Prudent Practices in the Laboratory Handling and Disposal of Chemicals (1995) / Chapter Skim
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Evaluating Hazards and Assessing Risks in the Laboratory
Evaluating Hazards and Assessing Risks in the Laboratory
Pages 29-62
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From page 29... ...
.'. :::.::: ·: ,, .:: :::: :~:: '-:::: ~ 2 " 'i' 5::::: Evaluating AM no 3.A INTRODUCTION 3.B SOURCES OF INFORMATION 3.B.1 Chemical Hygiene Plan 3.B.2 Material Safety Data Sheets 3.B.3 Laboratory Chemical Safety Summaries 3.B.4 Labels 3.B.5 Additional Sources of Information 3.B.6 Computer Services 3.B.6.1 The National Library of Medicine Databases 3.B.6.2 Chemical Abstracts Databases 3.B.6.3 Informal Forum 3.C TOXIC EFFECTS OF LABORATORY CHEMICALS 3.C.1 Basic Principles 3.C.1.1 Dose-Response Relationships 3.C.1.2 Duration and Frequency of Exposure 3.C.1.3 Routes of Exposure 3.C.1.3.1 Inhalation 3.C.1.3.2 Contact with Skin or Eyes 3.C.1.3.3 Ingestion 3.C.1.3.4 Injection 3.C.2 Types of Toxins 3.C.2.1 Irritants 3.C.2.2 Corrosive Substances 3.C.2.3 Allergens 3.C.2.4 Asphyxiants 3.C.2.5 Carcinogens 3.C.2.6 Reproductive and Developmental Toxins 3.C.2.7 Neurotoxins 3.C.2.8 Toxins Affecting Other Organs Dose-Resoonse Relationshins 3.C.3 `_ ~ Assessing Risks Due to the Toxic Effects of Laboratory Chemicals 3.C.3.1 Acute Toxicants 3.C.3.2 Corrosive Substances, Irritants, and Allergens 3.C.3.3 Carcinogens 3.C.3.4 Reproductive and Developmental Toxins 3.D FLAMMABLE, REACTIVE, AND EXPLOSIVE HAZARDS 3.D.1 Flammable Hazards 3.D.1.1 Flammable Substances 3.D.1.2 Flammability Characteristics 3.D.1.2.1 Flash Point 3.D.1.2.2 Ignition Temperature 3.D.1.2.3 Limits of Flammability 3.D.1.3 Classes of Flammability 29 Hazards and Risks in the Laboratory 31 31 31 31 33 33 33 34 35 35 35 35 35 36 36 37 37 38 38 39 39 39 39 40 40 40 40 40 41 41 41 43 43 44 46 46 46 46 46 48 48 49
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From page 30... ...
30 PRUDENT PRACTICES IN THE LABORATORY: HANDLING AND DISPOSAL OF CHEMICALS 3.D.1.4 Causes of Ignition 3.D.1.4.1 Spontaneous Combustion 3.D.1.4.2 Ignition Sources 3.D.1.4.3 Oxidants Other Than Oxygen 3.D.1.5 Special Hazards 3.D.2 Reactive Hazards 3.D.2.1 Water Reactives 3.D.2.2 Pyrophorics 3.D.2.3 Incompatible Chemicals 3.D.3 Explosive Hazards 3.D.3.1 Explosives 3.D.3.2 Peroxides 3.D.3.3 Other Oxidizers 3.D.3.4 Dusts 3.D.3.5 Explosive Boiling 3.D.3.6 Other Considerations 3.D.4 The Dirty Dozen 3.E PHYSICAL HAZARDS 3.E.1 3.E.2 Nonflammable Cryogens 3.E.3 High-Pressure Reactions 3.E.4 Vacuum Work 3.E.5 Ultraviolet, Visible, and Near-Infrared Radiation 3.E.6 Radiofrequency and Microwave Hazards 3.E.7 Electrical Hazards 3.E.8 Magnetic Fields 3.E.9 Cuts, Slips, Trips, and Falls 3.F BIOHAZARDS Compressed Gases 3.G HAZARDS FROM RADIOACTIVITY 50 50 50 50 51 51 51 51 51 54 54 54 55 56 56 56 57 57 57 57 57 57 58 59 59 59 60 60 60
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From page 31... ...
Section 3.B introduces the sources of information where laboratory workers can find data on toxic, flammable, reactive, and explosive chemical substances as well as physical, biological, and radioactive hazards. Section 3.C discusses the toxic effects of laboratory chemicals.
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From page 32... ...
and the OSHA Laboratory Standard (29 CFR 1910.1450) , the audience for MSDSs has been expanded to include laboratory workers in industrial and academic laboratories.
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From page 33... ...
LCSSs also include a concise critical discussion, presented in a style readily understandable to laboratory workers, of the toxicity, flammability, reactivity, and explosibility of the chemical; recommendations for the handling, storage, and disposal of the title substance; and first aid and emergency response procedures. Appendix B contains LCSSs for 88 chemical substances.
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From page 34... ...
4. Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices, 1994-1995, American Conference of Governmental Industrial Hygienists (ACGIH)
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3.C TOXIC EFFECTS OF LABORATORY CHEMICALS 3.C. 1 Basic Principles The chemicals encountered in the laboratory have a broad spectrum of physical, chemical, and toxicological properties and physiological effects.
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From page 36... ...
It is essential that all laboratory workers understand certain basic principles of toxicology and learn to recognize the major classes of toxic and corrosive chemicals. The next sections of this chapter summarize the key concepts involved in assessing the risks associated with the use of toxic chemicals in the laboratory.
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From page 37... ...
The time between exposure to a chemical and onset of toxic effects varies depending on the chemical and the exposure. For example, the toxic effects of carbon monoxide, sodium cyanide, and carbon disulfide are evident within minutes.
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Fortunately, the ventilation present in most laboratories prevents an equilibrium concentration from developing in the breathing zone of the laboratory worker. Even very low vapor pressure chemicals can be dangerous if the material is highly toxic.
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From page 39... ...
Corrosive effects can occur not only on the skin and eyes, but also in the respiratory tract and, in the case of ingestion, in the gastrointestinal tract as well. Corrosive materials are probably the most common toxic substances encountered in the laboratory.
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From page 40... ...
Strong dehydrating agents, such as phosphorus pentoxide and calcium oxide, have a powerful affinity for water and can cause serious burns upon contact with the skin. Finally, strong oxidizing agents, such as concentrated solutions of hydrogen peroxide, can also have serious corrosive effects and should never come into contact with the skin or eyes.
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From page 41... ...
The term "health hazard" includes chemicals which are carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotox~ns, nephrotox~ns, neurotox~ns, agents which act on the hematopoietic systems, and agents which damage the lungs, skin, eyes, or mucous membranes. The OSHA Laboratory Standard further requires that certain chemicals be identified as "particularly hazardous substances" and handled using special additional procedures.
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From page 42... ...
Because the greatest risk of exposure to many laboratory chemicals is by inhalation, it is essential that laboratory workers understand the use of exposure limits that have been established by agencies such as ACGIH TABLE 3.3 Examples of Compounds with a High Level of Acute Toxicity Acrolein Arsine Chlorine Diazomethane Diborane (gas) Hydrogen cyanide Hydrogen fluoride Methyl fluorosulfonate Nickel carbonyl Nitrogen dioxide Osmium tetroxide Ozone Phosgene Sodium azide Sodium cyanide (and other cyanide salts)
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From page 43... ...
However, the vast majority of the substances involved in research, especially in laboratories concerned primarily with the synthesis of novel compounds, have not been tested for carcinogenicity. Compounds that are known to pose the greatest carcinogenic hazard are referred to as "select carcinogens," and they constitute another category of substances that must be handled as "particularly hazardous substances" according to the OSHA Laboratory Standard.
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From page 44... ...
The determination of whether a suspected carcinogenic chemical must be treated as a "particularly hazardous substance" in the context of a particular laboratory use will be affected by the scale and circumstances associated with the intended experiment. The laboratory worker must decide whether the amount and frequency of use, as well as other circumstances, are such that additional precautions beyond the basic prudent practices of section 5.C are required.
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From page 45... ...
Many reproductive toxins are chronic toxins that cause damage after repeated or long-duration exposures with effects that become evident only after long latency peri45 oafs. Developmental toxins act during pregnancy and cause adverse effects on the fetus; these effects include embryo lethality (death of the fertilized egg, embryo, or fetus)
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From page 46... ...
In some cases it will be appropriate to handle these compounds as particularly hazardous substances using the special additional precautions outlined in section 5.D. 3.D FLAMMABLE, REACTIVE, AND EXPLOSIVE HAZARDS In addition to the hazards due to the toxic effects of chemicals, hazards due to flammability, explosibility, and reactivity need to be considered in risk assessment.
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From page 47... ...
If so, consider the total amount of the substance that will be used, the expected frequency of use, the chemical's routes of exposure, and the circumstances of its use in the proposed experiment. As discussed in this chapter, use this information to determine whether it is appropriate to apply the additional procedures for work with highly toxic substances and whether additional consultation with safety professionals is warranted [see Chapter 5, section 5.D}.
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From page 48... ...
However, with a flash point of - 18 °C and upper and lower flammable limits of 2.6% and 12.8% acetone in air, respectively (see Table 3.7) , it is clear that an acetone spill produces an extreme fire hazard.
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From page 49... ...
is a comprehensive listing of flammability data and ratings. The NFPA fire hazard ratings, flash points, boiling points, ignition temperatures, and flammability limits of a number of common laboratory chemicals are given
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In ammonium nitrate explosions, the ammonium cation is oxidized by the nitrate anion. These TABLE 3.8 Examples of Oxidants · Gases: fluorine, chlorine, ozone, nitrous oxide, steam, oxygen · Liquids: hydrogen peroxide, nitric acid, perchloric acid, bromine, sulfuric acid, water · Solids: nitrites, nitrates, perchlorates, peroxides, chromates, dichromates, picrates, permanganates, hypochlorites, bromates, iodates, chlorites, chlorates
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From page 51... ...
3.D.2.3 Incompatible Chemicals Accidental contact of incompatible substances could result in a serious explosion or the formation of substances that are highly toxic or flammable or both. Many laboratory workers question the necessity of following storage compatibility guidelines.
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From page 52... ...
Mercury, chlorine, calcium hypochlorite, iodine, bromine, hydrogen fluoride Acids, metal powders, flammable liquids, chlorates, nitrites, sulfur, finely divided organics, combustibles Nitric acid, hydrogen peroxide Ammonia, acetylene, butadiene, butane, other petroleum gases, sodium carbide, turpentine, benzene, finely divided metals Water Calcium hypochlorite, other oxidants Ammonium salts, acids, metal powders, sulfur, finely divided organics, combustibles Acetic acid, naphthalene, camphor, glycerol, turpentine, alcohol, other flammable liquids Ammonia, acetylene, butadiene, butane, other petroleum gases, hydrogen, sodium carbide, turpentine, benzene, finely divided metals Ammonia, methane, phosphine, hydrogen sulfide Acetylene, hydrogen peroxide Isolate from everything Hydrogen peroxide, nitric acid, any other oxidant Fluorine, chlorine, bromine, chromic acid, peroxides Nitric acid, alkalis Ammonia (aqueous or anhydrous) (continued on facing page)
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From page 53... ...
Ammonium nitrate and other ammonium salts Any oxidizable substance, such as ethanol, methanol, glacial acetic acid, acetic anhydride, benzaldehyde, carbon disulfide, glycerol, ethylene glycol, ethyl acetate, methyl acetate, furfural Chlorates, perchlorates, permanganates a produced in nitric acid-ethanol mixtures. SOURCE: Reproduced, by permission, from Hazards in the Chemical Laboratory, 4th edition, L
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From page 54... ...
. yamc Es, ~norgamc Nitrates, inorganic Nitrites, inorganic Water Acids Halogenated organic compounds | Halogenating agents Oxidizing agentsa Acids Heavy metals and their salts ~ Oxidizing agentsa J' Acids Strong bases Acids Reducing agentsa ~ Acids l Oxidizing agentsa Organic compounds Oxidizing agentsa Organic acyl halides ~ Bases Organic hydroxy and amino ~ compounds Organic anhydrides Bases Organic hydroxy and amino compounds Organic halogen compounds ~ Group IA and IIA metals | Aluminum Organic nitro compounds Strong bases Oxidizing agentsa Chlorates Chromates Chromium trioxide Dichromates Halogens Halogenating agents Hydrogen peroxide Nitric acid Nitrates Perchlorates Peroxides Permanganates Persulfates Reducing agentsa Sulfides, inorganic Reducing agentsa Ammonia, anhydrous and aqueous Carbon Metals Metal hydrides Nitrites Organic compounds Phosphorus Silicon Sulfur Oxidizing agentsa Arsenates Arsenites Phosphorus Selenites Selenates Tellurium salts and oxides Acids a The examples of oxidizing and reducing agents are illustrative of common laboratory chemicals; they are not intended to be exhaustive.
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From page 55... ...
Perchlorate salts can be explosive and should be treated as potentially hazardous compounds. For many years, sulfuric acid-dichromate mixtures were used to clean glassware (a sulfuric acid-peroxydisulfate solution is now recommended because disposal of chromate is a problem)
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From page 56... ...
slum permanganate with sulfuric acid and nitric acid with alcohols. 3.D.3.4 Dusts Suspensions of oxidizable particles (e.g., flour, coal dust, magnesium powder, zinc dust, carbon powder, and flowers of sulfur)
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From page 57... ...
It is important to use minimum amounts of these hazardous materials with adequate shielding and personal protection. A compound is apt to be explosive if its heat of formation is more than about 100 calories per gram (cal/g)
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From page 58... ...
Fires on quenching Fires on quenching Fires on quenching Fires on quenching Fires on removal from the inert atmosphere, especially if wet with organic solvent or when contacting combustible materials such as filter paper Exothermic reactions causing violent spills on scale-up due to inadequate provision for heat removal Dangerous peroxide concentration during distillation; explosion hazards, especially with ground glass joints Toxicity and role In forming nickel tetracarbonyl from steel gas lines and autoclaves Sensitivity to shock, sparks, and other forms of accidental detonation; sensitivity to heat, friction, impact, and light, as well as to strong oxidizing and reducing agents vacuum systems. Injury due to flying glass is not the only hazard in vacuum work.
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From page 59... ...
Some special concerns arise in laboratory settings. The insulation on wires can be eroded by corrosive chemicals, organic solvent vapors, or ozone (from ultraviolet lights, copying machines, and so forth)
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From page 60... ...
Wet floors around ice, dry ice, or liquid nitrogen dispensers can be slippery if the areas are not carpeted and if drops or small puddles are not wiped up as soon as they form. Attempts to retrieve 5-gallon bottles of distilled water, jars of bulk chemicals, and rarely used equipment stored on high shelves have often led to back injuries in laboratory environments.
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From page 61... ...
, defines dose equivalents as follows: for 61 x-ray, gamma ray, and electron radiations, Q x N = 1 and so 1 red = 1 rem; for neutrons or high-energy protons, Q x N = 10 and 1 rem = 0.1 red. Damage may occur directly as a result of the radiation interacting with a part of the cell or indirectly by the formation of toxic substances within the cell.
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