Tim Turney, Global Marketing Manager at Casella, shares expert insights on quantifying dust levels, so that businesses can protect workers from hazardous exposure levels.
Woodworking businesses across the UK are being visited by Health & Safety Executive (HSE) inspectors to help tackle occupational lung disease.
Wood dust is a substance hazardous to worker health, potentially causing skin disorders, asthma, rhinitis, nasal and lung cancer. Wood dust is produced when the material is processed, and the quantity and type of the exposure problem will depend on how it's processed.
Types of activity that can produce high dust exposures over a long period of time include machining operations such as sanding by machine, hand assembly of machined items or bagging of dust from extraction systems. Bad housekeeping is also an issue, for example, workers may use compressed airlines or sweeping to clean up, which should always be avoided.
Understanding the legal limits
These health hazards are covered by regulations, where exposure limits are typically set separately for hardwoods and softwood. There is a duty of care and a need to carry out a suitable risk assessment, ultimately to prevent exposure or adequately control it.
If there's a known dust exposure issue, then businesses should implement measures that control the hazard at source. If the risk assessment reveals a significant exposure risk, and businesses need to quantify what the dust levels are, then personal air sampling can offer a solution.
Exposure limits for hardwoods and softwoods vary depending on the location in the world, for example in the UK both hardwood and softwood dusts have a Workplace Exposure Limit (WEL):
- The WEL for hardwood dust is 3mg/m3 (based on an 8-hour time-weighted average).
- The WEL for softwood dust is 5mg/m3 (based on an 8-hour time-weighted average).
Exposure limits can be as low as 1mg/m3 in some countries, so businesses operating in multiple geographical areas should check the local limits. The WELS refer to an individual’s personal exposure, therefore the preferred method for air sampling is using a personal air sampling pump.
Air sampling, what is involved?
Air sampling involves wearing a personal air sampling pump, generally on the belt. The pump draws in volume of air with a very accurate flow, so that the total volume of air sampled is known. The pump is connected via a tube to a sampling head in the breathing zone, that is within 30 centimetres of the nose and mouth. The sampling head contains a filter, where the filter is weighed before sampling. This should be achieved using a recognised laboratory, with an accurate weighing scale that can weigh down to a few milligrams.
Generally, the pump is worn for the worker’s entire shift so that it samples their complete exposure. Once sampling is complete the filter is weighed again, so the weight difference reveals the weight of dust. In combination with the volume of air sampled, the concentration of dust can be calculated, and subsequently the exposure levels, which can be compared to permissible or recommended exposure limits.
To establish what flow rate to use, which sampling head to select and what filter media, businesses can refer to the relevant method provided locally. There is a level of competence required for air sampling to ensure an accurate sample is taken. For example, understanding how to handle filters, setting up the pumps and calibrating, are all important factors to make sure a highly accurate sample is achieved.
When selecting an air sampling pump, businesses should ensure that the following items are taken into consideration:
- The pump conforms to ISO 13137 which is the international standard for air sampling pumps.
- The pump is capable of flows greater than two litres a minute as that's mostly where sampling for word dust occurs.
- It's light and comfortable to wear for the worker, to ensure that the employee wears it for the whole day.
- It's robust and capable of the harsh environments and therefore has a good Ingress protection (IP) rating.
- That the pump is intrinsically safe, if it is potentially going to be used in flammable atmospheres.
Businesses should also get all the relevant equipment needed to do the sampling such as a flow meter to calibrate the pump and the relevant sampling heads, tube and other accessories. Personal sampling using a recognised method will ensure an accurate exposure assessment, and confidence in results.
Selecting the right equipment
Personal air sampling is the perfect tool to get accurate assessments of an individual's eight-hour exposure. However, this method can only provide an average. Other instruments such as real-time dust meters can help fill the gaps as to when exposure occurred. Real time instruments can:
- Allow a walk-through survey so problem areas can be easily identified, and exposed workers prioritised accordingly.
- Be left in an area to see when exposure is occurring. Are specific events and processes responsible for significant levels of overall exposure?
- Check on the effectiveness of control measures and instantly check the effects of process changes.
- Provide instant results, avoiding time waiting for a laboratory to weigh a sample.
- Be used as a training tool, show operators what they are exposed to, making them aware of the risk and illustrate how their activity changes dust levels.
Ultimately, wood dust is a significant risk to a worker’s health. Air sampling is a way to quantify exposure or measure residual risk and ensure control measures are effective. Personal sampling pumps, when used in a way demonstrated in an approved method, can provide accurate exposure levels. Real time instruments can complement this by allowing identification of sources and the immediate effectiveness of control measures.
