1 Occupational guidelines/standardsOccupational guidelines/standards Dr Leonard RitterDr Leonard Ritter Ui i fG lhUi i fG lh Occupational guidelines/standardsOccupational guidelines/standards Dr Leonard RitterDr Leonard Ritter Ui i fG lhUi i fG lh U n i vers i ty o f G ue l p hU n i vers i ty o f G ue l p hU n i vers i ty o f G ue l p hU n i vers i ty o f G ue l p h Dr Kersten Gutschmidt World Health Organization Content the concept of OEL the UK system international comparisons international comparisons OELs in developing countries some ‘links’ Occupational Exposure LimitsOccupational Exposure Limits introductionintroduction a there are over 12 million known natural occurring and synthesised chemicals; a 100 000 are produced on industrial scale; a 1000 are produced in large quantities; a 1000 - 2000 new chemical entities are introduced each year; a thousands of formulations, modifications and new formulations are constantly appearing ⇒ Occupational exposure limits (OELs) are intended for use in the practice of industrial hygiene as standards, guidelines or recommendations in the control of potential workplace health hazards. Environmental health paradigmEnvironmental health paradigm 2 United States ACGIH OHSA NIOSH AIHA Threshold Limit Values (TLVs)Threshold Limit Values (TLVs) Permissible Exposure Limits (PELs)Permissible Exposure Limits (PELs) Recommended Exposure Limits (RELs)Recommended Exposure Limits (RELs) Workplace Environmental exposure Limits (WEELs)Workplace Environmental exposure Limits (WEELs) Voluntary Enforceable Voluntary Voluntary Occupational Exposure LimitsOccupational Exposure Limits examplesexamples German y Maximum Workplace Concentration (MAKs)Maximum Workplace Concentration (MAKs) Enforceable Technical Exposure Limits (TRKs)Technical Exposure Limits (TRKs) Enforceable United Kingdom Maximum Exposure Limits (MELs)Maximum Exposure Limits (MELs) Enforceable Occupational Exposure Standards (OESs)Occupational Exposure Standards (OESs) Enforceable American Conference of Governmental Industrial Hygienists: “TLVs … represent conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse health effect.” Health and Safety Executive, United Kingdom: “A OES i th t ti t hi h di t t ApplicabilityApplicability “A n OES i s th e concen t ra ti on , a t w hi c h , accor di ng t o curren t knowledge, there is no evidence that it is likely to be injurious to employees ” German Research Association: “The MAK value generally does not have known adverse effects on the health of the employee…” • acute and chronic effects – acute effect - e.g. asphyxiation, unconsciousness or death produced by overexposure to solvent vapour – chronic effects - e.g. silicosis following exposure to crystalline silica dust over a long period • local and systemic effects Nature of health effectsNature of health effects – local effect - e.g. the effect of a corrosive substance splashed on the skin – systemic effect - e.g. damage to kidney following ingestion of cadmium ions • reversible and irreversible effects – reversible effects - e.g. skin irritation or anaesthesia – irreversible effects - e.g. chemical-induced cancer Acute effects Occur immediately or soon after exposure (short latency time); Often involves a high exposure over short period of time; Often reversible after ex p osure Chronic effects Occur over time or long after exposure (long latency time); Often involves low exposures over a long period of time; Man y effects are not reversible ; Acute versus chronic effectsAcute versus chronic effects p stops; Can be minor or severe; Relationship between exposure and symptoms usually obvious; Knowledge often based on human exposure. y; Usually severe but often unknown; Establishment of relationship between exposure and effect often problematic due to long latency period; Knowledge often based on animal studies. 3 Long-term exposure limit (8-hour TWA) Is intended to control effects which require prolonged and accumulative exposure by restricting the total intake by inhalation over one or more workshifts. Short-term exposure limits (usually 15 minutes) Is applied to control effects which may be seen after brief exposures. Ceiling The instantaneous concentration that should not be Averaging timeAveraging time Ceiling The instantaneous concentration that should not be exceeded during any part of the working exposure. Excursion Limit For substances for which no short-term limit is specified it is recommended that defined multiple times the long-term limit be used as a guideline for controlling short-term peaks. • OELs apply to exposure by inhalation. • Skin notation is given when absorption through the skin can add a potentially significant contribution to the systemic toxicity form inhalation. • Other routes of exposure such as ingestion do also Route of exposureRoute of exposure Other routes of exposure such as ingestion do also occur. • It is possible to compare exposures by the dermal or ingestion route to the inhalation exposure limits. The UK (COSHH) regulation defines two types of OELs: • Occupational exposure standards (OESs) are set at: – a level at which (based on current scientific knowledge) there is no indication of risk to the health of workers exposed by inhalation day after Occupational exposure limitsOccupational exposure limits United Kingdom (1)United Kingdom (1) day. • Maximum exposure limits (MELs) are set for: – substances which may cause most serious health effects and for which “safe levels” of exposure cannot be determined; – for substances which, although safe levels may exist, it is not reasonably practicable to control to those levels. Criteria for OESs: Crit. 1: A level exists at which there is no indication of an adverse health effect (threshold substance); and Crit. 2: Exposure higher than that derived under crit. 1 are unlikely to produce serious short- or long term-effects; it might reasonably be expected to identify and remedy the cause of excessive exposure in time; and Criteria for setting exposure limitsCriteria for setting exposure limits United Kingdom (2)United Kingdom (2) Crit. 3: Compliance with the OES, as derived under crit. 1, is reasonably practicable. Criteria for MELs: Crit. 4: Substance does not satisfy crit. 1 and/or 2 and exposure has, or is liable to have, serious health implications; or Crit. 5: Socio-economic factors indicate (although crit. 1+2 are met) that a higher level is necessary to be regarded as reasonably practicable 4 Setting of OESs and MELs: • identification of the critical effect; • determination of the no-observed-adverse effect-level (NOAEL) • uncertainty factors might be applied. • with regards to Crit. 2, effects include sensory and other effects, h th l i f fl hi h i ht lt i th i i t Criteria for setting exposure limitsCriteria for setting exposure limits United Kingdom (3)United Kingdom (3) suc h as th e s l ow i ng o f re fl exes w hi c h m i g ht resu lt i n th e i mpa i rmen t of safety. • takes account of whether industry can reasonably comply to OES. • MELs have been most often allocated to carcinogens, respiratory sensitisers and to other substances with no threshold (acceptability of risk); • OES are solely health based; • for MELs health is the primary consideration but socio-economic factors are also taken into account. Setting exposure limitsSetting exposure limits Acceptable riskAcceptable risk Nature of exposure- response/effect relationship Meaning of acceptable risk Threshold assumed to exist for all employees. Most likely that nothing adverse happens to anyone at the OEL. Threshold assumed to exis t except for susceptible people. No threshold. Severity of effect decreases at lower exposure. Most likely that nothing happens to most people at the OEL. The probability of adverse outcomes is insignificant or acceptably small at the proposed OEL. It is likely that only trivial effects occur at the OEL. • multi-media exposure: – dermal absorption – ingestion • effects of mixed exposures: – synergistic substances dditi b t Other factors referring to exposure limitsOther factors referring to exposure limits United Kingdom (4)United Kingdom (4) – a dditi ve su b s t ances – independent substances • compliance monitoring: – personal/workplace monitoring (active and passive) – biological monitoring (urine, blood other body fluids and tissues) – quality control and quality assurance OES and MEL listsOES and MEL lists United Kingdom (5)United Kingdom (5) Substance CAS Number ppm mg.m -3 ppm mg.m -3 Notes MDHS OEL summary and other guidance Health R phrases (in ASL) Long-term exposure limit (8 hour TWA reference period) Short-term exposure limit (15-minure reference period) 5 MAK, TRK and BAT lists MAK, TRK and BAT lists GermanyGermany TLV list TLV list ACGIHACGIH Comparison of OELs Comparison of OELs UK, Germany, ACGIHUK, Germany, ACGIH Benzene Country/ Organisation 8-hour TWA [ppm] 15-min reference value [ppm] Comment ACGIH 0.5 (TLV) 2.5 (STEL) health based; skin notification Germany 1 (TRK) 2.5 (TRK) 5 x TRK 5 x TRK all other settings for defined settings United Kingdom 3 (MEL) 3 x MEL - IPCS 1 (TWA) - EHC 150, health based To lu en e Country/ Organisation 8-hour TWA [ppm] 15-min reference value [ppm] Comment ACGIH 50 (TLV) 3x TLV health based; statistics; skin notification Germany 50 (MAK) 5 x MAK skin notification United Kingdom 50 (OES) 150 (OES) skin notification Harmonization of OELs Harmonization of OELs For occupational exposure standards more generally, the scope for harmonization may range from: a. full harmonization among countries, with common sets of criteria, exposure assessment, strategies and OELs; b. intermediate harmonization, with common criteria and methods and a common primary database, but with local OELs on national considerations and priorities; c. rudimentary harmonization, with better understanding among countries about all the factors that underpin local OELs. 6 Application of OELs in developing countriesApplication of OELs in developing countries Some factors to considerSome factors to consider • the workforce may include young children and the elderly; • working population may be affected by endemic disease, including parasitic infections, chronic diseases and malnutrition; • hours of work may not strictly be regulated resulting in longer shift periods and longer exposure duration; people may undertake certain hazardous operation in their • people may undertake certain hazardous operation in their homes and small enterprises (whereby also other family members get exposed); • many workers may be exposed to substances which have not been considered in developed countries because of minimal or non-existent exposures (e.g. textile, wood, grain and other dusts of vegetable and animal origin); • differences exist with regards to cultural attitudes to health and disease, socio-economic structure, level of education and degree of skill. 7 8 Conclusions (1)Conclusions (1) • OEL are intended as instruments in the control of potential workplace hazards which have the potential to cause acute and chronic health effects; • OELs are designed to protect workers or employees and might be enforceable or voluntary; • many developed countries and professional associations have d l d OEL li t d d h OEL tti d i d eve l ope d OEL li s t s an d d o h ave OEL se tti ng proce d ures i n place; • OELs are primarily health-based but might take socio-economic factors into consideration; • OELs are usually provided as an 8-hours TWA and a 15-minute reference level; • full harmonization among countries, with common sets of criteria, exposure assessment, strategies and finally OELs is not realistic because of cultural and socio-economic differences; Conclusions (2)Conclusions (2) • intermediate harmonization, with common criteria and methods and a common primary health-based data set, but with local OELs on national considerations and priorities seems to be more realistic; • in the same context, developing countries need to adapt OELs established in developed countries to the local circumstances established in developed countries to the local circumstances . . excessive exposure in time; and Criteria for setting exposure limitsCriteria for setting exposure limits United Kingdom (2)United Kingdom (2) Crit. 3: Compliance with the OES, as derived under crit 1 Occupational guidelines/standardsOccupational guidelines/standards Dr Leonard RitterDr Leonard Ritter Ui i fG lhUi i fG lh Occupational guidelines/standardsOccupational guidelines/standards Dr. i ht lt i th i i t Criteria for setting exposure limitsCriteria for setting exposure limits United Kingdom (3)United Kingdom (3) suc h as th e s l ow i ng o f re fl exes w hi c h m i g ht