Transcript This project is co-funded by the European Union and the Republic of Turkey Technical Assistance for Development of Regional Laboratories of Occupational Health Safety.

This project is co-funded by the European Union and the Republic of Turkey
Technical Assistance for
Development of Regional
Laboratories of Occupational Health
Safety Centre (ÍSGÜM)
EuropeAid/127200/D/SER/TR
This project is co-funded by the European Union and the Republic of Turkey
Occupational Exposure Limits, other
reference values and interpretation
of measurement results
Jan Gromiec, Ph.D.
Objectives
On completion of this course, participants should:
• fully understand the meaning of different types of
Occupational Exposure Limits
• be acquainted with the procedures and the rationale for
OEL derivation at the EU and national levels
• be acquainted with exposure assessment criteria in the
USA
• have a knowledge on a possible role of DNELs (DerivedNo-Effect-Levels) as the criteria of the assessment of the
occupational exposure to chemicals
• be able to interpret measurement results
The course outline
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Basic terms and definitions related
Occupational Exposure Limits (OEL)
OELs in the European Union
OELs in individual EU countries
Procedures of OEL setting
OELs in the USA (OSHA, ACGIH, NIOSH)
Derived-No-Effect Levels (DNELs)
Comparison of OELs and DNELs
Interpretation of measurement results
Calculation of uncertainties
to
Occupational Exposure Limit
(OEL)
Occupational exposure is a measure of the intensity and/or
extent to which the human body experiences a particular
hazard.
Quantitative health standard, expressed as a mean concentration
over a given period of time, which an air pollutant must not exceed if
the exposed workers’ health is not to be affected.
Limit value (old term)
Reference figure for the concentration of a chemical in air
NOTE:
• set for reference periods of 8 h
• temperature of 200C
• pressure of 101,3 kPa.
• The limit values for suspended matter are given in mg/m3 or
multiples of that for actual environmental conditions
(temperature, pressure) at workplace. The limit values of
fibres are given in fibres/m3
or fibres/cm3 for actual
environmental conditions (temperature, pressure) at
workplace.
(EN 689:1995)
• The effects of increasing exposure to chemical substances may be
viewed as a continuum:
• (1) no effects observed
• (2) compensatory effects or early effects of dubious significance
without adverse
• health consequences
• (3) early health impairment (clear adverse effects)
• (4) overt disease, possibly death.
• As with systemic health effects, responses to irritants may be
viewed as a continuum:
• 1) no effects observed; no awareness of exposure
• 2) very slight effects; awareness of exposure
• (3) slight irritant effects or nuisance (e.g. smell); easily tolerable
• (4) significant irritation/nuisance, overt health effects; barely
tolerable
• (5) serious health effects (e.g. pulmonary oedema); intolerable
To convert ppm to mg/m3
OEL in mg/m3 =
(OELinPPM)  ( gram MW)
24,45
OEL(m g / m )  24,45
gram MW
3
OEL in ppm =
Objectives of OEL setting
• to prevent or limit the exposure of workers
to dangerous substances at workplaces
to protect the workers that are likely to be
exposed to these substances
OELs began to be established in order to provide criteria on the basis
of which decisions could be made as to whether the airborne
concentrations of given substances were sufficiently low to prevent
adverse effects on health.
• OELs may be used for a number of purposes. to provide standards
or criteria against which measured exposure levels in existing
workplaces may be compared in order to ensure that
• They may also be used for design purposes
OELs at the EU level – legal aspects
• Council Directive 80/1107/EEC (amended by
Directive 88/642/EEC) – setting out measures for the
control of risks related to chemical, physical and
biological agents
• Council Directive 90/394/EEC – provisions for setting
up limit values for carcinogens
• Framework Directive 89/391/EEC – measures to
encourage improvements in the safety and health of
workers at work
• Council Directive 98/24/EC – legal basis for
Community OELs
• Commission Directive 2000/39/EC establishing the
first list of indicative OELs
Scientific Committee for Occupational
Exposure Limits to Chemical Agents (SCOEL)
• Set up by the European Commission Decision
95/320/95 of 12 July 1995
• to supply the Commission with opinions at the
latter’s request on any matter relating to the
toxicological examination of the chemicals for their
effects on health of workers.
• to give in particular advice on the setting of OELs
based on scientific data and where appropriate
propose values which may include:
- the eight-hour time weighted average (TWA)
- short-term limits/ excursion limits (STEL)
- biological limit values
Steps leading to the establishment of
EU OELs
• Preparation of a scientific dossier for review
• Evaluation of a scientific dossier
• Development of recommendation from the SCOEL
(scientifically based OEL) for the Commission services
• Development of a proposal for an OEL by the
Commission services
• Consultation of the Advisory Committee for Safety,
Hygiene and Health Protection of Workers
• Adoption of the implementing Directive
General procedure for setting OEL
proposals by SCOEL
• Assemble all available data on the hazards by the
substance
• Determine whether the database is adequate for the
setting of an OEL
• Identify the adverse effects due to exposure to the
substance
• Establish which adverse effect(s) is (are) considered
to be crucial in deriving OEL
• Identify the relevant studies which characterise these
key effects (quality of of these studies)
• Establish whether the substance acts via a nonthreshold or threshold mechanism (crucial for health
based OELs)
Indicative Occupational Exposure Limit Values
(IOELs) Commission Directive 2000/39/EC
• Definition: Indicative OELs are numerical values
which provide the threshold level of exposure to a
given substance below which no detrimental
effects to workers health are expected.
• Indicative OELs may be established in those cases
where a review of the total available scientific data
base leads to the conclusion that it is possible to
identify a clear threshold dose below which
exposure to the substance in question is not
expected to lead to adverse effects
Indicative Occupational Exposure Limit Values
(IOELs) Commission Directive 2000/39/EC, cntd
• For any chemical agent for which indicative
occupational exposure limit values are established
at Community level, Member States are required
to establish a national occupational exposure limit
value, taking into account the Community limit
value, determining its nature in accordance with
national legislation and practice
• Indicative occupational exposure limit values
should be regarded as an important part of the
overall approach to ensuring the protection of the
health of workers at the workplace, against the
risks arising from hazardous chemicals
Short-term Indicative OEL
A limit value above which exposure should not
occur and is related to a 15-minute period,
unless otherwise specified
(COMISSION DIRECTIVE 2000/39/EC of 8 June 2000)
OEL - STEL
Short-term exposure limits - peak limitations, intended as supplementary
to TWA and protecting against short-time effects like
annoyance,
irritation, CNS depression etc. in situations where OEL-TWA values were
set
at levels only slightly lower than the concentrations associated with
the risk of short-term exposure effects.
The definition stresses that STEL is not a ceiling value, the essential
difference being that no reference period is quoted for the ceiling
concentration. It should be noted, however, that among the already
published 90 indicative OEL values none refers to the ceiling
concentration.
Binding Occupational Exposure Limits
Values (BOELs)
• for some adverse effects (genotoxicity, carcinogenicity,
respiratory sensitization) it may not be possible on
present knowledge to define a threshold of activity
• „pragmatic” OELs are established at levels of sufficiently
low risk
• adopted by the Council of Ministers of the European
Communities under the procedure laid down in Article
118a of the Treaty. Such limit values reflect scientific data
as well as socioeconomic considerations and must be
transposed into national legislation as minimum
requirements
• if for a given substance the binding OEL has been
established, the Member States are obliged to introduce
into national legislation a limit value for this substance,
not exceeding the agreed BOEL
EC law on Occupational Safety and
Health (OSH)
• EC OSH Directives contain only minimum
requirements.
During
the
necessary
transposition into national legislation more
stringent provisions than laid down in the
EC Directives can be introduced by the
Member States
Legal bases: 137 Article of the EC-Treaty
Occupational Exposure Limits in Poland
• Maximum Admissible Concentration (MAC)
• Proposed by the MAC Commission, established by
the Minister of Labour and Social Policy
• Starting point:
-NOAEL or LOAEL for substances with systemic
activity
-human data or RD50 for irritants
• Use of uncertainty factors
• Ceiling MACs for substances highly irritating or
dangerous to life
• STEL (2x15 min. during a workshift)
• Analytical method required
• Conservative and restrictive approach
Maximum
admisible
concentrations
Legislation
level
Preparatory
level
MINISTER OF LABOUR
AND SOCIAL POLICY
Intersectoral
Commission for MAC
and MAI Values
demand for MAC-value
• Industry
• Health administration
(sanitary inspection)
• Labour administration
• State Labour
inspection
• Trade unions
• Research institutes
Biological tolerance limits
Medical preventive
measures
MINISTER OF HEALTH
AND SOCIAL
WELFARE
requirement for
MAC proposal
MAC
documentation
Methods of air
sampling and
analysis
POLISH
STANDARIZATION
COMMITTEE
Group of Experts for
Chemical Agents
Calling for
information
information
Bank of information
• exposure data
• health effects data
System of setting MAC-values in
Poland
Number of OELs in Poland, Germany
and USA
Maximum admissible concentrations of harmful to health chemical agents and dusts in the
working environment in Poland, USA and Germany
The number of chemical substances and dusts harmful to
health
800
710
700
600
498
500
433
400
441
369
300
200
514
261
203
223
690
The number of
chemical
substances, for
which were
established
Occupational
Exposure
Levels (OELV)
2000/39/CE),
2006/15/CE)
10 binding OEL
acc. to Dir.
98/24, 99/238
and 2003/18.
132
100
0
1985
1990
1995
2001
2002
2004
2005
2007
EU
USA
Germany
(ACGIH)
TO PREPARE DOCUMENTATIONS, THE EXPERTS
UTILIZE ALL THE AVAILABLE INFORMATION WHICH
USUALLY INCLUDES
 original bibliography collected through the data bases
(TOXLINE, MEDLINE, CANCER-CD, OSH-ROM,
NIOSHTIC,
CHEM-BANK,
RTECS,
HSDB,
ANALITICAL ABSTRACTS, CCINFOdisc, IRPTC,
CHEMICAL ABSTRACTS)
 available documentations on exposure limits in other
countries (USA, Germany, Sweden, EU)
 WHO Environmental Health Criteria
 IARC evaluation of the carcinogenic risk due to
chemicals
 other reviews
 unpublished documented data
MAC Documentation Content
• Summary
• Substance characterization,
uses and occupational
exposure
• Toxic effects on man
• Toxic effect on experimental
animals
• Carcinogenicity,
mutagenicity, teratogenicity,
embryotoxicity and effects
on reproduction
• Toxicokinetics
• Mechanisms of toxicity
• Combined effects
• Dose-effects and doseresponse relationships
• Bases for existing MACvalues and biological
tolerance limits
• Bases for proposed MACvalues and biological
tolerance limits
• Methods of determination in
the air and in biological
material
• Pre-employment and
periodical examinations expsoure contraindications
• References
The theoretical fundamentals for setting
hygienic standards comprise:
• results of epidemiological studies of a
relationship between the magnitude and
duration of exposure and the induced health
effects;
• results of medical observations of workers
exposed to given toxic agent under industrial
conditions;
• results of experimental animal studies.
Calculation of a MAC value
Calculation of a MAC value for a chemical substance
MAC = NOAEL/UF or LOAEL/UF
Uncertainty factor, UF, is calculated from the formula:
UF = A x B x C x D x E,
where
FACTOR
EXTRAPOLATION
A = max. 2 average human to sensitive human (intraspecies)
B = max. 10 for tests using exposures other than inhalation
= max. 3 for tests using inhalation exposure (interspecies)
C = max. 3 short term to long-term exposure
D = max. 3 LOAEL to NOAEL
E = max. 5 modifying factor (depending on expert’s opinion on the
completeness of data and for potential long-term effects)
Calculation of a MAC for irritant
substances
Calculation of MAC values from RD50 data
Calculation of a MAC value for the irritating substances is based
on RD50 value, representing the concentration that induces a 50%
reduction of the respiratory rate in experimental animals. MAC is selected
in the range from 1/10 to 1/100 of the RD 50 value.
TABLE
Calculation of MAC values from RD50 data
Concentration of
substance in
ambient air
RD50
1/10 RD50
1/100 RD50
Expected effects of the irritating activity of the substance in
humans
concentration tolerated by humans
concentration resulting in slight irritation of eyes, nose and throat
none or very slight irritating activity
Other MAC related issues
• number of MAC chemicals in Poland: 511,
capacity to produce 20 documentations/yr
• number of 10 t/yr MAC chemicals: 834 (2004),
most of them having MAC value assigned
• quality of OELs: expert assessment, multilevel
process, transparency
• no tradition of „private OELs” in Poland
• need for analytical methods to determine
compliance
Limit values in the USA
• ACGIH® Threshold Limit Values (TLV®)
• OSHA Permissible Exposure Limits (PEL)
• NIOSH Recommended Exposure Limits
(REL)
ACGIH TLVs
The longest tradition is behind the hygienic standards
published by ACGIH under the registered name of
Threshold Limit Values (TLVs), and annually updated
since 1946. The TLVs are not obligatory under current
US legal regulations; nevertheless, in view of the high
ACGIH reputation, they serve as an important guide on
the recommended limits of occupational exposures not only
in the USA but also in other countries.
•TLV-TWA (Threshold Limit Value - Time-Weighted
Average) is defined as the time-weighted average
concentration for a conventional 8-hour workday and a 40hour workweek, to which it is believed that nearly all
workers may be repeatedly exposed, day after day, without
adverse health effect.
ACGIH TLVs, cntd
•TLV-STEL (Short-Term Exposure Limit); this is defined
as a 15-minute TWA exposure which should not be
exceeded at any time during a workday, even if the 8hour TWA is within the TLV-TWA, Exposures above the
TLV-TWA up to the TLV-STEL should not be longer than
15 minutes and should not occur more than four times
per day. There should be at least 60 minutes between
successive exposures in this range.
•TLV-Ceiling represents a value of concentration
absolutely not to be exceeded at any moment.
The ceiling values refer mostly to irritant gases, and for
that type of chemical substances they are the only
applicable hygienic standards (no TLV-TWA are
available).
ACGIH TLVs, cntd
•
•
•
•
•
Individual susceptibility
Hypersensitivity
Procedures and process of setting TLVs
Health based criteria
TLV documentations
OSHA PEL values
OSHA was established in 1970 by the US Congress as an
institution subordinated to the Ministry of Labor and
entrusted with the task of developing and enforcing a law
on the health and safety of workers . The law is understood
as providing also for the hygienic standards, which should
“in the most suitable and practicable way, using the best
available proof, ensure that none of the workers suffers
health loss or reduction of the physiological parameters
even when regularly exposed to that agent at the level
specified by the relevant hygienic standard throughout
his/her whole working life „
OSHA PEL values establishment
• history of PEL establishment
• interpretation in U.S. Supreme Court rulings
• a conservative approach encumbered with the risk of an error to the
benefit of the worker to ensure that steps to be undertaken ensure
excessive rather than insufficient protection to the concerned worker
• PEL values should be based on the most recent scientific data
• the results of research and recommendations prepared mainly by
OSHA and NIOSH as the starting point
• clinical
observations (accidents,
poisonings, pathologies),
epidemiological data and animal test results used as the so-called
“toxicological proof.”
• NOAEL or LOAEL usually employed as a starting point
• uncertainty factors for individual human variability, inter-species
differences, incomplete data on the chronic toxicity, and the use of a
LOAEL value instead of a NOAEL value
• seting STEL and Ceiling values (definitions and interpretation
identical like in case of ACGIH TLVs)
OSHA PEL values establishment
• proposals for setting new, or modifying the existing PEL
values, together with the reasons justifying the new or
revised standard published in the Federal Register as a
Notice of Proposed Rulemaking
• the interested parties (representatives of industry,
employers, workers, federal agencies, scientific
institutions, etc.) may present their comments and
suggestions in writing
• public hearing of the authors of the proposals by the
representatives of the commenting institutions
• the participants present in writing arguments for, and
against, the proposed standard in question. OSHA
analyses all the notes, sets PEL values and publishes in
the Federal Register the full text of the documents
justifying the new or modified PEL value.
OELs in Russia
• Maximum Allowable Concentartions (MAC) started in
early 20’s.
• Numerical values much lower than elsewhere, based on
the concept of the “threshold hazardous effect” and set at
the level, that was supposed to correspond to a tissue
burden in exposed subjects which represent the minimum
dose that
triggers changes beyond the limits of
physiological adaptation reactions.
• Now under the auspices of the Ministry of Health (National
Commission on Occupational Exposure Limits).
• Based entirely on toxicological data, without reference to
occupational hygiene or epidemiology (the material
derived
mostly from Russian sources; the existing
exposure levels in industry, technical feasibility and
economic implication not taken into account.
OELs in Russia, cntd
• Generally considered to be the ceiling values, time
weighted average concentrations are established for
those substances that are highly cumulative.
• In most cases established during the Soviet period,
when the philosophy of hygienic standard development
was quite different from that in other countries and a high
coefficient of safety was usually applied.
• The implementation of these standards not as strict as
required.
• Not revised and still used in practice despite the policy
changes and other significant changes in socioeconomic structure.
OELs for carcinogens
• effective toxicity threshold does not exist or is impossible
to be determined; each exposure to carinogenic
genotoxic agent is assumed to be associated with the
risk of cancer development.
• not possible to determine the level of the substance
concentration which does not produce adverse health
effects in all the exposed individuals (a condition
specified by
most occupational exposure limit
definitions)
• for such substances the concentrations should be kept
as low as possible (if their complete elimination from the
production process is not feasible)
• legally binding exposure limits take into consideration the
socio-economic factors and are based on the concept of
acceptable cancer risk
OELs for carcinogens, cntd
• OELs for carcinogenic substances are based on
the data on the carcinogenicity of a specific
substance in humans (epidemiological data)
and/or experimental animals.
• Such limit may be derived from the data on unit
risk or from the slope factor of the doseresponse curve; in both cases the acceptable
risk serves as the criterion .
• In general, in the occupational setting, the
acceptable levels of cancer risk vary between
10-2 to 10-5
Classification of carcinogens
• Classifications referring mainly to the strength of proof of
their carcinogenic activity (IARC, ACGIH®, EU –
Directive 2004/37/EC).
• In most cases the substances and technological
processes are classified as:
 carcinogenic to humans,
 suspected of being carcinogenic to humans,
 carcinogenic to experimental animals,
 not classifiable as a human carcinogen,
 not suspected as a human carcinogen.
• In some countries information on cancerogenity and/or
mutagenicity included in the OEL list.
Human Health Hazard Assessment
(REACH legal text)
• REACH (Annex I, 1.0.1 ) defines the Derived NoEffect Level (DNEL), i.e. the level of exposure
above which humans should not be exposed.
• In the risk characterisation, the exposure of each
human population known to be or likely to be
exposed is compared with the appropriate DNEL
• The risk to humans can be considered to be
adequately controlled if the exposure levels
estimated do not exceed the appropriate DNEL
Derived No Effect Level (DNEL)
• Required for 10 tonnes/yr chemicals
• The purpose of DNELs is to act as the
reference value for determining adequate
control of exposure for specific scenarios
• DNELs (inhalation) for occupational exposure
comparable to MACs
Steps of DNEL derivation
• Collection of all available toxicity data; gathering
typical dose descriptors
• Decision on mode of action threshold vs. nonthreshold)
• Selection of relevant dose descriptor(s) for the
endpoint concerned
• Modification of the dose descriptor to the correct
starting point
• Application of assessment factors, where necessary
for the relevant exposure pattern
• Selection of the critical effect
Dose descriptors for DNEL derivation
• NOAEL (no observed adverse effect level)
• NOAEC (no observed adverse effect concentration)
• LOAEL/LOAEC (lowest observed adverse effect
level/concentration)
• Other dose descriptors (BMD, LD50, LC50, T25 etc.)
All available hazard information needs to be evaluated
(physical and chemical properties, epidemiological data,
human data, acute and chronic activity, local and
systemic
effects etc.)
Modification of dose descriptors
into the correct starting point
• correction for difference in bioavailability for the
same exposure route
• correction for different exposure routes
• correction for difference between experimental
and exposure conditions
• correction for differences in respiratory
volumes between experimental animals and
humans
Correction for difference between
experimental and exposure conditions
• repeated animal inhalation experiment –usually
6 hr/d
• occupational exposure –usually 8 hr/d
• general population exposure – 24 hr/d
• effects of exposure dependant on dose,
concentration or both?
Assessment factors (AF)
• Assessment factors are numerical values used to address
differences between experimental data and the human
situation taking into account the uncertainties in the
extrapolation procedure and the available data set
• Substance-specific information should be used in the
establishment of appropriate values for the various
assessment factors
• In the absence of substance-specific or analogous data
use default assessment factors
• It should be remembered that the default assessment
factors are based on experience and not strictly on
science and they may or not may be not suitable for a
given substance
Default assessment factors (AF)
Assessment factor
Interspecies
Systemic
effects
Local
effects
-differences in metabolic rate
per body weight
-remaining differences
AS
-
2,5
1 (2,5 metab.)
Intraspecies
-worker
-general population
5
10
5
10
Exposure
duration
-subacute to sub/semichronic
-sub/semichronic to chronic
- subacute to chronic
3
2
6
3
2
6
Dose/response
-reliability of dose/response,
LOAEL/NOAEL, severity of
effects
1 (NOAEL)
3-10 (LOAEL)
1 (NOAEL)
3-10 (LOAEL
Quality of database – completeness and consistency of available data: 1*
*deviations are possible
Quality of the database
• thorough analysis of available data
• lacking data (long-term effects)
• experimental conditions, quality of animals,
control groups, etc.
• consistency of data
For experiments carried out according to GLP
procedures and complete data, default
assessment factor is 1, in other cases expert
judgement
Calculation of a DNEL value
The overall assessment factor is obtained by simple
multiplication of individual assessment factors:
Endpoint specific DNEL =
NOAELcorr
NOAELcorr

AF1 xAF2 x...xAFn OverallAF
Care should be taken to avoid double counting several
aspects when multiplying the individual factors
No threshold substances
• Cancerogenic and mutagenic substances
cat. I and II
• DMEL (derived minimal effect level)
• DAEL (derived accepted effect level)
• Accepted risk of occupational cancer: 10-5
to 10-3
2-isopropoxyethanol
NOAEC=128 mg/m3 (28 days)
MAC
•
•
•
•
•
Interspecies: 1
Intraspecies: 2
Acute/chronic: 3
NOAEL: 1
Quality of data: 1
MAC =
DNEL
•
•
•
•
•
128 128

 21,3  20 mg / m3
23
6
Interspecies: 1
Intraspecies: 5
Acute/chronic: 6
NOAEL: 1
Quality of data: 1?
DNELinhal =
128
128

 4,27 mg / m3
1 5  6 11 30
2,2’-iminodiethanol (DEA)
NOAEL = 20 mg/kg (13 weeks)
MAC
•
•
•
•
•
Interspecies: 2
Intraspecies: 2
Subchronic: 2
NOAEL: 1
Quality of data: 2
DNEL
•
•
•
•
•
•
Interspecies: 4x2,5
Intraspecies: 5
Subchronic: 2
NOAEL: 1
Quality of data: 2?
DNELoral =
NOAEC = 20x70/10 = 140 mg/m3
MAC =
140
140

9
2  2  2 1 2 16
20
20

 0,1 mg / kg / d
10  5  2 1 2 200
DNELinhal = 0,1 mg/kg/dx70/10 =
mg/m3
0,7 mg/m3
Chloroethan
NOAEL = 26 800 mg/m3 (13 weeks)
MAC
Intraspecies: 2; Interspecies.:2; subchronic/chronic: 2;
NOAEL/LOAEL: 1; Quality of data: 4.
26800
26800

 837 ,5 mg / m 3
MAC = 2  2  2 1 4
32
Value 200 mg/m3 has been established since IOEL is 268 mg/m3
DNEL
Interspecies: 2,5; Intraspecies: 5; Subchronic/chronic: 2;
NOAEL/LOAEL: 1; Quality of data: 4?
DNELinhal=
26800
26800

 268 m g / m3
2,5  5  2 1 4
100
Roles of OELs and DNELs
assessment of occupational exposure
(compliance):
exposure/OEL
≤
1
risk characterisation under REACH:
exposure/DNEL
≤
1
OELs and DNELs: similarities
• the same objective, in general:
concentration, that would not result in
health impairment due to exposure
• the same starting point, though
assessment factors are different
OELs and DNELs: differences
• OELs are developed strictly for OSH purposes
and have direct application as a reference tool
for the systematic monitoring of exposure
• DNELs primarily not intended for OSH purposes
but as a tool for chemical safety assessment and
selection of proper RMM
• DNELs have no direct impact on workplace
regulations
OELs and DNELs: differences,
cntd.
• OELs are legally binding (responsibility of the Government) –
legal instrument of enforcement of health policy, compliance
supervised by governmental agencies or institutions
• DNELs introduced by companies only
• Representativeness and transparency of the OEL
establishment process – lack of expert judgement in the
DNEL derivation
• Different assessment factors; mostly default factors in DNELs
vs expert judgement in OELs
Conclusion of the occupational exposure
assessment in EN 689
The occupational exposure concentration is the arithmetic mean of the
measurements in the same shift with the appropriate reference period of
the OEL value of the agent of consideration. In the case of varying
averaging times this can be accounted for by time-weighting the values
(examples in Annex B).
A number of schemes can be devised to compare exposures with the
OELs (Annexes C and D). Whatever scheme is used, one of the three
following conclusions shpuld be made:
•the exposure is above the limit value: the reason should be identifiedand
appropriate measures to remedy the situation should be implemented as
soon as possible.The occupational exposure should be repeated
b)The exposure is well below the limit value and is likely to remain so on
the long-term basis due to the stability in the working conditions and the
arrangement of the work process. In this case periodic measurements
are not needed. Regular check is, however, required whether the
conditions at workplace are unchanged.
c)The exposure do not fit into categories (a) or (b). Here, even though
exposure may be below OEL, periodic measurements are still required.
When the exposure may be considered
acceptable
• Time weighted average (TWA)
concentration is below or equal to OEL.
• Short term concentration (15 min) is below
or equal to STEL
• The sum of the ratios of concentrations of
individual compounds to their OELs must
be less than or equal to one
Calculation of the occupational exposure
concentration from individual analytical values (Anex
B)
• This procedure only applies, when OEL has been set
as an 8-hr TWA
• The term „8-hr reference value period” relates to the
procedure whereby the occupational exposures in
any shift period are treated as equivalent to a single
uniform exposure for 8hr
• The 8-hr TWA may be represented mathematically
by:
c t
t
i i
i
c1t1  c2t2  ........ cntn

8
Examples of calculations (Annex B)
• The operator works for 7 h 20 min on a process in
which he is exposed to a substance with an OEL. The
average measured concentration during that period is
0.12 mg/m3
0,12  7,33  0  0,67
3
 0,11mg / m
8
Examples of calculations, cntd (Annex B)
Working period
Exposure mg/m3
Duration of
sampling, hr
08.00 bis 10.30
10.45 bis 12.45
13.30 bis 15.30
15.45 bis 17.15
0,32
0,07
0,20
0,10
2,5
2
2
1,5
0,32  2,5  0,07  2  0,2  2  0,11,5  0 1,25
 0,19 mg / m3
8
Examples of calculations, cntd (Annex B)
Working period
Task
Exposure mg/m3
Time, hr
07.30 to 08.15
Setting up
zero
0,75
08.15 to 10.30
Product run1
5,3
2,25
10.30 to 11.00
Break
zero
0,50
11.00 to 13.00
Product run2
4,7
2,00
13.00 to 14.00
Lunch
zero
1,00
14.00 to 15.45
General tidying
1,6
1,75
15.45 to 16.00
Break
zero
0,25
16.00 to 19.00
Extra product
run
5,7
3,00
Examples of calculations, cntd (Annex B)
A worker is engaged in a dusty process in a factory which is
running at a maximum production. He agrees to work his machine
an additional 3h on one day to complete some orders. Total shift
length is 11,5 h.
The 8-hr TWA:
0  0,75  5,3  2,25  0  0,5  4,7  2,0  0 1,0  1,6 1,75  0  0,25  5,7  3,0
 5,2mg / m3
8
Without additional 3 hr exposure:
5,3  2,25  4,7  2,0  1,6 1,75
 3,0mg / m3
8
Probability plot (Annex G)
This approach is the percentile method of expressing exposure
measurements, which uses a statistical analysis of the data in the form
of lognormal probability or cumulative frequency plot
To construct a lognormal probability plot:
1.Rank exposure data from rhe lowest to the highest.
2.Count the number of results and obtain the appropriate plotting
positions as shown in the examples in tables G.1, G.2. and G.3 of
Annex G.
3.Select log probability graph paper having a Y-axis capable of
covering the range of the exposure data.
4.Plot each exposure value against the corresponding plotting point on
the log probability paper, as shown in figure G.2 for the raw data in
table G.3.
Probability plot (Annex G), cntd
5.Fit the straight line to the data points, disregarding all points
outside the bounds of 1% and 99% probability. For all remaining
data give preference to those nearest the central 50% position,
that is in the 20% to 80% region;
6.If the data do not follow the straight line then the underlying
distribution may not be lognormally distributed, or may comprise
more than one sample population;
7.The geometric mean value is the 50% probability value and
may be read directly from the intersection of the fitted line with
the 50% probability line;
8.The geometric standard deviation (GSD) is the slope of the
lognormal plot and a measure of variability or dispersion of the
data
Example of a probability plot (EN 689,
Annex G
Probability plot (Annex G), cntd
The geometric standard deviation is given by:
GSD 
84%value
50%value
• The GSD can, together with the geometric mean be used, if required
to draw the theoretical „best fit” line for the data.
• Good for extrapolation to higher exposure levels or % probabilities
• Two statistical parameters characterise lognormal probability plot:
-the geometric mean (50% of results are below and above the value)
-the GSD (the slope of the cumulative exposure plot (measure of
variability of the results).
• The plot can be used to compare exposure data with OEL at any
probability level, or to estimate the percentage of exposures likely to
exceed a particular value.
• Normally not less than 7 data points are required for such
comparisons or estimates.
Evaluation of the occupational
exposure in EN 689, Annex C
a) Concentration is devided by OEL to obtain I (the subtance index)
I = C/OEL
For the results below LOD, ½ should be used.
b) If the index for the first shift is I ≤ 0.1, exposure is below the limit
value. If furhermore, it can be shown that this value is
representative for the long term working conditions the periodic
measurements can be omitted.
c) If each single index of at least three different shifts is I ≤ 0.25
exposure is below the limit value. If furhermore, it can be shown that
this value is representative for the long term working conditions the
periodic measurements can be omitted.
d) If the indices of at least three different shifts are all I ≤ 1 and the
geometric mean of all measurements is ≤ 0.5 then exposure is
below the limit value.
e) If an index is I > 1, exposure is above the OEL.
f) In all cases that do not fit into the above the procedure leads to no
decision.
Evaluation of the occupational exposure
in EN 689, Annex C, cntd
•If any of the conditions of b), c), or d) apply, then
the occupational exposure assessment can be
terminated..
•In the cases c), or d) the concentration can be
interpreted as the first periodic measurement. Its
result then may determine the time interval for the
next periodic measurement.
If the workers are exposed simultaneously or
consecutively to more than one agent during the
same workshift, this fact needs to be taken into
consideration.
Types of Mixture
•
•
•
•
•
Natural mixtures
Petroleum based mixtures
Formulated mixtures
Processing mixtures
Combined mixtures
Natural mixtures
• Source – extraction and/or processing naturally
occurring substances (mineral ores, vegetable
oils, tea etc.)
• Composition may be not known and vary
depending on source and season
• Defined by mostly by their physical properties or
technological processes
• In most cases no OELs assigned
• Specific ill-efects usually well documented
Petroleum based mixtures
• Sub-group of „natural mixtures”
• Relates to distillation fractions of oil (white spirit,
fuels, naphtas etc.)
• Defined by by physical properties (e.g. boiling
range)
• Composition may vary depending on origin and
processing
• The mixture and/or its components may have
been assignrd OELs
Formulated mixtures
• Produced by mixing components to a predefined formula to give products for specific
applications (paints, adhesives, cleaning
preparations)
• The composition is usually known; some
components may be already natural mixtures
• Composition is controlled
• No OEL for the mixture, individual components
may have been assigned OELs
Processing mixtures
• Arise from the technological processes (plastic
fumes, welding fumes, rubber fumes etc)
• Composition changes with process parameters
(temperature, pressure, oxygen supply etc)
• Contain both identified and unidentified
compounds
• Some compounds may have or may have not
OELs assigned
• Some of the process mixtures may have been
assigned OELs
What to measure?
• All, or many of the individual components
(require knowledge of the mixture components
and availability of the appropriate analytical
method)
• The „total mixture” (if OEL is for the mixture or if
the total mixture exposure serves as a measure
of control)
• A single substance, as a guide to exposure and
control
A single substance as a measure of
exposure
• Measurement methods not available for all
the pollutants
• Many components without OELs
• There are unidentified components
• Quantification of all components would be
excessively expensive
Selection of the key components to be
measured
• The existence of OELs
• Concentration in the mixture
• The toxicity of the individual
substances
Categories of possible joint toxic effects
• Independent action – each component acts in an
individual way in the human body which is different from,
and unaffected by, the effects of other components
• Additive action - the combined toxic effects are the
simple sum of toxic effects of each component acting
alone
• Synergistic action – the combined toxic effects are
greater than the simple sum of the toxic effects of the
single components acting alone
• Antagonistic effect – the combined toxic effects are less
than the simple sum of the toxic effects of each
component acting alone
Calculation of the additive exposure
If the workers are exposed simultaneously
or consecutively to more than one agent
during the same work-shift, the sum of the
ratios of measured exposures for individual
exposures (C) to their OELs must be less
than, or equal to, one, according to the
formula:
Cn
C1
C2

 ...
1
OEL1 OEL2
OELn
Test report
Reports shall be written of the occupational exposure assessment and
of any periodic measurement. According to EN 689, the report has to
contain:
 the name of the person(s) or institutions undertaking the assessment
and the measurements;
 the name of the substance considered;
 name and address of company;
 the description of workplace factors including the workplace
conditions during the measurements
 the purpose of the measurement procedure;
 the measuring procedure;
 the time schedule ((date, beginning and end of sampling)
 the occupational exposure concentrations;
 all events and factors liable to influence appreciably the results;
 details of quality assurance, if any;
 result of the comparison with the limit value (OEL).
Calculation of the expanded uncertainty
Calculation of the expanded uncertainty,
cntd
Uncertainty components in workplace air
measurement methods
• sampling:
-uncertainty associated with sampled air volume
-uncertainty associated with sampling efficiency
-uncertainty associated with sample storage and transportation, if
any
• analysis:
-uncertainty associated with method recovery
-uncertainty associated with analytical variability
-uncertainty associated with the calibration
-uncertainty associated with instrument drift
The uncertainty of each of those components is estimated and
calculated and then combined to obtain an estimate of the
uncertainty of the measurement method as a whole.
Sources of uncertainty in pumped
sampling
• Flow rate measurement - the calibration of the flow
meter (random error), the reading of the flow meter
(random error) and, where appropriate, correction of the
flow rate reading to ambient pressure and temperature.
The uncertainty of flow rate calibration should be
calculated from the data given on the flow meter test
certificate. The uncertainty of the flow rate reading
should be calculated from measurements carried out
under repeatability conditions.
• Pump flow stability
• Sampling time
Flow rate measurements
Uncertainty of the flow rate measurement for
different types of flow meters
Flow rate stability
• Pumps for personal air sampling are usually
selfregulating and maintain the set flow
independent of variation in back pressure
• EN 1232 and EN 12319 require that the flow rate
is maintained within ±5% of the set value
throughout the sampling period
• Assuming a rectangular probability distribution,
the maximum acceptable value for a nonrandomuncertainty component for the pump flow
stability is 5/√3
Uncertainty components associated with
sampling, cntd
• Sampling time may be measured very exactly with a
radio controlled clock, a quartz clock or stopwatch. The
major source of uncertainty in measurement of sampling
time is the accuracy with which the reading is taken, i.e.
to the nearest minute or second. The non-random
uncertainty component is very small in the case of long
term measurements (e.g. > 2 h) and can be disregarded,
but for short term measurements it needs to be taken
into account.
(for a 15 minute sample, if time is recorded to the
nearest minute, the RSD is 3.8%, assuming a
rectangular probability distribution)
Uncertainty associated with sampling
efficiency
• Influence of ambient conditions
(temperature, pressure, humidity)
• Influence of a flow rate
• Breakthrough volume (EN 1076)
• Efficiency when sampling with
bubblers/impingers and impregnated
filters
Uncertainty associated with sample
storage and transportation
• Non-random uncertainty component for storage can be
estimated by analysis of samples collected from a test
atmosphere or prepared by spiking sampling media with a
chemical agent. Calculated from the difference between the
mean results of replicate samples analysed immediately after
sampling/spiking and after the maximum storage period
specified in the method.
• Storage tests described in detail in EN 838 (passive dosimetry)
or EN 1076 (pumped methods)
• No need to take into consideration for gas and vapour samples
if transported in an appropriate manner as specified in the
method.
• The transport of aerosol samples has a component of
uncertainty associated with material losses from the sample
substrate or substrate contamination The upper limit for the
loading of the collection substrate can be determined as
described in EN 838 or ISO15767.
Uncertainty asssociated with analytical
recovery
• May be carried out following the tests described
in EN 1076 and EN 838 by the use of standard
test atmospheres.
• Results for vapour and gases methods are
normally corrected for desorption efficiency. It
can be calculated using spiked sampling media.
When the influence of ambient conditions and
other factors are not significant and results are
corrected for desorption efficiency, only the
uncertainty component associated with this
correction is taken into account.
Uncertainty asssociated with analytical
recovery, cntd
•Bias can be estimated from:
results obtained by analysing a suitable number of replicate
samples of certified reference materials
results obtained from replicate samples taken in the test gas
atmospheres
results from interlaboratory comparisons
results from recovery tests carried out on spiked sampling
media
Desorption efficiency can be calculated from the results of
replicate analyses of certified reference material or of sampling
media spiked at several levels covering the range of the
application of the method, dividing the mass of analyte
recovered by the mass applied, as specified in EN 838 and EN
1076.
Desorption efficiency
When desorption efficiency does not vary significantly with the
concentration (general case) and the results are corrected for
desorption efficiency, the random uncertainty component associated
with this correction is estimated and treated as an uncertainty
component. The random uncertainty component associated with
incomplete desorption is estimated as the relative standard deviation of
the mean of the desorption efficiencies for all levels.
If desorption efficiency correction is not applied to the results, the bias
component is estimated and treated as an uncertainty component. The
non-random uncertainty component associated with incomplete
desorption is estimated as the difference of the mean of the desorption
efficiency at all concentrations from unity and converted to a standard
uncertainty.
In some cases desorption efficiency varies with concentration. In this
case the random and non-random uncertainty components will be
estimated from the function relating the desorption efficiency to
concentration.
Uncertainty asssociated with analytical
variability
In general, the uncertainty associated with analytical variability
may be estimated either from data obtained under repeatability
conditions or from data obtained under reproducibility conditions.
When the analytical precision is determined from withinlaboratory reproducibility data, i.e. using quality control data,
most random and randomized uncertainty components are
included.
The uncertainty associated with the analytical precision is
determined by analysing calibration standards of the same
composition under repeatability conditions. In vapour and gases
methods this contribution is already incorporated in contributions
from the determination of the desorption efficiency and it does
not need to be taken into account.
If applicable, the random uncertainty component associated with
blank subtraction, or non-random uncertaintycomponent when
no blank subtraction is performed, need to be included.
General equations for combination of
uncertainty components
• To calculate the random and non-random components of
sampling uncertainty and analytical uncertainty, the
relevant individual uncertainty components are combined
according to equations:
General equations for combination of
uncertainty components, cntd
-are defined in 6.1
-are the corresponding relevant individual uncertainty
components;
-are the corresponding numbers of relevant individual
uncertainty components
Expanded uncertainty requirements for measurements
for comparison with OELs and periodic measurements
Reference period
Measuring range
Relative expanded
uncertainty
≤ 50%
short term (e.g.15
min)
0.5 to 2 times OEL
value
long-term
0.1 to < 0.5 times OEL ≤ 50%
value
long-term
0.5 to 2 times OEL
value
≤ 30%
Thank you for your attention