Introduction Any industrial activity involves some risk or hazard in terms of fire, explosion, toxic releases etc. which lead to injuries, loss of life & property ultimately adversely affecting the environment as a whole if not managed correctly resulting Truly speaking, any industrial installation should have Zero risk situation, but, it is impossible to achieve it.
Risk Assessment & Risk Management gives a framework for : Setting regulatory priorities Decision Making that cut across various environmental areas.
“Environmental Risk Assessment” may be broadly defined as a scientific enterprise in which facts and assumptions are used to estimate the adverse effects on human health or the environment that may result from exposures to specific pollutants or other toxic agents.
“Environmental Risk Management” refers to a decision making process involving risk assessment, technological feasibility, economic information about cost and benefits, statutory requirements, public concerns etc. “ Risk Communication” is the exchange of information about risk.
RISK ASSESSMENT : It is the systematic examinationof an actual or proposed industrial installation: (1) to identify potential hazard to occur & (2) to identify the possible consequences from these hazards which would assist in decision making for reducing risk to an acceptable level.
ALARP: Mgmt. must take all measures to reduce risks as low as reasonably practicable. (ALARP) and this is achieved through a technique called “Risk Assessment or Risk Analysis”.
What is Hazard? It is the property of a substance or a situation which has the potential to cause harm. The potential hazards can be of fire, explosion and release of toxic & harmful gases.
HAZARD By hazard we mean any physical activity, situation or condition with the potential to cause harm, like:
What is Risk? It is related to the consequences of identified hazard. It may also be defined as the unwanted consequences from a particular activity. Risk has two variables: Magnitude of consequences Probability or frequency of the occurrence. So, Risk = Frequency of the occurrence × Magnitude of consequences
What Is Risk? An expectation of loss Always an element of uncertainty Always refers to future Usually covers both severity and likelihood of a loss Usually refers to unwanted consequences
The consequences of an accident may be classified in different categories, as Personnel consequences Fatalities Impairment Environmental damage Economic loss Damage to material assets Production/service loss Information loss Image loss(i.e., damage to reputation)
Why Risk Assessment (Objectives of RA): (1) To prioritize safety investments : All organizations have limited resources. Risk assessment can be used to prioritize risks and ensure that investment is directed to the greatest risks. (2) Risk estimates aids in decision making. (3) Corporate Mgmt develops positive public relations with employees, community and the Govt.
RISK EVALUATION: There are four steps in the evaluation of a risk. Hazard Identification Exposure Assessment Hazard Assessment Risk Characterization
HAZARD IDENTIFICATION: It is an analysis to determine which of the discharges from a process or an accidental release will be a potential danger to public health. E.g. Chemicals such as CO, HCl and unburned organics would be established as potential sources of risk for an incinerator. The means of identifying hazard is complex. Various methods are used to collect and evaluate toxic properties ( properties that indicate the potential to cause biological injury, disease or death under certain exposure conditions).
HAZARD IDENTIFICATION:(Cont…..) Methods: EPI-DEMIOLOGICAL STUDY: Use of “epidemiological” studies deal with the incidence of disease among groups of people. The study attempts to correlate incidence of disease like cancer from an emission by evaluation of people with a particular disease and people without the disease.
HAZARD IDENTIFICATION: (Cont…..) Methods: (2) BIOASSAY: Long –term animal “bioassays” ( an evaluation of disease in a laboratory animal) is a very common method for hazard identification. e.g. Increased tumor incidence in laboratory animals is the primary health effect considered in animal bioassay. Exposure testing for a major portion of an animal’s lifetime (2 -3 years for rats and mice) provides information on disease susceptibility, primarily for carcinogenicity ( the development of cancer).
(2) EXPOSURE ASSESSMENT: This determines how much of an emission actually reaches the receptor. Human exposure includes ingestion (eating or drinking), dermal contact ( contact with the skin) & inhalation. These means of exposure are pathways to the human body. Thus, there is no risk without exposure. The exposure assessment attempts to define the route, amount, frequency and duration of exposure of a given population to a toxic substance. The principal pathways of exposure generally considered in exposure assessment are atmospheric transport, surface and ground water transport, ingestion of food materials etc.
(2) HAZARD ASSESSMENT : A hazard assessment is a determination of the relationship between the amount of exposure and the risk to public health. A person can drown in water, but that does not mean that a glass of water is a danger to health. Obviously, what defines a danger is not necessarily the presence of a particular chemical but rather the amount of that substance one is exposed to. This amount is called “dose”.
HAZARD ASSESSMENT : (Cont…..) Hazard assessment is also referred to as “Dose – response assessment”. Dose is usually expressed as milligrams of chemical received per kilogram of body weight per day. For toxic substances other than carcinogens, a threshold dose must be exceeded before a health effect will occur. For many substances, there is a dosage level below which there is no harm. However, at some given dosage, the threshold, a health effect will occur ( or, at least be detected).
(4) RISK CHARACTERIZATION: It estimates the health risk associated with the process under investigation. This characterization gives a number that represents the probability of adverse health effects from that process or from a substance released in that process.
RISK CHARACTERIZATION:(Cont…) Once a risk characterization is made, the meaning of that risk must be evaluated. Public health agencies generally only consider “risk” greater than 10 in 1 million to be significant risks warranting action.
MEASURE OF RISK Though the risks to the people from industrial hazards may be in the form of injuries , exposure to harmful releases etc., risks are generally measured in terms of deaths (since there is better accuracy in data pertaining to death). Risks are generally expressed as Individual risks Societal risks.
(1) Individual Risk ( IR) : This is the risk to an individual person. It is the probability of death occurring as a result of an accident at plant or an installation or a transport route. A simple way to express an IR is the “FATAL ACCIDENT RATE” (FAR).
Individual Risk ( IR) : (Cont……) “FATAL ACCIDENT RATE” (FAR) is the number of fatalities per 108 exposed hours. One person works on average = 7.5 hrs /day One person works on average= 7.5×5= 37.5hrs/wk One person works on average = 37.5×52wks(yr) = 1950 hrs/year ( Say, 2000 hrs.) Thus, 1000 persons in lifetime (50 yrs) would work = 1000×50×2000 = 100000000 i.e. 108 exposed hrs. “Exposed hours is the mean hrs. at work”
Individual Risk ( IR) : (Cont……) “FATAL ACCIDENT RATE” (FAR) typically varies in the range of 1 - 30. FAR of 1 means one fatal accident over 1000 working lifetimes or, One fatal accident per 50 yrs. For a site employing 1000 people.
RISK CHARACTERIZATION:(Cont…) (2) Population Risk (PR) : This is also known as “group risk” from an activity. It is the relationship between frequency of an accident and total number of people harmed. The is often plotted as FN curve showing the cumulative frequency (F) of accidents and Number of fatalities( N).
Objectives of Risk Assessment To prioritize safety investment (All organizations have limited resources. RA can be used to prioritize risks and ensure that investments is directed to the greatest risks). To make planning & decision especially for areas like plant design, plant safety reviews, preparation of emergency / disaster plan etc. To estimate financial risks. To develop positive public relations with employees, community and the Govt. To get approval of projects.
Objectives of Risk Assessment (Cont…) 6. To compare the estimated individual & societal risks against acceptance criteria. 7. To identify major risk contributors and to recommend remedial measures for risk reduction. 8. To carry out cost – benefit analysis for the implementation of the remedial measures. 9. To address land use planning issues including suitability of location, layout and design. 10. To develop appropriate contingency plan.
System Description: It is the compiled process information that are needed for the Risk Analysis. e.g. (1) Site Location (2) Weather Data (3) Process Flow Diagrams (PFD) (4) Piping & Instrument Diagram (P & ID) (5) Layout Drawing (6) Effluent & Emission Summary (7) Operating & Maintenance Procedures
Hazard Identification: It includes: (1) Checklists (2) Preliminary Hazard Analysis (PHA) (3) Hazard & Operability (HAZOP) Studies – It is a methodology for identifying and dealing with potential problems in industrial processes, particularly those which would create a hazardous situation or a severe impairment of the process. (4) Failure Mode and Effects (FMEA) - It prioritizes potential failures by looking into the probability of occurrence and likelihood of failure. (5) What – if – Analysis
Scenario Selection: It is used to list out all accidental release scenarios that have the potential to impact the members of the public outside the installation boundary. It considers: (1) Nature of the hazardous substance released & its operating T, P etc. (2) Inventory of hazardous substance
Consequence Estimation: It is used to determine the potential for damage or injury from particular incidents. By using this technique, the areas of the site which would be affected in the event of an emergency is located. Outcomes of an incident are analyzed using source & dispersion models and Explosion & Fire Models.
Likelihood / Frequency Estimation: It is used to estimate the frequency or probability of occurrence of an incident. Estimates may be obtained from historical incident data.
Risk Estimation: It combines the consequences and likelihood of all incident outcomes from all selected incidents to provide a measure of risk. This involves mapping the accident areas and risk pattern.
Utilization of Risk Estimates: It is the process by which the result from a risk analysis is used to make decisions.
What is Maximum Credible Accident (MCA) Analysis? It is a tool used to find the maximum potential damage an accident can cause. It helps in the identification of most vulnerable sections of the installation and facilities that pose maximum possible risk if the hazardous materials are released as a result of a failure. This may be due to leakage from a crack or fracture of the process vessel, vents, pump seals or overflow of a tank or vessel.
What is Maximum Credible Accident (MCA) Analysis? ( Cont….) The extent of consequences arising from the hazardous substances will largely depend on quantity released, location, wind condition and density of population.
Accident Scenarios of Risk Potential (1) BLEVE( Boiling Liquid Expanding Vapor Explosion): This is a type of explosion that can occur when a vessel containing a pressurized liquid is ruptured. Such explosions can be extremely hazardous. A BLEVE results from the rupture of a vessel containing a liquid substantially above its atmospheric boiling point. The substance is stored partly in liquid form, with a gaseous vapor above the liquid filling the remainder of the container. The primary cause is usually an external flame impinging on the shell of a vessel leading to sudden rupture of the shell. The explosion is sufficient to cause fragments of the container to fly over large distances of few kms. The released liquid results into a fire – ball having intense heat. It causes intense damage to life and property. LPG Storage vessels in petroleum installations can cause severe BLEVE.
Accident Scenarios of Risk Potential ( Cont…) (2) UCVE ( Unconfined Vapor Cloud Explosion): When a flammable gas or liquid escapes into the atmosphere and mixes with air , an explosive gas or vapor cloud can form. This flammable mixture will explode if ignited causing extensive damage to the surroundings.
Accident Scenarios of Risk Potential ( Cont…) (3) Jet Fires: Ejection of a flammable liquid from a vessel, pipe etc. can give rise to a jet flame if the material ignites. It is not easy to handle since a large jet flame has a substantial reach ( sometimes 50 m or more). The jet flames from a pressure relief valves can cause adjacent vessels to overheat and burst giving rise to BLEVE ( Boiling liquid expanding vapor explosion).
Accident Scenarios of Risk Potential Toxic Dispersion: The hazard due to toxic chemical depends on the condition of exposure and the type of chemical. It can range from sudden exposure at high concentrations to prolonged exposure at low concentrations. A very large release of toxic chemical ( Cl or H2S) usually have greater disaster potential than fires or explosion.
Risk Management & Control After assessing the risks , one recognizes the courses of actions that would control and minimize the risks to human health, property and environment ( objective of Risk Mgmt.) Risk Mgmt. involves resource allocation, cost – benefit analysis, acceptable risks etc.
Risk Management & Control ( Cont….) Risk Mgmt. involves: Reduction of risks to acceptable limits by judicious investments. (2) Relocating the activities on alternate sites / routes (3) Taking appropriate considerations when buying “Insurance Policy” of installations with potential high risks. (4) Preparing Emergency / Disaster plans to handle effectively any emergency situations with minimum damages.
Risk Management & Control ( Cont….) Effective Risk Mgmt. Depends on: Sound standards of engineering design must be used. Quality control procedures must ensure that all equipment conforms to design standards and specifications. All equipment must be inspected, maintained and tested at suitable intervals. Personnel must be experienced and trained.
Risk Acceptance / Tolerance The result of a risk assessment is a quantification of risk. It brings the level of risk that is acceptable to public, authorities & the industry. But, the question is how much risk can be acceptable or tolerable. The risk from an activity should be judged against the benefits from the activity, since no activity can claim to be totally risk free.
Risk Acceptance Criteria: Since all industrial activities involve risks including risks of fatality ( may be employees engaged in the activity or, common public outside). When an industrial activity imposes risk common public, it especially becomes the concern of regulators to assess the risk & evaluate it.
Risk Acceptance Criteria: (Cont……) A good risk criteria should recognize: Level of risk which is so high that it is considered unacceptable/ intolerable regardless of the benefits derived from the activity. Level of risk which is low enough to be considered negligible. Level of risk in between that is to be considered tolerable subject to their being reduced to “As Low As is Reasonably Practicable” (ALARP). Risks become tolerable when all practicable measures are taken to reduce risk to ALARP.
Risk Assessment Matrix Risk Assessment Matrix is a tool for ranking different activities / projects in terms of their potential benefit and the likely risks/cost in implementing them. It is a tool that standardizes qualitative risk assessment and facilitates the categorization of risk from threats to health, safety, environment and company reputation. I