U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Centers for Disease Control and Prevention
National Institute for Occupational Safety and Health
December 1997
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Centers for Disease Control and Prevention
National Institute for Occupational Safety and Health
December 1997
Mention of company names or products does not constitute endorsement by the Centers for Disease Control and Prevention (CDC).
DHHS (NIOSH) Publication No. 97-150
The Occupational Safety and Health Act of 1970 (Public Law 91-596) assures as far as possible every working man and woman in the Nation safe and healthful working conditions. The act charges the National Institute for Occupational Safety and Health (NIOSH) with recommending occupational safety and health standards and describing exposures that are safe for various periods of employment, including but not limited to the exposures at which no worker will suffer diminished health, functional capacity, or life expectancy as a result of his or her work experience.
This document represents the efforts of NIOSH researchers who have worked in collaboration with industry, labor, and other governmental organizations to protect the health of workers in the commercial drycleaning industry. Drycleaning is predominantly a small business industry with a substantial percentage of minority workers who are exposed to a wide array of hazards. The purpose of the document is to present the research findings and provide guidance to regulatory agencies and owners of drycleaning shops regarding hazard control measures. Control technologies and methods are presented for reducing occupational exposures to perchloroethylene (PERC), as well as for controlling exposures to spotting chemicals, fire, and ergonomic hazards. It is not intended to provide total information in all areas of safety and health.
Significant attention has been paid to the effects of perchloroethylene on the environment while the effects of perchloroethylene on workers have often been overshadowed. Health effects associated with exposure to perchloroethylene include depression of the central nervous system; damage to the liver and kidneys; and impaired memory, confusion, and dizziness. There is increasing evidence of human carcinogenicity. The uncontrolled use of PERC has the potential to cause widespread harm to the health of the workers, the people living near drycleaning shops, the general public, and the global environment.
This document is a positive contribution to worker health and safety. It is an essential reference on health and safety in the drycleaning industry, which I strongly recommend to all concerned. It is my hope that this document will assist in providing a safe and healthful working environment by describing the most effective control technologies and procedures.
Linda Rosenstock,
M.D., M.P.H.
Director, National Institute
for
Occupational Safety and Health
Centers for Disease Control
and Prevention
ABSTRACTThis report investigates control methods and technologies used in the drycleaning industry for reducing occupational exposures to tetrachloroethylene, also known as "perchloroethylene" (PERC). It also examines drycleaning machines that use petroleum-based solvents. It addresses methods for controlling exposures to spotting chemicals, fire, and ergonomic hazards in commercial drycleaning shops. Data were gathered during ten field surveys at drycleaning shops across the U.S. and through a World Health Organization (WHO) fellowship in Europe. The study by the National Institute for Occupational Safety and Health (NIOSH) looked at various categories of drycleaning equipment, such as transfer and dry-to-dry, vented and nonvented, and modern machines equipped with various vapor recovery devices. The evaluated shops maintained full-shift, time-weighted average (TWA) exposures to PERC below 25 ppm; however, peak exposures during machine loading and unloading were frequently near 2,000 ppm. Most operator exposures could have been further reduced during machine loading and unloading by additional control measures: the use of another cleaning media, such as petroleum-based solvents or water; the isolation of the drycleaning process through "satellite shops"; a switch to state-of-the-art drycleaning machines equipped with both refrigerated condensers and carbon adsorbers; and more effective use of local and general ventilation. Inhalation of spotting chemicals was not a significant hazard; however, isolation of this process would avoid unnecessary exposure to other workers. A number of recommendations are given to further reduce spotting chemical exposures. Ergonomic hazards usually involve repetitive motions and awkward postures. In drycleaning, these problems primarily occur at the pressing stations and can be controlled. Redesigned, adjustable workstations for pressing will decrease the awkward postures and excessive reaching. Frequent breaks and worker rotation will reduce worker repetition. Fire hazards can be reduced by a two-pronged approach. The greatest risk of fire and explosion in drycleaning shops comes from petroleum-based solvents used in some drycleaning machines. First, new petroleum-based solvents and machines, both of which are inherently safer than those traditionally utilized, are currently available and could serve as an alternative to PERC in some U.S. shops. Second, all shops should comply with appropriate National Fire Protection Association/Building Officials & Code Administration (NFPA)/(BOCA) codes to reduce the risk of fire not only in the drycleaning area but also throughout the entire shop. |
Under the authority of the Occupational Safety and Health Act of 1970 (Public Law 91-596), the National Institute for Occupational Safety and Health (NIOSH) conducts research to prevent occupational safety and health problems through the application of control technology in the workplace. The goal of this program is to assist in preventing hazardous exposures to workers and to document successful approaches and control measures.
This report evaluates control methods and systems for reducing perchloroethylene (PERC) exposures in commercial drycleaning shops throughout the United States. During ten field surveys, NIOSH researchers inspected various categories of drycleaning equipment, such as transfer and dry-to-dry, vented and nonvented, and modern machines equipped with various vapor recovery devices. This study also addressed control of health and safety hazards related to petroleum-based drycleaning solvents, control of exposure to spotting chemicals, and control of ergonomic risk factors.
Additionally, NIOSH researchers received a World Health Organization (WHO) fellowship to study methods and controls to reduce occupational exposure to and environmental emissions of PERC in Europe. This study involved gathering information concerning drycleaning regulations, equipment, exposure levels, work practices, and alternatives to PERC in Europe. Important research into new technologies for reducing emissions and exposure to PERC has been conducted in Europe. These technologies include improved design and engineering controls for PERC drycleaning machines and alternative technologies, such as cleaning with petroleum-based solvents or aqueous-based cleaning methods. The European visit enabled NIOSH researchers to learn about differences in the drycleaning processes between the U.S. and Europe. Findings from this fellowship are also included in this report.
Information gathered during the study was supplemented by a literature review. This report provides a reference for anyone interested in protecting drycleaning workers from exposures to PERC, spotting chemicals, ergonomic risk factors, and fire hazards. Individual in-depth and walk-through survey reports, which include more detailed information on specific characteristics of each drycleaning shop and control systems studied, are available from the National Technical Information Service, Port Royal Road, Springfield, Virginia 22161.
Manuscript Authored by: Gary S. Earnest, M.S., P.E.,
C.S.P. |
Manuscript Prepared by:
Bernice L. ClarkRobin F. Smith
Manuscript Edited by: Anne L. Votaw
Cover Prepared by: Anne M. Stirnkorb
Survey and Technical Assistance by:
Jim P. Agee |
Paul A. Jensen, Ph.D., P.E., C.I.H. | |
Phillip A. Froehlich, M.S. |
James H. Jones | |
Michael G. Gressel, M.S., C.S.P. |
Ronald J. Kovein | |
Ronald M. Hall |
Dennis M. O'Brien, Ph.D., P.E., C.I.H. |
The authors would like to thank the following individuals and organizations for providing input to the study protocol: International Fabricare Institute, Fabritec International, Dryclean U.S.A., Boewe Passat Corporation, Union of Needle Trades Industrial and Textile Employees.
The authors would like to thank the following individuals and organizations for providing input and general assistance throughout the study: Boewe Passat Corporation, MultiTEX Corporation, Realstar Corporation, Union Corporation, Hohenstein Institute, Kruessler Corporation, The World Health Organization, U.S. Environmental Protection Agency, Michigan Department of Public Health.
The authors would like to express a special thanks to Mr. Max Zimmerman.
INTRODUCTION
Background Profile of the U.S. Drycleaning WorkforcePerchloroethylene
(PERC)Link Between PERC
Exposure and CancerPERC Evaluation
CriteriaCurrent ExposuresSolvent
Alternatives to PERCHealth Effects of
Petroleum-Based Drycleaning SolventsEvaluation Criteria
for Mineral SpiritsExposure to
Spotting ChemicalsEvaluation Criteria
for Spotting ChemicalsCombined ExposuresErgonomic Risk
FactorsErgonomic Risk
Factors in DrycleaningErgonomic CriteriaFire HazardsFlammability of
Petroleum-Based SolventsFire Codes
SpottingMachine CleaningPressingTwo Basic Types of
MachinesTwo Primary Vapor
Recovery TechnologiesDrycleaning
Machine Types in the U.SThe Evaluated
Drycleaning MachinesThe Evaluated
Transfer Drycleaning MachineThe Evaluated
Dry-to-Dry, Vented Drycleaning MachineThe Evaluated
Dry-to-Dry, Nonvented MachineModern
"Fifth" Generation" Machine Technology
Air SamplingTransfer EquipmentDry-to-Dry, Vented
EquipmentDry-to-Dry, Nonvented
EquipmentDry-to-Dry, Nonvented
with Residual ControlStatistical
Analysis of Air Sampling DataReal-Time
MonitoringTransfer EquipmentDry-to-Dry, Vented
EquipmentDry-to-Dry, Nonvented
EquipmentDry-to-Dry, Nonvented
with Residual ControlGarment Off-GassingMachine
MaintenanceVentilationCase 1Case 2Case 3WaterproofingPersonal
Protective EquipmentHow Exposures
OccurMachine Design and
Number of MachinesVentilationMaintenance and
HousekeepingEquipment Operation
or Operating ProceduresOverall Control
StrategiesSubstitutionIsolationDrycleaning Machine
DesignMachine RetrofitsVentilationAdministrative
ControlsCost of New
Drycleaning MachinesSubstitution
RecommendationsIsolation
RecommendationsMachine Design
RecommendationsMaintenance
RecommendationsVentilations
RecommendationsWaterproofing
RecommendationsWork Practice
RecommendationsPersonal
Protective Equipment Recommendations
Garment TransferPressing
OperationsGarment BaggingGarment TransferMulti-Press
StationShirt Pressing
StationGarment Bagging
Area
Drycleaning
Machine DesignOccupancyHeat LoadEgressFire ExtinguishersFire Detection and
Suppression SystemsFigure 1. The drycleaning process flow diagram
Figure 2. Five-minute and fifteen-minute personal exposures to PERC from transfer equipment
Figure 3. Time-weighted average worker exposure to PERC from "fifth generation" drycleaning machines (four days of air sampling)
Figure 4. Operator exposure to PERC during clothing transfer, loading washer, and hanging clothing
Figure 5. Operator exposure to PERC from a dry-to-dry, vented drycleaning machine during unloading/loading
Figure 6. Real-time measurements of PERC concentration near carbon canister exhaust of dry-to-dry, vented drycleaning machine
Figure 7. Operator exposure to PERC from a dry-to-dry, nonvented drycleaning machine during loading, unloading, and hanging clothing
Figure 8. Operator exposure to PERC from "fifth generation" machine during the first cycle of the day
Figure 9. Operator exposure to PERC from "fifth generation" machine during unloading
Figure 10. A comparison of typical swatch off-gassing from a refrigerated, dry-to-dry drycleaning machine versus a "fifth generation," dry-to-dry drycleaning machine
Figure 11. Operator exposure to PERC during maintenance on lint and button traps of a dry-to-dry, vented drycleaning machine
Figure 12. Operator exposure to PERC while cleaning lint traps on a "fifth generation" machine
Figure 13. Operator exposure to PERC while cleaning the stills on two "fifth generation machines
Figure 14. Worker exposure to PERC during changing clay/carbon solvent filters on a transfer machine
Figure 15. Exposure to PERC while cleaning lint traps on two dry-to-dry, nonvented drycleaning machines
Figure 16. Airflow balance in/out of drycleaning room having effective general ventilation
Figure 17. Air currents near the drycleaning machine in a room having poor general ventilation
Figure 18. Average operator exposure to PERC during dip-tank waterproofing operations having no local ventilation
Figure 19. Operator exposure to PERC during dip-tank waterproofing operations having no local ventilation
Figure 20. Factors influencing worker exposure to PERC in drycleaning shops
Figure 21. Shrinkage comparison of wool, silk, and rayon garments because of drycleaning and wet cleaning
Figure 22. Percentage of garments having over 2% shrinkage when cleaned 1 and 5 times in solvent versus water
Figure 23. Concentration of PERC saturated air
Figure 24. PERC cylinder concentration during the vapor recovery process of a "fifth generation" drycleaning machine
Figure 25. Flow diagram and major components of a "fifth generation" drycleaning machine
Figure 26. Percentage of PERC samples in German drycleaning shops at various concentrations from 1990 to 1994
Figure 27. Real-time solvent concentrations measured over a basket which is slowly being filled with garments as they are spotted
Figure 28. Limits of flammability for combustible liquids
Table 1. Quantity of U.S. Drycleaners and Number of Employees
Table 2. Passive Air Monitoring Results Collected by International Fabricare Institute
Table 3. Hazards Studies in Plant Survey Reports 8
Table 4. Number of U.S. Drycleaning Machine Types and Emission Controls/1991
Table 5. Time-Weighted Average Worker Exposures to PERC (for entire survey
Table 6. Average Personal Exposure to PERC (operators only
Table 7. Results of One-Tailed T-Test Testing Hypothesis That Operators Are Exposed to >25 PPM (by shop/control technology
Table 8. Average Personal Exposure to PERC (all personal samples by job title)
Table 9. Characteristics of Potential Alternative Drycleaning Solvents
Table 10. Cost of Three Categories of Drycleaning Equipment
Table 11. Physical Properties of New Hydrocarbon and Currently Used Drycleaning Solvents
Table 12. Drycleaning Machine Design Requirements from German Law
Table 13. Methods of Control
Table 14. Recommended Maintenance Schedule for Drycleaning Machines
Table 15. TWA Perconal Solvent Exposures During Spotting
Table 16. Spotters Short-Term Solvent Exposures
INTRODUCTION
Historically, drycleaning was performed by hand, using petroleum-based solvents that had dangerously low flash points.1 In fact, drycleaning is believed to have originated in France in 1825 when a worker in a dye and cleaning factory spilled lamp oil, a flammable petroleum-based solvent, on a soiled tablecloth.1 When the tablecloth dried, the spots were gone. The drycleaning industry first used turpentine and kerosene before moving to benzene and gasoline. All of these solvents had one major disadvantage: they were flammable and caused fires and explosions.2
Over time, better petroleum-based solvents were introduced, having higher flash points. In 1928, W.J. Stoddard, president of the U.S. National Institute of Drycleaning (now the International Fabricare Institute), introduced Stoddard Solvent, a nearly odorless, petroleum-based solvent, which gained widespread acceptance in the industry.1 Stoddard Solvent™, having a flashpoint of approximately 49°C (120°F), reduced the risk of fire and explosion, but did not eliminate it. Petroleum-based solvents eventually were restricted in urban areas because of their inherent fire hazard.
Near the turn of the century, chemists learned to synthesize chlorinated hydrocarbons and produce them in large quantities. Many of these nonflammable solvents came into use for drycleaning. Early on, carbon tetrachloride was the favorite chlorinated hydrocarbon for drycleaning; but because of its toxicity and aggressiveness to metals, textiles, and dyes, it was gradually replaced in the 1940s and 1950s by trichloroethylene and tetrachloroethylene.2 Tetrachloroethylene is also commonly known as "perchloroethylene" (PERC).
In the 1960s, CFC 113, a chlorofluorocarbon solvent, was used in drycleaning, but never reached a significant market share. Because of its potential to deplete ozone and cause global warming, it is now banned in the U.S. and in most other countries under the Montreal Protocol. Today, approximately 90% of U.S. drycleaners use PERC in their machines.3 PERC (C2Cl4) is a colorless, clear, heavy liquid with an ethereal odor. The odor threshold is approximately 30 parts per million (ppm).4 However, because significant adverse health effects have been discovered, many countries have imposed stringent regulations for the control of PERC exposures and emissions.Back to the Table of Contents
THE NEED FOR CONTROLS Background
In the late 1970s and early 1980s, the National Institute for Occupational Safety and Health (NIOSH) sponsored an engineering control technology study in the drycleaning industry.5 Among other health hazards, this evaluation found high exposures to the drycleaning solvent PERC. In 1988, the Occupational Safety and Health Administration (OSHA) Director of Federal-State Operations conducted a nationwide query of the OSHA State Consultation Programs to assess which small businesses were considered to be "high risk." The drycleaning industry was the second most mentioned small business, preceded only by autobody repair shops.6 In 1993, NIOSH researchers conducted a preliminary hazard analysis and based upon that analysis decided to evaluate control of PERC exposures, spotting chemical exposures, ergonomic risk factors, and fire hazards.
Significant changes involving equipment, processes, and work practices have
occurred within the drycleaning industry since the earlier NIOSH study. These changes
include alternative solvents and cleaning methods; a shift away from older drycleaning
machines that require manual transfer of solvent-laden garments between washer and dryer
to modern, closed-loop machines; and innovations in vapor recovery equipment and other
technologies to reduce occupational exposures and environmental emissions. Many of these
changes have been initiated by new epidemiologic, toxicologic, and environmental data for
the primary solvent PERC. Nonetheless, many of the exposure problems identified during
studies in the late 1970s and early 1980s still exist in the U.S. because traditional
drycleaning machines are still being used. Many of the modern controls that have been
developed are cost prohibitive for small shops, and some work practices are
inadequate.Profile of the U.S. Drycleaning Workforce
The Business America on Disc® CD-ROM7 file includes 48,087 drycleaners in the U.S. The distribution by number of employees is shown in Table 1. If the number of employees/shop is a reliable estimate, between 150,000 and 365,000 individuals work in drycleaning shops. Seventy percent (33,853) of shops employ one to four workers. Unlike the OSHA list of employees, which does not include nonsalaried owners, the Business America definition includes owners on site as employees since many of these firms are family operated. The U.S. Environmental Protection Agency (EPA) recently estimated that there were 30,000 commercial drycleaning shops and approximately 244,000 employees. The National Occupational Exposure Survey8 (NOES) estimated that in 1982-83 there were over one-half million drycleaning shop employees in more than 40,000 plants potentially exposed to PERC.
Table 1
Quantity of U.S. Drycleaners and Number of Employees
Number of |
Number of |
Percentage of |
Minimum Total |
Maximum Total |
1-4 |
33,853 |
70 |
33,853 |
135,412 |
5-9 |
8,252 |
17 |
41,260 |
74,268 |
10-19 |
3,482 |
7 |
34,820 |
66,158 |
20-49 |
1,095 |
2 |
21,900 |
53,655 |
50-99 |
175 |
0.3 |
8,750 |
17,325 |
100-249 |
62 |
0.1 |
6,200 |
15,438 |
250-499 |
6 |
0.01 |
1,500 |
2,994 |
500-999 |
1 |
0.01 |
500 |
999 |
UNKNOWN |
1,161 |
2 |
1,161 |
1,161 |
TOTAL |
48,087 |
100 |
149,944 |
367,410 |
Potential Hazards
Perchloroethylene (PERC)
In the U.S. PERC is the most commonly used drycleaning solvent and is also occasionally used as a spotting agent. PERC can enter the human body through both respiratory and dermal exposure. Although nonflammable, if PERC is heated sufficiently, thermal decomposition will result in the formation of hydrogen chloride and phosgene gases. Symptoms associated with respiratory exposure include the following: depression of the central nervous system; damage to the liver and kidneys; impaired memory; confusion; dizziness; headache; drowsiness; and eye, nose, and throat irritation. Repeated dermal exposure may result in dry, scaly, and fissured dermatitis.9
Link Between PERC Exposure and Cancer.—The possible link between PERC exposure and cancer was first suspected through studies conducted by the National Cancer Institute (1977) and the National Toxicology Program (1986). A 1987 EPA study of PERC showed that, in addition to the numerous adverse health effects already known and outlined above, there was evidence of carcinogenicity. In December 1991, the EPA began regulating PERC as a hazardous air pollutant under Section 112 of the Clean Air Act.10 Other studies, including one at NIOSH, showed an elevated risk of urinary tract,11-13 esophageal,14 and pancreatic cancer15,16 among individuals who worked in drycleaning establishments; however, since most of these studies involved exposures to various solvents in addition to PERC, a conclusive link between PERC exposure and cancer could not be made.
Although PERC has been a known animal carcinogen since the early 1990s,17 the International Agency for Research on Cancer (IARC) did not find adequate evidence to classify the solvent as a possible human carcinogen until recently.18 In 1995 the IARC classified PERC in group 2A, meaning that it is probably carcinogenic to humans. IARC also has recently classified drycleaning in group 2B, meaning that it is possibly carcinogenic to humans. Cancer mortality research is continuing at NIOSH and other research organizations.
PERC Evaluation Criteria.—The current OSHA permissible exposure limit (PEL) for PERC is 100 ppm, as an 8-hour time-weighted average (TWA). The acceptable ceiling concentration is 200 ppm for five minutes in any three-hour period, not to exceed a maximum peak of 300 ppm.19 OSHA had lowered the PEL to 25 ppm in 1989 under the Air Contaminants Standard.20 In July 1992, the 11th Circuit Court of Appeals vacated this standard. OSHA is currently enforcing the 100 ppm standard; however, some states operating their own OSHA-approved job safety and health programs continue to enforce the lower limits of 25 ppm. OSHA continues to encourage employers to follow the 25 ppm limit.21 NIOSH considers PERC to be a potential occupational carcinogen.22 The American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV®) for PERC is 25 ppm.23
Current Exposures.—OSHA Integrated Management Information System (IMIS) data from 1984-1988 indicated that approximately 20% of exposures measured in U.S. drycleaning shops exceeded 100 ppm for PERC.24 The more recent and comprehensive data gathered by the International Fabricare Institute's (IFI) vapor monitoring service, using passive monitoring badges, reported a lower percentage of shops exceeding 100 ppm TWA. A summary of the IFI data is shown in Table 2.
Table 2
Passive Air Monitoring Results
Collected by International Fabricare Institute
| |
Before
1/1/87 |
1/1/87-9/30/89
|
After
10/1/89 |
| TRANSFER (AVG TWA PPM) |
55.3 ppm | 46.4 ppm | 42 ppm |
| %>25 ppm | 76.2% | 59.9% | 56.8% |
| %>100 ppm | 7.7% | 5.6% | 7.0% |
DRY-TO-DRY*** |
20.5 ppm | 16.1 ppm | 17.2 ppm |
| %>25 ppm | 24.3% | 18.5% | 18.6%* 17.2%** |
| %>100 ppm | 1.0% | 0.8% | 1.3%* 0.8%** |
*Denotes dry-to-dry
refrigerated with small vent to purge cylinder at end of dry cycle.
**Denotes dry-to-dry refrigerated with no vent.
***Denotes standard dry-to-dry with water-cooled condenser and vent at end of dry cycle.
Solvent Alternatives to PERC
Alternative drycleaning solvents are available, which can be effectively substituted for PERC. All petroleum-based, drycleaning solvents are aliphatic hydrocarbons having a carbon chain of eight to twelve carbons. Hydrocarbon solvents are usually produced through fractional distillation of crude oil to produce various cuts, such as gasoline, naphtha, Stoddard solvents, mineral spirits, and kerosene. There are inherent properties that all petroleum-based drycleaning solvents possess. These properties include flammability, solvent power, volatility, odor, and toxicity.25
Petroleum-based solvents have a much lower Kauri-Butanol (KB) value than PERC. The KB value is a relative index of solvent power. On this scale, benzene is equal to 100, and all other solvents are compared to it. Higher KB values imply better removal of oil and grease stains.26 Linear paraffins generally have relatively low KB values while aromatics generally have high KB values.
Volatility refers to the propensity of a liquid to vaporize and is quantitatively expressed as vapor pressure. The evaporation rates for Stoddard solvents are between three and six times higher than the reference solvent, n-butyl acetate. Newer petroleum-based solvents have rates as low as 10% of the reference solvent. Because petroleum-based, drycleaning solvents generally have a lower vapor pressure than PERC, the drying process takes longer for garments cleaned with these solvents than those with PERC.
Petroleum-based solvents have a distinctive odor. Linear and branched hydrocarbons have relatively low odors while naphthenes and aromatics have strong and usually objectionable odors. Petroleum-based solvents also provide a better living condition for the growth of bacteria when water is present. The products of metabolism can cause very unpleasant odors, which can be retained by the garments. Because of this, distillation is very important, as well as antibacterial additives in the solvent.27 Petroleum solvents are toxic, but they are generally thought to be less toxic than PERC. Because the vapor pressures are lower than PERC, exposures from inhalation will generally be lower.
Health Effects of Petroleum-Based Drycleaning Solvents.—Aliphatic hydrocarbons are asphyxiants and central nervous system depressants. Aliphatic hydrocarbons have different toxicological properties, often based upon the length of their carbon chains. Most will cause irritation of the skin and mucous membranes of the upper respiratory tract. Repeated and prolonged exposure may cause dermatitis. Aspiration of liquid aliphatic hydrocarbons may cause diffuse chemical pneumonitis, pulmonary edema, and hemorrhage. Contamination of aliphatic hydrocarbons by benzene will significantly increase the hazard.
The most common petroleum-based drycleaning solvents in the U.S. are Stoddard solvents and mineral spirits. Sufficient quantities of either of these solvents can cause central nervous system depression. Symptoms include inebriation followed by headache and nausea. In severe cases, dizziness, convulsions, and unconsciousness occasionally result. New petroleum-based solvents have recently been developed; however, there is a lack of health effects data for these new solvents.
Evaluation Criteria for Mineral Spirits.—Some shops use mineral spirits in their drycleaning machine. The current OSHA PEL for mineral spirits is 500 ppm, 8-hour TWA. There is no 15-minute short-term exposure limit or peak exposure limit. The NIOSH recommended exposure limit for mineral spirits is 350 mg/m3 or approximately 66 ppm. The American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV®) for mineral spirits is 100 ppm.28Exposure to Spotting Chemicals
The chemicals commonly used in the U.S. to treat stains through pre-spotting and post-spotting are trichloroethylene; various ketones, especially methyl isobutyl ketone; petroleum naphtha; and hydrofluoric acid. Individuals who perform the spotting process could be exposed to many of these toxic chemicals through skin or eye contact and inhalation of vapors. However, the primary hazard posed by the majority of the chemicals is skin damage, resulting from chronic or acute exposure, or injury to the eyes. Although chemicals that readily vaporize and have a high toxicity can pose an inhalation risk, previous studies have shown that inhalation exposures are minimized because of the limited quantities of chemicals and the intermittent nature and short duration of the spotting task.5 Commonly, PERC exposures during spotting are many times lower than OSHA standards, as are other spotting chemical exposures, which are often below detection limits.29
Trichloroethylene is a colorless, nonflammable, noncorrosive liquid, having a "sweet odor" that is characteristic of some other chlorinated hydrocarbons. Exposure to trichloroethylene vapor can cause irritation of the eyes, nose, and throat. Prolonged skin contact with liquid may cause dermatitis. Acute exposure depresses the central nervous system and may cause headache, dizziness, vertigo, tremors, and nausea, or vomiting. In extreme cases, unconsciousness and death have been reported. Trichloroethylene addiction and peripheral neuropathy have been reported.9
The ketone family includes acetone, diacetone, methyl ethyl ketone, methyl n-propyl ketone, and methyl isobutyl ketone. Methyl isobutyl ketone is the one ketone that is primarily used in paint, oil, and grease removers. The route of entry for ketones is inhalation of vapors or percutaneous absorption. These solvents produce dry, scaly, and fissured dermatitis after repeated exposure. High vapor concentrations may irritate the conjunctiva and mucous membranes of the nose and throat, producing eye and throat symptoms. High concentrations can produce narcosis with symptoms of headache, nausea, lightheadedness, vomiting, dizziness, incoordination, and unconsciousness.9
Petroleum naphtha is an organic solvent used to dissolve or soften oils, greases, paints, and varnishes. Route of entry for this chemical is inhalation of vapors or percutaneous absorption. Naphthas are irritating to the skin, the conjunctiva, and the mucous membranes of the upper respiratory tract. Skin "chafing" and photosensitivity may develop after repeated contact with the liquid. If confined against skin by clothing, the naphthas may cause skin burns. Sufficient quantities cause central nervous system depression, and symptoms include inebriation, headache, and nausea.9
Dilute hydrofluoric acid poses a greater risk than the other spotting chemicals of acute dermal exposure; however, many of these chemicals can cause occupational dermatitis from chronic exposure to the skin. Hydrogen fluoride and its aqueous solution, hydrofluoric acid, are primary irritants of skin, eyes, mucous membranes, and lungs. Thermal or chemical burns may result from contact. Chemical burns cause deep tissue destruction and may not become symptomatic until several hours after contact, depending on the concentration. Nosebleeds and sinus trouble may develop following chronic exposure to low levels of fluoride in air.9
Evaluation Criteria for Spotting Chemicals.—The following criteria for spotting chemicals applies to chemicals for which air sampling was performed. Trichloroethylene has a PEL of 100 ppm as an 8-hour TWA, and a short-term exposure limit (STEL) of 200 pm;19 The NIOSH recommended exposure limit (REL) is 25 ppm, as an 8-hour TWA.20 For 2-butoxyethanol, the OSHA PEL is 50 ppm27 and the NIOSH REL is 5 ppm.20 For hexylene glycol, NIOSH recommends a ceiling of 25 ppm.20 For methyl isobutyl ketone (MIBK), the OSHA PEL is 50 ppm, and the STEL is 75 ppm.27 For n-butyl acetate, both NIOSH and OSHA have a PEL/REL of 150 ppm, and the STEL is 200 ppm.20,27
Combined Exposures.—The combined exposures of the drycleaning solvent PERC with various spotting chemicals is a concern. The ACGIH TLV® value for PERC is 50 ppm. Because PERC and other drycleaning/spotting solvents have some similar health effects, the additive effect of exposure must be computed as a combined exposure (CE).
Ergonomic Risk Factors
Ergonomics is the study of human abilities and characteristics that affect the design of equipment, systems, and jobs. Its aims are to improve efficiency, safety, and well being. As such, ergonomics can be applied to relieve and prevent work-related injury or illness to the musculoskeletal system of the worker. Ergonomic risk factors can include excessive manual force, repeated and sustained exertions, temperature extremes, vibration, and awkward postures resulting from inappropriately designed workstations, equipment, and work methods. Other factors are excessive work rates and duration, external pacing of work, shift work, imbalanced work to rest ratios, and restriction of worker body movement. Work-related musculoskeletal disorders can result in damage to tendons, tendon sheaths, muscles, nerves, and ligaments of the area affected.30,31
Highly repetitive tasks may consist of rapid and frequent high velocity muscle contractions. Such tasks cause the muscles to develop less tension than when contracting slowly and thereby require more muscle effort and recovery than less repetitive tasks.32 Insufficient recovery time can contribute to the incident rate of cumulative trauma disorders and can compound the musculoskeletal symptoms from repetitive tasks. In one study that did not involve drycleaning workers, the prevalence of tenosynovitis and humeral tendinitis was significantly higher for workers engaged in machine-paced repetitive assembly work than for workers with variable tasks. Repetitive motions of the hands for some workers reached up to 25,000 cycles per workday.33
Awkward or sustained postures can pose a risk of biomechanical stress to the body, especially the joints of the upper extremities and surrounding soft tissue. Several shoulder ailments, such as thoracic outlet syndrome, have been associated with workers repeatedly reaching above shoulder level.34 Reaching above shoulder level is an activity that frequently occurs in drycleaning shops during pressing and hanging of garments. In addition, work postures involving elevated arms could accelerate tendon degeneration by increasing the friction of tendons.35 This increased friction could be related to a decreased amount of synovial fluid acting as a lubricant.
Ergonomic Risk Factors in Drycleaning.—Ergonomic risk factors in the drycleaning industry primarily occur among workers performing pressing operations that are dynamic and repetitive tasks, requiring reaching, precision gripping, and maintenance of awkward postures. These awkward postures are also present during material handling when heavy lifting may occur. In addition, pressers spend much of the day standing, which adds a potential risk for the lower limbs. Studies have shown that muscles subjected to static work require more than 12 times longer than the original muscle-contraction duration for complete recovery from fatigue.36 Information gathered by NIOSH researchers has shown a high incidence of back pain among laundry and drycleaning workers.37
Ergonomic Criteria.—Ergonomic risk factors related to garment pressing are evaluated through time study and evaluation of workstation design and anthropometry. High repetition/insufficient recovery time, awkward postures, and other risk factors all contribute to cumulative trauma disorders.27 Repetitiveness and recovery time are evaluated according to cycle time. Low repetition jobs are categorized as such if the cycle time exceeded 30 seconds or less than half the cycle time involved to perform the same kind of task. High repetition jobs are those with cycle times less than 30 seconds or over half the cycle devoted to similar tasks.38 Awkward and sustained postures are examined with respect to guidelines found in the current literature.
Fire Hazards
Drycleaning with petroleum-based solvents differs significantly from drycleaning with PERC. The difference goes beyond the fact that the petroleum-based solvents are flammable and PERC is not. However, when the health and safety hazards of petroleum-based solvents are considered, flammability is the most important property.
Flammability of Petroleum-Based Solvents.—Approximately 10% of drycleaning shops in the U.S. use traditional, petroleum-based solvents, such as Stoddard Solvent/mineral spirits. All of these solvents are flammable or combustible liquids. Mineral spirits is a class II, combustible liquid with a flash point of 49°C (120°F). Its lower explosive limit is 0.7% or 7,000 ppm.
Exposure to the products of combustion presents numerous hazards to humans. Most prominent among these are effects from heat, impaired vision because of smoke density or eye irritation, narcosis from inhalation of asphyxiants, and irritation of the upper or lower respiratory tracts. These effects often occur simultaneously during a fire and can contribute to physical incapacitation, loss of motor coordination, faulty judgment, disorientation, restricted vision, and panic. Smoke and gases are responsible for approximately 70% of deaths during a fire.39
Carbon monoxide is generally the most abundant toxic gas produced during a fire. Carbon monoxide is produced in an accidental fire when some of the carbon present in organic materials is incompletely oxidized. Because of the large number of textiles present in drycleaning shops, the production of hydrogen cyanide gas is another cause for concern during a fire. Hydrogen cyanide is produced from burning materials that contain nitrogen. Nitrogen is present in natural and synthetic materials, such as wool, silk, acrylonitrile polymers, and nylons. Hydrogen cyanide is a rapidly acting toxicant, which is approximately 20 times more toxic than carbon monoxide.27
Fire Codes.—The fire laws of the state, county, fire district, or community delegate general responsibility and authority to the fire officials involved in fire prevention activities. Many large cities have adopted some regulations from codes written by national technical organizations, such as the National Fire Protection Association (NFPA) or the Building Officials and Code Administrators (BOCA). Codes affecting drycleaners that are commonly adopted are:
NFPA 30—Flammable and Combustible Liquids Code,
NFPA 32—Standard for Drycleaning Plants,
NFPA 101—The Life Safety Code,
BOCA Basic Fire Prevention Code.
Some older, drycleaning shops are not required to comply with codes that were passed after that shop began operation. This process is known as "grandfathering." However, compliance with current codes should reduce the risk of a fire and the associated property damage, injury, or death. Compliance may also reduce property insurance premiums. According to NFPA 101, drycleaning plants are classified as industrial occupancies. According to NFPA 101 and the BOCA code for drycleaning plants, those facilities having greater than 60 gallons of combustible liquid present are considered a high hazard area.
THE STUDY
Research Objectives
NIOSH began the present study of the
drycleaning industry as a re-evaluation of the 1980 NIOSH Report. Investigators wanted to
determine which of the previous engineering control recommendations were still valid, in
addition to providing drycleaners with current recommendations for practical control
measures. The focus of this study was to determine the best controls for PERC exposure;
however, other health and safety hazards in the industry were evaluated on a more limited
basis.
NIOSH researchers prepared a preliminary hazard analysis (PHA) for the drycleaning industry. The PHA was based upon previous industry studies and walk-through surveys. For this PHA, a hazard was defined as an activity or condition that posed a threat of loss. During this analysis, the hazards listed below were identified:
p inhalation of PERC and other solvent vapors
p ergonomic risk factors
p exposure to hazardous chemicals used in the spotting process
p fire hazards
p direct (dermal) exposure to PERC
p thermal burns
p heat stress
p mechanical hazards
p electrical hazards
p slips/ trips/ falls
These hazards are listed from top to bottom in decreasing order of risk. The level of risk was based upon two factors:
1. likelihood of occurrence
2. severity of consequence
Each risk ranking is of a qualitative nature based upon the professional judgment of the authors. Because of limited resources, the authors concentrated on the following health and safety hazards in the drycleaning industry:
p inhalation of PERC and other solvent vapors
p ergonomic risk factors
p exposure to hazardous chemicals used in the spotting process
p fire hazards
The study objective was met by evaluating controls for the various hazards and documenting results in NIOSH reports as shown in Table 3.40-49
Table 3
Hazards Studies in Plant Survey Reports
ECTB |
PERC |
PERC |
|
Spotting |
|
Fire |
| 201-11a | X |
X |
||||
| 201-12a | X |
|||||
| 201-13a | X |
|||||
| 201-13b | X |
|||||
| 201-14a | X |
|||||
| 201-15a | X |
|||||
| 201-16a | X |
X |
||||
| 201-17a | X |
|||||
| 201-18a | X |
X |
X |
|||
| 201-19a | X |
X |
Study Design
Ten drycleaning shops were visited during walk-through and in-depth surveys between August 1993 and January 1995. Following literature searches and reviews of previous NIOSH research reports, NIOSH investigators conducted four walk-through surveys to observe a variety of drycleaning operations. Photographs were taken during these initial surveys, as well as limited air sampling and ventilation measurements.
Results of the walk-through surveys helped determine specific businesses of interest for the six in-depth surveys. NIOSH engineers, industrial hygienists, and ergonomists surveyed each site, evaluating equipment, controls, and potential hazards (exposures to PERC and spotting chemicals, ergonomic risk factors, and fire hazards). Air sampling, video-exposure monitoring, ventilation system measurements, and process and workplace observations were performed. These data were evaluated to determine the effectiveness of each control system. Plant reports were prepared, which presented the data and results of the analysis, conclusions, and recommendations. These plant reports have served as the basis for the findings outlined in this report, as has information gathered during a World Health Organization (WHO) fellowship to study drycleaning in Europe.
Typical Drycleaning Process
The walk-through and in-depth surveys of various commercial drycleaning shops in the U.S. revealed that although practices varied from one shop to another, the overall drycleaning process was similar. The typical process begins when garments are brought to the shop by customers or arrive by van from another "satellite shop," which does no drycleaning on site. Garments are initially tagged for identification. Prior to spotting or being loaded into the drycleaning machine, garments are typically inspected and sorted according to weight, color, and finish. Modern garments are made from many different types of fabrics, and most drycleaners have the tools to clean all types.
Spotting
Particular attention was paid to spotting during the surveys to determine if excessive exposures occurred during this process. The spotting process might assume greater importance if wet cleaning methods in the U.S. were more widely used. Information was gathered prior to shop visits to determine which spotting chemicals a particular shop used most frequently. Purchasing records and Material Safety Data Sheets were reviewed.
In a typical shop, garments with visible stains are routinely treated at the spotting station. Spotting involves the selective application of a wide variety of chemicals and steam to remove specific stains from the garments. The three general categories of stains are water soluble, solvent soluble, and insoluble. Stains rarely consist of a single substance. Spotting chemicals and chemical mixtures are either solvent-based liquids (dryside) or water-based detergents (wetside). Wetside chemicals, which may contain water, remove water-soluble stains; and dryside chemicals, which never contain water, remove solvent-soluble stains.
The spotting chemicals, contained in small, plastic squeeze bottles, are applied to the stain. Spotting usually occurs on a spotting board equipped with pressurized air, steam, and water guns designed to flush the chemicals and stains from the garment. Air, steam, a small brush, a spatula, and fingers are all used to help break up the stains and wash them away. A pedal-actuated vacuum is used to capture the spotting chemicals, which are either held in a local storage reservoir or transported to a vacuum canister for discard.
In addition to PERC, some of the more common chemicals and chemical families for spotting are other chlorinated solvents, amyl acetate, petroleum naphtha, oxalic acid, acetic acid, esters, ethers, ketones, dilute hydrofluoric acid, hydrogen peroxide, and aqueous ammonia. Each of these chemicals are used in limited quantities. Most spotting chemicals are purchased from a company that supplies proprietary products to the industry. However, some shops use their own concoctions, which are prepared by individuals highly skilled in the art of stain removal.50
The spotting process has two components: pre-spotting, which involves dryside chemicals to remove or loosen solvent-soluble stains; and post-spotting, which utilizes wetside chemicals to remove water-soluble stains. Water-soluble stains, which may further set during the drycleaning process, are pre-spotted before drycleaning. Post-spotting is often used if the stain was not visible before drycleaning, or if the stain was not completely removed after pre-spotting and drycleaning. However, some shops utilize the more time-intensive post-spotting exclusively since many spots are removed during drycleaning. Some spotting processes involve little use of tools; the solvent is simply squirted liberally on all the stains before the garments are cleaned in the machine.
Machine Cleaning
Drycleaning, a three-step process, involves washing, extracting, and drying. A diagram of this process can be seen in Figure 1. Before washing, a worker adds detergent to the solvent in one of two ways: 1) A charge detergent is added to the solvent in set concentrations. The charged solvent is re-used in successive loads, and fresh detergent is periodically added to maintain the proper detergent concentration. 2) Injection or no-charge detergent is added to each load, based on each load's weight. Water is added to the system before or during drycleaning and aids in removing water soluble soils from the fabric.
To begin washing, clothes are manually loaded into the machine, followed by the solvent. The contents of the machine are then agitated for a period of time, allowing the solution to remove soils. Next, the clothes are spun at a high speed to extract the solvent.
After extraction, the fabric is tumbled dry. The drying process may occur in the same machine or a different one, depending on the system. Recirculated warm air vaporizes the residual solvent. Unheated air is then passed through the system during the cool-down cycle. This step reduces wrinkles. Following cool-down in vented machines, fresh air is passed through the system to freshen and deodorize the clothing during the aeration step.27 Garments are then removed from the machine prior to pressing.
Figure 1. The drycleaning process flow diagram.
Drycleaners use filtration and/or distillation to recover and purify solvent. Filtration removes insoluble soils, nonvolatile residues, and loose dyes from the solvent and, in some cases, soluble soils. Filtration is usually a continuous process in which the solvent passes through either an adsorbent powder or filter cartridge, both needing periodic replacement. Additionally, new, powderless, spin-disc filters51 significantly reduce the generation of hazardous waste because they are regenerated instead of discarded.52
Distillation, used by 90% of the industry, removes soluble oils, fatty acids, and greases not removed by filtration. Drycleaning stills typically consist of a kettle, condenser, and separator. Distillation occurs by heating PERC to its boiling point. The PERC vaporizes and condenses back into a liquid form. During this process, nonvolatile impurities, which do not evaporate, remain at the bottom of the still and are discarded as hazardous waste. Both filtration and distillation produce solid wastes containing PERC.
Pressing
Pressing is generally a dynamic and repetitive task that requires reaching and precision gripping. Pressers usually stand at nonadjustable workstations for much of the day and reach well overhead for hanging garments. When a garment is placed on a pressing machine, it is pressed between two surfaces, at least one of which is heated to a temperature around 149°C (300°F).
Some of the equipment used by pressers includes general utility presses; puff irons; pants toppers; finishers; electric irons; bosom, body, and yoke presses; collar, cuff, and yoke presses; and sleevers. Because this equipment is highly specialized, drycleaners do not necessarily have all of these presses. Once the garments have been completely pressed, they are returned to the overhead rack and wrapped in plastic for customer pick-up.
Drycleaning Machine Control Technologies
Shops included in the current NIOSH study were collectively selected to represent a cross-section of the controls available within the drycleaning industry. The most important factor for site selection was the effectiveness of the control system for reducing exposures to PERC. The NIOSH study evaluated the primary working hypothesis that four general categories of drycleaning machines were capable of maintaining an 8-hour TWA personal exposure to PERC of less than or equal to 25 ppm.
The four general categories of drycleaning machines evaluated were:
Two Basic Types of Drycleaning Machines
Two basic types of machines are generally used in drycleaning: transfer and dry-to-dry. Transfer machines are older, less expensive, and require manual transfer of solvent-laden clothing between the washer and dryer, a source of high worker exposure. Dry-to-dry machines eliminate clothing transfer because items are processed in one step, entering and exiting the machine dry. Transfer machines process more clothing than comparably sized dry-to-dry machines because the process time is approximately half that of a dry-to-dry machine. To compensate, some owners of dry-to-dry machines reduce the cycle time, thereby increasing productivity. Such practices can also increase exposures that result from unevaporated residuals in the drycleaned clothing.53
Transfer machines are generally vented, but dry-to-dry machines can be vented or nonvented. Vented dry-to-dry machines exhaust residual solvent vapors directly into the atmosphere or through some form of vapor recovery system, usually during the aeration process. Nonvented dry-to-dry machines are essentially closed systems, which are open to the atmosphere only when the machine door is opened. These machines recirculate the heated drying air through a vapor recovery system and back to the drying drum, eliminating the aeration step. Unfortunately, significant concentrations of PERC remain in the drum at the end of the cycle.
Approximately 70% of the drycleaning machines found today in the U.S. are of the newer dry-to-dry design. Transfer machines are no longer manufactured in the United States because of the high solvent usage rate, emissions, and exposures during transfer. However, used or reconditioned transfer machines can still be purchased. Either PERC or petroleum-based solvents can be used in dry-to-dry or transfer machines, but PERC is the solvent of choice for the majority of U.S. drycleaners.
Two Primary Vapor Recovery Technologies
The two primary technologies used to recover PERC vapors from drycleaning machines are the carbon adsorber and the refrigerated condenser. Carbon adsorbers are used in approximately 35% of controlled machines and refrigerated condensers, in approximately 65%. Carbon adsorbers remove PERC molecules from the air by passing solvent-laden vapors over activated carbon with a high adsorption capacity. The carbon is then desorbed and the PERC recovered, or the carbon is discarded when saturated. Carbon desorption typically occurs with steam or hot air. Desorption can be done automatically after each load, at the end of the day, or it can be done at other intervals depending on the PERC concentration and amount of carbon. If not done regularly, the carbon bed will become saturated and ineffective.
Refrigerated condensers use a refrigerant to cool the solvent-laden air below the dew point of the vapor to recover the PERC. The number of transfer machines using refrigerated condensers is roughly equivalent to the number of transfer machines using carbon adsorbers. However, on dry-to-dry machines there are approximately twice as many refrigerated condensers in use (see Table 4).
Drycleaning Machine Types in the U.S.
In 1988, the International Fabricare Institute (IFI) conducted a national drycleaning plant and equipment survey in which 5.8% of U.S. drycleaners participated. Results of that survey indicated that 79% of the shops responding used PERC only, and another 9% of shops used PERC and another solvent. For all PERC drycleaning machines, regardless of age, approximately 34% were dry-to-dry nonvented, 32% were dry-to-dry vented, and the remaining 34% were transfer machines. For PERC drycleaning machines that were less than five years old at the time, approximately 62% were dry-to-dry nonvented, 31% were dry-to-dry vented, and 7% were transfer. The majority of PERC drycleaning machines had a capacity of 30-39 lb, followed by 40-49 lb, and 50-59 lb, respectively. The average cleaning volume was 1,926 lb of clothing per week.54
The Evaluated Drycleaning Machines
During the six in-depth surveys conducted in various U.S. commercial drycleaning shops, NIOSH investigators evaluated sources of emissions and exposures from machines in the four general categories given above. Descriptions of the specific drycleaning equipment evaluated follow.
The Evaluated Transfer Drycleaning Machine.—The transfer unit studied consisted of two separate machines: a J & T® Model 60, 60-lb washer and a Model SF-145 Hoyt® Solvo-miser reclaimer. Both machines were over ten years old. The washer and reclaimer were connected to a Kleenrite® Vapor Condenser. The reclaimer had an internal, water-cooled condenser and separate refrigerated, vapor condenser. The reclaimer operated in three different modes: dry, cool, and aerate. During the dry mode, recirculated air was heated and then cooled in the condenser to recover PERC. During the cool mode, the air was diverted to the separate vapor condenser and cooled to recover PERC. During the final aeration cycle, fresh air was drawn into the reclaimer and exhausted outside of the building.
The Evaluated Dry-to-Dry, Vented Drycleaning Machine.—An Omega® Model CE55, 55-lb dry-to-dry machine, which was about six years old, was evaluated. This machine had a refrigerated condenser as the primary vapor recovery device. The secondary vapor recovery device consisted of a small, centrifugal fan rated at 110 cubic feet per minute (cfm) that was ducted to a carbon canister. When the machine door was opened, a microswitch energized the fan to draw PERC-laden air from the cylinder through the activated carbon.
The Evaluated Dry-to-Dry, Nonvented Machine.—Two nonvented, refrigerated, dry-to-dry machines, each less than five years old, were evaluated: a Boewe® Permac Model P540, 46-lb dry-to-dry machine and a Fluormatic® Model M242, 30-lb dry-to-dry machine. Both had a refrigerated condenser as the primary vapor recovery device. Both machines were connected to a Rite-Temp® Model RTR1003AWC Chiller used to chill water for reclamation, distillation, and maintenance of proper solvent temperature. There were no secondary vapor recovery devices.
Modern "Fifth Generation" Machine Technology.—Modern, dry-to-dry, nonvented drycleaning machines with residual controls are commonly referred to as "fifth generation" machines. The design of "fifth generation" machines began in Germany where their use is now mandated primarily by the Second German Emission Standard. "Fifth generation" drycleaning machines have engineering controls which dramatically reduce residual PERC in the machine's cylinder at the end of the dry cycle. These closed-loop, dry-to-dry machines rely on both an integrated, refrigerated condenser and a large carbon adsorber to recover PERC vapors during the dry cycle. "Fifth generation" machines are much more effective at recovering solvent vapors while drying garments than are machines equipped with only a carbon adsorber or refrigerated condenser alone. They are capable of lowering the PERC concentration in the machine's cylinder to below 290 ppm at the end of the dry cycle.
"Fifth generation" machines use a single beam, infrared photometer to monitor the PERC concentration in the machine cylinder. An interlock on the machine door prevents the operator from opening the machine door until the PERC concentration in the cylinder is below 290 ppm. The drying cycle will continue to operate until the cylinder concentration is sufficiently low. Such sophisticated machines are expensive and not widely used in the U.S.
Two Boewe Passat® dry-to-dry, nonvented drycleaning machines with residual controls were evaluated. One machine was a model P546, 46-lb machine, and the other was a model P536, 36-lb machine. Both machines had an integrated, refrigerated condenser and a large regenerable carbon adsorber to recover PERC vapors during the dry cycle. These machines were designed to lower the PERC concentration in the machine cylinder at the end of the dry cycle. This was accomplished using a large carbon adsorption system to capture PERC in the airstream and a single beam infrared photometer to continuously monitor the PERC concentration in the machine cylinder. An interlock on the machine door prevented opening until the PERC concentration in the cylinder was sufficiently low. The machines had a cleaning cycle of 35 to 40 minutes; however, the drying cycle was often automatically extended to ensure that the PERC concentration in the cylinder was below 290 ppm. The operator could determine the PERC concentration in the cylinder by reading a printout from the infrared photometer. The emission-free, still-cleaning device required still-raking only once every three weeks. A dosing unit enabled the operator to perform garment waterproofing within the machine.
METHODOLOGY
The principle measurements in this study were air concentrations of PERC measured both with conventional air-sampling pumps with charcoal tubes, and real-time instruments.
Air Sampling
Personal, area, and background air sampling was conducted using NIOSH Method 1003 for PERC and other halogenated hydrocarbons. In this method, organic vapors were drawn through 100 mg/50 mg coconut shell charcoal tubes. Carbon disulfide was used to desorb the solvents from the charcoal tube. Analysis was done using a gas chromatograph, fitted with a flame ionization detector to determine PERC concentrations and, in some instances, to determine all halogenated hydrocarbons concentrations. Samples were collected over 120-minutes at a flow rate of 0.1 liters/minute and a volume of 12 liters. The limit of detection for this method is 0.01 mg/sample.55
Two-hour consecutive personal sampling was conducted on all of the machine operators, as well as on some of the spotters and pressers who worked in proximity to the drycleaning machines. Two-hour consecutive samples were used to determine full-shift TWA exposures.The purpose of conducting personal sampling was to compare worker perchloroethylene exposures to a TWA of 25 ppm. In addition to TWAs, 5-minute and 15-minute exposures were measured during some manual tasks. This was done at a flow rate of 0.1 liters/minute and a volume of 0.5 and 1.5 liters respectively.
Area sampling determined which areas of the shop had the highest concentrations and were collected at various distances and locations around the periphery of the drycleaning machine. Air samples were generally collected in front of and behind the drycleaning machines, in the pressing area, in the spotting area, in the hazardous waste storage area, near the customer counter, and outside of the building. These locations were similar for each shop evaluated. This data helped in the development of strategies to reduce the exposures.
Air sampling was also used to evaluate the risk of chemical inhalation during the spotting process. Air sampling was conducted for two days to evaluate worker exposures to PERC, trichloroethylene, 2-butoxyethanol, hexylene glycol, MIBK, and n-butyl acetate. Additionally, five area samples were taken to determine concentrations of PERC and trichloroethylene. The ratio of equilibrium vapor concentration to TLV was used to compute a vapor/hazard ratio. Peak and 8-hour TWA personal sampling of spotters were conducted for halogenated hydrocarbons that could be sampled using NIOSH Method 1003. When combined exposures of PERC and other spotting chemicals were involved, the combined exposure (CE) was determined as follows.
CE = C1/T1 + C2/T2 + . . . + Cn/Tn
Where:
Cn = Exposure to an individual contaminant (ppm)
Tn = The OSHA PEL for the individual contaminant (ppm)
If the value of CE is less than 1, the combined exposure is believed to be acceptable. When this calculation was used during the in-depth spotting evaluation, the OSHA PEL for each chemical was applied if available. For hexylene glycol, no OSHA PEL was available; therefore, the NIOSH ceiling of 25 ppm was used.
Real-Time Monitoring
Real-time monitoring was used to study how specific manual tasks and maintenance operations affected worker exposure to PERC. Some drycleaning procedures occurred frequently throughout the day, such as loading/unloading the machine, while others, such as cleaning the lint and button traps, were less often. Most of these tasks took between 5 and 30 minutes. Real-time monitoring of PERC exposures were performed using a MicroTIP® IS3000® (PHOTOVAC Inc, Thornhill, Ontario) with a 10.6 EV ultraviolet lamp. This instrument uses a photoionization detector (PID) to provide an analog output response proportional to the concentration of ionizable chemicals present in the air. The MicroTIP® was spanned, using 100 ppm isobutylene span gas, and calibrated for both PERC and mineral spirits, using five standard concentrations of PERC vapor and mineral spirits vapor. Instrument readings and actual concentrations were used to construct two calibration curves and find predictive equations. The following formula was used to convert the output of the PID (volts) to concentration of contaminant (ppm):
C(t) = IR(t) * CF* MR
where:
C(t) = concentration of vapor at time t (ppm)
IR(t) = instrument response at time t (volts)
CF = conversion factor from calibration equation
MR = MicroTIP® range
Information gathered using the MicroTIP® was electronically recorded on a Rustrak® data logger (Rustrak® Ranger, Gulton, Inc., East Greenwich, RI) and downloaded to a portable computer, using Pronto® software. During the gathering of real-time data, a video camera recorded worker activities. This videotape permitted detailed analysis of tasks for quantitative determination of work activities causing the highest exposures.
Real-time monitoring was used for brief periods of time and focused on worker exposure during manual tasks and maintenance operations which might be related to high exposures. The frequency of manual tasks varied from shop to shop. Some common activities and their approximate frequencies follow:
Maintenance procedure Approximate frequency
Still cleaning Daily Filter replacement Demand related Filling the tank Demand related Water separator Weekly maintenance Button/lint trap cleaning Daily
Specific questions addressed from real-time monitoring results included:
p Are
certain controls more effective at reducing exposures around cleaning and pressing
stations?
p Do
specific actions result in higher exposures?
p How
does air contaminant concentration decay over time?
Real-time monitoring was also used to study off-gassing of garments and to compare vapor recovery efficiency of the machines. A standard test swatch, approximately 5 in. by 6 in. and made of 51% rayon and 49% polyester, was added to several runs of the drycleaning machine. At the completion of the dry cycle, the test swatch was placed in a small glass test chamber. As the solvent residuals in the swatch vaporized, PERC concentrations were monitored and recorded, using the MicroTIP® and Rustrak® data logger. This method detailed garment off-gassing and provided continuous concentration profiles, which were used to quantitatively compare the vapor recovery system's performance for each machine evaluated.
Evaluation of Ventilation Systems
Another aspect of this study was the evaluation of ventilation system performance. The various components of both the local and general ventilation systems were documented in order to assess the role of the entire ventilation system in controlling worker exposures. Data gathered during study of the ventilation system was compared to recommended values in the literature.
The following factors were examined when appropriate:
p
exhaust hood design, dimensions, and locationA Kurz® Model 1440 Air Velocity Meter was used to measure air speed. Smoke tubes were used to qualitatively evaluate airflow patterns near the machine and within the building.
General dilution ventilation was evaluated at each drycleaning shop studied. General ventilation can reduce contaminant concentrations in large areas that are not controlled locally. As part of the evaluation, a layout of the facilities was obtained, showing locations of exhaust ducts and makeup air. Flow rates, face velocities, and airflow patterns in the building were documented. All of the data gathered were compared to design specifications when possible.
Ergonomic Evaluation
Hazards and risk factors present during the pressing operation were evaluated by examining work station design, anthropometry, and conducting time studies of the tasks performed. Based upon walk-through surveys, preliminary information indicated that high repetition/insufficient recovery time, and awkward postures might be risk factors present during pressing operations. Interaction of these and other risk factors have been shown to result in cumulative trauma disorders.35,55
Repetitiveness and recovery time were evaluated by examining cycle time. This was accomplished by videotaping and analyzing tasks in their elemental forms. Awkward and sustained postures performed during the pressing operation were examined to determine whether they were a problem in light of the general guidelines which can be found in the current literature. Each of the tasks were videotaped and measurements were made to determine height, reach, anthropometric envelope, and physical layout of the workstation.
Work Practice Observations
Because work practices often have a dramatic effect on exposures, observations recorded during site visits were an important aspect of this study. Of particular importance were activities related to loading/unloading the machines, maintenance procedures, pressing operations, spotting, and use of personal protective equipment.
CONTROL OF DRYCLEANING SOLVENT EXPOSURES
The following section gives results from the six in-depth drycleaning surveys, discusses exposures and emissions, and suggests control options for U.S. commercial, drycleaning shops. Information gathered during the WHO fellowship in Europe is included primarily in the sections addressing substitution and "fifth generation" drycleaning machines.
Sampling and Monitoring Results
Air Sampling
Results of personal air sampling can be seen in Table 5. Generally, air samples gathered near the drycleaning machine had higher PERC concentrations than those farther away from the machine. Similarly, the more time a worker spent near the drycleaning machine, the higher the PERC exposures tended to be. Those drycleaning machines that were designed to lower the PERC concentration, emitted from the machine cylinder, were more effective than traditional machines at reducing worker exposures. Operators received the highest exposures from loading and unloading the machine; whereas, pressers were primarily exposed from garment off-gassing.
Table 5
Time-Weighted Average Worker Exposures to PERC
(for entire survey)
Transfer Equipment.—All but one of the daily TWA personal samples taken on the transfer machine operator and two pressers were below 25 ppm. The transfer machine operator was exposed to 19.5 ppm TWA PERC for the entire survey. The operator's two-hour samples ranged from 3.9 to 42.3 ppm. The two pressers, who did not work in as close proximity to the transfer machine as the operator, were exposed to 3.3 and 3.8 ppm TWA PERC during the entire survey. Statistical analysis showed a significant difference between the operator's and pressers' TWA exposures.
NIOSH investigators gathered 5- and 15-minute personal air samples on charcoal tubes during transfer operations and filter changing (Figure 2). Neither of these activities exceeded the OSHA ceiling of 200 ppm or OSHA peak of 300 ppm. Exposure during transfer operations was 57.5 ppm for a 5-minute period and 21 to 22 ppm during a 15-minute period. The reason for the differences between 5- and 15-minute concentrations was due to time taken for tasks. Exposure during filter changing was approximately 121 ppm for 5 minutes and 118 ppm for 15 minutes.
Figure 2. Five-minute and fifteen minute personal
exposures to PERC from transfer equipment.
The highest area concentrations were above the reclaimer door. The geometric mean concentration in that area was 15.2 ppm, which was significantly different from all other areas. It seems logical that these area concentrations would have been the highest because the air was heated, and the PERC was in the vapor state during loading/unloading the reclaimer, but the solvent and air in the washer were not heated.
Dry-to-Dry, Vented Equipment.—All of the individual personal samples taken for the dry-to-dry, vented machine were below 25 ppm. The machine operator was exposed to 15.8 ppm TWA PERC for the entire survey. Two-thirds of these exposures resulted from loading and unloading the machine. The two pressers were exposed to 5.0 and 2.5 ppm TWA PERC for the entire survey. The highest geometric mean area concentrations measured, 9 and 12 ppm PERC, were near the drycleaning machine where a vapor leak was detected. The next highest geometric mean concentrations, 6 and 8 ppm PERC, were above the machine door.
Dry-to-Dry, Nonvented Equipment.—The machine operator, a presser, and a clothing inspector were sampled at the shop having two nonvented dry-to-dry machines, and all individual personal samples were below 25 ppm. The machine operator was exposed to 7.8 ppm TWA PERC for the entire survey. Nearly half of this exposure resulted from loading and unloading. The presser and inspector were exposed to less than 1 ppm TWA PERC. The highest area samples, 5.4 and 5.7 ppm PERC, were taken above the drycleaning machines' doors. The next highest concentrations were behind the machines.
Dry-to-Dry, Nonvented with Residual Control.—Figure 3 summarizes personal air samples gathered for the two dry-to-dry, nonvented machines with residual controls. All of the personal samples were well below 25 ppm and were dramatically lower than exposures on any other machines evaluated. The operator of the "fifth generation" machine had the highest exposure to PERC, ranging from 0.31 to 4.9 ppm TWA. Almost all of the operator two-hour samples were below 2 ppm PERC, and most samples were below 1 ppm. The only exception to these low exposures occurred when the operator raked the still bottoms of both machines. During the last morning of sampling, the operator was exposed to approximately 12 ppm over a two-hour period and 4.9 ppm full-shift TWA PERC primarily because of cleaning the stills. If the stills had not been cleaned, the TWA exposure probably would have been less than 2 ppm.
Figure 3. Time-weighted average worker exposure to
PERC from "fifth generation" drycleaning
machines. (Four days of air sampling.)
The pressers were protected from PERC vapors originating from the machine by ventilation and barriers between the pressing station and drycleaning machine. All of the PERC concentrations measured near the presser's breathing zone were at or below the limit of detection, 0.01 mg/sample. This minimal exposure resulted from almost no PERC retention in the clothing. Little PERC was detected on samples outside of the drycleaning room. This nondetection of PERC can be attributed to excellent machine design and ventilation near the machines. The highest area concentrations, ranging from 0.0 to 1.9 ppm, were detected above and behind the drycleaning machines.
Statistical Analysis of Air Sampling Data
Summaries of the personal air sample results and their statistical analysis are in Tables 5, 6, 7, and 8. All of the TWA and mean exposures to PERC in these tables were below 25 ppm. However, some of the individual two-hour samples exceeded 25 ppm, and so did a small number of the daily TWA exposures. Time-weighted average exposures would have been somewhat lower if sampling had occurred for a full 8-hour shift; however, air sampling generally occurred when the drycleaning machines were in operation, typically six or seven hours per day.
Statistical analysis was performed on log transformed air sampling data for PERC. A two-way analysis of variance (ANOVA) showed that job title and shop had a significant effect upon concentration (p<0.0001). A multiple comparison test with 5% significance level, least significant difference (LSD), was used to analyze concentration differences.
Table 5 gives the TWA personal air samples by job for each shop evaluated. The TWA exposures in the table are for the duration of the entire survey. At each shop evaluated, the machine operator had consistently higher exposures than did any other job title. Most of the workers performing other jobs were exposed to less than one-third of the machine operator's exposure. Much of the difference can be attributed to the fact that the other jobs did not include the peak exposures associated with loading and unloading the machine.
Table 6 provides arithmetic and geometric mean personal exposures to PERC by shop for machine operators and the results of the two-way analysis of variance (2-WAY ANOVA). It also includes the concentration range and geometric standard deviation. This statistical analysis indicates that the operator of the advanced, "fifth generation" drycleaning machines was exposed to significantly lower PERC concentrations than operators of any other type of machine. Differences between operator exposures at all other shops were not statistically significant.
*Different letters indicate a
statistically significant difference using the least significant difference test. (
= .05)
Table 7 gives the results of a one-tailed ( = 0.05) t-test, comparing operator exposure to
PERC at each shop evaluated to 25 ppm. All of the machines studied maintained operator
exposures to PERC below 25 ppm with the exception of the shop having two dry-to-dry,
vented machines. Another shop with similar equipment, but only one machine, was able to
control exposures below 25 ppm. Part of this difference may be due to production volume;
this shop had two machines and a higher volume of garments, which required machine
loading/unloading nearly twice as often.
Statistically significant at ( = .05)
Table 8 is a summary of personal exposures to PERC by job title across shops. As expected, the machine operator had the highest mean exposure to PERC, which was 13.3 ppm for all shops evaluated. The machine operators' exposures were significantly different from exposures experienced by presse