assessing & managing worker’s exposures bioaerosols during the treatment of organic waste dr...
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Bioaerosols are defined as a collection of aerosolised biological particles including actinomycetes, bacteria, fungi, protozoa and their componentsTRANSCRIPT
Assessing & Managing worker’s exposures bioaerosols during the treatment of organic waste
Dr Peter Sykes
Cardiff School of Health SciencesCardiff Metropolitan University
Main aims
• To provide an overview of the potential risks associated with occupational exposures to bioaerosols.
• To summarise the main findings of our research programme.
• To discuss risk assessment and risk mitigation strategies.
Bioaerosols are defined as a collection of aerosolised biological particles including actinomycetes, bacteria, fungi, protozoa and their components
Bioaerosols in the context of organic waste treatment
• The presence of fungi and bacteria are fundamental to the composting process. (total viable counts of 106 and – 1010 have been measured in ambient air at composting facilities)
• Shredding, turning and screening cause micro-organisms to be aerosolised, forming ‘bioaerosols’
Moving Waste
Characterising Workers exposure
• Workers on composting sites, whose job it is to handle the compost at various stages − feedstock handling, heap turning, final screening and grading − may therefore be at risk of considerable exposure to bioaerosols, depending on the task and the control measures in place (Stagg et al., 2010).
The effects of exposure to organic dust on respiratory health may lead to or exacerbate a number of distinct identifiable conditions.
• 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)
Cause for concern?
• Only one 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
Our Research Programme• Establishing an evidence-base to inform risk
assessment• Monitoring undertaken at four sites, Two open
windrow sites, one in-vessel composting facility and one enclosed windrow facility were used.
• 280 samples taken, monitoring consisted of– Personal monitoring – Static monitoring– Fixed to outside of vehicles– Real time monitoring
• Personal Exposure assessment/task analysis
• Cab Filtration StudyPhase One – Initial assessmentPhase Two – Post cab cleaning and filter changePhase three – One month after cleaning and filter
change • Health Study – Questionnaires, Lung Function and IgG
tests (ongoing).
Methods
• Inhalable and respirable dust fractions were determined by gravimetric analysis in accordance with MDHS 14/3 (HSE, 2000) using IOM inhalable and Higgins-Dewell cyclonic respirable samplers.
• Endotoxin levels were determined using Limulus Amebocyte Lysate assay (LAL).
• β-(1-3)Glucan levels were estimated using a specific blocking agent to establish the contribution that these compounds gave to the original endotoxin assay.
Summary of research findings
• Workers exposure to dust is generally low (<2 mg/m3).
• Manual sorting and Screening of waste gave rise to the highest results.
• High peak exposures form all activities involving the movement of waste indicating a potential risk in waste collection.
• Despite low dust levels endotoxin concentrations and to a lesser extent β-(1-3) Glucan were consistent with levels thought to be related to clinical symptoms.
• High exposure levels witnessed in vehicle operators (Poor protection factors).
Employee exposure to Inhalable Dust, Endotoxin and β-(1-3) Glucan by activity.
Process No. of
Samples
(n=117)
Dust
mg/m3
GM (GSD)
Min - Max
Endotoxin EU/m3
GM (GSD)
Min - Max
Glucan
ng/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
Summary of Research Findings – Cab Study• In general vehicle maintenance and cleanliness were poor. Large
variation in vehicle filter efficiencies (45% - 99%).
• Poor procedures for exiting vehicle cabs in operational areas.
• Workers boots and over clothing unclean
• Only one operative wearing RPE.
• Cleaning and maintenance program had a significant reduction in vehicle operator exposure levels but then increased over time.
Interpreting the monitoring data• Current dust levels in COSHH inappropriate• Guidelines 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.
• Workers at composting sites are exposed to high levels of bacterial endotoxin consistent with adverse respiratory outcomes even though in most cases, their personal dust exposure is below the suggested regulatory levels.
• Dose-response data for the biological components
present in the dust encountered at composting sites are not well established at this time and site operators should adopt precautionary measures when assessing and managing these potential risks.
Figure 3.13: Linear Regression of Inhalable Endotoxin versus Inhalable Dust
-2 -1 0 1 2-2
0
2
4
6
Log10 Inhalable Dust (mg/m3)
Log 1
0 Inh
alab
le E
ndot
oxin
(Eu/
m3 )
Figure 3.14 : Linear Regression of Inhalable Endotoxin versus Inhalable Dust
-2 -1 0 1 2-2
0
2
4
6
------ 90 EU/m3 1.53 mg/m3
------ 10 mg/m3 Nuisance Dust Level
Log10 Inhalable Dust (mg/m3)
Log 1
0 Inh
alab
le E
ndot
oxin
(Eu/
m3 )
----- 90 EU/m3 Ξ 1.53 mg/m3
----- 10mg/m3 nuisance dust level
Scientific determination of risk or practical risk management ?
What the law requires….• In addition to general duties under MHSWR and
HASAWA……
• Compost workers exposed to Group 2 biological agents as defined in Schedule 3 Paragraph 2 of the COSHH Regs.
• Moreover compost emissions contain substances that may be a potential cause of occupational asthma (therefore Appendix 3 of COSHH applies)
Legal Requirements
No specific sector guidance or statement of evidence as for poultry dust for example, but..
• Exposure has to be prevented or reduced ‘so far as is reasonably practicable’
• Suitable health surveillance required
• Personal monitoring may be needed
• Not able to use an acceptable threshold approach
Way forward….???• Occupational Bioaerosol Risk Assessments need to be site-specific
and task-specific
• Site design and zoning needs to be considered with proportionate controls in force within these zones
• Suitable decontamination procedures required for movement from high risk to low risk areas.
• Cleaning and maintenance logs needed for vehicles
• RPE may be required – risk based judgement
• Monitoring employee exposure levels is problematical (combination of viable and non-viable?)
Development of specific guidance• Is monitoring required?
• What to Monitor?
• Is health surveillance required? What should it entail?
• Is RPE required? Type?
• Suggestions for good Practice
• How to control the vehicle cab environment
• Reducing exposures SFAIRP
Conclusions• Robust risk mitigation and risk management procedures are required to
minimise employee exposure to bioaerosols
• There is a need to raise awareness in employees and managers of the potential risks and how they should be managed.
• A need for education and training
• In the absence of specific legislation and guidance, precautionary stance needed – reasonably practicable
• Levels in COSHH provide little help
• AFOR guide offers practical advice
