All chemicals and the manner in which they are intended to be used must be scrutinized by the user to identify potential hazards before acquiring the materials or conducting a procedure. Once, the hazards have been identified, commensurate hazard controls and emergency equipment must be planned and acquired or developed to adequately control the hazards to a negligible risk level and to respond to any emergencies which may arise. The following text provide chemical users with a basic knowledge and the resources to accomplish these necessary goals.
1.1) Introduction: There is a preferred way to perform all work with chemicals which can both reduce the probability of an accident or exposure to a negligible level and reduce it the potential consequences should one occur. Before using a chemical, a person should ask "What would happen if…?" Answers to this question will first require an understanding of the hazards associated with the chemical. This information will mainly dictate the precautions to be taken. Few chemicals are without hazards of various kinds and degrees. The following text is a summary of the potential hazardous properties chemicals may possess and users must be aware of and protect against.
1.2) What is a Hazardous Chemical? The Occupational Safety and Health Administration (OSHA) defines a hazardous chemical as any chemical which is a physical hazard or a health hazard. Physical hazard means a chemical for which there is evidence that it is a combustible liquid, a compressed gas, explosive, flammable, an organic peroxide, an oxidizer, pyrophoric, unstable (reactive), or water-reactive. Health hazard means a chemical for which there is evidence that acute (immediate) or chronic (delayed) health effects may occur in over-exposed people. Exposure being related to the dose (how much), the duration and frequency of exposure (how long and how often), and the route of exposure (how and where the material gets in or on the body), whether it be absorption through: the respiratory tract (inhalation); the skin; the digestive tract (ingestion), and/or percutaneous injection through the skin (e.g. accidental needle stick). These health effects can be: transient, persistent, or cumulative, local (at the sight of initial contact with the substance) and/or systemic (after absorption, distribution, and possible biotransformation, at a site distant from initial contact with the substance). The term health hazard includes chemicals which are carcinogens, toxic or highly toxic, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents which act on the hematopoietic system, and agents which damage the lungs, skin, eyes, or mucous membranes (see detailed descriptions of the individual physical and health hazards).
1.3) Defining the Hazards Associated with Chemicals: Although safety hazards related to the physical characteristics of a chemical can be objectively defined in terms of testing requirements (e.g. flammability), health hazards definitions are less precise and more subjective. Physical hazards may manifest as fires, explosions, excessive temperatures, or the release of large volumes of gas or toxic or flammable gases or vapors. Health hazards, depending on the exposure, may cause measurable changes in the body, such as decreased pulmonary (lung) function. These changes are generally indicated by the occurrence of signs and symptoms in the over-exposed person, such as shortness of breath, a non-measurable, subjective feeling.
The determination of occupational health hazards is complicated by the fact that many of the effects or signs and symptoms occur commonly in non-occupationally exposed populations, so that effects of exposure are difficult to separate from normally occurring illnesses. Occasionally, a substance causes an effect that is rarely seen in the population at large, such as angiosarcomas (a rare cancer), caused by vinyl chloride exposure, thus making it easier to ascertain that the occupational exposure was the primary causative factor. More often, however, the effects are common, such as lung cancer. The situation is further complicated by the fact that most chemicals have not been adequately tested to determine their health hazard potential, and data does not exist to substantiate these effects. In addition, not all people are affected to the same degree by the same chemical. Each has different levels of susceptibility depending on a variety of factors including: age, inherited characteristics (relating to body chemistry and metabolism), weight, general health, and so forth.
There have been many attempts to categorize health effects and to define them in various ways. Generally, the terms "acute" and "chronic" are used to delineate between effects on the basis of severity or duration. "Acute" effects usually occur rapidly as a result of short-term exposures, and may be of short duration. "Chronic" effects generally occur as a result of long-term exposure, and may be of long duration.
The acute effects referred to most often are irritation, corrosion, sensitization, and death. Although these are important health effects, they do not adequately cover the considerable range of acute effects which may occur as a result of occupational chemical exposure, such as, for example, narcosis (light headedness).
Similarly, the term chronic effects is often used to cover only carcinogenesis (cancer), teratogenesis, (effects on the unborn) and mutagenesis (chromosomal damage). These effects are obviously a concern in the workplace, but again, do not adequately cover the area of chronic effects, including, for example, blood dyscrasias (such as anemia), chronic bronchitis and liver atrophy.
1.4) The Importance of Understanding & Controlling Chemical Hazards: The goal of defining precisely, in measurable terms, every possible health effect that may occur in the workplace as a result of chemical exposures cannot realistically be accomplished. This does not negate the need for chemical users to know about the possible health effects as well as the physical hazards of the hazardous chemicals they use, and to protect themselves from these effects and hazards (see Section 1 – Chemical Hazard Overview). Controlling possible hazards may require the application of engineering hazard controls (substitution, minimization, isolation, ventilation) supplemented by administrative hazard controls (planning, information and training, written policies and procedures, safe work practices, and environmental and medical surveillance). Personal protective equipment (e.g. gloves, goggles, coats, respirators) may need to be considered if engineering and administrative controls are not technically, operationally, or financially feasible. Typically, combinations of all three will be necessary to control the hazards (see Section 2 – Principles for Controlling Hazards).
1.5) Much To Consider: It should also be kept in mind that the risks associated with the possession and use of a hazardous chemical are dependent upon a multitude of factors, all of which must be considered before acquiring and using a hazardous chemical. Important elements to examine and address include: the knowledge of and commitment to safe chemical use practices of all who handle the chemical; its physical, chemical, and biological properties and those of its derivatives; the quantity received and the manner in which it is stored and distributed; the manner in which it is used; the manner of disposal of the substance and its derivatives; the length of time it is on the premises, and the number of persons who work in the area and have open access to the substance. The decision to procure a specific quantity of a specific hazardous chemical is a commitment to handle it responsibly from receipt to ultimate disposal. Each operation in which it is handled and each period between operations presents opportunities for misadventure.
"Compressed gas" means: a gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 70oF (21.1oC); a gas or mixture of gases having, in a container, an absolute pressure exceeding 104 psi at 130oF (54.4oC) regardless of the pressure at 70oF, or a liquid having a vapor pressure exceeding 40 psi at 100oF (37.8oC).
"Organic peroxide" means an organic compound that contains the bivalent -O-O- structure and which may be considered to be a structural derivative of hydrogen peroxide where one or both of the hydrogen atoms has been replaced by an organic radical. Organic peroxides are oxidizers and fuels in one, and are therefore unstable and potentially explosive. "Peroxidizable" means a chemical which will form organic peroxides when exposed to air.
"Unstable (reactive)" means a chemical which in the pure state, or as produced or transported, will vigorously polymerize, decompose, condense, or will become self-reactive under conditions of shocks, pressure, or temperature.
"Carcinogens" are chemicals which cause cancer. "Select carcinogens" include those which: are regulated by OSHA as carcinogens (20 CFR 1910); are listed under the category, "known to be carcinogens," (PDF format) in the Annual Report on Carcinogens published by the National Toxicology Program, or are listed under group 1 ("carcinogenic to humans") by the International Agency for Research on Cancer Monographs.
Target organ effects. The following is a target organ categorization of effects which may occur, including examples of signs and symptoms and chemicals which have been found to cause such effects. These examples are presented to illustrate the range and diversity of effects and hazards found in the workplace, and the broad scope employees must consider in this area. The examples are not intended to be all inclusive.
"Toxic" All chemicals are considered toxic, or capable of producing injury to some degree, should they gain access into the body in sufficient concentration (see the toxicity rating chart shown below). To say that all chemicals which are toxic are hazardous, would be including all materials. Therefore, to narrow the definition of "toxic," the Occupational Safety and Health Administration defines "toxic" as chemicals which have an average lethal dose (LD50) or lethal concentration (LC50, indicates average lethal inhalation exposure) of: