Technologies for Controlling Work-Related Illness

Technologies for ControllingWork-Related Illness

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ContentsPage

Control Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Control at the Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Controlling Dispersion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Control at the Worker.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Integration of Health Hazard Controls into Workplace Management . . . . . . . 85

Case Study: Controlling Worker Exposure to Cotton Dust . . . . . . . . . . . . . . . . . . 85Byssinosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85The OSHA Cotton Dust Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Changes in Cotton Dust Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Costs of Compliance with the Cotton Dust Standard . . . . . . . . . . . . . . . . . . . . . 88

Case Study: Controlling Worker Exposure to Silica Dust. . . . . . . . . . . . . . . . . . . . 89R,gulatory Activities for Silicosis Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Control Technologies: Engineering Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Control Technologies: Personal Protection and Administrative Controls . . . . 91Strategies for Silica Dust Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Case Study: Controlling Worker Exposure to Lead . . . . . . . . . . . . . . . . . . . . . . . . . 92Some Features of the OSHA Lead Standard .......,. . . . . . . . . . . . . . . . . . . . 9 2Control Methods: Engineering and Respirators. . . . . . . . . . . . . . . . . . . . . . . . . . . 93Medical Removal Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Changes in Air Lead Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Changes in Blood Lead Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Summary of Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Extent of Control Technology Usage in the United States . . . . . . . . . . . . . . . . . . . 97Information About Controls and Areas for Research . . . . . . . . . . . . . . . . . . . . 97

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

LIST OF TABLESTable No. Page5-1,5-2,

5-3.5-4.

5-5.

5-6.5-7.

5-8.

5-9.5-10.

5-11.

Principles of Controlling the Occupational Environment . . . . . . . . . . . . . . . 80Benefits of New Technologies for Controlling Worker Exposure toVinyl Chloride Monomer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Suggested and Recommended Levels for Cotton Dust Exposure . . . . . . . . . 88Cotton Dust Measurements Before Promulgation of the OSHACotton Dust Standard and Percentage of Companies Claiming Compliancewith the Standard in North Carolina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Estimated and Realized Costs of Compliance with the OSHACotton Dust Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Measures To Reduce Air Lead and Blood Lead Levels . . . . . . . . . . . . . . . . . 93Blood Lead Levels That Trigger Medical Removal From and Return toLead-Contaminated Atmospheres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Medical Removal Protection Transfers in a Sample ofLead Industry Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Reductions in Average Air Lead Levels, 1977-78 and 1981-82. . . . . . . . . . . 95Average Blood Levels Before and After Promulgation of the OSHALead Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Projected Industry-Wide Annual Costs of Compliance With Air LeadLevels of 50 to 150 micrograms/m3 . . . . . . . . . . :. . . . . . . . . . . . . . . . . . . . . . 96 ,

LIST OF FIGURESFigure No. Page

5-1. Generalized Occupational Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775-2. Generalized Model for Control of Workplace Hazards . . . . . . . . . . . . . . . . . . 78S-3. Vinyl Chloride Reactor System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

5.Technologies for Controlling

Work-Related Illness

This chapter describes the principles and tech-nologies for controlling workplace health haz-ards—toxic substances and harmful physicalagents found in the workplace. For clarity andsince the control principles are similar for bothtoxic substances and harmful physical agents, dis-cussion focuses on control of the former. Empha-sis is given to technologies proven to be the mosteffective for protecting workers’ health—thosethat prevent hazard generation or that preventworker contact with the hazard. Three case stud-ies commissioned by OTA illustrate these prin-ciples and technologies as applied in controllingwork-related exposure to cotton dust, silica, andlead. In addition, the extent of the use of controltechnologies in United States workplaces is dis-cussed.

Health hazards, as defined by public health sci-ence, cause disease by an agent (hazard source)transmitted through the environment by a vec-tor (transmission of hazard) to a host or a recep-tor (worker) who is affected. This model includesworkplace hazards to which workers are exposed(see fig. 5-1). For workplace hazards, the source–the point at which the hazard is generated—maybe a gas, a liquid, or a solid if it is a substance,or a form of energy if it is a physical agent. Trans-mission or dispersion of the toxic substance orharmful physical agent is generally through work-place air or by direct contact. The worker at riskmay receive (absorb) the hazard through inges-tion, the skin, or by inhalation (see fig. 5-2).

A control technology system can include hazardcontrol at any or all of these three points—source,transmission, or worker. Hazard controls appliedat the source, such as isolation of a process, orin the transmission or dispersion path, such aslocal exhaust ventilation, are generally called“engineering controls. ” Those worn by the work-

Figure 5-1 .—Generalized Occupational Exposure

~

Source Workplace Worker

Generation Transfer Exposure

—Gas — Respiratory— Liquid — Dermal—Solid — Ingestion— Energy

er, such as protective clothing or a respirator, aregenerally called “personal protective equipment.“

A hierarchy of control methods is commonlyused. The first choice is control at the source,which can be done by design or modification ofa process or equipment or by substitution of lesshazardous materials. If the source is unalterablethrough design or substitution, the next choice isto control or contain the dispersion of the con-taminant by isolation of the source, preventingthe toxic substance from becoming airborne, orby removing the contaminant through local ex-haust or general dilution ventilation. Finally, con-trol at the worker may include administrative con-trols, personal protective equipment, and workpractices. (Personal protective equipment is dis-cussed in ch. 8, and the hierarchy of controls isdiscussed in ch. 9.)

77

78 ● Preventing Illness and Injury in the Workplace

Figure 5-2.—Generalized Model for Control of Workplace Hazards

Zone Isource

Production process

CONTROL SYSTEMSThere have been many attempts to define con-

trol technology. Brandt (71) described it as a sys-tem designed to control contaminant emission anddispersion along the pathway to the worker.Bloomfield (61) cited ventilation to reduce levelsof airborne contaminants as the primary meansof engineering control. The International LabourOffice (229) includes several techniques in con-trol technology: ventilation; process changes; sub-stitution of process, equipment, or material; isola-tion of stored material, equipment, process, andworkers; and education of management, engi-neers, supervisors, and workers. Caplan (96)defined engineering controls for industrial hygienepurposes as “installation of equipment, or otherphysical facilities, including if necessary selectionand arrangement of process equipment, that sig-nificantly reduces personal exposure to occupa-tional hazards.” Smith (450) defined control tech-nology as substituting less dangerous substances,equipment, or processes; limiting releases or pre-venting buildup of environmental contamination;

Zone Illreceptor

Photo credit: NIOSH

This electrostatic precipitator is used to remove oilmists from the atmosphere of a machine shop

limiting contacts between worker and toxic mate-rials by personal protective equipment; and in-troducing administrative changes.

Ch. 5—Technologies for Controlling Work-Related Illness ● 7 9

For this assessment, a hazard control system in-cludes:

1. control at the emission source by substitu-tion of materials, change of process or equip-ment, or other engineering means,

2. control of the transmission or dispersion ofthe contaminant by isolation, enclosure, ven-tilation, or other engineering means, and

3. control at the worker by personal protectiveequipment, work practices, administrativecontrol, training, or other means.

The controls in No, 1 and No. 2 are commonlycalled “engineering controls. ”

Training workers, supervisors, managers, engi-neers, and other concerned persons about a haz-ard and its control underlies the effectiveness ofcontrol solutions. Hazard-free operation requiresrigorous maintenance of controls, and goodhousekeeping is essential to control secondarysources of contamination. Work practices (e.g.,instructions that liquids should be poured awayfrom the worker) and administrative procedures(e.g., that workers spend limited time in the pres-ence of hazards) are also important parts of a con-trol system. Table 5-1 is a compilation of hazardcontrol principles and includes examples of con-trol measures.

One tenet of effective hazard control is that asystem should be designed in a way that the con-trols are automated or inherent in the operationof the system. Thus, hazard controls should func-tion even in the absence of continuous worker andmanager attention. For instance, enclosing a proc-ess to prevent emission of toxic substances toworkplace air is a more reliable, and likely lessexpensive, control than respirators, where effec-tiveness is difficult to measure, protective fit isdifficult to achieve. Although systematic designwill consider a variety of control methods andcombinations, engineering solutions are preferredbecause they depend less on routine human in-volvement for effectiveness. For example, ground-ing home electrical appliances provides greaterprotection against electrical shock than instruc-tions to remember not to simultaneously touchan ungrounded appliance and a metal surface.

Photo credif: OSHA, Office Of Informatlon and Consumer Affairs

Engineering controls include the enclosure ofoperations and using remote controls. This photoillustrates equipment designed to handle very toxic

radioactive materials

Because of the continuing need for human in-tervention and attention in the use of personalprotective equipment, practicing industrial hy-gienists employed by business, government, andunions have long recognized that such equipmentshould be turned to only after other means of pro-tection have been exhausted (see ch. 9). Occupa-tional Safety and Health Administration (OSHA)standards require the use of engineering and workpractice controls except for the time period nec-essary to install such controls, when engineeringand work practice controls are infeasible (in-cluding many repair and maintenance activities),

80 . Preventing Illness and Injury in the Workplace

Table 5=1 .–Principles of Controlling theOccupational Environment

Point of application ofthe control measure Control measure

At or near the hazardzone. . . . . . . . . . . . . . . . . .

To the general workplaceenvironment . . . . . . . . . . .

At or near the worker . . . . .

Adjuncts to the abovecontrols . . . . . . . . . . . . . . .

Substitution ofnonhazardous or lesshazardous material

Process modificationEquipment modificationIsolation of the sourceLocal exhaust ventilationWork practices

(housekeeping)

General dilution ventilationLocal room air cleaning

deviceWork practices

(housekeeping)Work practices

(housekeeping)Isolation of workersPersonal protective

equipment

Process monitoringsystems

Workplace monitoringsystems

Education of workers andmanagement

Surveillance andmaintenance of controls

Effective process-peopleinteraction and feedback

SOURCE (576)

when they are insufficient, and in emergencies (seech. 9). For instance, engineering solutions to re-duce airborne lead concentrations to the OSHAstandard are difficult to apply in lead smelters,and OSHA allows respirator programs while thesolutions are engineered.

Of course, the nature of some jobs requires reli-ance on personal protective equipment. For in-stance, firefighters depend on self-containedbreathing apparatus when fighting fires.

Control at the Source

Control at the source can be achieved by de-sign of new or modification of existing processesor equipment, or by the substitution of less haz-ardous materials-all done, preferably, before theprocess or equipment is installed and operated.

The industrial hygiene literature repeatedly pointsto source control as the most effective means ofpreventing work-related illness.

Designing Controls

Designing equipment to eliminate contact be-tween hazard and worker is the most effective wayto control exposure (71). The control of vinylchloride monomer (VCM) provides an exampleof successful design eliminating a health hazard(see also box N in ch. 12). In the 1960s, beforeVCM was recognized as a carcinogen, it was iden-tified as a cause of acro-osteolysis (bone deteriora-tion, especially in the finger tips). This finding ledthe American Conference of Governmental Indus-trial Hygienists (ACGIH) to revise the ThresholdLimit Value (TLV) exposure limit from 500 partsper million (ppm) to 200 ppm in 1970 (5).

Revision of the exposure limit meant that thefirms that followed ACGIH recommendations hadto find ways to reduce worker exposure. Analy-sis by design engineers identified two methods bywhich the high exposures associated with clean-ing the VC reactor vessel could be reduced: elim-ination of reactor fouling or mechanical or chem-ical removal of the polymer buildup. Hydraulicreactor cleaning technology was adopted that re-duced the frequency of worker cleaning from onceper several reactor charges (loading the reactor)to once per 25 to 30 charges and thereby reducedworker exposure (256).

When VCM exposure was recognized in 1974as strongly related to angiosarcoma of the liver(a rare and deadly cancer) by health professionals,OSHA mandated a permissible exposure limit of1 ppm. Feasible engineering and work practicecontrols were required to reduce exposure belowthis level (617).

Again, industrial hygiene analysis determinedthat exposure to gases during reactor cleaning wasa major problem. Re-investigation led the designengineers back to earlier considerations, of eithereliminating the fouling or finding an automatedcleaning method. But this time the design criterionwas to reduce drastically exposure from over 200ppm down to 1 ppm, and mechanical cleaningalone was found to be inadequate. However,


spraying a simple coating solution on interior re-actor walls before mixing each batch preventedpolymer buildup, Automating and enclosing thereactor cleaning process by installing a permanent-ly mounted nozzle inside the reactor (see fig. S-3) very effectively contained the VCM gases andgreatly reduced worker exposure (256).

Commercial use of this design demonstratedthat the new reaction vessels needed cleaning onlyonce every 500+ polymerization batches, greatlyimproving the productivity of the process. Thedeveloper, B.F. Goodrich, now uses the innova-tive process in its vinyl chloride monomer plantsboth here and abroad and also licenses it world-wide to other chemical manufacturers. Table 5-2shows the benefits of this control technology(256).

This example illustrates the advantages of ap-plying engineering controls to the prevention ofwork-related illness. Engineers sought solutionsto a recognized health problem by first consider-ing methods that would eliminate exposure suchas by automating cleaning or by preventing build-up of materials that require removal. This exam-ple also shows that production costs can be re-duced and productivity increased, as Brandtpostulated some 35 years ago in his book on oc-cupational health engineering (71).

Health hazards can also be eliminated or con-trolled by changing an industrial process. For ex-ample, the National Institute for OccupationalSafety and Health (NIOSH) recently conducteda study of dry cleaning machine operators exposedto perchloroethylene, a widely used solvent,known to cause contact dermatitis, central ner-vous system depression, liver damage, and anes-thetic death. NIOSH investigators found higherexposure levels of perchloroethylene vapors inprocesses involving separate washing and dryingmachines than in processes that combined thesetwo steps in one machine. The two-step processrequires manual transfer of clothes, resulting inunnecessary worker exposure, which is avoidedin the combined process.

Substitution

Substitution of a less toxic agent for a moretoxic one is an important means of control, butcare must be taken that the substitute does not

Figure 5-3.-Vinyl Chloride Reactor System

Coatingsolutiontank

CoatingWater

solution

Internal flushnozzle

Reactor

II

Table 5-2.—Benefits of New Technologies forControlling Worker Exposure toVinyl Chloride Monomer (VCM)

Reduction in worker exposure to VCM.Reduction in VCM emissions to the atmosphere.Closed reactor operation—entry only for normal

maintenance.Savings in labor.Reduction in reactor downtime due to cleaning and, as a

result, increase in productivity.Polymer buildup lost as scrap is eliminated.Reduction of rupture disc changes due to polymer

buildup.Constant and maximum process side heat transfer

coefficient in the reactor.SOURCE: (25S).

itself harbor toxic properties. For example, asbes-tos, an excellent insulator, is found widely inbuildings, ships, and other places requiring ther-mal insulation. However, as its toxic properties,especially its carcinogenicity, were recognized,other materials were considered as a replacement.Several materials are suitable, depending on theapplication and the temperature range to be in-sulated. These include insulating concrete, ver-miculite, fiberglass, and rockwool. While noneof these is yet known to cause cancer, precautions


should be taken to control exposure to thesematerials during installation (80).

Silica dust, which can cause lung disease, is oneof the oldest known occupational health hazards,and its control well illustrates the principle of sub-stitution (see case study, later in this chapter).Silica dust is a problem in “sand blasting, ” incleaning and polishing moldings and metals, andin mining and quarrying, where it is generated byexplosives and mining machinery.

In foundries, silica dust is generated duringcleaning, during chipping and grinding of castingsbecause some sand from the cores and molds re-mains on the castings, and during abrasive clean-ing, which generates airborne silica dust. Ifabrasive cleaning is performed by sand blasting,silica dust may be generated from both the blastsand and the mold and core sand.

The most direct method of eliminating silicadust is to make substitutions for silica-containingmaterial. A number of silica-sand substitutes areavailable for abrasive blasting, including metallicshot and grit, garnet, nut shells, cereal husks, andsawdust, and have been widely used in abrasiveblasting operations and to some extent in found-ries (560).

In some cases, silica dust can be eliminated bysubstitution of a nonabrasive process—by clean-ing castings by the salt bath process, acid pickl-ing, or ultrasonic cleaning. Water jetting and la-ser cutting to remove excess metal from castingshave been considered as alternatives to chippingand grinding (435).

Controlling Dispersion

If a source cannot be altered through design orsubstitution, the next choice is to control or con-tain the dispersion of the contaminant. This maybe done by isolating the source, preventing thetoxic material from becoming airborne, or by ven-tilation.

Isolation

Isolation of a process involves the placementof a barrier between the process and the worker.In dusty operations for example, there are threebasic means of isolation: enclosure of an opera-

tion (to prevent dust, fumes, or vapors fromescaping into occupied areas); automation,through the use of unattended machines; and dis-tance, to place operations away from workers.

Isolation by enclosure has been used effectivelyto reduce silica exposure in foundries (359,569,577). Abrasive blasting operations maybe locatedin enclosed, ventilated booths. Enclosure is alsoused to reduce worker exposure in the asbestostextile industry. Card machines, among the dusti-est parts of the asbestos textile manufacture proc-ess, can be completely enclosed and asbestos dustfiltered from the air exhausted (80). Enclosure hasbeen applied successfully in containing contamina-tion from radioisotopes since the beginning of thenuclear industry. A variation is to protect work-ers from physical and chemical hazards by locat-ing their work stations in ventilated controlbooths.

Many jobs with risk of exposure to toxic sub-stances can be automated. For instance shakeout(a method for removing foundry sand from moldsor parts) in a foundry can be done by ventilatedmachines rather than by hand. Automobiles maybe spray painted or welded by automated ma-chines to remove workers from exposure to spraypaint and solvent and welding fumes, respectively.

Finally, explosive or extremely toxic materialscan be stored in remote and inaccessible areas andhazard-generating operations may be removedfrom areas where workers are concentrated.Open-air sand blasting can be done at a distancefrom other work sites to reduce the number ofworkers at potential risk. Persistently leakypumps and piping for the transport of toxic sub-stances can be isolated by placing them in areasremote from workers.

Wetting

Wetting dust to prevent it from becoming air-borne is used to reduce worker exposure. Spray-ing is a primary means of dust control in mining,but it is considered to be inadequate alone andis usually used in conjunction with ventilation(230,394). Substitution of wet processing andspraying for dry operations has been widely usedto control silica dust. In foundries, adding mois-ture to sand has been found to reduce dust con-

Ch. 5—Technologies for Controlling Work-Related illness ● 8.3

centrations substantially (435,569). By contrast,wet processing in the manufacture of portland ce-ment appeared to have no effect on respirable dustlevels (419).

Local Exhaust Ventilation

Local exhaust ventilation is one of the mostcommonly used engineering controls. It aims toprotect the worker by capturing generated gases,vapors, fumes, or particles in an exhaust airstream and discharging them away from work-ers. Examples are laboratory fume and kitchen-range hoods, both of which use fans to exhaustcontaminated air, Industrial operations are oftenplaced in hoods to obtain maximum contaminantcontrol with minimal exhaust air volume.

For example, local exhaust can be applied inaluminum reduction operations to reduce workerexposure to carcinogenic particulate, in spraypaint booths to control paint mist and solventvapors, in garages to control carbon monoxidefrom auto exhaust, and in foundries to controlsilica exposure from abrasive blasting and grinding.

NIOSH is currently investigating “push-pull”ventilation. Generally, local exhaust ventilationdepends on “pulling” air away from the opera-tion and exhausting it at some distance from theworker, If the emission source is over two feetfrom the exhaust, a great quantity of room airmust be pulled into the exhaust, significantly re-

This hood in a secondary lead smelter illustrates theuse of local exhaust ventilation

ducing control effectiveness. Furthermore, energycosts are increased to heat the air that replacesthe exhausted air.

Using a jet of air “upwind” from the exhaustpushs the emissions toward the exhaust. This iscommonly referred to as push-pull ventilation.NIOSH showed that push-pull ventilation con-trolled emissions from chrome plating tanks withjust 25 percent of the exhaust needed if only pullwas used. The system thus controlled emissionsand reduced energy costs (582).

A successful local exhaust ventilation sys-tem.—As already indicated, controlling exposuresis best done by considering design of the healthhazard control at the time a process is establishedand carefully monitoring performance of the sys-tem. Anderson (20) describes the effective designof a control system in a large electronics plant.

The process begins when a manufacturing engi-neer asks to add or change a chemical process.The request is submitted to the facilities engineer-ing department and an engineer is assigned re-sponsibility for installing the equipment to satisfyprocess, safety, health, and other requirements.Part of the facilities engineer’s responsibility is toreview the need for local exhaust ventilation withthe industrial hygienist, who is responsible for pro-viding health protection information including de-tails about hood design and air volume require-ments. The preliminary design is then reviewedby the environmental engineering department todetermine the need for air cleaning devices andemission permits. After the process design iscompleted, it is given a final review by the indus-trial hygiene, environmental engineering, safety,maintenance, and manufacturing engineering de-partments.

Installation is supervised by a coordinator whoensures that contract specifications are followed,Changes must be approved by the facilities engi-neer. The contract coordinator informs the facil-ities engineer when the job is done and puts awarning tag on each completed hood.

Before the hood can be used it must be adjustedto meet design specifications by the facilities engi-neer and the maintenance ventilation technician,who enters information about the system in a data


base for scheduling preventive maintenance and the gradual introduction and mixing of fresh airwho also tags the hood to indicate that this has with, and exhausting of, workplace air. Con-been done. After this the hood is inspected by the tinuous air exchange in buildings reduces non-industrial hygienist, who reviews its use with the taminants that resist other control means whileworkers and ensures that the proper chemical contributing to maintenance of a comfortable en-identification labels are placed at each station. vironment. General dilution ventilation is defined

Hood effectiveness is measured periodically anddata entered into a computer. Each week the com-puter system generates a card for each hood per-forming below specified levels for review by theindustrial hygienist. If the hood is in need of at-tention, the card is forwarded to building main-tenance. If that department is unable to fix thehood, the facilities engineering department treatsthe failure as a unique project, and then followsthe same procedure that is used in designing a newhood,

If a hood is found to be dangerously deficientby the ventilation technician, it is tagged “Do NotOperate” and immediately reported to the depart-ment manager, facilities engineering department,and industrial hygiene department.

The main features of this well-thought-out sys-tem for designing and managing controls are:

● coordination among all concerned parties,. integration of occupational health concerns

at the beginning and throughout the designprocess,

. integration of occupational health concernsfollowing installation, and

● execution of a well-planned preventive main-tenance program.

The company has found that this approachgreatly lowers costs by reducing the need toretrofit processes. Before this method wasadopted, newly installed exhaust systems fre-quently failed because of improper design or in-stallation. Post-installation approval guaranteesall concerned parties that the system works fromthe start as it was designed. A well-planned,computer-based, preventive maintenance pro-gram assures continued effectiveness.

General Dilution Ventilation

as “the process of supplying or removing air bynatural or mechanical means, to or from anyspace” (71). The air circulation systems found inmost buildings are examples of general dilutionventilation.

This technique requires careful planning, andit can fail if inadequate consideration is paid tocontaminant generation rates. Furthermore, pro-vision must by made for adequate fresh “makeup”or “replacement” air, for heating or cooling themakeup air, and for avoiding contamination ofmakeup air.

Recent interest in energy conservation hasadded new considerations. Increased building in-sulation has greatly reduced the flow of air from“leaks,” which requires more makeup air. Chap-ter 16 describes particular problems among officeworkers in new “tighter” buildings, Office work-ers report health effects from microorganisms,organic chemicals, asbestos, tobacco smoke, andother sources in buildings with inadequate ven-tilation (25).

Control by general ventilation is aided byremoving sources, such as smoking, and by clean-ing air. Since most building ventilation systemsnow recirculate air, cleaning the air becomes espe-cially important. This is a relatively new prob-lem; before energy conservation was given em-phasis, accepted engineering practice was tocompletely exchange building air to avoid con-tamination buildup. Now, building air is oftencleaned and then recirculated to reduce energycost. Systems are available for cleaning both gasand particulate, but care must be taken to ensurethat the system is reliable and the cleaning com-plete (563).

Neither local nor general ventilation acts to pre-vent generation of hazards; it can only captureor dilute contaminated air and take it to anotherlocation. The air may still have to be cleaned

While local exhaust systems are applied at a before discharge to the ambient environment, toparticular point to remove contaminants at rela- meet Environmental Protection Agency or othertively high rates, general dilution ventilation is ambient-air standards (6,562,563).

Ch 5- Technologles for Controlling Work-Related Illness ● 8 5

CASE STUDY:CONTROLLING WORKER EXPOSURE TO COTTON DUST

86 . Preventing Illness and Injury in the Workplace—

The quote was made in reference to a respira-tory disease suffered by workers in English- tex-tile mills 150 years ago. That disease—byssinosis,or “brown lung’’—was recognized in this countrymuch later than in Europe. The reasons for thelate recognition are complex. Many occupationalhealth authorities suggest ignorance or refusal torecognize particular respiratory diseases that werecommon to mill workers to spare employers thecosts of installing controls. In addition, social con-ditions inhibited workers from making their com-plaints known and prevented actions on thosecomplaints. Also, local and State Governmentswere reluctant to act because they feared the lossof textile industry jobs as a result of requiring pre-vention of work-related injury and illness. Finally,a lack of scientific studies showing an associationbetween cotton dust and illness in the UnitedStates contributed to the tardy recognition of thedisease and inhibited action to prevent it untilOSHA came into being (124).

The OSHA Cotton Dust Standard

Although the exact disease-causing agent with-in cotton dust has eluded identification, it isknown that the dusts from the early stages ofprocessing are more hazardous than those fromlater stages. Opening cotton bales and sorting,picking, and blending raw cotton present greaterrisks than do weaving and finishing.

In 1964, the American Conference of Govern-mental Industrial Hygienists considered the evi-dence for establishing a recommended limit forcotton dust exposures. Two years later, the Con-ference agreed on a Threshold Limit Value of1,000 micrograms/m3 as the maximum exposurethat was consistent with maintaining workers’health. In 1969, the Secretary of Labor incor-porated ACGIH’s recommended TLV into Fed-eral standards for employers with Governmentcontracts (see ch. 11 for a discussion of the Walsh-Healey Act).

The Occupational Safety and Health Act of1970 required that the newly established OSHAadopt the Walsh-Healey Act standards and applythem to all the Nation’s workplaces. Thus, the cot-ton dust standard of 1,000 micrograms/m3 was

adopted as a startup standard by OSHA in 1971(see Ch. 12).

In 1974, ACGIH revised its TLV downward to200 micrograms/m3 (the method of measurementchanged also, and the “new” 200 micrograms/m3

is not directly comparable to the ‘ old” 1,000micrograms/m 3). That same year, the Director ofNIOSH recommended that exposure to cottondust should be reduced to the lowest feasible level,and that it should in no case exceed 200 micro-grams/m 3.

In 1976 OSHA proposed a 200 micrograms/m3

standard. The final standard, issued in 1978, setthree different exposure limits—200 micrograms/m3

for cotton yarn manufacturing, 750 micrograms/m3 for “slashing and weaving” operations, and 500micrograms/m 3 for exposures in other operations.This standard was contested by the textile indus-try through legal suits. While the Supreme Courtupheld the standard for the textile industry in1981, in the same year the current administrationmoved to reconsider it. This action is pending.Table 5-3 shows how the suggested and recom-mended levels for cotton dust came downwardafter the substance was regulated as a health haz-ard in the United States.

Changes in Cotton Dust Levels

Table 5-4 presents North Carolina Departmentof Labor measurements of the percentage of tex-tile plant departments that were in compliancewith the OSHA cotton dust standard i n 1981. Ascan be seen, just two years after promulgation ofthe new standard and during the period the stand-ard was being challenged in the courts, over halfthe departments complied with the standard.Some problems remain, as higher frequencies ofnoncompliance were found in the early stages ofthe process-opening, picking, carding, drawing,and combing. In these stages, workers are exposedto the more hazardous dusts associated with un-processed cotton. overall, however, the cottonindustry is coming into compliance with the newstandard.

The industry trade association, the AmericanTextile Manufacturers Institute, estimates thatabout 75 percent of the industry was in compli-

ance within two years of the standard being in-troduced. Some plants that have been completelymodernized are in full compliance (413).

In 1981, the U.S. textile industry purchased $1.6billion worth of new machinery. About 70 per-cent of those purchases were for the purposes ofmodernization to increase productivity (413) inthe face of increased foreign competition and, tosome extent, to comply with the OSHA stand-ard for reduced cotton dust levels.

Ruttenberg (413) concludes that it is impossi-ble to decide the relative importance of increas-ing productivity and compliance with OSHA reg-ulations in the modernization of the Americantextile industry’, but that both have made a con-tribution.

The U.S. Occupational Safety and HealthAdministration dust regulations have had a dra-matic effect on . . . processing equipment design

Photo credit O. SF/A, Office of Information and Consumer Affairs

The spinning of cotton fibers into yarn and weavingyarn into fabric are two of the operations regulated bythe OSHA cotton dust standard. In recent years, thetextile industry has invested heavily in modernizedequipment in order to comply with the standard and

to improve productivity

and purchasing. Machine suppliers modifiedequipment to comply with OSHA regulations andthis equipment has been accepted on a worldwidebasis as well as in the USA. The dust controlshave also contributed to much better operatingresults. . . (U.S. Department of Commerce (551).Quoted in 413).


Table 5-3.-Suggested and Recommended Levels for Cotton Dust Exposure

Level a

Organization Year (micrograms/m3)

American Conference of Governmentalindustrial Hygienists (ACGIH) . . . . . . . 1964

ACGIH recommendation . . . . . . . . . . . . . 1968Secretary of Labor . . . . . . . . . . . . . . . . . . 1968Occupational Safety and Health Admin-

istration (OSHA). . . . . . . . . . . . . . . . . . . 1971British Occupational Hygiene

Society . . . . . . . . . . . . . . . . . . . . . . . . . . 1972

ACGIH recommendation . . . . . . . . . . . . . 1974National Institute for Occupational

Safety and Health (NIOSH) . . . . . . . . . 1974OSHA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1976OSHA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1978

1,0001,0001,000

1,000

500

200200b

200

tentative recommendationformalWalsh-Healey Act standard

OSHA standard

recommended standard forBritain

formal

recommendationproposed standardfinal standard

~he levels from 1964 through 1972 were based on techniques that measured the concentration of total dust in the workplaceatmosphere. From 1974 on, the levels are based on the use of the vertical elutriator —a device that measures the quantityof small, resplrable dust particles. Levels based on the these two methods are not dirwctly comparable

%he 200 limit is for yard manufacturing, 750 for slashing and weaving, and 500 for all other processes The Iim!t goes upas the cotton dust becomes cleaner

SOURCE Adapted from (413).

Table 5-4.—Cotton Dust Measurements Before Promulgation of theOSHA Cotton Dust Standard and Percentage of CompaniesClaiming Compliance with the Standard in North Carolina

Range of measurementsbefore OSHA standard

Area of plant (micrograms/m3)

Opening . . . . . . . . . . . . . . 300-3,000Picking. . . . . . . . . . . . . . . 700-1,700Carding . . . . . . . . . . . . . . 300-1,800Drawing . . . . . . . . . . . . . . 400-800Combing . . . . . . . . . . . . . NARoving . . . . . . . . . . . . . . . NASpinning ., , . . . . . . . . . . 200-300Winding . . . . . . . . . . . . . . 1,200Twisting. . . . . . . . . . . . . . 1,200Slashing. . . . . . . . . . . . . . NAWeaving . . . . . . . . . . . . . . 400-1,000Knitting , . . . . . . . . . . . . . NAWaste Processing . . . . . NAOther . . . . . . . . . . . . . . . . NA

Companies claimingLimit under compliance in

OSHA standard North Carolina(micrograms/m3) (percent)

53200 61200 52200 63200 61200 81200 83200 76200 80750 100750 96

10085

500 97SOURCE: (413).

Tougher government regulations on workers’health have, unexpectedly, given the [U. S.] indus-try a leg up. Tighter dust-control rules for cottonplants caused firms to throw out tonnes of old in-efficient machinery and to replace it with the latestavailable from the world’s leading textile machin-ery firms. (The Economist (160). Quoted in 413).

Costs of Compliance with theCotton Dust Standard

OSHA contracted for an economic analysis ofthe expected costs of compliance with the cottondust standard, and the contractor assumed thatcompliance would be accomplished by “add-on”


ventilation equipment. However, the availabilityof newer production equipment, which increasedproductivity and reduced cotton dust exposures,resulted in much lower costs than those estimatedat the time the standard was considered. As tables-5 indicates, the initial 1974 estimates of capital

Table 5-5.—Estimated and Realized Costs ofCompliance with the OSHA Cotton Dust Standard

Millions of1982 dollars

Preregulatory estimatesOSHA contractor, 1974 . . . . . . . . . . . . . . 1,941Revised OSHA contractor, 1974 . . . . . . . 1,388ATMl a contractor, 1977 . . . . . . . . . . . . . . 875OSHA, 1978 . . . . . . . . . . . . . . . . . . . . . . . . 970

Postregulatory estimateOSHA contractor, 1982 . . . . . . . . . . . . . . 245aAmer~can Textile Manufacturers !rTStitUte

SOURCE (413)

costs for compliance were nearly $2 billion (in1982 dollars). At the time of promulgation in1978, OSHA estimated costs of just under $1 bil-lion (in 1982 dollars). Thus, while cost estimatesplummeted more than 50 percent by the time thestandard was issued, the reduced estimate was stillalmost four times higher than the actual costs re-ported in 1982 in a poststandard contract report.

Although most of the more productive, lessdusty machinery now in use in U.S. textile millswas available in the mid-1970s, its potential usewas ignored in the early estimates of compliancecosts. Even if purchase of new technology hadbeen anticipated, it would have been difficult toassign the proper fraction of its costs to dust con-trol. In the event, new technologies greatly re-duced the costs.

CASE STUDY:CONTROLLING WORKER EXPOSURE TO SILICA DUST

Silica is a major component of the earth’s crust;it is the sand covering the beaches, the sandsprinkled on icy winter streets, the grit in the duston windy days—it is everywhere. It is also widelyused in industry. Over 402 million tons of silica-containing sand were produced in the UnitedStates in 1980. Of this total, nearly 300 milliontons were used for glassmaking, as molding sandin foundries, and as industrial abrasives. Since itis ubiquitous, silica is frequently found as an un-wanted constituent of ores mined for other minerals.In those cases, it must be removed and discarded.

Silicosis is a disabling lung disease resultingfrom the inhalation, deposition, and retention inthe lungs of respirable crystalline silica dust. Acutesilicosis can occur within six months following ex-posure to extremely high silica dust concentra-tions. Silicosis victims appear to suffer moreepisodes of chest illness than workers without thedisease. The mortality for nonmalignant respira-tory disease is significantly higher among work-ers receiving compensation benefits for silicosisthan in the general population. A complicationof silicosis, progressive massive fibrosis, resultsin significant impairment in lung function and

may result in respiratory failure and secondaryheart disease. Tuberculosis and other pulmonaryinfections may complicate acute or chronic sili-cosis and significantly shorten life expectancy.Hickey, et al. (210) discuss these silica-relatedhealth problems and reported associations be-tween worker exposure to silica dust and an in-creased risk of lung cancer.

Since diagnostic procedures do not detectsilicosis at a reversible stage, and since medicaltreatment will not alter the course of the diseaseafter it is found, emphasis on exposure controlis imperative. Yet, even though the cause of thedisease has been well understood and technologiesfor controlling exposure have been available fordecades, silicosis continues to occur in the UnitedStates at an alarming rate. A minimum of 59,000cases of silicosis may be expected based on knowl-edge about current exposure levels and numbersof exposed workers at risk in 1980 in U.S. indus-try (210).

Hickey, et al. (210) estimate that there are 1.3million production workers with potential expo-sure to silica dust—40 percent of whom are in

90 ● Preventing Illness and Injury In the Workplace

workplaces lacking exposure control. Historicallythe most severe exposures to silica have occurredin granite and stone working, foundries, mining,and abrasive blasting. Workers producing andusing silica flour (silica ground so fine that it ap-pears to be refined grain flour) have recently beenrecognized to be at high risk for silicosis, becauseof the extremely fine size of the particles produced.

Regulatory Activities forSilicosis Control

The current OSHA standard for silica is basedon an equation that limits the total amount of freesilica to 100 micrograms per cubic meter. Thisstandard was adopted as a start-up standard in1971 (see ch. 11). Evaluation of the silica stand-ard shows that it may be inadequate at its pres-ent level. In 1974, NIOSH recommended limitingsilica exposure to 50 micrograms per cubic me-ter—half the current level. The studies on whichNIOSH based its recommendation used pulmo-nary function performance as the measure ofhealth effect—a more sensitive indicator ofsilicosis than X-ray methods.

In certain circumstances, such as in abrasiveblasting where alternatives to silica are available,substitution may be the most appropriate methodof control. The United Kingdom banned the useof silica sand for abrasive blasting in 1948, andNIOSH has recommended a similar prohibitionin this country (560). Sweden banned silica as anabrasive in manual abrasive blasting in 1981 (210).A California standard requires that prior to use,not more than 1 percent, by weight, of abrasivesand must pass a No. 70 U.S. standard sieve (0.3mm). After use, the sand must have no more than1.8 percent of its weight as particles 5 micrometersor less in diameter (211). These restrictions on sizereduce the number of respirable particles.

In 1978, OSHA conducted a technological fea-sibility assessment and economic impact analy-sis for a specific standard addressing use of silicasand in abrasive blasting (211). The study con-sidered three alternatives: banning use of silicasand in abrasive blasting, setting minimum cri-teria on size and hardness of blasting sand, andcontrolling exposure through work practices. Todate no revised standard has been issued.

However, due to the serious silicosis problem,OSHA has made a special effort to enforce theexisting silica standard. In 1972, silica was oneof five major health hazards selected for specialenforcement efforts in the ‘Target Health HazardProgram” (414). Silica was again given priorityin the 1975 National Emphasis Program, as oneof the major worker health hazards in foundries(339). In both cases OSHA industrial hygienistsfocused health inspections on plants where silicawas likely to be found.

Control Technologies:Engineering Methods

Silicosis is an entirely preventable disease. Ex-posure occurs whenever materials containing crys-talline-free silica are processed and dust is gener-ated. Processes include abrasion (sand blasting,grinding, milling, etc. ) that creates dusts of par-ticularly small particle size (less than 5 microme-ters in diameter). These dusts are too small to beeasily seen as a “cloud.” Too small to settle, theyremain airborne and “respirable’’—-that is, theymay readily pass through the upper respiratorypassages and be deposited in the alveolar spacesof the lung (the small air sacs deep in the lungwhere gas is exchanged with the blood).

The most direct method of eliminating silicadust is to substitute less hazardous materials forthe silica-containing material. This control hasbeen widely used in abrasive blasting operationsand to some extent in foundries. Silica-sand sub-stitutes include metallic shot and grit, garnet, nutshells, cereal husks, and sawdust. Olivine (mag-nesium iron silicate) has been used for mold mak-ing in foundries to reduce silica dust exposure, butit is not clear how effective this method will be(210).

Process change may also be used to controlsilica dust exposure. For instance, water may beadded to foundry molding sand or sprayed on atthe point of dust generation in granite sawing andprocessing of portland cement. In some situations,dust-producing abrasive processes may be re-placed by other types of cleaning such as saltbaths, acid pickling, or ultrasonic cleaning. Waterjetting and laser cutting for removal of excessmetal from castings have been considered as alter-

——


substitutes that are suitable for replacing silica. should be refined to provide a better way ofAlso, for those situations where engineering con- worker protection. Information about the toxicitytrol maybe infeasible, further improvement in res- of silica and technologies for controlling exposurepirator effectiveness is necessary. Medical proce- could be provided to workers and employers usingdures for detection of the early stages of silicosis it.

CASE STUDY:CONTROLLING WORKER EXPOSURE TO LEAD

Early efforts against industrial lead intoxicationin this country were championed by Alice Hamil-ton. Her autobiography, Exploring the DangerousTrades (199), presents many examples of terribleexposures that were corrected when managers andowners were convinced that lead was causing the“colic, “ “lead fits, ” and blindness that occurredin lead workers. Until they were convinced, own-ers and managers preferred to believe that the ill-nesses resulted from bad personal habits—drink-ing, smoking, or the consumption of coffee.

Some firms refused to act voluntarily, andstates began passing “lead laws” in the 1910s thatset limits on occupational exposures. These earlyefforts were the forerunners of the revised OSHAlead standard, which was issued in 1978.

The current standard regulates exposure to leadin over 40 different industries. With only few ex-ceptions, most industries comply with the s Omicrograms/m 3 permissible exposure limit forworkplace air concentration. The exceptions in-clude primary and secondary lead smelting andlead-acid battery manufacture, where controls aremost difficult and economic conditions have beenunfavorable. (Primary smelters purify lead fromlead concentrate, which is lead ore enriched bymilling. Secondary smelters recover lead fromdiscarded lead-containing products—in particu-lar, worn-out batteries. Battery plants make lead-acid batteries. ) Although the standard was con-tested by both union and management and it isimpossible to be certain of the future of these in-dustries or of the burdens placed on them by thestandard, it is clear that workers’ health has been

improved as measured by reduced lead levels intheir blood.

Some Features of the OSHALead Standard

The lead standard sets limits on ambient con-centrations of the metal in workplace air, requiresengineering controls and work practices to reachthose limits, and requires that workers be in-formed about lead, its effects, and the methodsused to protect against them. TWO features—Medical Removal Protection (MRP) and the ex-tended time periods granted to selected industriesbefore engineering controls are required—dis-tinguish the lead standard from other OSHAhealth standards.

MRP requires employers to measure workers’blood lead levels regularly. If the measuredconcentration of lead in the blood exceeds certainlimits, the worker must be removed from lead ex-posure until the level drops to an acceptable value.For up to 18 months, the employer must main-tain the worker’s wages and seniority status evenif the person cannot perform his or her regularjob.

OSHA requires that air lead levels be reducedto an effective concentration of 50 micrograms/m 3.Since reported exposures have ranged above 2,000micrograms/m 3, reaching the regulatory limitposes many problems for employers. The regu-lation gives companies 3 to 10 years to attain theso micrograms/m3 limit through engineering con-trols; in the meantime, employers can require the

Ch. 5—Technologies for Controlling Work-Related Illness ● 91

natives to chipping and grinding in foundries.Vacuum cleaning may be substituted for dustycompressed air cleaning and screw conveyors usedinstead of dust-producing pneumatic conveyors.However, care must be taken to assure that suchtreatment, while suppressing visible dust, alsocontrols the smaller, more hazardous, respirablesilica dust particles.

Where silica remains in use and worker expo-sure is possible, local exhaust ventilation may beused to capture and carry dust away. Environ-mental Protection Agency or other ambient-airstandard regulations may require that ventilatedair be cleaned before discharge to the outside.

Control Technologies: PersonalProtection and Administrative Controls

Respiratory protection and face, eye, and bodyprotection against physical injury are also re-quired by OSHA in specific regulations for abra-sive blasting. NIOSH has specified the respiratortypes required for protection from various air con-centrations of silica, but these often prove to beinadequate in practice (210). Employer-providedand -maintained protective clothing and facilitiesfor changing at work plus training about personalhygiene prevent exposed workers from exposingfamily members to silica dust when taking workclothing home.

NIOSH (and others) recommend: administra-tive measures that help reduce risk of silicosis;training managers and workers about the hazardsof silica dust; the effective use of personal pro-tection equipment; and work practices that pre-vent the generation of silica dust, Dust-reducingpractices include vacuum cleaning, regular main-tenance of dust-producing and dust-controllingsystems, and good housekeeping. Dusty workmay be scheduled or located to reduce the num-ber of workers at risk. However, Hickey, et al.(210) report that company dust-control policiesare often unenforced.

Strategies for Silica Dust Control

One might ask why a well-recognized, entirelypreventable, work-related illness, for which theetiology is understood and for which engineering

and other controls are available, remains a prob-lem. Hickey, et al. (210) note some possiblereasons:

●

●

●

●

the current OSHA standard is inadequateand based on outdated information,compliance with the inadequate standard isinsufficiently monitored,accurately measuring silica concentrations inrespirable dust samples is difficult and costly,andthere is too much reliance on after-the-factcontrol methods that control the dust afterit is generated rather than on methods thateliminate silica dust.

An underlying reason for failure of worker pro-tection against silicosis is the cost of controllingexposures.

To attack this problem, Hickey, et al. (210) sug-gest promulgating a protective standard based onthe latest medical knowledge and streamlining en-forcement by developing an accurate, inexpensive,and rapid measurement method. These initialsteps will provide the basis for developing moreeffective technology to prevent generation of silicadust. Greater emphasis should be placed on pre-venting generation than on refinement of meas-ures for control after the dust is generated. Re-search should be conducted to find nontoxic

Photo credit OSHA, Office of Information and Consumer Affairs

Abrasive blasting workers are frequently exposed tohigh levels of silica dust

——

Ch. 5—Technologies for Controlling Work-Related Illness . 93

use of respirators to reduce workers’to airborne lead.

Control Methods: Engineeringand Respirators

exposures

Table 5-6 lists categories of control measuresthat can be employed to reduce lead exposures.In general, major changes in processes will be in-troduced only when a plant is rebuilt for otherreasons. (An example of the costs involved in sub-stituting a new process in primary smelters com-pared with adding on controls is presented inch.16.) Add-on controls, in particular better ventila-tion, are probably the most common form of engi-neering controls, although far simpler controls—such as covering stockpiles and putting tops onreaction vessels—are an important part of engi-neering controls.

A number of process innovations are beingmade in the secondary smelting industry and in

Table 5-6.—Measures To Reduce Air Lead andBlood Lead Levels

A.

B.

c.

D.

E.

Measures that affect air lead levels in the plant1. Changes in production processes (direct smelting

processes, more automated battery productionlines)

2. Add-on controls (ventilation systems)3. Changes in operating practice (keeping floors

cleaner)4. Greater or lesser use of lead-emitting equipmentMeasures that do not affect air lead levels but limittimes workers spend in lead-contaminated at-mospheres1. Isolation booths with filtered air supply2. Changes in work practices to limit time in high

lead areasMeasures that do not affect air lead levels but limitworkers’ lead absorption1. Respirators2. Showers, changing clothes before and after enter-

ing work areas3. Business cycle factors: layoffs, overtimeMeasures that do not necessarily affect exposure ofthe work force as a whole but affect the distributionof exposures among the work force1. Monitoring of workers and removing those with

biological indicators of exposure to areas withlower lead contamination

2. Rotation of workers3. Firing of highly exposed workersExternal measures that impact on lead exposure1. Changes of lead level in out-of-plant environment2. Changes of lead content in food and water

SOURCE (164)

battery manufacture that reduce worker exposureto lead. A major source of lead exposure here hasbeen the breaking open of old lead storage bat-teries. Goble, et al. (184) mention two new proc-esses that significantly reduce the liberation of leadin that process. In addition, technological changesrecently introduced in the manufacture of newlead storage batteries reduce worker exposurewhile increasing productivity.

Table 5-6 includes personal protective equip-ment as well as business cycle factors that influ-ence the number of workers exposed. The role ofrespirators in providing protection until engineer-ing controls are installed is clearly recognized inthe OSHA standard. The standard does requirethat ultimately compliance shall be achievedthrough the use of feasible engineering controls.

Medical Removal Protection

The OSHA lead standard provides that whenthe amount of lead in a worker’s blood exceedsa trigger level, he or she is to be removed fromexposure or placed in an area of lower exposureuntil the blood lead level drops (see table 5-7).When the amount falls to a specified reinstatementlevel, the worker can return to his or her regularjob.

When the OSHA standard was being consid-ered, employers pointed at MRP as a source ofhigh costs. They argued that older, more experi-enced workers who were paid a premium for theirknowledge would be removed to less skilled jobs,causing losses in productivity. In addition, sinceMRP requires that the worker’s wages be main-

Table 5-7.—Blood Lead Levels That TriggerMedical Removal From and Return to

Lead-Contaminated Atmospheres

Blood lead Ievelsa

(micrograms/100g blood) for

Date Removal Return

March 1979 . . . . . . . . . . . 80 60March 1980 . . . . . . . . . . . 70 50September 1981b . . . ~ . . 60 40March 1983b . . . . . . . . . . 50 40%Vorkers’ blood levels are to be monitored quarterly except workers with 10WJIS

greater than 40 micrograms/100g are to be monitored monthly.b Many firmS have been given extensions of the time fOr the 60/40 and 50/40

trlgffers

SOURCE (164)

94 Preventing Illness and Injury In the Workplace

tained, experienced workers doing less skilled jobswould still receive the pay associated with theirprevious positions.

Table 5-8 summarizes three years’ data aboutmedical removal from companies seeking relieffrom the lead standard. These data represent aworst-case group and may not be representativeof the industry. In both the primary smelter andthe battery industries reported, the percentage ofworkers on MRP transfer and the share of work-time spent on transfer peaked in the second year.The data for primary smelters is reasonably com-plete, based on 5 of 7 smelters and about 2,120workers each year, compared with a total of about2,500 workers; it is less complete for the batteryindustry, based on only 8 plants and about 1,300workers in an industry that employs about 30,000people. In the secondary smelting industry, thepercentage of workers on MRP and the propor-tion of worktime on MRP transfer increased eachyear. The data in this case are certainly incom-plete, and the facilities reported may not be rep-resentative of the entire industry; the data in table5-8 are based on about 640 workers out of a totalof some 3,000 workers in the industry. If the dataare representative, the secondary smelters are en-countering greater problems complying with theOSHA standard.

Goble, et al. (184) compared the percentage oftotal worktime on MRP transfer to projections oftransfers that had been made based on assump-tions of so or 100 micrograms/m3 air lead levelsin the industries. They found that the reportedpercentages of transfer worktime agree reasonably

well with achievement of 100 micro~grams/m3 airlead levels, supporting the conclusion that effec-tive air lead levels are between 50 and 100 micro-grams/m 3. Given that blood lead levels are relatedto worker health, these changes are evidence thatlead-related diseases and disorders should bedeclining.

The number of terminations of workers becauseblood lead levels remained above the reinstate-ment values even after removal to lower exposuresituations is apparently small. An examination ofthe new-hire and termination rates before andafter imposition of the OSHA lead standard didnot show an increase. That observation is incon-sistent with the idea that employers would ter-minate “leaded-up” workers and replace themwith new hires.

Changes in Air Lead Levels

Although some data about air arid blood leadlevels are available, they are often unsuitable formaking precise estimates of levels, of high ex-posure. For instance, although 67 percent of sec-ondary smelter workers in 1977 were exposed togreater than 200 micrograms/m3 airborne lead,neither the maximum exposure level nor the aver-age exposures of the highly exposed workers inthis group were reported. Goble, et al. (184) madea number of assumptions and then calculated ap-proximate average air lead exposure levels in thethree industries in 1977-78 and in 1981-82 (seetable s-9). Air lead levels dropped by about one-quarter in primary and secondary smelting and

Table 5-8.—Medical Removal Protection Transfers in a Sample of Lead Industry Plants

Average number per plant PercentPlants Lead exposed Workers on worktime

Industry Year In survey In industry workers MRPa transfer on MRP1979 5 7 465 21 1.0

Primary lead smelting . . . . . . . 1980 5 7 419 31 2.11981 5 7 492 18 1.31979 6 36 120 4 1.0

Secondary lead smelting. . . . . 1980 6 36 104 9 4.61981 6 36 96 11 6.91979 8 136 176 2 0.4

Battery manufacture. . . . . . . . . 1980 8 136 140 8 1.91981 8 136 162 6 1.5

aMflP, M@c~ Removal Protactlon.

SOURCE: (1S4 from data available in 103).

—


Table 5-9.— Reductions in Average Air Lead Levels,1977-78 and 1981-82

Average airlead levels

(micrograms/m’) PercentIndustry 1977-78 1981-82 reduction

Primary lead smelting. . . . . 740 565 24Secondary lead smelting . . 285 205 28Battery manufacture . . . 160 80 50Seven battery plants . . . . . . 160 90 50SOURCE (184)

by half in battery plants. Confidence about thevalidity of these estimates, especially for batteryplants, is increased by the access Goble, et al. hadto detailed, company-collected exposure datafrom seven battery plants. The percentage reduc-tion observed in those plants is the same as thecalculated reduction for the industry overall.

The data in table 5-9 show what are probablyminimal estimates of reductions in air lead levelsbecause of systematic errors in the calculations.Clearly, however, levels are coming down. Equal-ly clearly, there is some distance to go before theeventual goal of 50 micrograms/m 3 is reached.OSHA recognized that engineering control of airlead levels would take time, up to 10 years in someindustries. The decreases shown in table s-9 wereachieved in less than 5 years and during the periodwhen the standard was still being challenged inthe courts.

Changes in Blood Lead Levels

Data on blood lead levels for the period beforepromulgation of the lead standard are not so plen-tiful as air lead data. The estimates shown in table5-10 for 1977-78 are from information presentedin OSHA hearings. The data shown for 1981-82are from measurements reported in a Charles

Table 5-10.—Average Blood Levels Before and AfterPromulgation of the OSHA Lead Standard

Approximate averageblood lead levels

(micrograms/100g blood)

Industry 1977-78 1981-82 Difference

Primary lead smelting. . . . . 49.4 41.6 7.8Secondary lead smelting . . 56.5 44.2 12.3Battery manufacture . . . . . . 53.2 42.4 10.8Seven battery plants . . . . . . 53.0 38.3 14.7SOURCE (184)

River Associates (103) report prepared for OSHA,and those are probably more reliable.

A satisfying drop in blood lead levels was seenin less than 5 years between 1977 and 1982. Notshown on the table is the finding that the num-ber of workers with blood lead levels greater than80 micrograms/100g blood dropped from l,553(2 percent of 2,200 primary smelter workers plus16 percent of 3,170 secondary smelter workersplus 6 percent of 16,700 battery workers) to about20 (0.1 percent of 2,470 primary smelter workersplus 0.6 percent of 3,000 secondary smelter work-ers and no battery workers).

Furthermore, the number of workers withblood lead levels above 40 micrograms/100gdropped from 17,217 to 6,738. This significant de-crease is especially important because that is thelowest action level required at any stage of MRP.In other words, the almost 9,000 workers whohave moved from the over-40 to under-40 micro-grams/100g category are now at a level thatmeans they would not have to be removed fromtheir current jobs even as the threshold level formedical removal drops.

In 1978, OSHA had estimates prepared of theblood lead levels to be expected if the statutorylimits for lead were set and realized at 50, 100,or 200 micrograms/m3. The levels were expectedto fall as exposures decreased and workers elimi-nated some of the lead accumulated during theirprevious high exposures.

Measured blood lead levels two-and-a-halfyears after the introduction of the standard wereconsistent with projections made on the basis ofachieving a level near so micrograms/m3 in thebattery industry and 100 micrograms/m3 in theother two industries (184). These measurementsare somewhat surprising because the air lead levelsin the industries are above so or 100 micro-grams/m 3. Effective respirator programs and at-tention to personal hygiene have probably con-tributed to the lowering of blood lead levels.

Although no blood lead level has been estab-lished below which symptoms are never found,and there is no level at which symptoms will nec-essarily occur, there is agreement that lower bloodlead levels are associated with lower risks (174).


OSHA has established 40 micrograms/100g as anaction level; when the lead standard is fully im-plemented, workers with blood levels above 50micrograms/100g must be removed from lead ex-posure until their blood lead levels drop below40. The Centers for Disease Control (558) haveconcentrated on 30 micrograms/100g as a levelat which concern should be raised.

costs

Capital expenditures for current controls runat about $1,000 to $1,500 per worker each year.To that must be added the expense of respirators,clothing, and facilities for personal hygiene(showers, changing rooms, etc.)–between $1,000and $1,700 per worker per year. Monitoring andmedical surveillance cost about $500 per workerannually, and the tranfer costs under MRP areexpected to run between $300 and $600 per work-er yearly. Taken altogether, complying with thelead standard is estimated by Goble, et al. to costbetween $2,800 and $4,300 per worker yearly.

In addition to the current costs, Goble, et al.(184) project that future conventional industrialhygiene controls will cost between $8,000 and$9,000 per worker per year in secondary smeltersand battery plants. Future costs in primary smelt-ers are expected to be lower, about $5,200.

Table 5-11 presents estimates of the engineer-ing cost of reducing air lead levels to 50 or 150

Table 5-1 I.—Projected lndustry-Wide Annual Costs ofCompliance With Air Lead Levels of

50 and 150 micrograms/m3

Millions of 1962 dollars

Industry 50 150micrograms/m 3 micrograms/m 3

Primary lead smelting . . 15.5 16.0Secondary lead

smelting . . . . . . . . . . . 24.5 26.4Battery manufacture . . . 97.4 not done

SOURCE: (1S4).

micrograms/m3. The costs are quite close. Onereason is that (according to engineers employedby Charles River Associates (184)) the best con-ventional engineering controls will not reduce ex-posure to 150 micrograms/m3. Another reason isthat isolation booths, if installed, could reduce ex-posures to less than 50 micrograms/3 for aboutthe same as it would cost to reach 150 micro-grams/m 3.

Major process changes, although costing morein capital expenditures, are expected to result inoperating savings. In general, the capital costs ofprocess change may be appropriate if a new plantis to be built, but they outweigh the costs of add-ons in an existing plant unless significant tax sav-ings or credits accompany installation of the newprocess.

Summary of Improvements

The data about workplace air lead and bloodlead levels show that both have decreased sincethe issuance of the OSHA lead standard. Whilethe air lead levels have dropped about 25 percentin primary and secondary smelters and about sopercent in battery plants, they still remain muchhigher than 50 micrograms/m3 that is the goal ofthe standard. At the same time, however, bloodlead levels have dropped appreciably, and in gen-eral are close to the levels predicted for reachingair lead levels between 50 and 100 micrograms/m3.A number of factors—including decreases in leaduptake from the environment in general, changesin the methods for measuring lead, errors in themodel that is used to project blood leads basedon air leads, and greater-than-expected impactsof respirator programs and hygiene practices—have contributed to the apparent better realiza-tion of reductions in blood levels than was pre-dicted. Whatever combination of factors is respon-sible, the falls in blood lead levels are gratifyingand bode well for better health among leadworkers.


EXTENT OF CONTROL TECHNOLOGY USAGE IN THE UNITED STATESThe National Occupational Exposure Survey

(NOES) (see chs. 2 and 12) includes data that de-scribe the extent of the usage of control technol-ogies for the prevention of work-related illness.NOES, conducted from 1980-82, estimates the ex-tent of worker exposure to potentially hazardousworkplace agents. This survey was conducted asa followup to a similar survey, the National Oc-cupational Hazard Survey, conducted in 1972-74.

The sample of businesses in the NOES surveyconsists of approximately 4,000 establishments in67 metropolitan areas throughout the UnitedStates. The sample represents all nonagriculturalbusinesses covered under the Occupational Safetyand Health Act. Data were collected onsite byteams of engineers and industrial hygienists spe-cially trained for the survey.

NOES was conceived for the purpose of record-ing specific worker exposures to potential work-place health hazards. Among the questions thatthe survey attempted to answer were:

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What occupational groups are exposed towhat types of potential health hazards in theUnited States?In what types of industries are these hazardsfound?What control technologies are present to pre-vent work-related disease in terms of plantoperation and occupational safety and healthpractice?What are the exposures by intensity, dura-tion, type of control?What trade name products were present?

Both surveys included questions about demog-raphy and occupational safety and health prac-tice, followed by a walk-through survey of theplant work area to inventory potential exposures.A series of questions specifically aimed at the prac-tice of using controls was asked in NOES.

With the control questions asked in NOES itis possible to analyze the extent of engineeringcontrol usage in the manufacturing sector of thecountry. Areas include practices of material sub-stitution, process change, and the managementof personal protective equipment programs. Thesedata are unique in that there are no other com-prehensive assessments of work-related exposurecontrol practice. Control technology usage maybe classified by plant size and by industry, allow-ing distributions to be done for comparison.

These data may be used to pinpoint patternsof control technology use within and among in-dustry groupings, giving insight about areas whereimprovement is needed. This analysis may alsobe used to assist in setting priorities for controltechnology research.

Information About Controls andAreas for Research

The vinyl chloride, industrial solvent, lead, cot-ton dust, and silica examples show that controltechnologies for workplace exposures can be engi-neered once commitment to control is made.Commitment, however, is often difficult toachieve. For example, in the regulatory proceed-ings concerning new health standards, argumentsare often raised about the harmful health effectsof existing exposure levels, and the costs and fea-sibility of controls (see ch. 14 and box 12-1 in ch.12). In addition, opposition to some governmentalregulation may result simply from employers’ con-cern that an outside authority is telling them whatthey must do to protect workers.

However, as shown by the vinyl chloride andcotton dust examples, the installation of technol-ogies to control workplace hazards can be accom-panied by greater productivity. As seen in the caseof the ventilation control system in the electronics


industry, there are advantages to planning, install-ing, and maintaining control technologies in a sys-tematic way. Anticipation of work-related healthproblems very often reduces the cost of theircontrol.

Access to information about control technol-ogies for workplace health and safety could beimproved. Perhaps the greatest current need is forpublished information about controls in the occu-pational safety and health literature. While thereare journals dedicated to toxicology and epidemi-ology, there are none specific to industrial hygieneengineering. Industrial hygiene journals infre-quently and engineering technical journals onlyrarely include articles about technologies for con-trolling worker exposure to hazardous materials.Yet it has been suggested that such informationshould be part of every engineer’s training andbe readily available as reference material to thepracticing engineer (587).

Published information about specifics of work-place control is sparse for several reasons. First,and probably most significantly, companies thatdevelop controls simply do not take the time topublish details since it is not their business. Onthe other hand, it is likely that some consider theinformation proprietary and keep it unpublishedfor competitive reasons.

In some cases, such as for the control of expo-sures to vinyl chloride, a few companies marketnew technology for preventing work-related in-jury and illness. This, however, appears to be in-frequent and be limited to very large companiessuch as B.F. Goodrich and Dupont. Probablymost companies that have found and use inno-vative control technologies in their plants simplyhave yet to explore workplace control technol-ogies as a market.

University and government researchers havepublished some practical information that can beused by design engineers but the volume of thismaterial is limited. One widely used handbookspecific to ventilation is the ACGIH VentilationManual that is published annually (6). Programssuch as the NIOSH Control Technology Assess-ments have produced useful information for haz-ard control in some specific and some genericmanufacturing processes (see ch. 12).

There is also a dearth of new approaches in thisarea. For instance, First (173) pointed out that littlehas been added to the theory of ventilation sincetwo Ph.D. theses done at Harvard in the 1930s.The tendency has been to retrofit control solu-tions after problems appear rather than to an-ticipate them. Yet there is promise of new meth-ods on the horizon.

Brief and colleagues (74), recognizing the limita-tions of retrofit solutions in preventing work-related injury and illness, have explored tech-niques for designing new plants with new controlsystems built in. They have found that in the past

retrofit control procedures were recommendedwithout being able to judge the effectiveness ofcontrols, until after installation and operation.This retrofit approach is probably not as cost ef-fective as designed-in controls, although cost ef-fectiveness was rarely tested. In many cases ad-ditional administrative and personal protectiveprograms were used to achieve desired workerprotection.

We have embarked on a new era involvingsome major companies and government agenciesinvestigating the impact of engineering design onthe workplace environment. The objective is sim-ple. It states that we will attempt to design intoour plants and operating facilities the necessaryengineered controls to meet occupational healthstandards. Intuitively, we believe that it is morecost-effective to install engineering controls in newplant designs than to retrofit later. Equally as im-portant is the practicality of having an environ-mentally sound plant at the start, rather than onewhich requires modifications later. Retrofitting .controls may be difficult to implement due tophysical factors and the time to implement thechanges after the plant is running.

In this innovative approach, design is based onselection of process equipment controls appropri-ate to the process. The key is to determine emis-sion rates of contaminants from each type of proc-ess equipment used. These data may then be usedto build a near-field dispersion model (a mathe-matical expression of the release and buildup ofcontaminant in workers’ breathing zones) to cal-culate collective concentrations to which work-ers could be exposed. By trying various combina-tions of equipment and controls in the model andtesting them against recommended health stand-

Ch. 5—Technologies for Controlling Work-Related Illness 99

ards, engineers can predict potential worker ex- plied, particularly in plant design stages. Technol-posure and thus design processes with optimum ogies are available but information about specificworker protection and production. These in- solutions is difficult to find because it is seldomvestigators stress the need for interaction between published. Retrofit is the dominant mode evenengineers and occupational safety and health pro- though there is recognition that solutions shouldfessionals at the design stage for this to succeed. be designed into new processes.

Thus, control technology for work-related ill-ness prevention is possible but insufficiently ap-

SUMMARYWorkplace exposures to toxic substances can

be controlled at their source, during transmission,and at the worker. Control at the source includeschanges in the design of a process and substitu-tion of nontoxic or less toxic materials. Control-ling the transmission of a toxic substance can bedone by isolating or enclosing hazard sources,wetting toxic dusts to prevent dispersion, install-ing local exhaust ventilation to capture and carrytoxic substances away, or reducing toxic concen-tration through the use of general dilution ventila-tion. Control at the worker includes the use ofpersonal protective equipment (see ch. 8), workpractices, and administrative procedures. Engi-neering controls that can be designed into a workprocess to control hazard sources and dispersionof contaminants are preferred to other measuresthat may provide less reliable protection. Train-ing (see ch. 10) of supervisors and workers is re-quired to make sure control programs are ef-fective.

Three case studies prepared for this assessmentprovide information on controls for health haz-ards. Exposures to cotton dust cause a debilitatingrespiratory disease known as byssinosis. In theyears following the issuance of a revised OSHAhealth standard concerning cotton dust, the U.S.textile industry has invested heavily in moderniz-zing its operations. The new equipment has led toimproved productivity in this industry, as wellas reduced worker exposures.

Data about workplace air lead and blood leadlevels show that both have decreased since the is-suance of the revised OSHA lead standard in1978. The possible factors to explain the improve-ments in blood lead levels include changes in ex-posures to lead in the workplace air, the use ofmedical removal protection, decreases in theamount of lead absorbed from the environment,changes in lead measuring methods, and improve-ments in respirator programs and hygiene practices.

Silicosis—a disabling lung disease-is causedby silica dust. Control measures include substi-tution with safe abrasives, ventilation, wetting,as well as the use of respirators, work practices,maintenance of ventilation systems, and goodhousekeeping practices.

A considerable amount of information abouthow to design and implement control technologyfor worker protection is available but is not widelydisseminated. Research on improved control tech-nology design and implementation is also needed.For example, little has been added to the basictheory about ventilation since the 1930s. The Na-tional Occupational Exposure Survey conductedby NIOSH collected information which will giveestimates of the extent of worker exposure to po-tential hazards and the current practice of con-trol technology use. These data can potentiallyassist in setting priorities for research on improvedcontrols.

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Technologies for Controlling Work-Related Illness

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