Silica dust in the air, generally as particles too small to be visible to the naked eye, is an inevitable accompaniment to South African gold mining. The inhalation of silica dust may cause silicosis, an occupational lung disease (OLD).
In 2003, AngloGold Ashanti's South Africa region established a 'wellness in the workplace forum' - a multi-disciplinary body comprising experts from the areas of dust control, noise in the workplace, radiation, TB and HIV/AIDS. The forum has taken over the work of the regional dust steering committee. Similar forums will be established at an operational level during 2005 to ensure that this integrated approach to occupational health is cascaded through the company.
Kobus Dekker, (occupational environment, safety and health manager - occupational hygiene) is responsible for dust and noise control. Dust management involves both the implementation of dust control systems and the education and training of employees to implement these.
"Behaviour is the critical factor," says Dekker. "As part of our efforts to educate and inform employees, we have recently produced a training video, which is being rolled out to mines this year. This will be shown to all employees as part of their induction and again annually on return from leave."
A number of other significant developments have taken place this year:
- automatically triggered in-stope water blasting, whereby the face is washed down immediately after blasting, is currently in development phase. The project is being tested at Tau Lekoa Mine, which is unique in AngloGold Ashanti in that it uses hydropower instead of compressed air to power underground machinery such as rockdrills. "Water at high pressure has the effect of liberating dust in the air," explains Kobus, "so it made sense to pilot the project at Tau Lekoa." This project began in September 2004 and is expected to be complete by this year-end. If successful, the project will be extended to Kopanang Mine, to test it in a normal compressed air environment.
- footwall treatment has also been successfully rolled out. Footwalls are sprayed with a chemical mixture that binds dust onto the footwall. Dekker explains, "A number of variables have to be considered in the chemical mix: the speed of air over the airway, the number of people and amount of equipment traffic, as well as the quantity of dust released from ore being carried in hoppers." The project has been rolled out to all the South Africa region mines, with some 372 kilometres of footwall treated in total. "This is not a once-off treatment, but has to be repeated at intervals which vary according to mining conditions and volumes," says Dekker.
Results are encouraging. Dust levels are measured daily on all mines, through the use of gravimetric pumps issued to a sample of employees. Target levels of total respirable dust have been set for the various workplaces, ranging from 0.24 mg/m3 for underground to 0.40 mg/m3 for surface areas. This is significantly below the limit of 1.00 mg/m3 recommended by NIOSH (the National Institute for Occupational Health and Safety: an international occupational health and safety organisation based in Washington DC).
Between 2002 and 2004, the percentage of employees at the South African operations exposed to levels of total respirable dust in excess of 1.00 mg/m3 has decreased from 2.4% in 2002 to zero for the second and third quarters of 2004.