All employees at AngloGold Ashanti's South African operations are given chest X-ray examinations on engagement and at intervals varying from six to 12 months depending on occupation, as part of the company's TB surveillance programme.
TB in silica-exposed employees is a compensable disease in South Africa. Despite significant interventions to identify, treat and prevent exposure, TB infection rates in the South African gold mining industry have increased in recent years. These higher rates are attributable to the increasing average age of the workforce and the increasing levels of HIV/AIDS in a silica exposed workforce.
Digital diagnostic radiology (DDR) has revolutionised the application of TB examinations in recent years, facilitating earlier detection of the disease. The fixed digital radiology units at each of AngloGold Ashanti's two occupational health centres (at Vaal River and West Wits) can handle up to 450 X-ray images per day. Although the capital costs associated with these systems are high, running costs are significantly cheaper and, most important, their technological benefits are proving to be significant.
Now, in a move to take this sophisticated technology to the rock face, on 22 August 2005, a mobile DDR unit was commissioned to serve the four mines in the Vaal River area; Tau Lekoa, Kopanang, Moab Khotsong and Great Noligwa. Together these mines employ about 17,000 people. Following on from this, in late 2005, approval was given for the purchase of another mobile DDR unit for the three shafts in the West Wits area, which together employ a further 13,000 people. The second unit will be commissioned in the first quarter of 2006.
"The mobile units have the same characteristics as the fixed machines, but offer the advantage of direct access to employees," says Dr DB de Villiers, occupational medical practitioner for the Vaal River region.
Elaborating on the benefit of DDR when compared with standard X-ray technology, Dr de Villiers says, "The radiation dose that was present in the mass-miniature X-rays previously used is virtually eliminated; only one image is taken and then digitally manipulated; no developing of film is required as images are stored digitally; this in turn saves the cost of potentially hazardous chemicals used in the developing process, as well as the cost and space involved in storing conventional X-ray films over time." The DDRs can be transmitted electronically, so the image is available in the occupational health centres, TB clinics and wards, removing the need for repeat X-rays at those sites once one DDR has been taken. As South African law requires that occupational medical surveillance records be retained for 40 years, the issue of saving space is a significant one. Discussions are currently in progress with the Medical Bureau of Occupational Diseases (MBOD) regarding the possible future submission of X-rays in digital format.
"The introduction of the mobile units means that, instead of having to travel to the occupational health centre, employees are now examined at the shaft, on the way to or from work. says De Villiers. "Symptom screening is done on site and the X-ray can be read immediately. The experienced crew can then refer patients showing signs of TB to the hospital."
At Vaal River, the mobile unit services the four shafts on a weekly cycle. Employees from the metallurgical plant and service departments arrange to visit the closest shaft. As the equipment is highly sensitive, an elaborate procedure is in place for transport and connection to the four docking stations. "The sequence covering travel from point to point, and securing the X-ray machine resembles the pre-flight check of an aircraft," says De Villiers. The docking stations are powered with 380 volt power supply and fibre-optic computer network connections. Setting up and moving the unit is a team effort between AHS radiology and maintenance staff, and the information technology, human resources and asset protection departments based at the various shafts.
De Villiers notes that, looking ahead, even greater benefits are foreseen in being able to individually riskrate employees for TB. Variables such as age, past medical history, occupation, and years underground would be combined in a risk matrix to determine the frequency of TB screening. Low risk employees would only need to be screened every three years, whilst those at high risk would be screened by DDR every six months.