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Assessing and controlling bioaerosol exposures in workplace environments”
Dr Peter SykesCentre for Health, Safety & EnvironmentCardiff Metropolitan University
Introduction
Centre for Health, Safety and Environment
Established in 2001, CHSE provides research andconsultancy services in a broad range of areas
- Bioaerosols- Occupational health and well-being- Development of online learning platforms- Chemical incident management- Worker engagement, culture and climate- Environmental public health ( Malaria, N&D)
Main aims• To provide an overview of the potential risks
associated with occupational exposures to bioaerosols.
• To discuss possible risk assessment and risk mitigation strategies.
• To use our work in the waste industry as a case-study to discuss exposure assessment methods, interpretation of data and risk control options.
Bioaerosols are defined as a collectionof aerosolised biological particlesincluding actinomycetes, bacteria, fungi,protozoa and their components
Bioaerosols
Fungi
Actinomycetes
Bacteria
Endotoxin
Key occupational environments where risk from bioaerosols may be found?
• Waste treatment.• Livestock and poultry farming.• Arable farming.• Waste water treatment.
Other occupational environments where bioaerosol risks may be found
• Food industry.• Laboratories.• Workshops that use metal working fluids.
Also, workplaces with problems with indoor molds and infrequently serviced and maintained air conditioning systems.
Health effects of bioaerosols
Bioaerosols have the potential to cause an adverse effect on health by:• Irritation.• Inflammation.• Sensitisation.• Infection.
Bioaerosols are a well documented occupational hazard.
• Aspergillosis• Allergic Rhinitis and Asthma• Extrinsic allergic alveolitis (Farmers Lung)• Chronic Obstructive Pulmonary Disease (COPD)• Toxic Pneumonitis / ODTS• Upper airway irritation/ mucous membrane
irritation• Accelerated decline in Forced Vital Capacity (FVC)
Know the hazard/ what’s the risk?
Risk is a function of likelihood and severity
Currently employee exposure levels are poorlycharacterised.
No dose-response estimates or safe levels of exposurehave been established
There is a lack of approved protocols for monitoringand no WEL’s
Exposures are a complex mixture
Risk Assessment and evidence gaps…
Workplace exposure limits for bioaerosols.
• Setting limits is problematical.• Limited dose-response data available.• Exposure scenarios differ between industries and
workplaces.
Exposure limits and no effect levels have been suggested by research studies.
Workplace exposure limits have been adopted in other countries for some components/scenarios, e.g. organic dusts (Norway – 5 mg/m3, Denmark - 3 mg/m3), Endotoxin (Netherlands – 90 EU/m3).
Exposure Assessment.Quantification of bioaerosols can be carried out in two ways:
• Culture based methods- Short sample time,- Extensive laboratory work required - Not suitable for all components of a bioaerosol
• Non Culture based methods- Enumeration of specific components of the bioaerosol,
e.g. Quantitative Polymerase Chain Reaction (qPCR), Endotoxin assay, Mycotoxin assay, Aflotoxins assay.
The method chosen will depend on the process and the micro-organism or component to be enumerated.
Sampling.
General guidelines for bioaerosolsampling can be found in:
BS EN 13098:2001 Workplace atmosphere — Guidelines for measurement of airborne micro-organisms and Endotoxin. (Currently under review - 18/30370311 DC)
Three principal methods of sampling….
Impaction - Direct impaction on to selective agar (Culture based method)
Single stage Andersen sampler Hand-held Microbial Sampler
Impingement in to liquid (Culture and non-culture methods)
All-glass impinger SKC Biosampler
CIP-10 Cyclonesampler
Coriolis Cyclone sampler
Filtration (Culture and non-culture methods)
IOM sampling head Button sampler Gravimetric sampler
What does the Legislation require?In addition to general duties under HASAWA & the MHSWR……
COSHH’2002 provides further requirements in relation to the assessment and control of biological agents which are of particular relevance
In these regulations, a biological agent
‘ means a micro-organism, cell culture, or human endoparasite, whether or not genetically modified, which may cause infection, allergy, toxicity or otherwise create a hazard to human health’
(SI 2002/2677)
COSHH – Biological AgentsGroup 1 – unlikely to cause human diseaseGroup 2 – can cause human disease and may be a hazard to employees; it is unlikely to spread to the community and there is usually effective prophylaxis or treatment availableGroup 3 – can cause severe human disease and may be a serious hazard to employees; it may spread to the community, but there is usually effective prophylaxis or treatment availableGroup 4 – causes severe human disease and is a serious hazard to employees; it is likely to spread to the community and there is usually no effective prophylaxis or treatment available.’(SI 2002/2677)
Many compost organisms not categorised therefore not on the ‘approved list of biological agents’
Legal RequirementsNo specific sector guidance or statement of evidence in many cases asfor poultry dust for example, but..
Exposure has to be prevented or reduced ‘As Low as ReasonablyPracticable (ALARP)’
Suitable health surveillance required
Personal monitoring may be needed
Not able to use an acceptable threshold approach
Instruction, information and training on asthmagens
Site specific/task specific bioaerosol risk assessment in key!!
Bioaerosols in the context ofwaste treatment
Considerable evidence exists confirming thatworkers in the waste treatment sector canexperience high exposures to bioaerosols.
High risk activities include sorting/picking of waste,cleaning and maintenance activities and operationswhere waste is being moved resulting in bacteriaand fungi becoming airborne.
Workers have been shown to be exposed to a millionto 100 million organisms
Moving Waste
Cause for concern?Bunger et al (2007) conducted a longitudinal study conducted to date (218 workers).
Study describes increased MMI, COPD and accelerated decline in lung function, 2 cases of EAA and one ODTS (Bunger et al, 2007).
Only a 5 year study so symptoms may have not have become apparent
Van Campen et al (2016) conducted a 16 year follow up study and concluded an increased risk of cough with phlegm indicating chronic bronchitis but no higher incidence of deterioration in pulmonary function was found in waste workers
Exposure characterisationTo date no dose-response estimates or safe levelsof exposure have been established for organicdust exposure within the composting industry.
No approved protocols for monitoring exposures
Viable and non-viable species are clinicallyrelevant
Exposures are known to be highly variable
Problems with bioaerosols arising from waste treatmentVery complex aerosol – hundreds of differentspecies of bacteria, fungi, spores, cellcomponents, toxins and VOC’s.
Composition and concentration highly variable
Heavily influenced by season, processing methods,waste composition, temperature moisture levels.
Our Research ProgrammeEstablishing an evidence-base to inform riskassessment
Monitoring undertaken at numerous sites, open andenclosed windrows, IVC’s, MBT’s, EfW’s, waste transferstations and HWRC’s.
>700 samples taken, monitoring consists ofPersonal monitoringStatic monitoringFixed to outside of vehiclesReal time monitoring
MethodsInhalable and respirable dust fractions weredetermined by gravimetric analysis in accordancewith MDHS 14/4 (HSE, 2014) using IOM inhalableand Higgins-Dewell cyclonic respirable samplers.
Endotoxin levels were determined using LimulusAmebocyte Lysate assay (LAL).
β-(1-3)Glucan levels were estimated using aspecific blocking agent to establish thecontribution that these compounds gave to theoriginal endotoxin assay.
Methods
One hour static and personal sampleswere collected using IOM sampling headsto enumerate the following viable species
Total mesophilic bacteriaThermophilic actinomycetesAspergillus fumigatusTotal mesophilic fungi
Interpreting the monitoring data
Current dust levels in UK legislation inappropriateGuidelines for ‘no-effect’ levels for environmental endotoxin have been suggested by Rylander (1997)
Toxic pneumonitis 2000 EU/m3
Airways inflammation 100 EU/m3
Systemic effects 1000 EU/m3
Netherlands have adopted a legal limit of 90 EU/m3 for endotoxin (A third of our results exceeded this level)No-effect levels as low as 10 ng/m3 have been suggested for β-(1-3) Glucan.
Interpreting Viable data (HSE,2003)
Process No. of Samples(n=117)
Dustmg/m3
GM (GSD)Min - Max
Endotoxin EU/m3
GM (GSD)Min - Max
Glucanng/m3
GM (GSD)Min – Max
Manual Sorting 18 1.47 (3.14)0.22 – 11.92
86.11 (5.77)7.06 – 1954.15
1.55 (6.47)0.09 – 127.42
Shredding 25 0.92 (2.73)0.08 – 4.70
48.68 (12.37)0.80 – 1837.73
1.32 (22.64)bld – 95.77
Turning 46 0.77 (2.75)0.07 – 7.22
21.14 (6.27)0.95 – 2144.44
0.6 (8.51)bld – 83.33
Screening 28 1.24 (3.33)0.20 – 17.73
33.76 (18.37)0.75 – 22656.25
1.25 (22.62)bld – 274.51
Employee exposure to Inhalable Dust, Endotoxin and β-(1-3) Glucan by activity.
Exposure levels by activity - IVCME1
GM (min – max)GSD
TH2
GM (min – max)GSD
GN3
GM (min – max)GSD
AF4
GM (min – max)GSD
TF5
GM (min – max)GSD
Manual sorting 1.07x105
(7.3x103 –1.13x106)4.31
2.3x104
(3.6x103 –5.2x106)11.89
4.02x103
(8.93x10–7.37x104)9.34
8.4x104
(3x103-9.97x106)12.24
1.45x105
(8.95x101 -7.58x106)29.15
Screening 1.1x104 3.2x105 1.04x102 1.1x104 1.3x104
Shredding 1.4x104 1x103 2.6x103 5.5x104 1.2x105
Turning 7.04x103
(3.1x103-1.6x104)3.19
7.22x103
(2.9x103-1.8x104)3.64
3.25x102
(9.61x101-1.1x104)5.60
4.06x103
(2.2x103-7.5x103)2.38
4.87x103
(1.4x103-1.7x104)5.84
1. Mesophilic Bacteria (ME)2. Thermophilic actinomycetes (TH)3. Gram negative bacteria (GN)4. Aspergillus fumigatus (AF)5. Total fungi(TF)
Summary of research findings
Workers exposure to dust is generally low (<2 mg/m3).
Manual sorting, screening, cleaning and maintenance gaverise to the highest results.
High peak exposures from all activities involving themovement of waste indicating a potential risk in wastecollection.
Despite low dust levels endotoxin concentrations and to alesser extent β-(1-3) Glucan were consistent with levelsthought to be related to clinical symptoms.
High exposure levels witnessed in vehicle operators (Poorprotection factors).
Cab exposure study
To establish vehicle operators’ exposure levels toinhalable and respirable dust endotoxin and β-(1-3)Glucan at composting sites.
To investigate the exposure reduction between theoutside and inside of vehicle cabs.
To evaluate the impact that cab cleanliness and vehiclefilter maintenance has on operator’s exposure levels.
Witnessed very poor cleaning and maintenance ofvehicles used on composting sites.
Some but very few operatives wearing RPE.
Workers perceive vehicle cabs to be a safeenvironment.
U N I V E R S I T Y O F W A L E S I N S T I T U T E, C A R D I F F | A R T H R O F A P R I F Y S G O L C Y M R U, C A E R D Y D D
Methods
Three phased monitoring strategy
Phase One Initial assessment
Phase Two Post cab cleaning and filter change
Phase three One month after cleaning and filter change.
Cab cleanliness ( scored 1 good – 5 bad), site/ operatorpractices such as doors and windows open, wereassessed and noted on each visit.
U N I V E R S I T Y O F W A L E S I N S T I T U T E, C A R D I F F | A R T H R O F A P R I F Y S G O L C Y M R U, C A E R D Y D D
ResultsCab cleanliness and filter maintenance was verypoor.
Working with vehicle doors and windows open wasa common practice.
4/8 vehicles sampled at first visit had a maintenanceschedule to replace filters after 500 hours.Remaining vehicles had no maintenanceprogramme in place.
Two vehicles had door panels missing!!
Results
Cleaning and filter change resulted in a significantdecrease (ANOVA p<0.05) in operator’s exposure todust, endotoxin and β-(1-3)Glucan.
Inside cab measurements significantly lower thanoutside measurements (p<0.05) – as high as 60-70 %reduction afforded by being inside the cab.
Practices such as windows being left open, inactive airconditioning had a significant effect on operator’sexposure (p<0.05).
DiscussionHSE guidance advocates the use of a vehicle with air filtration fitted to thecab, including the following features:
pre-filters, to protect the main HEPA filter;pressure gauges to show the system is working properly;alarms to sound when filters clog;overpressure above 10 Pa inside the cab to prevent dusty air ingress;door seals - heavy-duty neoprene or other suitable material; and self-closingdoors.Check that the clean air is turned on and working.Check any air conditioning self-test every time you start the vehicle.Keep doors and windows closed.If this is not possible, use RPE for moving waste.
Experiences from this study shows a different scenario
DiscussionEmployee exposure levels were high initially prior to cleaning butthe study demonstrates that exposure levels can be significantlyreduced by effective cleaning and maintenance.
Poor employee awareness of the potential risks from bioaerosolexposure.
No formal risk assessments or control measures in place.
Vehicle maintenance and staff practices were poor
Not common practice to wear RPE within the vehicles
Conclusions
Workers at composting sites are commonly exposed to levels of bacterial endotoxin and viableorganisms in excess of suggested dose-threshold levels even though in most cases, theirpersonal dust exposure is below the suggested regulatory levels (HSE, 2003 – RR130)
Currently unsure of the potential risk posed by inhalation of bioaerosols at wastetreatment sites.
Need to manage these potential risks with caution at this present time due to the gaps inour knowledge.
Body burdens and reliable dose-response estimates have not been established
No Workplace Exposure Limits exist for endotoxin and β-(1-3)Glucan.
Current general dust limits in the COSHH Regulations 2002 do not consider the biologicalcomposition of the dust experienced at composting sites
ConclusionsRobust risk mitigation and risk management proceduresare required to minimise employee exposure tobioaerosols to include vehicle cleaning and maintenance.
There is a need to raise awareness in employees of thepotential risks and how they should be managed.
RPE needs to be considered in operational areas, evenwithin vehicle cabs.
Consideration should be given to health surveillance andmonitoring employee exposures to dust at compostingsites.
Way forward….???
More in-depth consideration for bioaerosolexposures is needed at the design phase forthese facilities
Occupational Bioaerosol Risk Assessmentsneed to be site-specific and task-specific
Exposure should be prevented or where notpossible reduced ALARP
Key considerationsZoning - Site design and zoning needs to be considered with proportionate controlsin force within these zones
Decontamination - Suitable decontamination procedures required formovement from high risk to low risk areas.
Procedures for vehicles - Cleaning and maintenance logs needed for vehicles
Health surveillance
Monitoring - employee exposure levels is problematical (combination of viable andnon-viable?)
RPE - RPE may be required in vehicles – risk based judgement
General Procedures – wheel washing, drop heights, stockpiles, dust suppression,cleaning and maintenance
Key Reference Material
Bunger J, Schappler-Scheele B, Hilgers R, Hallier E. A 5-year follow-up study on respiratory disorders and lung function in workers exposed to organic dust from composting plants. : Int Arch OccupEnviron Health. (2007) Feb;80(4):306-12.Crook, B., Easterbrook, A. & Stagg, S. (2008) Exposure to dust and bioaerosols in poultry farming. RR655. Norwich : HSE BooksSearl A. (2010). Exposure-response relationships for bioaerosol emissions from waste treatment processes. Defra Project; WR0606.Searl, A. & Crawford, J. (2012) Review of Health Risks for workers in the Waste and Recycling Industry. Edinburgh : IOMSkogstad, M., et al. (2011) Long-term occupational outcomes of endotoxin exposure and the effect of exposure cessation. Occup Environ Med 2012;69:107-112.Stagg, S., Bowry, A., Kelsey, A. & Crook, B. (2010). Bioaerosol emissions from waste composting and the potential for workers’ exposure. RR786. Norwich : HSE BooksStagg, S., Sandys, V., Crook, B., Wood, J. & McAlinden, J. (2013) Occupational Hygiene implications of processing waste at Materials Recycling Facilities (MRFs): Exposure to bioaerosol and dust. RR977. Norwich : HSE BooksSwan, J.R.M., Kelsey, A., Crook. B. & Gilbert, E.J. (2003). Occupational and environmental exposure to bioaerosols from composts and potential health effects - A critical review of published data.Research Report 130. Norwich : HSE BooksVan Kampen, V., et al. (2016) Effects of bioaerosol exposure on respiratory health in compost workers: a 13 year follow-up study. Occup Environ Med 2016;73:829-837.
