4.1) Risks = Hazards x The Probability of Exposure: Risks or potential harm that may result from hazardous chemical use, are a function of the chemicals hazards or dangers, and the probability of exposure, or likelihood or odds the hazards are going to be realized. More simply stated, the risks are equal to the hazards times the probability of exposure.
Risks include acute and chronic health effects, for example, irritation or cancer, and physical effects such as fires or explosions. The hazards are physical and health hazards (see Section 1 – Chemical Hazard Overview). Note – some come in varying degrees (e.g., toxic and highly toxic, combustible and flammable, irritant and corrosive). The probability of exposure is influenced obviously by the chemical quantity and manner of use, storage and disposal, but also by the number of individuals exposed and their individual susceptibility, and by various physical, chemical and/or biological factors. Some of these factors include: physical form, detection/warning properties, vapor pressure, exposure limits, biological half-life, etc.
For example: beryllium is an agent which can damage the lungs, it is a sensitizer to certain individuals who are genetically sensitive, and it is a potential carcinogen. It has significant hazards. In the solid, metal form, the probability of exposure is negligible and therefore the risks are minimal.
Risks (minimal) = Hazards (significant) x The Probability of Exposure (negligible) (or in mathematical equivalents – very small number = large number x almost zero).
However, if one grinds beryllium into a respirable particle or burns it to a fume, the probability of exposure becomes very significant, as do the risks.
Risks (very significant) = Hazards (significant) x The Probability of Exposure (significant) (or in mathematical equivalents - very large number = large number x large number).
4.2) Chemical Risk Assessment Form Tool (CRAFT): The Chemical Risk Assessment Form Tool (CRAFT) (PDF format) can be used as an aide to chemical users in conducting their initial chemical risk assessments. The Form is broken into three sections which correspond to the three parts of the expression "RISKS = HAZARDS x THE PROBABILITY OF EXPOSURE." It is designed to help chemical users understand how the expression relates to the specific chemicals they use.
The top of the first page pertains to the "HAZARDS" part of the expression and lists health and physical hazards associated with chemicals (see Section 1 – Chemical Hazard Overview). It provides a reminder of the possible hazards and serves as a place to list those identified when researching the hazards as part of planning chemical use. The bottom of the first page lists a number of indicators for the degree of some hazards. Information on these indicators provides the chemical users with a relative risk matrix rating (less risky – more risky) based on the particular indicator identified. The top of the second page pertains to the "RISKS" part of the expression and lists some common acute and chronic health effects and well as common physical effects associated with hazardous chemicals. Below this are a couple health effects indicators which provide the chemical users with a relative risk matrix rating (less risky – more risky) based on the particular indicator identified. The bottom of the second page pertains to the "THE PROBABILITY OF EXPOSURE" part of the expression and lists a number of indicators that affect the likelihood or odds the hazards are realized. Again, information on these indicators provides the chemical users with a relative risk matrix rating (less risky – more risky) based on the particular indicator identified.
For example: Chemical quantity is an exposure hazard indicator and a factor that has a great affect on the degree of risk. Small quantities and lower concentrations are inherently less risky than large quantities and high concentrations (see the Table below).
This and many other factors are listed in the relative risk matrix and explained below in the Guide to Reading a Material Safety Data Sheet.
4.3) Guide to Reading a Material Safety Data Sheet: These are notes to help you understand the information on a Material Safety Data Sheet (MSDS). Some MSDS's may not contain all of the sections or categories of information reflected in this guide. If you require assistance in interpreting the information contained in an MSDS or you would like additional information on a hazardous chemical, contact the Department of Risk Management & Safety at 621-1790.
Section I - Product Identification:
Manufacturer's Name: The manufacturer of the product is listed along with the manufacturer's address.
Emergency Telephone Number: The telephone number of people other than the manufacturer who may provide information for a chemical emergency; a spill, explosion, fire, etc.
Chemical Name and Synonyms: Chemical name of the material, if it is a single element or compound, along with other terms for the substance.
Trade Name and Synonyms: The name the product is sold by along with other terms for the formulation.
Chemical Family: General class of compounds to which a material belongs (e.g. ether, mineral acid, ketone, etc.).
Formula: Formula for the number and types of atoms contained in the substance if it is a single element or compound.
Section II - Hazardous Ingredient Information:
Hazardous Ingredients: Listed by chemical name in one of three divisions (paints, preservatives and solvents; alloys and metallic coatings, or hazardous mixtures of other liquids, solids, or gases) unless the product is a bona fide trade secret.
Percentage: Percent by weight or volume of each ingredient. The approximate percentage of each hazardous ingredient is included for each ingredient greater than 1% except for carcinogens and those chemicals which could be released from a mixture in concentrations which would exceed the Permissible Exposure Limit (PEL) or Threshold Limit Value (TLV). These ingredients must be listed if present in a concentration greater than 0.1%. Higher quantities and concentrations are inherently more risky (see the Table below).
PEL: Term used by the Occupational Safety and Health Administration (OSHA) to express the legal airborne concentration of a material to which people can be exposed to at work. Usually stated in parts per million of the toxic substance in air (ppm) or milligrams of the toxic substance per cubic meter of air (mg/M3). OSHA has established PEL's for approximately 650 chemical. PEL's are listed in CFR 29 1910.1000 (for information on PEL's, call RM&S at 621-1790). The PEL's were originally adopted from the 1969 TLV's (see below). Since they are law, they are updated and added to very infrequently.
TLV: Term used by the American Conference of Governmental Hygienists (ACGIH) to express the airborne concentration of a material to which nearly all persons can be exposed day after day, without adverse health effects. TLVs may appear as: TLV-TWA or time-weighted average, which is an average eight-hour exposure limit; TLV-STEL or short-term exposure limit, which is a fifteen-minute exposure limit, or TLV-C or ceiling, which is a limit which should never be exceeded without protection. ACGIH has established TLV's for approximately 850 chemical. TLV's are listed in ACGIH,s publication, Threshold Limit Values for Chemical Substances and Physical Agents (for information on TLV's, call RM&S at 621-1790). The TLV's are updated and added to on a yearly basis.
PELs and TLVs provide a general indication regarding the materials degree of risk (see the Table below). However, they are not fine lines between safe and dangerous concentrations nor are they a relative index of toxicity. They should not be used to assess exposures by anyone untrained in the discipline of Industrial Hygiene.
* ppm = (mg/M3)(24.45/MW)
Section III - Physical Data:
Boiling Point: Temperature at which a liquid changes to a vapor at a given pressure, usually stated in of at one atmosphere pressure. For mixtures, the initial boiling point or boiling range may be given. Flammable and toxic chemicals with low boiling points present special fire and/or inhalation hazards (see the Table below).
Vapor Pressure: Pressure exerted by a vapor above its own liquid in a closed container, usually stated in millimeters of mercury (mm of Hg) at 20oC (unless stated otherwise). Vapor pressure provides an indication of how readily a material will go into the air. Flammable and toxic chemicals with high vapor pressures present special fire and/or inhalation hazards (see the Table below).
As stated above - vapor pressure (VP) indicates how readily a chemical will go into the air and exposure limits (TLVs or PELs) indicate how risky it might be to breathe a particular chemical. An expression called the Vapor Hazard Ratio (VHR) looks at both factors at once. It is a mathematically derived value that indicates how many more times the exposure limit would be exceeded if the air was saturated with the chemical. Chemical with higher VHRs are inherently more risky.
** [(VP @ temperature of use)(106)/atmospheric pressure]/TLV or PEL
Atmospheric pressure is 760 mmHg at sea level
Vapor Density: Relative density or weight of a vapor or gas compared to an equal volume of air. Air is rated as 1.0. A figure greater than 1.0 indicates a vapor or gas heavier than air and vice versa. Concentrated vapors and gases which are heavier than air can accumulate in low places.
Solubility in Water: The amount of a substance which can be dissolved in a given volume of water. Expressed usually in terms of milligrams per liter or in general terms such as "negligible." Chemicals which are water soluble are usually absorbed more readily by ingestion. Chemicals which are less water soluble are usually absorbed more readily by inhalation and through the skin. The routes of exposure have a bearing on the degree of risk (see the Table below).
In the body, absorbed chemicals may remain or be changed (i.e., biotransformed) to more or less water-soluble substances. This, and the absorbed chemicals' volatility have bearing on how chemicals are excreted from the body. The biological half-life indicates how long it takes for half of the absorbed dose to be excreted from the body and this has a bearing on the risks (see the Table below).
Appearance and Odor: Brief description of the substance at normal room temperature and atmospheric conditions (e.g. viscous, colorless liquid with an aromatic hydrocarbon odor). In general, smaller and more fluid substances enter the body easier (see the Table below). Health hazards cannot cause harm unless they get in or on the body.
Odor and appearance, as well as irritation, may provide an indication of exposure and possibly a semi-qualitative level (see the Table below). Odor and irritation levels are published in the literature for commonly used chemicals. However, not all chemicals are visible, smell, and/or cause irritation. A good example is carbon monoxide, a colorless, odorless, tasteless, non-irritating, toxic gas. Analytical methods must be used to detect such chemicals. Chemicals that are more difficult to detect or are detectable by odor or irritation at levels above their safe exposure limit (i.e., have poor warning properties) are inherently more risky.
pH: An expression of the acidity or alkalinity of an aqueous solution by the logarithm of the reciprocal of the hydrogen ion concentration. It provides an indication of the corrosivity of the substance as does the oxidizer status (see the Table below).
Specific Gravity: Weight of a volume of substance to an equal volume of water. A ratio of less than one means the material is lighter than water and vise versa.
Percent Volume by Weight: Percent of a liquid or solid (by volume) that will evaporate at an ambient temperature of 70oF.
Evaporation Rate: Rate at which a material is converted to the vapor state at any given temperature and pressure.
Section IV - Fire and Explosion Hazard Data:
Flash Point and Method Used: Lowest temperature at which a liquid will give off enough flammable vapor to ignite. Since flash points vary according to how they are obtained, the method used must be listed. Chemicals with lower flash points present a greater flammability hazard (see the Table below).
Flammable Limits: Range of concentrations over which a flammable vapor mixed with air will flash or explode if an ignition source is present. Range extends between lower explosive limit (LEL) and upper explosive limit (UEL) and is expressed in percentage of volume of vapor or gas in air (0 – 100%). Chemicals with a broad flammable range (i.e., range between the LEL and the UEL) and/or a flammable range in the lower percentages, present a greater flammability hazard (see the Table below).
Extinguishing Media: Fire-fighting material for use on substance that is burning, Fire-fighting material should be indicated by its generic name (e.g. water, foam, dry chemical, etc.).
Special Fire Fighting Procedures and Precautions: Listing of certain fire-fighting materials unsuitable or unsafe to use on the burning substance. Also, a listing of special handling procedures and personal protective equipment.
Unusual Fire and Explosion Hazards: Hazards which might occur from overheating or burning of substance, including any chemical reactions or changes in chemical form or composition. Also, any special hazards which may need to be considered while extinguishing a fire.
Section V - Health Hazard Data:
Threshold Limit Value: Explained previously in Section II.
Effects of Overexposure: Covers immediate (acute) and long-term (chronic) effects of overexposure to the substance. May include information from human experience and animal tests. Toxicity data may also be provided in the form of average lethal dose or concentration (LD50 or LC50, respectively). These are average doses or concentrations that cause death in a living system, by a particular exposure route. The units are usually milligrams of the toxic material per kilogram body weight of the animal it is tested in (mg/Kg), parts per million of the toxic material in air (ppm), or milligrams of the toxic material in a cubic meter of air (mg/M3). Example: the oral rat LD50 for phenol is 414 mg/kg. These values can be used to provide a relative degree of toxicity (see the Table below).
Emergency and First-Aid Procedures: Emergency information and first aid instructions for treatment of acute inhalation, ingestion, and skin or eye contact.
Section VI - Reactivity Data:
Stability: Indication of whether the substance is susceptible to dangerous decomposition and under what conditions it might occur.
Conditions to Avoid: Conditions which may cause hazardous consequences or damage to the substance (e.g. heat, shock, cold, light).
Incompatibility: Common materials or contaminants with which the specific substance may come in contact and release large amounts of energy, flammable vapor or gas, or produce toxic vapor or gas.
Hazardous Decomposition Products: Hazardous materials that may be produced in dangerous amounts if the substance is exposed to burning, oxidation, heating or allowed to react with other chemicals.
Hazardous Polymerization: Polymerization is a chemical reaction in which two or more small molecules combine to form larger molecules that contain repeating structural units of the original molecules. A hazardous polymerization is an unintended and uncontrolled polymerization reaction that may create a great deal of heat and may release a hazardous substance. This listing may indicate whether such a reaction is possible and under what conditions. It may also indicate how long "inhibitors" in the substance will prevent such a reaction from occurring.
Section VII - Spill or Leak Procedures:
Spill and Leak Procedures: Immediate steps to be taken to assure safety to people and property in the event of a spill or leak of the substance including equipment and personal protective equipment. Methods for control and clean-up are described.
Disposal Method: May describe a method for disposing of excess, used, or spilled material. Includes advisory to comply with all applicable Federal, State and Local laws and regulations.
Section VIII - Special Protection Information:
Protection: Requirements for respiratory protection should ventilation recommendations not be feasible. Included will be the type of breathing apparatus required and any special conditions and limitations of use.
Ventilation: Type of ventilation, if needed when working with the substance. Local exhaust captures or contains the volatilized or aerosolized substance at the source. General ventilation dilutes the volatilized or aerosolized substance to an acceptable level.
Protective Gloves: The appropriate gloves, if needed, to prevent hand contact (e.g. rubber, vinyl, neoprene).
Eye Protection: Type of eye protection device to be worn when working with the substance.
Protective Equipment: Additional protective measures or equipment recommended when working with the substance (e.g. apron, boots, glove box).
Section IX - Special Precautions:
Precautions to be Taken in Handling and Storage and Other Precautions: Describes additional precautions to be considered or may give special emphasis to information or warning stated in other sections of MSDS.
All contents copyright © 2009. Arizona Board of Regents.