in the Chemical Laboratory Edited by NORMAN V. STEERE, 140 Melbourne Ave., S1E. Minneopolir, Minn. 554 14
XCXII. Identifying Multiple Causes of Laboratory Accidents and lniuries-Part 2 Norman V. Steere, CSP. Safety Consultanf. 140 Melbourne Ave., S. E. Minneapolis, Minn. 55414
In the first part of this article we stated the premise that there is a lack of eomprehensive data on causation of laboratory accidents and injuries, suggested some reasons for the lack, and outlined some of the limitations of accident reporting systems. In this part we will describe a model for analyzing causal factors, a classification of injury-causing energy exchanges, and a hierarchy of countermeasures for preventing or limiting accidents and injuries.
CONCEPTUAL MODEL FOR ANALYSIS OF CAUSAL FACTORS A broad system for analysis of accident and injury factors was proposed in 1949 by John Gordon, a physician who compared injury prevention to disease prevention (9). For disease transmission there must be three factors-a susceptible host, a disease agent, and a reservoir of infection. Similarly, for injuries t a occur there must be a susceptible host, an injury agent, and an environment. Gordon argued that injury prevention could be based an the same approach that had been effective for disease prevention: systematic study of all factors and the interactions between them. with control measures directed a t one or more of the factors. In 1961 James Gibson, a n experimental psyehalogist, described same significant human (host) factors to be considered. and proposed a classification of dangers which serves as an excellent basis for description of injury (agent) forces. Considering injuries to be produced only by interchange of energy, Gibson proposed classifying sources of injury by the forms of physical energy involved-chemical, electrical, thermal, radiant, and mechanical (10). Delivery of energy in amounts greater than the injury threshold of the body or part of the body will cause injuries, hut injuries can also be caused by factors which interfere w ~ t hnormal energy exchange within the body. Haddon suggested that mjuries caused by excess energy delivery be grouped in one class, and those caused by interference with energy ex-
change in another (11). The second group af injuries included physiological impairment and tissue or whole-body death caused by interference with body thermoregulation (frostbite, death by freezing) or oxygen utilization (vascular accidents, drowning, suffocation. CO and HCN poisoning). For the purpose of evaluating laboratory hazards and injury causes, we have added the hazard of biologieal-microbiological interferences with physiological systems, subdivided radiant energy into ionizing and nan-ionizing, and grouped thermal energy into fire hazards and nan-fire hazards. In this classification, chemical hazards include excess energy delivery and interference with energy exchange, including CO and HCN effects on oxygen utilization. Nan-fire thermal energy hazards include excess energy delivery and excess enerm removal. Fire hazards include excess energy delivery, chemical energy effects of toxic fire gases, and any interference with oxygen utilization. The model we propose for classifying laboratory hazards in terms of energy delivery or interference with energy exchange is shown in Figure 1. Far comparison with the "American Recommended Practice far Compiling Industrial Accident Causes," American Standard No. Z 16.2-1941, referred to in the first part of this article (with the incorrect title cited in ( 5 ) ) , the model lists examples of accident types and hazardous conditions. Some types of laboratories in which hazards may he present are also listed. (See Figure 1.) For analysis of possible causes of laboratory accidents and injuries we recommend a nine-cell matrix in which host, agent, and environment are evaluated before. during, and after the energy transfer or in: terference. This type of matrix was developed far traffic safety programs by Haddon and revised by Waller for research on falls and home safety (12). In the matrix of Figure 2, the Host will usually he the injured person, but a damaged structure or object could be considered the Host if the matrix is used for analysis of non-injury events. The Agent
...a
WID
feature
will be the injury or damage foree-the excess energy transfer or interference with energy exchange. Use of this matrix will be illustrated after a discussion of control measures.
CONTROL MEASURES TO PREVENT OR LIMIT LABORATORY ACCIDENTS AND INJURIES Laboratory accidents and injuries can be prevented by measures which control the transfer of excess energy, or which prevent interference with energy exchange in physiological systems. Table 1 lists four categories of such control measures, with specific examples for use in laboratories. Table 1 also lists examples in three categories of control measures to limit damage when laboratory accidents and injuries are not prevented. Development of specific control measures for the particular problems of s laboratory or a laboratory complex will require thorough analysis of the hazards present and study of possible control measures in detail. The more difficult part of the problem will be the evaluation of the cost and effectiveness of various control measures, and the technical, administrative and training measures necessary t o provide the control measures selected. The seven categories of control measures in Table 1 are based on those proposed by Haddon lor control of injuries (11). This author invites suggestions for other control measures which may be useful. It is important that the effect of control measures be evaluated before they are implemented, and regularly thereafter. Same efforts a t control measures may be found t o be ineffective because the original eanditions change, or because the measure was not well chosen. Some preventive measures may in fact contribute to causingother accidents. Consider the U.S.A. Standard Practice for Occupational and Educational Eye and Face Protection. Haw much scientific evaluation was made originally and since adaption of the standard in September, 1968? What is the evidence to support a statement that the recommended and preferred eye protection for laboratory operations consists of "flexible-fitti~tg goggles with hooded ventilation"? It is difficult to be^ lieve that such eve ~rotectionis necessarv for all laboratory operations. or that such eye protection is sufficient for every situa-
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(Continued onpngeA288J Volume 50,Number 5, M a y 1973 / A287
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tion. While we strongly suppart adequate eye protection, more research and reports of laboratory experience are needed. Emphasis on the ided'.for safety research is expressed by Haddon, Suchman and Klein " . . . the introduction and enforcement of insufficiently evaluated measures may lead t o a n inappropriate choice of emphasis and may, as a result, dissipate funds, time, and public concern that might be applied to more effective measures." (1) This point should be kept in mind as various standards for laboratory safety are developed, and should underline the need for thorough evaluation of laboratory accident and injury causes. Figure 3 illustrates same accident and injury factors and some control measures in the appropriate cells of the matrix described in Figure 2. Figure 3 does not in-
elude all of the factors that should be eonsidered in evaluation of a'ecidents or injuries. Use of the model described in Figures 2 and 3 may be made either before or after occurrence of a damaging event.
FACTORS TO BE CONSIDERED IN A LABORATORY FIRE To see how the model may be used after a damaging event: we have selected some of the factors which should be considered for investigating a serious laboratory fire which started in ethyl ether.
Host Factors Knowledge of the flammability of the material? Low temperature flash point, high vapor pressure, low ignition temperature, wide flammable range
Knowledge of conditions under which peroxides develop and concentrate? Tests of peroxides? Knowledge of methods of removal? Knowledge of shock sensitivity? Disposal methods? .Knowledge of safe procedures for solvent transfer? Procedures written? Ventilation, ignition control, bonding and grounding Knowledge of fire extinguisher locations, type needed, methods of actuation and operation, effective range and duration, effectiveness of extinguisher, extinguishing capacity? Knowledge of what t o do if clothing catches fire? (14) Knowledge of the importance of leaving area filled with smoke? (14) Knowledge of how to report the fire, alert occupants, and summon Fire Dept.? Were the dangers perceived? (10) Was there enough light for visibility? Was there any defect in the sense organs?
Figure 1. Model of System for Classifying Laboratory Hazards Hazards 1. Mechanical
2. Electrical 3. Ionizing
Energy Delivery or Interference Mechanical energy delivered in excess of injury threshold
Electrical energy delivered in excess of injury threshold Ionizing radiation delivered in excess of injury threshold
4. Non-Ionizing
Non-ionizing radiation delivered in excess of injury threshold
5. Biologics1 & Microbiological
Interference with energy exchange in physiological systems
Interference with energy exchangeoxygen utilization Interference with energy exchangeoxygen utilization Thermal energy delivered or removed in excess of injury threshold Interference with body thermoregulation
9. Fire
Falls on same level Falls to different level Cauaht in Struck by falling object flying object Struck against sharp object Contact with electric current Overexposure, absoiption, inhalation, or inzestion Overexposure
Inhalation, ingestion, or absorption, or contact Contact, inhalation, absorption, or ingestion
6. Chemical
7. Atmospheric pressure differentials 8. Thermalnon-fire
Accident Type (Examples)
Inhalation of excess carbon monoxide Exposure for too long 01too extreme conditions Contact with temperature extremes
Hazardous Conditions (Examples) Working surface hazard .item and plathrms I'nguardcd pump belts
Unsafe design Unsafe design or construction, unguarded conductor, defective device Improperly guarded X-ray device, misuse of isotopes, containment failure, imnroner ventilation
Inadequate guardin:, unrafe deilan. mxlequatrlg I;~l,cledmmtamcr.. imprqwr\mlilar!on I'nvafe wntarncr, unlahcled rmt;untr. madequate label. monmer ventllarwn. lack of boieetive equipment . . Improper ventilation, or improper design
A288 /Journal of Chemical Education
Almost every laboratory Laboratories using X-ray equipment, radioisotopes, high-energy accelerator, or hieh - voltaee - eauioment . . Laser laboratories Microwave laboratories
Laboratories in whieh carbon monoxide is used or produced
Environmental hazard eg. oxygen deficiency or oxmen excess, etc. ~lclaboratoriesusing Bunsen burners, hot plates, heating mantles or baths, steam, etc. All laboratories using compressed or cryogenic fluids, or refrigeration
Improper dress Improper ventilation
Thermal energy delivered in excess of iniurv threshold toxic fire ga& Interference with body thermaregulation Interference with energy exchangeoxygen utilization
Every laboratory
llazardour arrangement Inadequate x u a r d m ~unsnie , deitgn, deitct~\ecquqxnent
material by unsafe or unguarded container Exposure to temperature extremes
Laboratories with Hazards (Examplesof potentialexposures)
I n d e q u a t e means of egress Fire hazard unguarded by adequate extinguishing equipment or systems
All laboratories with any paper, books, wooden furniture, combustible construction or contents, or combustible or flammable chemicals
Figure 2. Matrix for Analysis of Factors in
Laboratory Injuries and Accidents
Was the physiological condition appropriate to the task? Was there erosion of individual spare capacity? (12)
Agent Factors Was there a precautionary label on the container? Adequate information? Legible? Was material of container appropriate to conditions of use? Was the size of the container appropriate to the conditions of use?
Agent
Was there any impairment of the sensory system, as from stroke, perceptual disability, or other? Was there any temporary incapacity? (as from illness, medicine, or other ingested materials) Was there a lack of previous training to discriminate the dangers? Was there misdirected attention? Was the reaction to the emergency inappropriate or ineffective? (11)
Environment Factors Ventilation; Ignition control; Spill control equipment Lighting; Fire extinguishers; Rescue equipment Fire-resistant storage for other flammable liquids
Table 1. Measures to Prevent or Limit Laboratory Accidents and Injuries 1. Prevent Aeeumulation of Hazardous Amounts of Energy Pressure limits Ignition source contra1 Noise limits (eg. "intrinsically safe" Chemical quantity limits electrical equipment Temperature limits far hazardous atmospheres) Speed limits Radiation limits (quantity or intensity) Chemical concentration limits Combustible loading limits Ventilation Voltage limits 2. Prevent or Modify Release of Energy Safety valves Rupture discs Engineering design Electrical fuses Containment vessels Elevator cable inspection Safety belts Padded dashboards Emergency brakes Bottle carriers Explosion suppression Explosion relief Inerting Automatic fire extinguishing systems 3. Provide Time or Space Separation Between Energy a n d Damageable Structure Aircraft flight control Guards on vacuum pump belts and other rotating machinery Radiation exposure limits Fire & smoke detection systems Fire alarm systems Fire and evacuation drills Proximity limits Gas and vapor monitoring systems Exposure time limits Remote handling devices 4. Provide Barrier to Bloek or Attenuate Energy Transfer Safety glasses Face shields Chemical splash goggles Bench shields Safety helmets Safety shoes Electrical insulation Thermal insulation Protective gloves Protective clothing Self-contained breathing Radiation shielding apparatus Heat-reflective clothing Sound absorbing material Fire-resistant construction Filters Energy-absorbing walls Blast mats Blast-resisting walls Ear orotectors 5. Raise Damage Threshold to Prevent or Reduce Damage Strengthen design Physical conditioning Fire~resistantconstruction Develop tolerance to exposures of certain chemicals Immunization Acclimatization 6. Provide Optimum Emergency Response First aid training Cardiopulmonary resuscitation training Ambulance service Decontamination supplies & procedures Phone or radio to call help Decompression chamber Emergency water sources Spill control equipment & procedures Organized, equipped, trained and practiced emergency squad High-quality emergency care facilities provided with poison control information and any special antidotes or treatment facilities that may be needed for emergencies that can be anticipated 7. Provide Services t o Reduce Damage Results Repair services, temporary utilities and other measures to restore buildings and equipment to ~.~~ f i r l l use ... Clinical, corrective and rehabilitative services necessary to restore injured persons (11) ~~~~
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Fiaure 3. Some Factors to Be Considered For Prevention or Post-Event Investigation of Laboratory Accidents & lniuries
Emergency .hutoil runtrols prm Kled & ~ ~ c ~ ~ s , l h I
