Safety watchdog outlines risk and relevant safety measures
Workplace Health and Safety Queensland (WHSQ) has issued a safety alert after a July incident involving a truck driver who began feeling unwell after transporting grain to a feedlot with his semi-trailer.
With investigations continuing, it appears that, for reasons yet to be established, during the transportation he was exposed to a fumigant that produced phosphine gas, which is commonly used to control insect infestations in grain.
Fumigants, including aluminium phosphide, are used in the agriculture industry to kill pests such as grain weevils, the work safety watchdog noted.
“Aluminium phosphide is a solid fumigant that reacts with moisture in the air to release highly toxic phosphine gas.
“If the manufacturer’s directions aren’t followed, there is a serious risk to those who transport or store the grain.
“Reducing timeframes or applying aluminium phosphide fumigants in poorly-sealed containers, such as a semi or B-double trailer covered with a tarpaulin, will not effectively control pests and creates a serious risk to people from any remaining phosphine gas.
“Phosphine gas is toxic when breathed in at concentrations approaching or exceeding the workplace exposure standard of 0.3ppm using a time weighted average over an 8 hour work day, or 1ppm as a 15 minute short term exposure limit.”
Early symptoms of exposure may include respiratory problems including coughing, double vision, dizziness and headaches, fatigue and gastrointestinal disturbances such as pain, nausea, vomiting and diarrhoea.
Exposure to high levels of phosphine gas can cause damage to the kidneys, liver and heart, as well as pulmonary oedema (fluid in the lungs), convulsions and death.
Phosphine gas is heavier than air and hazardous concentrations can develop quickly in enclosed, poorly ventilated, or low-lying areas.
Aluminium phosphide is a poison under the Poisons Standard June 2021 and has a high potential for causing harm at low exposures and requires special precautions during handling and use.
The Chemical Usage (Agricultural and Veterinary) Control Regulation 2017 requires users to be qualified, or in the case of infrequent use, under the direct supervision of a qualified person.
Users must store, handle, use and dispose of aluminium phosphide in accordance with the product label and safety data sheet which contains information on the fumigation, ventilation and re-entry periods as well as precautions required to manage the health and safety of workers and others.
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WHSQ advises a safe system of work for fumigation activities, including:
- Store canisters correctly to prevent deterioration of the tablets
- Ensure fumigation is conducted in well-sealed enclosures and fumigation and ventilation periods are followed
- Allow only qualified workers to use aluminium phosphide while on the farm and engage a licensed pest-management technician to fumigate products that have left the farm
- Where fumigation is a routine practice, it is recommended to have equipment available and calibrated to measure the concentration of phosphine
- Make and keep records of agricultural chemical applications and worker training
- Provide workers with personal protective equipment (PPE) required by the product label
- Provide workers with information, training and instruction in the proper use and wearing of PPE, and the storage and maintenance of PPE
- Ensure PPE is maintained, repaired and replaced so that the equipment remains clean and hygienic, and in good working order.
Following the product use and control requirements on the label will significantly reduce the likelihood of a similar incident occurring, WHSQ added.
The safe system of work and control measures put in place should also be reviewed regularly to make sure they work as planned.