Occupational exposure to hazardous chemicals in laboratories 1990 OSHA Laboratory Standard 29 CFR 1910.1450
The following description of a laboratory chemical hygiene plan corresponds with Section (e:1-4), Chemical hygiene plan-General, of the 1990 OSHA Laboratory Standard. This plan should be made readily available to employees and employee representatives.The chemical hygiene plan shall include each of the following elements and shall indicate specific measures that the employer will take to ensure laboratory employee protection:
- Stand operating procedures relevant to safety and health considerations to be followed when laboratory work involves the use of hazardous chemicals;
- Criteria that the employer will use to determine and implement control measures to reduce employee exposure to hazardous chemicals, including engineering controls, the use of personal protective equipment and hygiene practices; particular attention shall be given to the selection of control measures for chemicals that are known to be extremely hazardous;
- A requirement that fume hoods and other protective equipment are functioning properly, and specific measures that shall be taken to ensure proper and adequate performance of such equipment;
- Provisions for employee information and training as prescribed [elsewhere in this plan];
- The circumstances under which a particular laboratory operation, procedure or activity shall require prior approval from the employer or the employer’s designee before implementation;
- Provisions for medical consultation and medical examinations...;
- Designation of personnel responsible for implementation of the chemical hygiene plan, including the assignment of a chemical hygiene officer and, if appropriate, establishment of a chemical hygiene committee; and
- Provision for additional employee protection for work with particularly hazardous substances. These include “select carcinogens”, reproductive toxins and substances which have a high degree of acute toxicity. Specific consideration shall be given to the following provisions, which shall be included where appropriate:
(a) establishment of a designated area;
(b) use of containment devices such as fume hoods or glove boxes;
(c) procedures for safe removal of contaminated waste; and
(d) decontamination procedures.
The employer shall review and evaluate the effectiveness of the chemical hygiene plan at least annually and update it as necessary.
Setting up a Safe and Healthy Laboratory
A laboratory can only be safe and hygienic if the work practices and procedures that are followed there are safe and hygienic. Such practices are fostered by first giving responsibility and authority for laboratory safety and chemical hygiene to a laboratory safety officer who, together with a safety committee of laboratory personnel, decides what tasks must be accomplished and assigns responsibility for carrying out each of them.
The safety committee’s specific tasks include conducting periodic laboratory inspections and summarizing the results in a report submitted to the laboratory safety officer. These inspections are properly done with a checklist. Another important aspect of safety management is periodic inspections of safety equipment to ensure that all equipment is in good working order and in designated locations. Before this can be done, an annual inventory of all the safety equipment must be made; this includes a brief description, including size or capacity and manufacturer. Of no less importance is a semiannual inventory of all laboratory chemicals, including proprietary products. These should be classified into groups of chemically similar substances and also classified according to their fire hazard. Another essential safety classification depends on the degree of hazard associated with a substance, since the treatment a substance receives is directly related to the harm it can cause and the ease with which the harm is unleashed. Each chemical is put into one of three hazard classes chosen on the basis of grouping according to the order of magnitude of risk involved; they are:
- ordinary hazard substances
- high-hazard substances
- extremely hazardous materials.
Ordinary hazard substances are those that are relatively easily controlled, are familiar to laboratory personnel and present no unusual risk. This class ranges from innocuous substances such as sodium bicarbonate and sucrose to concentrated sulphuric acid, ethylene glycol and pentane.
High-hazard substances present much greater hazards than ordinary hazards. They require special handling or, sometimes, monitoring, and present high fire or explosion hazards or severe health risks. In this group are chemicals that form unstable explosive compounds on standing (e.g., hydroperoxides formed by ethers) or substances that have high acute toxicities (e.g., sodium fluoride, which has an oral toxicity of 57 mg/kg in mice), or that have chronic toxicities such as carcinogens, mutagens or teratogens. Substances in this group often have the same kind of hazard as those in the group that follows. The difference is one of degree—those in group 3, the extremely hazardous materials, have either a greater intensity of hazard, or their order of magnitude is much greater, or the dire effects can be released far more easily.
Extremely hazardous materials, when not handled correctly, can very readily cause a serious accident resulting in severe injury, loss of life or extensive property damage. Extreme caution must be exercised in dealing with these substances. Examples of this class are nickel tetracarbonyl (a volatile, extremely poisonous liquid, the vapours of which have been lethal in concentrations as low as 1 ppm) and triethylaluminium (a liquid that spontaneously ignites on exposure to air and reacts explosively with water).
One of the most important of the safety committee’s tasks is to write a comprehensive document for the laboratory, a laboratory safety and chemical hygiene plan, that fully describes its safety policy and standard procedures for carrying out laboratory operations and fulfilling regulatory obligations; these include guidelines for working with substances that may fall into any of the three hazard categories, inspecting safety equipment, responding to a chemical spill, chemical waste policy, standards for laboratory air quality and any recordkeeping required by regulatory standards. The laboratory safety and chemical hygiene plan must be kept in the laboratory or must be otherwise easily accessible to its workers. Other sources of printed information include: chemical information sheets (also called material safety data sheets, MSDSs), a laboratory safety manual, toxicological information and fire hazard information. The inventory of laboratory chemicals and three associated derivative lists (classification of chemicals according to chemical class, fire safety class and the three degrees of hazard) must also be kept with these data.
A file system for records of safety-related activities is also required. It is not necessary that this file either be in the laboratory or be immediately accessible to laboratory workers. The records are mainly for the use of laboratory personnel who oversee laboratory safety and chemical hygiene and for the perusal of regulatory agency inspectors. It should thus be easily available and kept up to date. It is advisable that the file be kept outside the laboratory in order to reduce the possibility of its destruction in the event of a fire. The documents on file should include: records of laboratory inspections by the safety committee, records of inspections by any local regulatory agencies including fire departments and state and federal agencies, records dealing with hazardous waste disposal, records of taxes levied on various classes of hazardous waste, where applicable, a second copy of the inventory of laboratory chemicals, and copies of other pertinent documents dealing with the facility and its personnel (e.g., records of attendance of personnel at annual laboratory safety sessions).
Causes of Illness and Injury in the Laboratory
Measures for the prevention of personal injury, illness and anxiety are an integral part of the plans for the day-to-day operation of a well-run laboratory. The people who are affected by unsafe and unhygienic conditions in a laboratory include not only those who work in that laboratory but also neighbouring personnel and those who provide mechanical and custodial services. Since personal injuries in laboratories stem largely from inappropriate contact between chemicals and people, inappropriate mixing of chemicals or inappropriate supply of energy to chemicals, protecting health entails preventing such undesirable interactions. This, in turn, means suitably confining chemicals, combining them properly and closely regulating the energy supplied to them. The main kinds of personal injury in the laboratory are poisoning, chemical burns and injury resulting from fires or explosions. Fires and explosions are a source of thermal burns, lacerations, concussions and other severe bodily harm.
Chemical attack on the body. Chemical attack takes place when poisons are absorbed into the body and interfere with its normal function through disturbance of metabolism or other mechanisms. Chemical burns, or the gross destruction of tissue, usually occur by contact with either strong acids or strong alkalis. Toxic materials that have entered the body by absorption through the skin, eyes or mucous membranes, by ingestion or by inhalation, can cause systemic poisoning, usually by being spread via the circulatory system.
Poisoning is of two general types—acute and chronic. Acute poisoning is characterized by ill effects appearing during or directly after a single exposure to a toxic substance. Chronic poisoning becomes evident only after the passage of time, which may take weeks, months, years or even decades. Chronic poisoning is said to occur when each of these conditions is met: the victim must have been subjected to multiple exposures over long periods of time and to metabolically significant amounts of a chronic poison.
Chemical burns, usually encountered when liquid corrosives are spilled or splashed on the skin or in the eyes, also occur when those tissues come in contact with corrosive solids, ranging in size from powdery dusts to fairly large crystals, or with corrosive liquids dispersed in the air as mists, or with such corrosive gases as hydrogen chloride. The bronchial tubes, lungs, tongue, throat and epiglottis can also be attacked by corrosive chemicals in either the gaseous, liquid or solid states. Toxic chemicals also, of course, may be introduced into the body in any of these three physical states, or in the form of dusts or mists.
Injury through fires or explosions. Both fires or explosions may produce thermal burns. Some of the injuries caused by explosions, however, are particularly characteristic of them; they are injuries engendered either by the concussive force of the detonation itself or by such of its effects as glass fragments hurled through the air, causing loss of fingers or limbs in the first case, or skin lacerations or loss of vision, in the second.
Laboratory injuries from other sources. A third class of injuries may be caused neither by chemical attack nor by combustion. Rather they are produced by a miscellany of all other sources—mechanical, electrical, high-energy light sources (ultraviolet and lasers), thermal burns from hot surfaces, sudden explosive shattering of screw-capped glass chemical containers from the unexpected build-up of high internal gas pressures and lacerations from the sharp, jagged edges of newly broken glass tubing. Among the most serious sources of injury of a mechanical origin are tall, high-pressure gas cylinders tipping over and falling to the floor. Such episodes can injure legs and feet; in addition, should the cylinder stem break during the fall, the gas cylinder, propelled by the rapid, massive, uncontrolled escape of gas, becomes a deadly, undirected missile, a potential source of greater, more widespread harm.
Safety sessions and information dissemination. Injury prevention, dependent on performance of laboratory operations in a safe and prudent manner, is, in turn, dependent on laboratory workers being trained in correct laboratory methodology. Although they have received some of this training in their undergraduate and graduate education, it must be supplemented and reinforced by periodic laboratory safety sessions. Such sessions, which should emphasize understanding the physical and biological bases of safe laboratory practice, will enable laboratory workers to reject questionable procedures easily and to select technically sound methods as a matter of course. The sessions should also acquaint laboratory personnel with the kinds of data needed to design safe procedures and with sources of such information.
Workers must also be provided with ready access, from their work stations, to pertinent safety and technical information. Such materials should include laboratory safety manuals, chemical information sheets and toxicological and fire hazard information.
Prevention of poisoning and chemical burns. Poisoning and chemical burns have a common feature—the same four sites of entry or attack: (1) skin, (2) eyes, (3) mouth to stomach to intestines and (4) nose to bronchial tubes to lungs. Prevention consists in making these sites inaccessible to poisonous or corrosive substances. This is done by placing one or more physical barriers between the person to be protected and the hazardous substance or by ensuring that the ambient laboratory air is not contaminated. Procedures that use these methods include working behind a safety shield or using a fume hood, or utilizing both methods. The use of a glove box, of course, of itself affords a twofold protection. Minimization of injury, should contamination of tissue occur, is accomplished by removing the toxic or corrosive contaminant as quickly and completely as possible.
Prevention of acute poisoning and chemical burns in contrast with the prevention of chronic poisoning. Although the basic approach of isolation of the hazardous substance from the person to be protected is the same in preventing acute poisoning, chemical burns and chronic poisoning, its application must be somewhat different in preventing chronic poisoning. Whereas acute poisoning and chemical burns may be likened to massive assault in warfare, chronic poisoning has the aspect of a siege. Usually produced by much lower concentrations, exerting their influence through multiple exposures over long periods of time, its effects surface gradually and insidiously through sustained and subtle action. Corrective action involves either first detecting a chemical capable of causing chronic poisoning before any physical symptoms appear, or recognizing one or more aspects of a laboratory worker’s discomfort as possibly being physical symptoms connected with chronic poisoning. Should chronic poisoning be suspected, medical attention must be sought promptly. When a chronic poison is found at a concentration exceeding the allowable level, or even approaching it, steps must be taken either to eliminate that substance or, at the very least, to reduce its concentration to a safe level. Protection against chronic poisoning often requires that protective equipment be used for all or much of the workday; however, for reasons of comfort, the use of a glove box or a self-contained breathing apparatus (SCBA) is not always feasible.
Protection against poisoning or chemical burns. Protection against contamination of the skin by a particular splashed corrosive liquid or scattered poisonous airborne solid is best done by the use of safety gloves and a laboratory apron made of a suitable natural or synthetic rubber or polymer. The term suitable here is taken to mean a material which is neither dissolved, swelled nor in any other way attacked by the substance against which it must afford protection, nor should it be permeable to the substance. The use of a safety shield on the laboratory bench interposed between apparatus in which chemicals are being heated, reacted or distilled and the experimenter is a further safeguard against chemical burns and poisoning via skin contamination. Since the speed with which a corrosive or a poison is washed from the skin is a critical factor in preventing or minimizing the damage these substances can inflict, a safety shower, conveniently located in the laboratory, is an indispensable piece of safety equipment.
The eyes are best protected from splashed liquids by safety goggles or face shields. Airborne contaminants, in addition to gases and vapours, include solids and liquids when they are present in a finely subdivided state as dusts or mists. These are most effectively kept out of the eyes by conducting operations in a fume hood or glove box, although goggles afford some protection against them. To afford additional protection while the hood is being used, goggles may be worn. The presence of easily accessible eyewash fountains in the laboratory will often eliminate, and certainly will, at least, reduce eye damage through contamination by splashed corrosives or poisons.
The mouth to stomach to intestines route is usually connected with poisoning rather than with attack by corrosives. When toxic materials are ingested, it usually happens unwittingly through the chemical contamination of foods or cosmetics. Sources of such contamination are food stored in refrigerators with chemicals, food and beverages consumed in the laboratory, or lipstick kept or applied in the laboratory. Prevention of this kind of poisoning is done by avoiding practices known to cause it; this is feasible only when refrigerators to be used exclusively for food, and dining space outside of the laboratory, are made available.
The nose to bronchial tubes to lungs route, or respiratory route, of poisoning and chemical burns deals exclusively with airborne substances, whether gases, vapours, dusts or mists. These airborne materials may be kept from the respiratory systems of people within and outside of the laboratory by the concurrent practices of: (1) confining operations that either use or produce them to the fume hood (2) adjusting the laboratory air supply so that the air is changed 10 to 12 times per hour and (3) keeping the laboratory air pressure negative with respect to that of the corridors and rooms around it. Fume- or dust-producing operations that involve very bulky pieces of apparatus or containers the size of a 218-l drum, which are too large to be enclosed by an ordinary fume hood, should be done in a walk-in hood. In general, respirators or SCBA should not be used for any laboratory operations other than those of an emergency nature.
Chronic mercury poisoning, produced by the inhalation of mercury vapours, is occasionally found in laboratories. It is encountered when a pool of mercury that has accumulated in a hidden location—under floorboards, in drawers or a closet—has been emitting vapours over a long enough period of time to affect the health of laboratory personnel. Good laboratory housekeeping will avert this problem. Should a hidden source of mercury be suspected, the laboratory air must be checked for mercury either by the use of a special detector designed for the purpose or by sending an air sample for analysis.
Preventing fires and explosions and extinguishing fires. The principal cause of laboratory fires is the accidental ignition of flammable liquids. Flammable liquid is defined, in the fire safety sense, as being a liquid having a flashpoint of less than 36.7 °C. Ignition sources known to have caused this kind of laboratory fire include open flames, hot surfaces, electric sparks from switches and motors found in such equipment as stirrers, household-type refrigerators and electric fans, and sparks produced by static electricity. When ignition of a flammable liquid occurs, it takes place, not in the liquid itself, but above it, in the mixture of its vapours with air (when the concentration of vapour falls between certain upper and lower limits).
Preventing laboratory fires is accomplished by confining the vapours of flammables completely within the containers in which the liquids are kept or the apparatus in which they are used. If it is not possible to contain these vapours completely, their rate of escape should be made as low as possible and a continuous vigorous flow of air should be supplied to sweep them away, so as to keep their concentration at any given time well below the lower critical concentration limit. This is done both when reactions involving a flammable liquid are run in a fume hood and when drums of flammables are stored in safety solvent cabinets vented to an exhaust.
A particularly unsafe practice is the storage of such flammables as ethanol in a household-type refrigerator. These refrigerators will not keep vapours of stored flammable liquids from the sparks of its switches, motors and relays. No containers of flammables must ever be put in this type of refrigerator. This is especially true of open vessels and trays containing flammable liquids. However, even flammables in screw-capped bottles, kept in this type of refrigerator, have caused explosions, presumably by vapours leaking through a faulty seal or by the bottles breaking. Flammable liquids that require refrigeration must be kept only in explosion-proof refrigerators.
A significant source of fires that occur when large quantities of flammables are poured or siphoned from one drum to another is sparks produced through the accumulation of electric charge produced by a moving fluid. Spark generation of this sort can be prevented by electrically grounding both drums.
Most chemical and solvent fires that occur in the laboratory and are of manageable size, may be extinguished with either a carbon dioxide or dry-chemical type fire extinguisher. One or more 4.5 kg extinguishers of either kind should be supplied to a laboratory, according to its size. Certain special types of fires require other kinds of extinguishing agents. Many metal fires are put out with sand or graphite. Burning metal hydrides require graphite or powdered limestone.
When clothing is set afire in the laboratory, the flames must be put out quickly to minimize the injury caused by thermal burns. A wall-mounted wrap-around fire blanket extinguishes such fires effectively. It may be used for unassisted smothering of flames by the person whose clothing is on fire. Safety showers may also be used to extinguish these fires.
There are limits to the total volumes of flammable liquids that may be safely kept in a particular laboratory. Such limits, generally written into local fire codes, vary and depend on the materials of construction of the laboratory and on whether it is equipped with an automatic fire-extinguishing system. They usually range from about 55 to 135 litres.
Natural gas is often available from numbers of valves located throughout a typical laboratory. These are the most common sources of gas leaks, along with the rubber tubes and burners leading from them. Such leaks, when not detected soon after their onset, have led to severe explosions. Gas detectors, designed to indicate the level of gas concentration in the air, may be used to locate the source of such leakage quickly.
Prevention of injury from miscellaneous sources. Harm from tall, high-pressure gas cylinders falling, among the most familiar in this group of accidents, is avoided easily by strapping or chaining these cylinders securely to a wall or laboratory bench and putting cylinder caps on all unused and empty cylinders.
Most of the injuries from jagged edges of broken glass tubing are sustained through breakage while the tubing is being put into corks or rubber stoppers. They are avoided by lubricating the tube with glycerol and protecting the hands with leather work gloves.
Appendix A to 1910.1450—National Research Council recommendations concerning chemical hygiene in laboratories (non-mandatory)
The following guidelines concerning proper laboratory ventilation correspond with the information provided in Section C. The Laboratory Facility; 4. Ventilation - (a) General laboratory ventilation, Appendix A of the 1990 OSHA Laboratory Standard, 29 CFR 1910.1450.Ventilation
(a) General laboratory ventilation. This system should: Provide a source of air for breathing and for input to local ventilation devices; it should not be relied on for protection from toxic substances released into the laboratory; ensure that laboratory air is continually replaced, preventing increase of air concentrations of toxic substances during the working day; direct air flow into the laboratory from non-laboratory areas and out to the exterior of the building.
(b) Hoods. A laboratory hood with 2.5 linear feet (76 cm) of hood space per person should be provided for every 2 workers if they spend most of their time working with chemicals; each hood should have a continuous monitoring device to allow convenient confirmation of adequate hood performance before use. If this is not possible, work with substances of unknown toxicity should be avoided or other types of local ventilation devices should be provided.
(c) Other local ventilation devices. Ventilated storage cabinets, canopy hoods, snorkels, etc. should be provided as needed. Each canopy hood and snorkel should have a separate exhaust duct.
(d) Special ventilation areas. Exhaust air from glove boxes and isolation rooms should be passed through scrubbers or other treatment before release into the regular exhaust system. Cold rooms and warm rooms should have provisions for rapid escape and for escape in the event of electrical failure.
(e) Modifications. Any alteration of the ventilation system should be made only if thorough testing indicates that worker protection from airborne toxic substances will continue to be adequate.
(f) Performance. Rate: 4-12 room air changes/hour is normally adequate general ventilation if local exhaust systems such as hoods are used as the primary method of control.
(g) Quality. General air flow should not be turbulent and should be relatively uniform throughout the laboratory, with no high velocity or static areas; airflow into and within the hood should not be excessively turbulent; hood face velocity should be adequate (typically 60-100 lf/min) (152-254 cm/min).
(h) Evaluation. Quality and quantity of ventilation should be evaluated on installation, regularly monitored (at least every 3 months), and reevaluated whenever a change in local ventilation is made.
Incompatible materials are a pair of substances that, on contact or mixing, produce either a harmful or potentially harmful effect. The two members of an incompatible pair may be either a pair of chemicals or a chemical and a material of construction such as wood or steel. The mixing or contact of two incompatible materials leads either to a chemical reaction or to a physical interaction that generates a large amount of energy. Specific harmful or potentially harmful effects of these combinations, which can ultimately lead to serious injury or damage to the health, include liberation of large amounts of heat, fires, explosions, production of a flammable gas or generation of a toxic gas. Since a fairly extensive variety of substances is usually found in laboratories, the occurrence of incompatibles in them is quite common and presents a threat to life and health if they are not handled correctly.
Incompatible materials are seldom mixed intentionally. Most often, their mixing is the result of a simultaneous accidental breaking of two adjacent containers. Sometimes it is the effect of leakage or dripping, or results from the mixing of gases or vapours from nearby bottles. Although in many cases in which a pair of incompatibles is mixed, the harmful effect is easily observed, in at least one instance, a not readily detectable chronic poison is formed. This occurs as the result of the reaction of formaldehyde gas from 37% formalin with hydrogen chloride that has escaped from concentrated hydrochloric acid to form the potent carcinogen bis(chloromethyl) ether. Other instances of not immediately detectable effects are the generation of odourless, flammable gases.
Keeping incompatibles from mixing through the simultaneous breaking of adjacent containers or through escape of vapours from nearby bottles is simple—the containers are moved far apart. The incompatible pair, however, must first be identified; not all such identifications are simple or obvious. To minimize the possibility of overlooking an incompatible pair, a compendium of incompatibles should be consulted and scanned occasionally to acquire an acquaintance with less familiar examples. Preventing a chemical from coming in contact with incompatible shelving material, through dripping or through a bottle breaking, is done by keeping the bottle in a glass tray of sufficient capacity to hold all of its contents.