.  

"The problem is asthma. Both of my children have asthma. Princesse's asthma started when she turned two, now she's five years old. For Asimahle it started at three months, now she's eight months. It affects me directly because it attacks them literally every night an I have no means to take them to hospital," said Mathebula. 

Then there's the case of 57-year-old Reuben Tau. He was diagnosed with tuberculosis and permanently laid off work.   

"I can't even hold a job because of the severity of my condition, meanwhile I have to take care of a few small children." 

The Department of Environmental Affairs in 2007 acknowledged that this area is an air pollution hotspot. 

Since then, it has been declared a priority zone. Dr. Khumalo is the Director of Air Quality management at the Environmental Affairs Department.  

"So the work that we are doing in the priority areas is that the minister has established air quality management plans which are the plans that we are implementing now to try and reduce the levels of pollution to acceptable levels", said Dr. Khumalo.  

Like most countries, South Africa is working towards moving to cleaner technologies, but its a move that may take a while to achieve.