Chemical Safety

Chapter 2: Chemical Safety Principles and Concepts

2.1 Introduction

The hazards of chemicals vary widely and appropriate caution must always be used. Every chemical can be hazardous in certain circumstances. For example, even water can be a serious health hazard under certain conditions and when the proper personal protective equipment is not used (e.g. drowning). An understanding of the hazards of chemicals and how they enter the body can help those working with chemicals devise procedures to work with them safely.

This chapter presents information on the physical and health hazards associated with chemicals, factors affecting toxicity, routes of exposures, and general measures that can be taken to control chemical exposures.

2.2 Physical Hazards

The following terms are frequently used when describing the physical hazards associated with chemicals:

• Combustible liquid: Any liquid, or mixture with 1% or more of a liquid, with a flashpoint above 140° F but below 200° F.
• Compressed gas: A gas or gas mixture with an absolute pressure exceeding 40 p.s.i. at 70° F, or exceeding 104 p.s.i. at 130° F, or a liquid having a vapor pressure exceeding 40 p.s.i. at 100° F as determined by ASTM D-232-72, a standard of the American Society of Testing and Materials.
• Explosive: A chemical that causes a sudden, almost instantaneous release of gas, pressure, and heat when subjected to sudden shock, high temperature or pressure.

  Flammable:
  
  

  • Aerosol: A material that can produce a flame or flashback from a valve opening.
  • Gas: Any gas at ambient conditions that will cause a flammable mixture with air in concentrations of 13% or less.
  • Liquid: Any liquid, or mixture with 1% or more of a liquid, with a flash point below 141° F.
  • Solid: A material that is liable to cause fire through friction, contact with moisture, spontaneous reaction, or retained heat, or which can be readily ignited and burns with enough persistence or violence to cause a serious health hazard.

• Organic peroxides: An organic compound with a bivalent O-O structure, which may be considered a peroxide derivative with one or both of the hydrogen atoms replaced with an organic molecule. They present dangerous fire and explosion risks; many are strong oxidizers.
• Oxidizer: A chemical that initiates or supports combustion of other materials, causing fire by itself or by the release of oxygen or other gasses.
• Pyrophoric: A material that will ignite spontaneously in air at or below 130° F.
• Unstable: Any material, which will vigorously decompose, polymerize, condense, or will become self reactive when exposed to conditions of shock, pressure, or temperature.
• Water-reactive: A material which can react with water or steam to produce a gas which is either toxic or flammable.

2.3 Health Hazards

The following are health hazard classes as defined by the Occupational Safety and Health Administration:

• Carcinogen: A material which causes or potentially causes cancer according to the International Research on Cancer, or is listed as such in the National Toxicology Program Annual Report on Carcinogens http://ehis.niehs.nih.gov/roc/ .
• Corrosives: Chemicals that cause visible destruction of, or irreversible alterations in, living tissue by chemical action at the site of contact.
• Irritants: Chemicals which are not corrosive, but which cause reversible inflammatory effects on living tissue at the site of contact.
• Mutagen: A material that damages chromosomes.
• Sensitizer: A chemical, which will cause an allergic reaction in a substantial number of exposed people.
• Target organ effects:
  
  
  • Cutaneous hazards: damage the skin
  • Eye hazards: damage the eye
  • Hematopoetic toxins: damage the blood and/or blood forming organs
  • Hepatotoxic: damage the liver
  • Nephrotoxic: damage the kidneys
  • Neurotoxins: damage the nervous system
  • Pulmonary toxins: damage the lungs
  • Reproductive toxins: affect the fetus
• Teratogen: A material that causes birth defects
• Toxic: A chemical with an oral lethal dose of 50-500 mg/kg, a cutaneous lethal dose of 200-1000 mg/kg, or a lethal concentration in air of 200-2000 ppm.
• Highly toxic: A material with an oral lethal dose of <50 mg/kg, a cutaneous lethal dose of <200 mg/kg, or lethal concentration in air at <200 ppm.

2.4 Factors Affecting Toxicity

All chemicals are hazardous under some conditions. An understanding of the factors that affect toxicity is helpful in devising safe procedures to prevent hazardous exposures. Some of these factors are briefly discussed below:

• Dose: Perhaps the single most significant factor of concern is the amount of exposure to the chemical. An exposure to a large amount of the chemical is usually of more concern than exposure to a small amount. For most chemicals, there is a level of exposure below which no adverse effects are likely to be observed.
• Toxicity: Chemicals vary widely in how toxic (poisonous) they are. Exposure to small amounts of highly toxic chemicals can be a greater danger than exposure to large amounts of less toxic chemicals.
• Duration and frequency: One-time exposures that are of short duration are of less concern than multiple exposures of long duration, all other factors being equal. Thus, when there has been a chemical exposure, an important piece of information concerns duration and frequency.
• Synergistic effects: Many situations involve exposure to two or more chemicals at the same time. When this happens, it is possible that the combined exposures are more hazardous than what one might expect from simply adding the two effects together. While information to exposures to a single chemical is often available, good information on the possible toxic effects to chemical mixtures is often not available.
• Individual characteristics: Each person is unique. While there are many similarities in response to chemical exposures, responses may vary dramatically among individuals. For examples, males can react differently than females. Special concern is often given for women who are pregnant. Some individuals are allergic or hypersensitive to certain chemicals.
• Acute and chronic effects: Acute effects are those that show up immediately after a chemical exposure occurs. A good example of an acute effect is the spillage of acid on the skin--a chemical burn will occur immediately. Chronic effects are those that occur after a significant amount of time passes and usually are the result of multiple exposures over a period of time. Cancer is a typical example of a chronic effect because cancers caused by chemical exposures often do not show up until 20 or more years after the initial exposure.

2.5 Routes of Exposure

There are three major routes of entry for a chemical to enter the body: inhalation; direct contact (to skin and eyes); and ingestion. Injection is a fourth, though much less common, route of entry for chemicals. An understanding of these routes of entries enables one to develop procedures or controls to prevent hazardous exposures to chemicals.

• Inhalation hazards: Inhalation of chemicals is the most common route of entry a chemical can take to enter the body. Chemicals that could be inhaled include:
  
  
  • Gases
  • the vapors of volatile liquids
  • mists and sprays of both volatile and nonvolatile liquid substances
  • solid chemicals in the form of particles, fibers, and dusts
• Direct (skin/eye) contact hazards: Many chemicals (e.g. corrosives) can injure the skin directly, while others may cause irritation or an allergic reaction. In addition to causing local toxic effects, many chemicals may be absorbed through the skin and/or eyes in sufficient quantity to cause systemic effects. The main avenues by which chemicals enter the body through the skin are hair follicles, sebaceous glands, sweat glands, and cuts or abrasions of the skin. Direct contact effects and absorption of chemicals through the skin depend on a number of factors, including:
  
  
  • chemical concentration
  • chemical reactivity
  • the solubility of the chemical in fat and water
  • the condition of the skin
  • the duration of contact
• Ingestion hazards: Ingestion of chemicals is a less common route of entry into the body. However, persons using chemicals can easily ingest chemicals into the body via contaminated hands if they are not washed prior to eating, drinking, smoking, applying cosmetics, or sticking part of the hand or a writing tool that has become contaminated into the mouth.
• Injection hazards: This route is the least likely for chemical exposures. Accidental injection of chemicals through needles is unlikely. However, if needles are contaminated or contaminated glassware breaks, there is the possibility of injecting chemicals into the body. Injections can also occur through high pressure streams of liquids or gases.

2.6 Controlling Chemical Exposures

Using the information presented in the earlier sections of this chapter and knowing the specific hazards of the chemicals to be used, one can design procedures to minimize hazards. At no time should any campus employee be exposed to any chemical above the OSHA Permissible Exposure Limit (PEL) or Short Term Exposure Limit (STEL). These limits have been established by OSHA as protective of virtually all workers. You may request assistance from the Division of Research Safety ((217) 333-2755) in developing or reviewing procedures to control chemical exposures.

Control techniques fall into three broad classes in order of preference: engineering controls, administrative controls, and personal protective equipment.

• Engineering controls: Options for engineering controls are those that eliminate the hazard through methods such as changing the procedures or substituting less hazardous materials for more hazardous materials. Conducting work with hazardous chemicals in a fume hood or glove box, and providing secondary containment in the event of spills are examples of engineering controls.
• Administrative controls: Whereas engineering controls are controls that work passively once they are established, administrative controls require that workers take active steps. Examples of administrative controls are posting hazard signs on laboratory doors, minimizing exposure time when working with hazardous chemicals, restricting access to areas where hazardous chemicals are used, working with highly odorous chemicals during non-office hours, and adopting standard operating procedures like those listed in Chapter 3.
• Personal protective equipment: Personal protective equipment includes items such as gloves, eye protection, suitable clothing, and respirators. Because such equipment is the last line of defense against exposure to hazardous chemicals, these are the options last employed. Note that selection of appropriate personal protective equipment is not always straightforward. In the case of gloves, there are a wide variety of types depending on the specific application. Although some types of personal protective equipment may be suitable for a wide range of applications, each operation should be assessed individually.