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• Despite the role of risk assessment as the scientific foundation for many national and international regulatory guidelines, the phrase “risk assessment”:
– Means different things to different people.
– Is broad and may apply to areas other than health
Strategic risks
• Risks which affect business survival or the long-term sustainability of an operation. Businesses respond by acting on opportunity or managing potential threats.
Health Risks
• The likelihood of harm to humans or to the environment where risk may not exist if exposure to a harmful substance or situation does not or will not occur.
• In short, risk assessment takes many different forms, depending on its intended scope and purpose and the available data and resources.
Mining industry
• There are a large number of hazards in the mining sector that can pose a potential risk to health and wellbeing.
The Physical Hazards • The physical environment where exploration, mining,
ore extraction and processing takes place can cause health impacts in the following ways: – Musculoskeletal disorders – Noise-induced hearing loss associated with occupationally
related excessive noise exposure – Hand arm vibration syndrome and other musculoskeletal
consequences from hand-arm transmitted vibration – Skin cancer from working outdoors in direct sunlight – Effects from both ionising and non-ionising radiation – Heat exhaustion, hypothermia and various other health
effects from exposure to extremes of temperature
Hazards from particles
• Crystalline silica( Prolonged exposure) had elevated risk: – Silicosis (170-fold) – Arthritis (4.6-fold) – End stage kidney disease (1.9-fold) – There is also now good evidence that prolonged exposure to crystalline silica
increases the risk of lung cancer (1.6-fold)
• Diesel particulate exposures occur in underground mines because of diesel powered mobile equipment, used primarily for drilling and haulage. – Diesel particulate is an IARC Group2A probable human carcinogen and several
epidemiological studies from other industries suggest there is an excess risk of lung cancer
Chemical hazards
• Mercury and other metals
• Carbon monoxide
• Organic solvents
Relevance to mining industry
• Heath Risk Assessment
• Vs.
• Occupational Risk Assessment
Objectives of Health Risk Assessment • The objective of health risk assessment is based on
toxicology data to provide scientific information to produce a quantitative estimate of risk.
• The process also aids in predicting risk associated with exposure to hazardous substances and for decision making for regulatory purposes.
• Its main outcome is a statement of the probability that when humans or other environmental receptors (e.g., plants, animals) are exposed to a chemical agent, they will be harmed and to what degree.
Health Risk Assessment • Risk assessment is multidisciplinary team work:
– Chemistry – Biology – Toxicology – Pharmacology – Physics – Statistics, computer science – Medicine – Technology – Science policy
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• In 1983, the National Academy of Sciences in the United States developed a four-step paradigm for risk assessment and risk management.
• Hazard identification: – Examining toxicity data to determine effects of a chemical
on health of humans or other organisms.
• Dose-response assessment: – Extrapolating toxicity data from high-dose studies to
predict the likely effect of low doses of the chemical (also referred to as hazard characterisation).
• Exposure assessment: – Magnitude, frequency and duration of exposure to a
chemical (for example, exposures from proposed or actual manufacture, use or disposal of a chemical).
• Risk characterisation: – Estimates potential for, and magnitude of, risk to an
exposed individual or population.
Dose–Response Relationships
• In general, protection from toxic effects depends upon maintaining exposures below some established “safe” level.
• Different dose-response relationships may be found if a substance produces different toxic effects. For instance, short-term exposure to high concentrations of benzene may produce lethal effects (acute toxic effects), whereas cancer may be induced as a result of long-term exposure to relatively low concentrations (chronic carcinogenic effects).
Threshold and non-threshold effects—general considerations
• There are adverse effects that occur only after a threshold dose has been reached. Exposures associated with doses below the threshold are, therefore, harmless.
• Secondly, there are adverse effects which it is thought may occur at any dose; for such effects there is no harmless dose and no threshold dose. For this second group, increasing dose increases the probability of the effect occurring.
Threshold effects in occupational exposure
• In assessing an acceptable level of a particular substance in the workplace, the procedure usually starts from an experimental database of animal or (preferably) human data (e.g., from epidemiological studies) giving a no-observed-adverse-effect level (NOAEL) or a lowest-observed-adverse-effect level (LOAEL) to derive an occupational exposure limit (OEL) at a lower exposure value which compensates for the uncertainties in the data.
Threshold effects in occupational exposure
• In practice, in workplace situations a subjective safety factor in the range 10–100 of the NOAEL or LOAEL to the limit is used for most substances where the database is from animal studies, and of about 10 when the data are from human studies.
Occupational exposure limits in air • American Conference of Governmental Industrial Hygienists (ACGIH):
– Threshold limit values (TLV®):,
• The National Institute for Occupational Safety and Health (NIOSH)/Occupational Safety and Health Administration (OSHA) system: – Permissible exposure limits (PEL) originally based on the ACGIH TLV values.
• In Germany: – Maximale arbeitsplatzkonzentrationen (MAK, maximum concentration values
in the workplace) and – Technische richtkonzentrationen (TRK, technical exposure limits).
• In the Netherlands: – Nationale MAC-lijst (maximaal aanvaarde concentratie).
• The United Kingdom: • Has a system based on the occupational exposure standard (OES) and the maximum exposure
limit (MEL).
• South Africa
How risk is expressed
• Risk is a statistical expression of probability on a population basis; risk can be expressed as relative or absolute
• The probability of expression of a specified risk is a function of both the intrinsic toxicological properties ( hazard) and the frequency, duration and intensity of exposure
• In quantitative terms, risk is often expressed in terms of probability estimates from zero (harm will not occur) to one (absolute certainty that harm will occur).
Risk Characterization
• Risk characterization is the estimation of the incidence and severity of the adverse effects likely to occur in a human population or environmental compartment due to actual or predicted exposure to a substance, and may include risk estimation, i.e., the quantification of that likelihood.
How is risk assessment used?
• To set standards: – Air, water etc. in the work and the general
environment.
• Licensing and regulation of toxic compounds.
• Identification and clean-up of hazardous waste sites.
• Identification of special handling requirements for chemicals.
• Registration of pesticides.
Risk Management
• An open and continuing dialogue is required to ensure all interested parties, including the general public, are well informed as to the ongoing technology developments in the field of Nanotechnology. As much has been written in the popular press, quality information is required to assist policy makers to distinguish “science fact” from “science fiction’’.
Governmental Agencies/Industry and Funding
Academic Scientists including: Chemistry, Physics, Biology, Medicine, Engineering, Toxicology, Information Technology
Regulatory Agencies/Policy Makers
Pharmaceutical companies
General Public
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Occupational Health Risk Assessment
• Health risk assessment involves four key elements:
– Identification of hazards,
– Examination of the potential health effects,
– Measurement of exposures and
– Characterisation of the risk.
• An Occupational Health Risk Assessment is therefore the structured and systematic identification and analysis of workplace hazards with the aim of reducing the risks of exposure to these hazards through the development and implementation of avoidance, control and control failure recovery measures. In the occupational setting, it is the preliminary component to health risk management.
• Health risk management is the decision-making process involving considerations of political, social, economic and engineering factors combined with risk assessment information to develop, analyze and compare options and to select between them.
Assessing Exposure Levels
• The aim of estimating exposure levels is to characterize exposures in terms of their intensity and duration for Similar Exposure Groups (SEGs), processes, tasks and areas.
Rating of exposure
• In practice, exposure ratings can range from negligible through low, medium/moderate, and high to very high/critical.
Criteria for rating exposures
EXPOSURE RA TING
OEL EXPOSURE BAND
Low Less than 50% of OEL (<0.5 x OEL)
Medium/Moderate Between 50-100% of OEL (>0.5 - 1 x OEL)
High At or greater than OEL (>OEL)
Analysing the Health Risks and Prioritising Actions
• Once the exposures have been estimated by hazard, SEG and by process, task or area then it is time to analyze the potential health risks and the significance of those health risks categorised.
• This is often best done through the use of a ‘risk rating table’ or ‘risk assessment matrix
The risk rating can be qualitative by assigning a rating
Levels of Exposure with
Existing Control
Measures Exposure Band
OEL/ Standards-based
Low Medium High
Health risk rating Description 0-50% of OEL 50-100%of OEL Above OEL
1 Exposure at this level is unlikely to lead to
harm.
NO/VERY LOW
RISK
LOW RISK
MEDIUM RISK
2 Non-life threatening reversible health effects.
3 Adverse health effects that are permanent but
do not significantly affect quality of life or
longevity. Health effects that may be mildly
limiting or disabling and therefore could lead to
a change of occupation and lifestyle.
LOW RISK
MEDIUM RISK
CRITICAL RISK
4 Adverse health effects that are generally
permanent and could lead to a significant
reduction in quality of life and/or longevity.
Continued exposure is generally likely to lead to
permanent physical or mental disability or a
long term limiting illness.
• or it can be quantitative by using a pre-defined numerical ranking by using the formula:
RR = C x PrE x PeE x U RR = Risk Rating C = Consequence PrE = Probability of exposure PeE = Period of Exposure U = Uncertainty
Calculated risk rating Classification of risk Action
400 and above Intolerable risk Requires immediate discontinuation/shutdown
200-399 Very high risk Requires immediate mitigation action with a program to develop a permanent solution
70-199 High risk Requires mitigation action as soon as possible
20-69 Potential risk Requires mitigation action and/or monitoring
Under 20 Tolerable risk Requires monitoring
Risk Determination Method
• The current Risk Committee for Mines and Works (RCMW) will use the following method to determine the risk on mines:
• Risk classification will be based on the Department of Minerals and Energies exposure rating categorization as shown in the table below and the Risk weighting on the American Industrial Hygiene Association’s exposure rating categorization.
• The current classification bands for airborne particulates
Exposures 10% of the OEL and 50% of the
OEL or mixtures of exposures 0,1 and 0,5
C
Exposures 50% of the OEL and < OEL or
mixtures of exposures 0,5 and 1
B
Exposures OEL or mixtures of exposures 1 A
Description Category
Proposed Risk Bands
• From the information obtained from the statutory reports submitted to the DME, a risk band can be established.
• The AIHA weighting will be modified and incorporated into the current DME classification bands and be used to allocate a weighted risk band.
DME
Category
Risk
Weighting(
original
2006
proposal)
Risk Weighting
(Revised 2007)
see note 4
Description
A 4 2 Exposures OEL or mixtures of exposures 1
B 2 1 Exposures 50% of the OEL and < OEL or mixtures
of exposures 0,5 and 1
C 1 0 Exposures 10% of the OEL and 50% of the OEL
or mixtures of exposures 0,1 and 0,5
D 0 - Exposures <10% of the OEL
• The weighted risk band will be multiplied by the base levy per risk shift to give the levy payable per shift. This would then mean a proportional increase in the levy to the risk. The higher the risk the higher the levy payable.
• To ensure that the past high exposures are accounted for and also take cognizance of the long latency period a moving average system will be used; this moving average will be calculated over a seven (7) year period.
• Occupational Risk Assessment relies heavily on exposure levels in comparison to OELs
• No dose-response relationship, i.e., effect identification at every dose.
• Risk is assessed per exposure level and not per risk of disease or severity of disease
Relevance to problem at hand
• Reconcile the two approaches:
– Calculate cumulative exposure per mine (data obtained from occupational measurements over years).
– Calculate risk per mine using the benchmark dose modelling.
Benchmark dose modeling
• An alternative to the NOAEL/LOAEL approach is the benchmark dose method.
• In this procedure, the dose–response curve is fitted to the experimental data in the range of experimental observation by appropriate curve-fitting modeling.
Hnizdo, E.; Sluis-Cremer, G. K. (1993) Risk of silicosis in a cohort of white South African gold miners. Am. J. Ind. Med. 24: 447-457
• Dose-response relationship for cumulative silica exposure and silicosis based on data from Hnizdo and Sluis-Cremer (1993).
BMDs
• Risk:
– 1% of silicosis for a Cumulative Silica Exposure of 1.31 mg/m3 year
– 5% of silicosis for a Cumulative Silica Exposure of 1.90 mg/m3
– 10% of silicosis for a Cumulative Silica Exposure of 2.24 mg/m3
• Risk assessment is a tool.
– Define
• The problem.
• The scope
• The purpose
• Apply the risk assessment tool.
