Occupational exposure: Mineral sand mining and processing workers
Workers involved in the mining and processing of mineral sands contain radioactive minerals are occupationally exposed to ionising radiation. Current industry exposures are low; regulations, controls and exposure monitoring are required to keep exposures low.
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Mineral sand ores contain titanium bearing minerals of ilmenite, rutile and leucoxene as well as the mineral zircon. They also contain trace quantities of the radioactive elements of uranium and thorium particularly monazite which is a mineral with reasonable thorium concentration (5-7%). Due to the radioactive nature of the ore, ionising radiation exposure in the mining and processing of mineral sands comes externally from gamma radiation emitted, or internally from the inhalation of ore and process dusts.
Dry plant separation processes and the processing, handling and storage of monazite carries the highest exposure risk, predominantly from the inhalation of the dust exposure pathway.
Occupational exposures in the mining and milling of mineral sands in Australia are low. Data from the Australian mineral sands industry (2000–2008) shows average exposures for workers in dry separation plants to range 1.3–3.1 mSv (milliseiverts) per year during that period. Exposure to mining operators is much lower (<0.1 mSv per year) due to vehicle shielding, cabin ventilation and lower concentrations of radionuclides in the ore compared with processed materials.
In comparison, average background radiation exposure in Australia is 1.5 mSv per year from natural sources. Currently, Australians are exposed to an average of 1.7 mSv per year from medical exposures.
Ionising radiation has been proven to cause harmful short-term effects at very high doses received in short periods of time (>500 mSv); these exposures are not possible in mineral sands mining and milling. The increased risk of cancer has been shown to occur for longer term exposures at doses greater than 100 mSv; these exposures could occur in mineral sands mining and milling without the use of appropriate controls. At current exposures, the risks are very low and comparable with the risks of exposure from background and medical radiation exposure.
In Australia the use of irradiating apparatus and radiation sources is regulated. Each state and territory is responsible for enforcing their respective radiation safety act and regulations in their jurisdictions. The Australian government is responsible of enforcing the radiation safety act and regulations of commonwealth entities only.
Organisations/employers are responsible for:
- devising, implementing, and regularly reviewing their radiation management plan
- regulatory compliance
- induction and ongoing training of workers, including contractors.
Workers are responsible for:
- following radiation protection practices specified in the radiation management plan
- complying with legitimate instructions of the employer or designated radiation safety officer
- participate in radiation protection training.
Operators of each mineral sand mine and mill are required to have an approved Radiation Management Plan that complies with the requirements of the Code of Practice and Safety Guide for Radiation Protection and Radioactive Waste Management in Mining and Mineral Processing. All relevant controls for radiation protection must be included in this plan and the plan must be adhered to.
Controls must adhere to the hierarchy of control. Minimising time, increasing distance and shielding can be used to reduce gamma radiation exposure, while ventilation is critical to reduce exposure from the inhalation pathway. When required, respiratory protection may be needed as an additional control.
The Australian State and Territory jurisdictions have uniform annual limits for public and occupational exposure: 1 mSv for the public and 20 mSv for workers who are occupationally exposed. Despite this, there are different definitions of who is ‘occupationally exposed’ and who should wear personal dosimeters. You can further discuss occupational radiation exposure with your facility’s Radiation Safety Officer or the relevant state or territory regulator.
For a pregnant radiation worker, the dose to the unborn child is restricted to the same as a member of the public – 1mSv. See Occupational exposure: Management of pregnant workers factsheet.