Occupational guidelines/standardsDr Leonard Ritter Occupational guidelines/standards Dr Leonard Ritter University of Guelph Dr Kersten Gutschmidt World Health Organization Content the co
Trang 1Occupational guidelines/standards
Dr Leonard Ritter
Occupational guidelines/standards
Dr Leonard Ritter
University of Guelph
Dr Kersten Gutschmidt
World Health Organization
Content
the concept of OEL the UK system international comparisons OELs in developing countries some ‘links’
Occupational Exposure Limits
introduction
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 paradigm
Trang 2United States
ACGIH
OHSA
NIOSH
AIHA
Threshold Limit Values (TLVs)
Permissible Exposure Limits (PELs)
Recommended Exposure Limits (RELs)
Workplace Environmental exposure Limits (WEELs)
Voluntary Enforceable Voluntary Voluntary
examples
Germany Maximum Workplace Concentration (MAKs) Enforceable
Technical Exposure Limits (TRKs) Enforceable
United Kingdom Maximum Exposure Limits (MELs) Enforceable
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
Applicability
“An OES is the concentration , at which, according to current 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 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
Nature 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 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 exposure
Chronic effects
Occur over time or long after exposure (long latency time);
Often involves low exposures over a long period of time;
Many effects are not reversible;
Acute versus chronic effects
p stops;
Can be minor or severe;
Relationship between exposure and symptoms usually obvious;
Knowledge often based on human exposure.
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.
Trang 3Long-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
exceeded during any part of the working exposure
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 alsoOther 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 limits
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 limits
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
Trang 4Setting 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,
United Kingdom (3)
such as the slowing of reflexes which might result in the impairment
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
Acceptable 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 exist 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 limits
United Kingdom (4)
– additive substances
– 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 lists
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 Short-term exposure limit (15-minure reference period)
Trang 5Germany ACGIH
Comparison of OELs
UK, Germany, ACGIH
Benzene
Country/
Organisation
8-hour TWA
[ppm]
15-min reference value [ppm]
Comment
notification
2.5 (TRK)
for defined settings
based
Toluene
Country/
Organisation
8-hour TWA
[ppm]
15-min reference value [ppm]
Comment
statistics; skin notification
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
Trang 6Some 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
Trang 8Conclusions (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
developed OEL lists and do have OEL setting procedures in
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;
• 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