Introduction to workplace characterization and
evaluation
Gunnar Damgård NielsenPhD, Dr Sc (Pharm)
Updated 24.03.2015
Bhopal (1984) ≥ 2000 death due to methylisocyanate exposure
Bhopal was asleep when the gas struck. Simple advice to move upwind or stay indoors and seal doors and windows with damp cloths could have saved thousands but Union Carbide had not told people what to do if there was a leak.
Crowds of terrified people fled.
Bhopal's hospital was overwhelmed, lacking information about the gas or antidote.
After this, redesign of the American chemical industry to just in time production
Overall - what went wrong?• Storage of a large quantity of a hazardous
compound in close proximity to a densely populated area
• Wrong design of the plant and processes
• Insufficient education of the workers
• No operating emergency plan
Large quantities of dangerous substances are regulated by the Seveso III directive (2012/18/EU)
Types of hazard
•Chemical exposure, e.g white spirit•Biological exposure, e.g. legionella•Ergonomic loads (e.g. heavy lifting)•Noise•Cold/warm/draught•Fall•Electricity (shock)•Psychological effects, e.g. stress•Explosions, e.g. Bhopal
General procedure for workplace characterization.Each process steep is evaluated separately
Raw material reception
Weighing/mixing/manipulation/dilution
Production of product
Filling/packing
Storing/transport
Degree of mechanization•Manual•Mechanical•Automatic
Operation•Start-up•Normal •Breakdown•Maintenance•Closing
Langaa Jensen, J & O. Broberg. Analyse af produktionsprocesser. Ed. T. Schneider. Teknink Arbejdshygiejne. Bd.I. København, Arbejdstilsynet, Arbejdsmiljøinstituttet, 1996, 22-34.
Composed ofunit operations
Evaluation of chemical exposures
• Qualitative exposure assessment used for hazard based prevention
• Quantitative exposure assessment used for risk based prevention
Control banding (CB): qualitative or semi quantitative risk assessment and risk management approaches
used World-Wide. Differ from place to place.
• Initiated within the pharmaceutical industry due to many compounds with limited toxicological data.
• Modern development by the UK Health and Safety Executive (HSE), but not intended for evaluation of pesticides, pharmaceuticals, process generated hazards, e.g. wood and silica dust, and welding fumes or otherwise regulated compounds as lead and asbestos.
• Hazards bands from EU risk R-phrases (replaced by new EU-CLP classification) (HSE)
• Exposure from amount of chemical handled (low, medium, high) and volatility or dustiness (low, medium, high).
• Integrates to control guidance (risk management).• Limitation: lack of quantitative exposure data; CB is a complement to
classically industrial hygienen approaches
Zalk and Nelson. History and evaluation of control banding: a review. J Occup Environ Hyg 2008, 5, 330-346
Hazard based risk management
Classification and labelling Toxicological data bases
Google: reach-it or http://echa.europa.eu
Information on Chemicals
E.g. toluene
C & L inventory
Select/find toluene
• GHS• Dangerous
substance directive (R/S sentences)
http://echemportal.org
Substance search
e.g. toluene
Different databases recommended by ECHA and OECD
Risikovurdering (Risk Assessment)
A. Farevurdering (Hazard Identification)(iboende egenskaber hos stof)
B. Dosis-effekt/respons sammenhæng (Dose-effect/response relationship)
(fx fastsættelse af NOAEL og LOAEL)
C. Eksponeringsvurdering (Exposure Assessment)
(koncentration/dosis)
Risikokarakterisering (Risk Characterisation)(incidens/alvorlighed/sandsynligheder)
Risk assessment of occupational exposures follows the general approaches for risk assessment
Quantitative exposure assessment
• Determined by measurement• Estimated from the scientific
literature• Estimated by model calculations
Aims of measurement•Control of production process, e.g. compliance
with OEL
•Health surveillance and epidemiological studies
•Source identification, e.g. from a leakage
If measurements are performed, it should be possible to interpret or use the results
Stationary sampling•Process emission•Room mean level
From Baron PA et al. 2003
Two different measurement strategiesPersonal sampling
Exposure assessment of gases and vapours
•Measurement methodsa) Collection on adsorbent tubes followed by
desorption and determination by GC or HPLC.
b) Direct reading instruments (indicator tubes, IR,photoionization detector, portable GC)
•Exposure assessment based on literature data
•Exposure assessments from the mass balance equation
•Exposure assessment from modelling, e.g. evaporation from solvents 1)
1.Lennert et al. Evaluation of evaporation and concentration distribution models – a test chamberStudy. Ann Occup Hyg 1997, 41, 625-641.
Measurement of gases and vapours
Solid sorbent tube/sampler: for longer measurement time
Snapshot: Indicator/detector tube. Read out as change of colour
Passive (diffusion) sampling of gases and vapoursQ=D (A/L) C T
Q=amount collectedD=diffusion coefficientA=sampling areaL=length of diffusionC=air concentrationT=sampling time
GC
HPLC
Estimation of gas/vapor concentrations
Maximum concentration (a worst case concentration(c)): saturated vapour concentration 1)
From the mass balance equation1), i.e. Emission (m)/mixing volume (V): C= m/V x p. Where inadequate mixing, the total ventilation rate may be multiplied by a mixing factor “p” in the range from 0.3 to 0.7 1)
Dispersion modelling (air velocity, diffusion and turbulence) 1)
Exposure models 2)
1) Jayjock MA. Assessment of inhalation exposure potential from vapours in the workplace. Am Ind Hyg Assoc J 1998; 49: 380-385.
2) WHO. Principles of characterizing and applying human exposure models. Geneva 2005.
Example 1. Use of the mass balance equation. Assumption: The offending agent evaporates immediately in a room andthe air exchange does not contribute to the mixing volume
100 ml of a cleaning product with 1% limonene (density: 0.84 g/ml) is diluted to 10 L wash water, e.g. 0.1 ml limonene/L or 84 mg/L wash water
The floor (8 m x 9 m) and the floor-to-ceiling height (4 m): Volume=288 m3
It is assumed that the wash water level after the cleaning is 1 mm=0.1 cm. The total amount left on the floor is 103 cm3/m2 x 8 m x 9 m x 1L/103 cm3 = 72 L (greatly overestimated)
C=mass/volume=72L x 84 mg/L / 288 m3 = 21 mg/m3
There is no expected toxicological effect from MOS/MOE = C/NOAEL of this the level
Limitations: The cleaner is close to the source, but the evaporation neednot be immediately. However as he/she is moving around in the room, the scenario is considered realistic
Example 2. Use of the mass balance equation to estimate body burden
Used amount of product (W mg) with the fraction (f) of the active compound.Emission during the production period: W•f mg
Volume (V m3) of working area with the air exchange rate (A hour-1) and working time (t hours): Mixing volume: V•A•t m3 when > V
Mean exposure concentration: W•f/ V•A•t mg/m3
Inhalation does during a t hour work period (1.25 m3/hour or 10 m3/8 h): (W • f • 1.25)/(V • A • b.w) mg/kg b.w. The body weight is b.w.
This value can be compared with a NOAEL from human or animal studies to estimate MOS/MOE.
For extended evaluation of exposure risks in relation to pregnancies, c.f. Mikkelsen et al.Kemikalietestning og risikovurdering. Dansk Kemi 2003; 84(1):17-20.
Evaluation strategies of particle exposuresZone of similar exposure/similar exposure groups (SEG)
Large (Visual cue; ~mg/m3)
Particles Nano (Background correction
induces uncertainty)
SEG
Hazard Based evaluation
Risk based evaluation
Personal sampling (6-10/SEG)
• Risk management• Epidemiology
Mass Number Surface area
Far field agglomeration?
SEG depending on exposure metrics with biological relevance
• Risk management• Epidemiology
Ramachandra et al. A strategy for assessing workplace exposures to nanomaterials. J Occup Environ Hyg 2011; 8: 673-685
Exposure assessment of particles
•Collection on filters and weighing 1,2)
•Direct reading instruments 1,2)
•Data from the literature
•Evaluation from models 3, 4)
1) McMurry PH. A review of atmospheric aerosol measurements. Atmospheric Environment 2000,34,1959-19992) Baron P. Personal aerosol sampler design: a review. Appl Occup Environ Hyg 1998, 13, 313-320.3) Tielemans et al. Conceptual model for assessment of inhalation exposure: defining modifying factors.
Ann Occup Hyg 2008, 52, 577-5864) Cherrie and Schneider. Validation of a new method for structured subjective assessment of past concentrations.
Ann Occup Hyg 1999, 43, 235-245.
Mass aerodynamic diameter
1 g/cm3
The aerodynamic diameter is the diameter of a unit densitysphere that has the same settling velocity as the particle
The particle size distribution can be obtained by means of a cascade impactor
The size of the dust determines where the dust is deposited and wherean offending effect occurs. Different samplers are used for the
different depositions
0.1 1 10 1000
20
40
60
80
100
Diameter, mikrometer
%
Particle characterizationOccupational exposure characterization
Inhalable fraction is the part of the aerosol particles that can pass the naresThe thoracic fraction can pass to the thoraxThe respirable fraction can pass to the alveoli
Outdoor air exposure characterization
PM10 (”Particulate matter); corresponds to the thoracic fractionPM2.5
Sampling of dust on filters
Inhalable dust Respirable dust
Pump
Pump
Examples of samplers
Inhalable dustMedian diameter: 100μm
Thoracic dust fractionMedian diameter: 10μm
Respirable dustMedian diameter: 4μm
IOM sampler (standard) - IOM with foam
Button sampler - -
Grimm optical aerosolmonitor (real time)
Grimm optical aerosolmonitor (real time)
Grimm optical aerosolmonitor (real time)
- - Cyclone
Dekati two-stage cascade impator
Dekati two-stage cascade impator
Dekati two-stage cascade impator
Linnainmaa et al. Laboratory and field testing of sampling methods for inhalable and respirable dust. J Occup Environ Hyg 2008, 5, 28-35.
Direct reading instruments for dust characterization
Most use light scattering
Thorpe A. Assessment of personal direct-reading dust monitors for the measurementof airborne inhalable dust. Ann Occup Hyg 2007, 51, 97-112.
Personal (portable) direct-reading dust monitors
• Most often based on light scattering (laser or diodes).• Responses depend on particle size, shape and density,
and on the refractive index.• Needs calibration with appropriate particle distributions.• Underestimate often inhalable dust level.• More appropriate for respirable dust concentrations (due
to calibration)
Thorpe A. Assessment of personal direct-reading dust monitors for the Measurement of airborne inhalable dust. Ann Occup Hyg 2007,51, 97-112.
Examples of nanoparticle sizing instruments• TSI fast Mobility Particle Sizer (FMPS)• Engine Exhaust Particle Sizer (EEPS)• Scanning Mobility Particle Sizer ((SMPS)
Airborne particles measured with EEPs or FMPS: 6-560 nm
Impactor collects particles> 1 µm
Charging of particles
Electrometer: Size distributionSmall particles
Large particles
Zimmerman et al. Comparison of three nanoparticle sizing instruments: the influence of particle morphology. Atmos Environ 2014; 86: 140-147.
Dust emission increases with:
• Amount of substance (not proportional a)
• Energy input a)
• Handling time (the dust emission is often maximal in the beginning of a process) a)
• Proportional with the drop height b)
a) Hjemsted K., Schneider T. Documentation of a dustiness drum test. Ann. Occup. Hyg. 1996; 40: 627-643.
b) Cowherd et al. Dust inhalation exposures from the handling of small volumes of powders. Am. Ind. Hyg. Assoc. J. 1989; 50: 131-138.
Dust emission by transferring 3.8 L of a powder at 1-min intervals to a 23 L bucket over a 30 min interval. Lab size 36.8 m3 and an air exchange rate 4.5 •hour-1 a)
Compound Number of transfers
Transferedkg
Drop Heightcm
Respirabledust (mg/m3)
SP b)
(mg/m3)Emission factor (mg/kg)
Talc 43 88 14 3.7 34
Talc 42 88 22 12 56 107
NaCl 28 100 14 16 85 118
NaCl 29 100 22 39 124 181
Cement 29 126 14 3.5 14 15.4
Cement 29 126 22 6.8 39 36.8
DY4 dye 36 54 14 - 5.6 19.3
DY4 dye 36 54 22 - 12 29.7
a) Cowherd et al. Dust inhalation exposures from the handling of small volumes of powders. Am. Ind. Hyg. Assoc. J. 1989; 50: 131-138.
b) Suspenden particulate matter: open-face 37-mm cassett at 1,8 L/min
Dust exposures from the scientific literature. Example, ”default values” for pharmaceutical processes
Process mg/m3 Process mg/m3
Dumping from drums 0.9 Film coating 0.1
Dumping from bags 1.2 Sieving 0.8
Scooping out of drums 0.8 Granulating 0.9
Filling drums from a blender 0.6 Compressing 0.08
Bin transfers 0.2 Packing 0.01
Digging centrifuge 0.3 Sampling 0.01
Milling 2.3 Encapsulating 0.05
Tray dumping 2.7
Neumann & Sargent. Setting occupational exposure limits for pharmaceuticals.Occupational Medicine: State of the Art Reviews. 1997; 12: 67-80.
Reporting of exposure assessment
• Summary: Main points/conclusions• Introduction: Problem formulation, study design and
sampling approaches• Methods: Data gathering (analytical- and modeling),
formulae used, assumptions and default values• Results and exposure characterization: • Conclusion: Main outputs from the exposure assessment
and interpretation in the context of compliance checking and risk assessment
The Interdepartmental Group on Health Risks from Chemicals. Guidelines for good exposureAssessment practice for human health effects of chemicals. Institute of Environmental Health,University of Leicester 2004. ISBN 1 899110 39 9
Process Com-pound
Amount handlee(Wi,X) a)
Concen-tration b)
(Ci,X)
Rele-vantOEL orSTEL
C/standard(OEL or STEL)
Time (t)
C x t Other hazardsc)
Trans-port(i)Pro-cess(i)
ABC
Wi,A
Wi,B
Wi,C
Ci,A
Ci,B
Ci,C
OELA
OELB
OELC
Ci,A/OELA ti,A Ci,A x ti,A
Transport (i+1)
a) Ergonomic risk is considered if ……b) Dust, gases and vapoursc) For example, noise (N), mechanical accident (A), burn (B)….
Example of a content of an exposure assessment and risk characterization report
TWA for compound A: ΣC,i,A x ti,A/Σti,A = Mean A; Hazard index: Mean A/OELATWA for compound B: ΣC,i,B x ti,B/Σti,B = Mean B; Hazard index: Mean B/OELBIf additive: Sum = Mean A/OELA + Mean B/OELB + etc.Accepted if 1≥Sum and not accepted if 1<Sum
Risk management
Prioritized risk management strategiesControl strategy ExampleElimination/source control Substitution (enzymes, white spirit,
vegetable oil-based press wash, electric forklifts)
Engineering control Ventilation, operations and maintenance (e.g. prevents leaks)
Administrative controls Education (isocyanates)
Work practices Housekeeping, personal hygiene(Pb)
Personal protective equipment Respirators
Roelofs CR, Barbeau EM, Ellenbecker MJ, Moure-Eraso R. Prevention strategies in industrial hygiene: a critical literature review. AIHA Journal 2003; 64: 62-67.
Substitution
• Granulation and encapsulation of enzymes• Elimination of white spirit from paints• Vegetable oil-based press wash• Electric forklifts versus diesel driven
engine• Pigments in a paste versus dry pigments
All ventilation systems have to be controlled and cleaned periodically, and
maintained properly 3)
1) Breum and Valbjørn. Arbejdstilsynet informener. Ventilation I kontorer,industri m.m. Oktober 81.
2) Tseng et al. Correlation between airflow patterns and performance of a laboratory fume hood. J Occup Environ Hyg 2006, 3, 694-706.
3) Estill et al. The impact of maintenance and design for ventilation systems.Appl Occup Environ Hyg 2002, 17, 344-351.
Types of ventilation systems1,2)
General ventilation
Clean air should be supplied so the worker is in the clean air zone, whereas the polluted air is captured by the ventilation system
Shunt with polluted air? Should supply clean air
Purpose: Control of the manyminor sources
Local exhaust ventilation for a specific source control
The capture air velocity has to be sufficient
D
In a distance of one diameter(D) from the exhaust outlet the air velocity is 10% of the outlet air velocity at the opening
In a distance of 2D from the opening, the air velocity is < 5% of the velocity at the opening
Closed system (encapsulation)