6 minute read
Personal Sampling: the start of a new era?
AUTHORS: SAMANTHA HALL1, ADAM CLARKE1, RICHARD KAYE2, PRAMUKH JAYASEKERA3 AND PAUL KAYE2 1 HEALTH AND SAFETY EXECUTIVE, SCIENCE AND RESEARCH CENTRE, HARPUR HILL, BUXTON, SK17 9JN 2 SCHOOL OF PHYSICS ENGINEERING & COMPUTER SCIENCE, UNIVERSITY OF HERTFORDSHIRE, HATFIELD, AL10 9AB 3 DSTL, PORTON DOWN, SALISBURY, SP4 0JQ
Measuring exposure to airborne hazards in the workplace is a common task undertaken by occupational hygienists, yet personal sampling techniques used in the UK have hardly changed in the last 60 years.
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Jerry Sherwood and Don Greenhalgh were the first to develop practical personal airborne sampling techniques, described in the second volume of the Annals of Occupational Hygiene in 1960 [1]. Their method included a sampling head attached by tubing to a pump which, it was suggested, could be ‘worn in the pocket of a laboratory coat or hip pocket of trousers’. This set-up is fundamentally still in use today, although the individual components have advanced.
The limitations of these traditional personal sampling techniques include the bulkiness of the pump, the opportunity for the connecting tubing to snag on items in the workplace, maintenance and costs. The “one day survey” is still a common occurrence which presents many challenges for hygienists. Given that the majority of sites only have one survey per year, at most, the hygienist needs to make every second count. Time taken to set up the samplers and calibrate pumps is time that could be spent gathering contextual information, determining similarly exposed groups (SEGs), making observations and talking to workers, which are far more valuable than the exposure result.
For sites and hygienists to take a positive approach to taking measurements to inform risk assessments the sampling technology needs to be quick and easy to set-up, affordable and accessible. Sampling devices, filter technology and associated analytical techniques also need to keep pace with ever decreasing exposure limits. High flow rates are becoming a regular requirement to gather more sample material in shorter sampling times and lower concentration environments so that detectable amounts are collected.
Numerous advancements have been made including the development of all-in-one devices, filter media and simultaneous real-time monitoring. Small, lightweight samplers are more likely to achieve user acceptance.
All-in-one sampling devices may provide these features and negate the need for tubing and a separate pump. However, there are disadvantages to the all-in-one devices. They are sometimes less able to cope with the high flow resistances produced by certain collection media, increased loading or the attachment of flow meters.
Existing all-in-one samplers include the CIP10, which was originally developed to be robust and practical for use in coal mines and offers a higher flow rate than some, at ten litres per minute [2]. The sampler is based on the rotation of a foam which can collect the respirable, thoracic or inhalable fractions.
Another example is the ultrasonic personal aerosol sampler [3] which claims the advantage of being ‘ready-togo’ out of the box. It measures PM2.5 to PM10 particulate sizes which do not allow for comparison with workplace exposure limits. The sampler also incorporates wireless connectivity through an app and has built-in sensors including GPS and automatic flow control.
The Defence Science and Technology Laboratory (Dstl) and the University of Hertfordshire have jointly developed a new all-in-one personal aerosol sampler, the CPAS [4] that is small, lightweight and low-cost. The CPAS is designed to measure the inhalable fraction of airborne particles. The sampler flow rate can be calibrated prior to attending site and the device then automatically corrects for flow rate changes due to filter loading. The CPAS continuously records data on the sampling flow rate, sampling time, ambient temperature and relative humidity.
Before any personal sampler is used to take measurements in the workplace, it is important that it is validated to make sure that it samples the expected healthrelated size fraction efficiently. The CPAS sampler is currently undergoing extensive evaluation at the Health and Safety Executive’s Science and Research Centre in Buxton. The sampler is being tested in calm air chambers and using a large dust tunnel. Its performance is being compared to that of the IOM sampler [5] and the inhalable sampling convention [6]. The samplers are being exposed to aluminium oxide powders of different sizes that span the inhalable size range.
Further to the laboratory-based performance assessment, there are other factors that should be considered to evaluate the effectiveness of a personal sampler. Some factors will only become apparent when a sampler is deployed in the workplace. Trialling new samplers by experienced occupational hygienists is therefore also important to highlight practical factors that are revealed in “real” circumstances.
Dstl are interested to hear from occupational hygienists about which sampler features are deemed essential and about useful future developments. Please follow this link to a short survey if you’d like to contribute by sharing your views.
It’s important that the UK is open and progressive in its approach to exposure assessment. HSE is currently in the process of establishing a research project to investigate the use of sensor networks and wearable technology which could allow exposure to be mapped across sites, highlighting ‘hot-spots’ and focusing attention in the right place. This could be a game-changer for site risk assessment and occupational hygiene. The research will be carried out as a shared research project between HSE and industry sponsors. More details about the scope of the project, as well as how to take part, can be found on HSE’s website.
Innovations incorporating optical particle counters (OPCs) with all-in-one samplers such as the CPAM, a variant of the above-mentioned CPAS where ‘M’ indicates real-time aerosol concentration monitoring, could have a huge impact on the occupational hygiene profession. Hygienists must use their experience
to anticipate activities that could carry an increased exposure risk whilst also ascertaining when they are taking place. Often on large sites this presents a serious challenge, and it is commonplace to stumble across an activity of concern by chance. Having an indication of all your samples, and their real-time concentrations linked to a smart device would be invaluable and direct the hygienists to the areas of concern immediately, ensuring the exposure scenario can be identified, observed and mitigated.
It is essential that we do not forget about our own health, safety and wellbeing. Adopting small simple all-inone air sampling devices will eliminate the days of handling heavy sampling equipment, reduce stress from time consuming pre and post calibrations and improve worker acceptance and engagement.
This publication and the work it describes were co-funded by Dstl and the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
©Crown Copyright, Health and Safety Executive 2020
REFERENCES:
1. Sherwood RJ, Greenhalgh DMS. (1960) Apersonal air sampler. Ann Occup Hyg; 2: 127–32.
2. https://www.tecora.com/en/produit/ individual-dust-sampler-cip10/
3. https://www.a1-cbiss.com/ultrasonicpersonal-air-sampler-upas.html
4. UK Patent GB 2560611, date of
Publication- 17/06/20
5. https://www.skcltd.com/products2/ sampling-heads/iom-sampler.html
6. BS EN 481:1993 Workplace atmospheres — Size fraction definitions for measurement of airborne particles
