Technical Assistance for Development of Regional Laboratories of Occupational Health Safety Centre (

1
Technical Assistance for Development of Regional
Laboratories of Occupational Health Safety Centre
(ÍSGÜM)
This project is co-funded by the European Union
and the Republic of Turkey

• EuropeAid/127200/D/SER/TR

2
Occupational Exposure Limits, other reference
values and interpretation of measurement results
This project is co-funded by the European Union
and the Republic of Turkey

• Jan Gromiec, Ph.D.

3
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
  (Derived-No-Effect-Levels) as the criteria of the
  assessment of the occupational exposure to
  chemicals
• be able to interpret measurement results

4
The course outline

• Basic terms and definitions related to
  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

5
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.

6
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 6891995)

7

• 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.

8

• 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

9
To convert ppm to mg/m3

• OEL in mg/m3
• OEL in ppm

10
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

11
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

12
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
  latters 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

13
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

14
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
  non-threshold or threshold mechanism (crucial
  for health based OELs)

15
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

16
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

17
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)

18
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.

19
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

20
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

21
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

22
System of setting MAC-values in Poland
Maximum admisible concentrations
Biological tolerance limits Medical preventive
measures
Methods of air sampling and analysis
MINISTER OF HEALTH AND SOCIAL WELFARE
MINISTER OF LABOUR AND SOCIAL POLICY
POLISH STANDARIZATION COMMITTEE
Legislation level
requirement for MAC proposal
Preparatory level
Intersectoral Commission for MAC and MAI Values
Group of Experts for Chemical Agents
MAC documentation
Calling for information
information
demand for MAC-value

• Bank of information
• exposure data
• health effects data

• Industry
• Health administration (sanitary inspection)
• Labour administration
• State Labour inspection
• Trade unions
• Research institutes

23
Number of OELs in Poland, Germany and USA
24
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

25
MAC Documentation Content

• Dose-effects and dose-response relationships
• Bases for existing MAC-values and biological
  tolerance limits
• Bases for proposed MAC-values and biological
  tolerance limits
• Methods of determination in the air and in
  biological material
• Pre-employment and periodical examinations -
  expsoure contraindications
• References

• 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

26
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.

27
Calculation of a MAC value
Calculation of a MAC value for a chemical
substance MAC NOAEL/UF or LOAEL/UF Uncertaint
y factor, UF, is calculated from the formula UF
A x B x C x D x E, where FACTOR EXTRAPO
LATION 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 experts opinion on the
completeness of data and for potential long-term
effects)
28
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
29
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

30
Limit values in the USA

• ACGIH Threshold Limit Values (TLV)
• OSHA Permissible Exposure Limits (PEL)
• NIOSH Recommended Exposure Limits (REL)

31
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 40-hour workweek, to which it is believed
  that nearly all workers may be repeatedly
  exposed, day after day, without adverse health
  effect.

32
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 8-hour 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).

33
ACGIH TLVs, cntd

• Individual susceptibility
• Hypersensitivity
• Procedures and process of setting TLVs
• Health based criteria
• TLV documentations

34
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

35
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)

36
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.

37
OELs in Russia

• Maximum Allowable Concentartions (MAC) started in
  early 20s.
• 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.

38
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 socio-economic structure.

39
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

40
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
  dose-response 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

41
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.

42
Human Health Hazard Assessment (REACH legal text)

• REACH (Annex I, 1.0.1 ) defines the Derived No-
  Effect 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

43
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

44
Steps of DNEL derivation

• Collection of all available toxicity data
  gathering typical dose descriptors
• Decision on mode of action threshold vs.
  non-threshold)
• 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

45
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.)

46
Modification of dose descriptorsinto 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

47
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?

48
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

49
Default assessment factors (AF)
Assessment factor Assessment factor Systemic effects Local effects
Interspecies -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 database completeness and consistency of available data 1 deviations are possible Quality of database completeness and consistency of available data 1 deviations are possible Quality of database completeness and consistency of available data 1 deviations are possible
50
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

51
Calculation of a DNEL value

• The overall assessment factor is obtained by
  simple
• multiplication of individual assessment factors
• Endpoint specific DNEL
• Care should be taken to avoid double
  counting several aspects when multiplying the
  individual factors

52
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

53
2-isopropoxyethanolNOAEC128 mg/m3 (28 days)

• DNEL
• Interspecies 1
• Intraspecies 5
• Acute/chronic 6
• NOAEL 1
• Quality of data 1?
• DNELinhal

• MAC
• Interspecies 1
• Intraspecies 2
• Acute/chronic 3
• NOAEL 1
• Quality of data 1
• MAC

54
2,2-iminodiethanol (DEA)NOAEL 20 mg/kg (13
weeks)

• MAC
• Interspecies 2
• Intraspecies 2
• Subchronic 2
• NOAEL 1
• Quality of data 2
• NOAEC 20x70/10 140 mg/m3
• MAC
• mg/m3

• DNEL
• Interspecies 4x2,5
• Intraspecies 5
• Subchronic 2
• NOAEL 1
• Quality of data 2?
• DNELoral
• DNELinhal 0,1 mg/kg/dx70/10
• 0,7 mg/m3

55
ChloroethanNOAEL 26 800 mg/m3 (13 weeks)

• MAC
• Intraspecies 2 Interspecies.2
  subchronic/chronic 2
• NOAEL/LOAEL 1 Quality of data 4.
• MAC
• 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

56
Roles of OELs and DNELs
assessment of occupational exposure (compliance)
exposure/OEL
1 risk characterisation under REACH
exposure/DNEL 1
57
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

58
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

59
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

60
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
• 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.
• The exposure do not fit into categories (a) or
  (b). Here, even though exposure may be below OEL,
  periodic measurements are still required.

61
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

62
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

63
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

64
Examples of calculations, cntd (Annex B)
Working period Exposure mg/m3 Duration of sampling, hr
08.00 bis 10.30 0,32 2,5
10.45 bis 12.45 0,07 2
13.30 bis 15.30 0,20 2
15.45 bis 17.15 0,10 1,5
65
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
66
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
• Without additional 3 hr exposure

67
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
• Rank exposure data from rhe lowest to the
  highest.
• 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.
• Select log probability graph paper having a
  Y-axis capable of covering the range of the
  exposure data.
• 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.

68
Probability plot (Annex G), cntd

1. 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
2. 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
3. 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
4. The geometric standard deviation (GSD) is the
   slope of the lognormal plot and a measure of
   variability or dispersion of the data

69
Example of a probability plot (EN 689, Annex G
70
Probability plot (Annex G), cntd

• The geometric standard deviation is given by
• 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.

71
Evaluation of the occupational exposure in EN
689, Annex C

• Concentration is devided by OEL to obtain I (the
  subtance index)
• I C/OEL
• For the results below LOD, ½ should be used.
• 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.
• 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.
• 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.
• If an index is I gt 1, exposure is above the OEL.
• In all cases that do not fit into the above the
  procedure leads to no decision.

72
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.

73
Types of Mixture

• Natural mixtures
• Petroleum based mixtures
• Formulated mixtures
• Processing mixtures
• Combined mixtures

74
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

75
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

76
Formulated mixtures

• Produced by mixing components to a pre-defined
  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

77
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

78
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

79
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

80
Selection of the key components to be measured

• The existence of OELs
• Concentration in the mixture
• The toxicity of the individual substances

81
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

82
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

83
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).

84
Calculation of the expanded uncertainty
85
Calculation of the expanded uncertainty, cntd
86
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.

87
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

88
Flow rate measurements
89
Uncertainty of the flow rate measurement for
different types of flow meters
90
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
  non-randomuncertainty component for the pump flow
  stability is 5/v3

91
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. gt 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)

92
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

93
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.

94
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.

95
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.

96
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.

97
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 within-laboratory 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.

98
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

99
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
100
Expanded uncertainty requirements for
measurements for comparison with OELs and
periodic measurements
Reference period Measuring range Relative expanded uncertainty
short term (e.g.15 min) 0.5 to 2 times OEL value 50
long-term 0.1 to lt 0.5 times OEL value 50
long-term 0.5 to 2 times OEL value 30
101
Thank you for your attention