The Australian Institute of Occupational Hygienists said there are a range of actions miners can take to combat outbreaks of Legionnaires’ disease on-site.
While silicosis is currently at the forefront of people’s minds when it comes to diseases of which miners need to be aware, there are common health risks to which no industry is immune.
Legionnaires’ disease is known for resurfacing in the news every so often, but it can be more serious than an occasional nuisance.
A severe form of pneumonia, Legionnaires’ can be deadly if left untreated. In Australia, there are an average of 400 reported cases of the disease every year.
The Australian Institute of Occupational Hygienists (AIOH) is working to empower miners with the tools they need to stop legionella bacteria becoming a problem in the first place.
How are miners at risk?
Legionella – the bacteria that causes Legionnaires’ – is found naturally in soil, freshwater and even compost and potting mix. In the right conditions, the bacteria can blossom in potable water storage tanks, water distribution pipework, cooling towers and water recirculation systems where nutrient sources like dust, dirt and algae can support its growth. In water temperatures between 20–50°C, legionella can bloom basically anywhere there is standing moisture.
All up, that means lots of places on a mine site.
“Water is used in many different ways in a mining environment, so there are plenty of opportunities for legionella bacteria to grow to high numbers,” principal occupational hygienist Nicola Power told Safe to Work on behalf of the AIOH.
“The most common source of legionella bacteria exposure is contaminated or poorly maintained cooling towers, because the exposure pathway is from mist, and bacteria can travel long distances in the air. There are many reported cases of contamination each year, and multiple cases of Legionnaires’ disease in miners have been reported.”
But cooling towers are not the only source of contamination.
An underground miner in Western Australia contracted Legionnaires’ disease in 2020 from an underground wash bay where the miner had used high-pressure water-blasting equipment to clean heavy machinery.
According to the WA Government’s notifiable infectious disease dashboard, men are 3.1 times more at risk of contracting Legionnaires’. There are also an average of 72 cases reported in WA every year, despite the disease being difficult to diagnose.
Water reticulation systems, as well as recycled and natural source waters used for dust-suppression, drilling, vehicle wash-down and irrigation, can all present an exposure risk if not properly managed.
Sprinkler systems, safety showers and fire water systems are often overlooked because they’re rarely used, giving bacteria an opportunity to grow.
Even areas like stagnant bodies of water, particularly underground, can present a risk if conditions are right.
“One of the greatest risks for miners, believe it or not, is actually on-site showers, evaporative air-cooling systems and misting machines, which inherently provide a lovely, warm environment for bacteria,” Power said. “In mining camps, plumbing is often above-ground, where hot weather can create the perfect temperature for legionella bacteria to thrive.
“The other big risk factor is processes that create water mist, like dust suppression, drill sprays and high-pressure washing.”
What can be done?
While regulation will vary from state to state, all mines in Australia are required to have management plans in place for preventing risk to health.
Power said all mines should include routine treatment for, and monitoring of legionella in their site emergency response plan or water management plan.
“To prevent outbreaks of Legionnaires’ disease, all water sources on-site need to be managed,” she said. “Good system design and maintenance are the most important factors in preventing legionella growth.”
Power also warned against assuming site water sampling will be enough.
“Water sampling and analysis will take seven to 10 days to detect and report legionella bacteria,” she said. “This is typically too late to respond to any risk.”
Power said responses to the detection of legionella should include:
interim exposure controls, such as equipment shutdown, exclusion zones or use of respiratory protective equipment (RPE)
investigation of the source
identifying factors that contributed to its growth
assessing whether controls such as cleaning and maintenance have failed
determining the extent of affected systems
taking action to prevent future growth, such as cleaning to remove bacteria on surfaces and in biofilm, and disinfection.
Occupational hygienists like Power can help with identifying such risks and help mines determine suitable controls to prevent the growth of legionella, as well as undertaking water monitoring.
As part of these controls, miners should first identify all sources of on-site water mists and aerosols and try to design systems that don’t create an environment in which bacteria will thrive.
If such systems are unable to be designed out, then miners should assess exposure levels of mists and aerosols and review risk management strategies for the tasks and activities that generate them. These strategies may include using alternate, clean water sources, keeping water moving and at safe temperatures and using extraction ventilation.
Power said water treatment plant operators should be well trained and resourced with a strategy in place to monitor for the bacteria.
“This includes carrying out appropriate planned maintenance, remedial treatment or corrective actions to prevent legionella as necessary – chlorinated water is not immune to legionella bacteria growth so the key to prevention is ‘CCC’ – clean, cool and constantly moving water in your water pipes and tanks,” she said.
By adopting these processes and controls and ensuring they are diligently implemented, mines can stay on track to keeping their sites legionella-free.
This feature also appears in the January-February issue of Safe to Work.