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Chapter 2 Guide to Chemical Hazards

Chapter 2 Guide to Chemical Hazards. Chapter Outline. Introduction Toxicity Source of Information The Properties of Chemicals. Introduction. Chemicals and laboratory intruments can harm you if not handled properly. Introduction. Chemicals can be classified as Toxic Explosive

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Chapter 2 Guide to Chemical Hazards

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  1. Chapter 2Guide to ChemicalHazards

  2. Chapter Outline • Introduction • Toxicity • Source of Information • The Properties of Chemicals

  3. Introduction • Chemicals and laboratoryintrumentscanharmyou if not handledproperly

  4. Introduction • Chemicalscanbeclassified as • Toxic • Explosive • Flammable • Reactive • Carcinogenic

  5. Introduction • Somechemicalscanharmyou in more than one way • Consider every chemical as hazardous • Degree of hazard vary from one chemical to another

  6. Introduction • Example: gasoline and alcohol • Both are flammable, but gasoline is more flammable • Gasoline ignites easily, burn or explode more vigorously than alcohol

  7. Introduction • Working with chemicals can be safe if proper precautions are followed • Your laboratory instructor will guide you on how to work safely in the laboratory

  8. Toxicity “What is it that is not poison? All things are poison and nothing is without poison. It is the dose only that makes a thing not a poison.” Paracelsus

  9. Toxicity • Any substance could be harmful to living organisms • Hazardous chemical: any chemical that presents a hazard either under normal use or in a foreseeable emergency (OSHA)

  10. Toxicity • Factors that affect toxicity are variable: • Dose (amount of substance to which one is exposed and the length of time of exposure to the substance)

  11. Toxicity • Route of exposure • Inhalation through lungs by breathing • Ingestion through digestive system (eating, drinking, chewing gum, smoking, applying cosmetics, using contaminated beaker in lab for drinking, eating with contaminated hands, etc…) • Absorption through body opening (skin, eyes, ears) or • Injection (e.g. contaminated sharp objects)

  12. Route of exposure

  13. Toxicity • Other factors (e.g. gender, age, lifestyle, allergic factors, genetic disposition, mode, …) • Toxic effects can be • immediate or delayed • reversible or irreversible • local or systemic

  14. Toxicity • Toxic effects may vary from • Mild and reversible (e.g headache from inhaling ethyl acetate that disappears when inhaling fresh air, • to Serious and irreversible (e.g. birth defects from excessive exposure to a toxic chemical during pregnancy or cancer from excessive exposure to a carcinogen)

  15. Toxicity • Toxic effects can be: • Acute poisoning • Exposure to a toxic substance that lasts for  24 h • Often, the effect is sudden, can be painful, severe, or fatal • Normally, single exposure is involved (e.g. exposure to hydrogen cyanide, carbon monoxide)

  16. Toxicity • Chronic poisoning • Repeated exposures with time intervals in months or years • Symptoms may not be immediate (e.g. lead or mercury poisoning, exposure to pesticides or radiation) • Substances in combination • 2 or more hazardous materials are present and the combined effect is greater than the effect of individual substance

  17. Toxicity • Examples: • exposure to alcohol and chlorinated solvents (combined effect) • Cyanide and amyl nitrite (antagonistic effect) • Allergens • Substances that produce immunologic reaction • Asthma-like symptoms or dermatitis

  18. Toxicity • Generally, toxic effect from a substance is dependent on severity of exposure • more severe the results are expected from larger / more frequent exposure • Minimizing exposure means reducing or preventing harm. How to achieve this?

  19. Toxicity • Ways of Reducing Exposure • Minimize exposure through ingestion • Do not eat or drink in lab • Do not put your hands or fingers in your mouth • Wash your hands before leaving lab or if contaminated • When in lab keep your hands away from your eyes, ears, or nose unless you wash them • Do not touch your skin if injured • Be very careful when working with sharp objects

  20. Toxicity • Minimize exposure through skin • Use proper gloves • Discard gloves after use and wash your hands • Minimize exposure through inhalation • Labs should be well ventilated • Use fume hoods/safety cabinets when necessary • If a chemical is spilled on your clothes or skin • Wash the affected area immediately and thoroughly with running water

  21. Sources of Information • Material Safety Data Sheets (MSDS) • MSDS describes the hazards of a chemical and the precautions that must be taken to avoid harm • MSDS should be made available in laboratories for workers and students to read before carrying out any experiment

  22. Sources of Information -MSDS • MSDS should at least contain • Name of the hazardous chemical (names with % if mixture) • Some of physical and chemical properties (e.g. vapor pressure, boiling point, flash point, density, …) • Physical hazards of the substance (e.g. flammable, explosive, corrosive, …) • Health hazards (e.g. corrosive, irritant, carcinogen, …) • Routes of entry (e.g. inhalation, ingestion)

  23. Sources of Information -MSDS • Exposure limits: permissible exposure limit (PEL) and threshold limit value (TLV) if established • Can the substance cause cancer or not • Precautions to be taken when using the substance • Control measures, work practices, and PPE • Emergency and first aid procedures • Date of preparation / revision • Name of manufacturer and address

  24. Sources of Information -MSDS • Examples on MSDS Acetone Nitric acid Water

  25. Sources of Information -MSDS • Understanding an MSDS • CAS registry no: a unique number assigned to each chemical by ACS CAS (Chemical Abstracts Service) • Ceiling limit: concentration in ppm or mg/m3 that must not be exceeded in a specified time period (typically 15 min)

  26. Sources of Information -MSDS • Chemical name: IUPAC, CAS, common chemical name • Example: 1,2-ethanediol (IUPAC) or ethylene glycol (common) • Composition of mixtures: includes all hazardous components present in concentrations >1% and all carcinogens in concentrations >0.1%

  27. Sources of Information -MSDS • Control measures: list types of PPE (e.g. lab coats, glove, respiratory equipment) , fumehood, glovebox, safety cabinet, etc… • Fire and explosion hazard data: • Flash point: “lowest temperature at which the vapor of the chemical can be ignited by a flame when the chemical is slowly heated in a special apparatus” • Autoignition temperature: “lowest temperature at which a chemical ignites spontaneously in the air”

  28. Sources of Information -MSDS • Flammable limits: volatile flammable chemicals have min and max vapor concentrations in air below and above which they cannot be ignited. Increase in temperature decreases the lower flammable limit and increases the upper limit. Increase in pressure decreases the lower flammable limit and increases the upper limit. • Recommended extinguishing media: some chemicals (e.g. Mg) ignites more vigorously when in contact with water or carbon dioxide.

  29. Sources of Information -MSDS • First Aid: describes procedures of emergency first aid. Perform the first aid if qualified, call the ambulance. • Health Hazard Data: Lethal Dose Fifty (LD50) Lethal concentration Fifty (LC50)

  30. Sources of Information -MSDS LD50 (lethal dose fifty) is the lethal single dose (usually by ingestion) in mg of chemical per kg of animal body weight that is expected to kill 50% of the test animal population within a specified time. LC50 (lethal concentration fifty) is the lethal concentration of a chemical in air expressed as ppm of gases and vapors or as mg/L of air for dusts and mists expected to kill 50% of the test animal population within a specified time by inhalation.

  31. Sources of Information -MSDS • Permissible exposure limit (PEL): concentration of a hazadous chemical in the air in ppm or mg/m3. It is the max concentration in the breathing air that can be inhaled without harm by an adult worker for 8 h a day, 40 h a week, during his/her working lifetme – provided that the worker is a person of average health.

  32. Sources of Information -MSDS • Physical/chemical properties: Boiling point Melting point Vapor pressure Specific gravity Solubility Appearance and odor: liquid, solid, or gas (at room temperature); color, crystalline, or amorphous; etc.. Evaporation rate

  33. Sources of Information -MSDS • Precautions for spills and cleanup: describes how to properly cleanup of a spill or release (can it be put in a landfill or an approved disposal facility). • Reactivity: some chemicals react vigorously with other chemicals; others are self-reactive or unstable and decompose vigorously if disturbed. • Short-term exposure limit (STEL): concentration in ppm or mg/m3 that should not be exceeded for more than a short period (usually 15 minutes).

  34. Sources of Information -MSDS • Target organ: name of an organ(s) (kidney, liver, skin, eyes, etc.) or system(s) (respiratory system, central nervous system, etc.) that are likely to be adversely affected by an overexposure to the chemical. • Time-weighted average (TWA): worker’s exposures are to be measured and averaged over an 8-hour day. If the TWA does not exceed the PEL or TLV for a worker, then he or she is not harmed.

  35. Sources of Information -MSDS • Threshold limit value (TLV): this number is a concentration limit (similar to PEL). PEL limit is a legal limit; the TLV limit is a voluntary, recommended limit.

  36. Sources of Information -Labels

  37. Sources of Information -Labels • Labels on bottles of chemicals provide critical information about the chemical • Label should contain: • name of the chemical; • one of 3 signal words: Danger, Warning, or Caution, to indicate the relative degree of severity of the hazard(s) of the chemical;

  38. Sources of Information - Labels Danger: signifies that the hazards can cause serious injury (e.g., blindness, loss of a limb) or death. Warning: signifies that the hazards can cause less than serious injuries. Caution: warns users to be careful when using, handling, or storing the chemical

  39. Sources of Information -Labels • main foreseeable hazard(s) when used; • precautionary measures that will protect users from the harmful effects of those hazards; • first aid instructions; • instructions in case of fire, if applicable; • methods to handle spills or leaks, if appropriate;

  40. Sources of Information -Labels • instructions if the chemical requires unusual handling and storage procedures; and • name, address, and telephone number of the manufacturer or supplier

  41. Hazards and their Ratings

  42. How to Read MSDSs and Labels Pages 16 - 20

  43. MSDS & Properties of Chemicals • MSDS provide also other useful information about chemicals (e.g. solubilities, volatility, reactivity, classification of chemicals) • Examples: • Reactivity of Chemicals

  44. MSDS & Properties of Chemicals • Reactivity of Chemicals • MSDS provides information on the incompatibility of chemicals • Example: adding acetic acid to an oxidizing agent (e.g. chromic oxide, nitric acid, perchloric acid, potassium permanganate) produces a vigorous reaction. If reaction conditions are not minimized (e.g. quantity, temperature) the reactioncould be disastrous. • Acetic acid could not be stored near an oxidizing agent.

  45. MSDS & Properties of Chemicals • Differing solubilities in water • Knowledge of differing solubilities in water and other solvents helps you decide how to dissolve a substance • Examples: • All nitrates are soluble in water • Some chlorides and sulfides are soluble in water • Some of the insoluble chlorides are slightly soluble in warm water • Solubility of some sulfides varies depending on pH

  46. Properties of Chemicals • Classifying Hazardous Chemicals • All chemicals are hazardous in one way or another • You must know the hazards of each chemical before dealing with it • To facilitate knowledge about hazards of chemicals, chemicals are classified in groups

  47. *Refer to Appendix 2 for more examples

  48. Properties of Chemicals • Solvents and Their Hazards • Examples of some solvents • Water • Organic solvents (methanol, hexane, ether): mostly flammable • Flammable solvents do not burn; their vapor burns

  49. Properties of Chemicals • Solvents and Their Hazards • More rate of vaporization produces more flammable vapors • Vaporization increases with temperature • All flammable liquids and solids must be kept away from oxidizers and ignition sources

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